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IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. IEEEJOURNAL OF DIPILIH Forum di QUANTUM ELECTRONICS, VOL. 5, NO. 5, NO. 4,JULY/AUGUST 1999 4, Juli / Agustus 19991143 1143

Clinical Optical Tomography and NIR Spectroscopy Optical Tomography klinis dan NIRSpektroskopifor Breast Cancer Detection untuk Breast Cancer DetectionSB Colak, MB van der Mark, GW't Hooft, JH Hoogenraad, ES van der Linden, and FAKuijpers SB Colak, MB van der Mark, GW't Hooft, JH Hoogenraad, ES van der Linden, danFA Kuijpers(Invited Paper)(Diundang Paper)AbstractThe results of the first set of clinical trials with the Abstrak-Hasilpertama ujiklinis dengan

Philips optical mammography prototype system are summarized.Philips optik sistemprototipe mamografi diringkas.This optical mammo prototype is designed to image the interiorPrototipe mammo optikini dirancang untuk gambar interiorof the female breast with the help of near-infrared (NIR) laserdari payudara wanitadengan bantuan dekat-inframerah (NIR) laserlight transmission measurements.transmisi cahaya pengukuran.This study is expectedto leadStudi ini diharapkan untuk memimpinto optical tomography systems for breast cancer detection.untuk sistem tomografi optikuntuk deteksi kanker payudara.ThisInipaper presents information on the design of the optical mammomenyajikan informasimengenai desain optik mammo

system, the clinical measurements and the imaging results fromsistem pengukuranklinis dan hasil pencitraan darian initial group of ten patients, and discussions about ongoingkelompok awal sepuluhpasien, dan diskusi tentang berkelanjutanresearch on optical tomography.penelitian tentang tomografi optik.I ndex TermsBiological tissues, biomedical infrared imaging, I ndex Syarat-Bi ologi

jaringan, biomedis inframerah imaging,

image reconstruction, medical diagnosis, optical spectroscopy,gambar rekonstruksi,diagnosa medis, optik spektroskopi,optical tomography.optik tomography.I. I I. Aku

NTRODUCTION ENDAHULUANBBREAST TUMOR is the leading form of cancer in the REAST TUMOR adalah bentuk kankerterkemuka difemale human [1]. perempuan manusia [1]. In contrast to this, it is also one of the Berbedadengan ini, juga merupakan salah satu darimost treatable forms of cancer, if it can be diagnosed early. sebagian besar jenis kanker dapatdisembuhkan, jika dapat didiagnosa dini.The growth rate of breast cancer is exponential with a doubling Tingkat pertumbuhan kanker

payudara adalah eksponensial dengan dua kali lipattime of about three months. waktu sekitar tiga bulan. Most primary cancers of breast are

Kebanyakan kanker payudara primer adalah


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detected by the patients themselves when the average size is terdeteksi oleh pasien sendiriketika ukuran rata-rataabout 2.5 cm. sekitar 2,5 cm. About half of these are already metastatized to Sekitar setengahdari ini sudah metastatized untukthe lymph nodes. kelenjar getah bening. The survival chance of breast cancer drops

Kesempatan kelangsungan hidup kanker payudara tetesfrom a rate of about 95% when the lump is about 0.5 cm size, dari laju sekitar 95% ketika

benjolan sekitar 0,5 cm ukuran,to a rate of 75% when the cancer is treated at a size of about ke tingkat 75% bila kankerdiperlakukan pada ukuran sekitar2.5 cm. 2,5 cm. With this information, it is an obvious conclusion that Dengan informasi ini,ini adalah kesimpulan yang jelas bahwa

practical and safe diagnosis techniques for this cancer is highly praktis dan aman teknikdiagnosa kanker ini sangatdesirable. diinginkan. The topic of this report, the medical optical imaging Topik laporan ini,optik pencitraan medis

associated with near infrared (NIR) spectroscopy, is expected berhubungan dengan inframerah dekat (NIR) spektroskopi, diharapkanto make routine and frequent mammography practical. untuk membuat mamografi rutin dansering praktis.At the moment, the reliability of the conventional imaging Pada saat ini, keandalan dari

pencitraan konvensionaltechniques for breast cancer is not perfect. teknik untuk kanker payudara adalah tidaksempurna. The most common Paling umummethod of breast imaging, X-Ray mammography, has a high metode pencitraan payudara, X-Ray mamografi, memiliki tinggifalse diagnosis ratio for cancer [2]. diagnosis palsu rasio untuk kanker [2]. The ultrasoundimaging Ultrasound imagingtechniques can differentiate between solid tumors and cysts. teknik dapat membedakan antaratumor dan kista padat.However, further clinical studies are required to evaluate Namun demikian, studi klinis lebihlanjut diperlukan untuk mengevaluasithis promising technique and increase its specificity. teknik menjanjikan ini danmeningkatkan kekhususan. The Itumagnetic resonance imaging (MRI) provides excellent soft Magnetic Resonance Imaging(MRI) menyediakan lunak baiktissue contrast, but it has to be made more practical for jaringan kontras, tetapi harus dibuat

lebih praktis untukapplication in breast imaging. aplikasi dalam pencitraan payudara. Both of these lattermethods Kedua metode terakhirManuscript received February 23, 1999; revised June 4, 1999. Naskah diterima 23 Februari1999; direvisi 4 Juni 1999.SB Colak, MB van der Mark, GW't Hooft, and JH Hoogenraad are SB Colak, MB van derMark, GW't Hooft, dan JH Hoogenraad adalahwith Philips Research Labs, 5656AA Eindhoven, The Netherlands. dengan Philips ResearchLabs, 5656AA Eindhoven, Belanda.ES van der Linden is with Academic Hospital Maastricht, 6202AZ ES van der Linden adalahdengan Rumah Sakit Akademik Universitas Maastricht, 6202AZ

Maastricht, The Netherlands. Maastricht, Belanda.


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FA Kuijpers is with Philips Medical Systems, 5680DA Best, The FA Kuijpers adalah denganPhilips Medical Systems, 5680DA Best, The

Netherlands. Belanda.Publisher Item Identifier S 1077-260X(99)07525-5. Penerbit Item Identifier S 1077-260X(99) 07525-5.

show improved sensitivity if used together with chemical menunjukkan peningkatansensitivitas jika digunakan bersama dengan kimiacontrast agents injected into the patient [2]. agen kontras disuntikkan ke pasien [2].Another promising method for tissue characterization and Lain metode yang menjanjikanuntuk jaringan karakterisasi dandiagnosis is optical imaging [3]. diagnosis optik pencitraan [3]. Due to their advanced en-Karena mereka maju en -gineering stage, the optical techniques offer a variety of gineering panggung, teknik optikmenawarkan berbagainew imaging modalities including time-of-flight methods with modalitas pencitraan barutermasuk waktu-of-penerbangan metode dengan

ultra-fast laser pulses, optical coherence tomography, photon laser ultra cepat pulsa,tomografi koherensi optik, fotondensity wave imaging, among many others. kerapatan gelombang pencitraan, di antara

banyak lainnya. Most of these Kebanyakanmodalities are currently being studied in a variety of insti- modalitas saat ini sedang belajar di

berbagai insti -tutes and research groups, including ours. apapun dapat menjadi kelompok dan penelitian,termasuk kita. These are briefly Ini sebentarsummarized in the following paragraphs. dirangkum dalam paragraf berikut.Optical radiation has been first used in diaphanoscopy in Radiasi optik telah digunakan didiaphanoscopy pertama di1929 to image breast tumors by shadowing effect [4]. 1929 sampai gambar payudara tumoroleh efek bayangan [4]. In Didiaphonoscopy, the difference in the absorption coefficient of diaphonoscopy, perbedaandalam koefisien penyerapanvarious tissues enables the detection of inhomogeneities in the berbagai jaringanmemungkinkan deteksi di inhomogeneities

breast. dada. The areas of dense tumor or hematoma look darker, Bidang padat tumor atauhematom terlihat lebih gelap,while the pockets of cyst look clearer as compared to the sedangkan kantong kista terlihatlebih jelas dibandingkan dengan

surrounding tissues. jaringan sekitarnya. Diaphanography, which is based on thisDiaphanography, yang didasarkan padabasic idea, has been tested in several hospitals in the 1980's, Ide dasar, telah diuji di beberaparumah sakit di tahun 1980-an,as preliminary examination tool before a biopsy. sebagai alat pemeriksaan pendahuluansebelum biopsi. As has been Seperti telahsummarized before [5], the breast cancer detection rate is about diringkas sebelum [5], kanker

payudara tingkat deteksi adalah30% with the conventional diaphanography. 30% dengan diaphanography konvensional.In the 1990's, we have seen many other new modalities of Pada tahun 1990, kami telahmelihat banyak modalitas baru dari

medical optical imaging. optik pencitraan medis. This has been primarily due to the Ini telahterutama karena


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strong advancements in near-infrared (NIR) laser and detector kemajuan kuat di dekat-inframerah (NIR) laser dan detektortechnologies, suitable for biological tissue characterization. teknologi, cocok untukkarakterisasi jaringan biologis.For example, an advanced version of diaphonoscopy has Sebagai contoh, sebuah versi

lanjutan telah diaphonoscopybeen studied with scanned (fiber) laser light [6]. telah dipelajari dengan scan (serat) sinarlaser [6]. In another Laininvestigation, optical measurements have been extended with penyelidikan, pengukuran optiktelah diperpanjang denganlight which is modulated at near-gigahertz frequencies, to cahaya yang dimodulasi padafrekuensi di dekat-gigahertz, untukobtain better contrast and resolution in the images [7]. memperoleh kontras dan resolusi yanglebih baik pada gambar [7]. This Iniapproach is under current clinical study [8]. Pendekatan ini berdasarkan studi klinis saat ini[8]. Time resolved Sisa diselesaikan

transillumination with short laser pulses has been studied for transillumination dengan pulsalaser pendek telah dipelajari untukthe extraction of different tissue parameters [9]. ekstraksi parameter jaringan yang berbeda[9]. Such short Pendek seperti

pulse methods have also been applied in actual mammographic metode denyut nadi juga telahditerapkan di mammographic aktualimaging trials with volunteer patients [10]. pencitraan pengadilan dengan relawan pasien[10]. During the recent Selama baruyears, there has also been a good amount of breast tissue tahun, ada juga yang baik jumlah

jaringan payudaraspectroscopy done on volunteers [11]. Spektroskopi dilakukan pada sukarelawan [11]. Thesestudies have Studi tersebut telahfurther resulted in mammographic imaging systems which lebih lanjut mengakibatkan sistem

pencitraan yang mammographicare also under current clinical trials [12]. juga dalam uji klinis saat ini [12]. In some cases,Dalam beberapa kasus,medical contrast agents have also been tried to evaluate their agen kontras medis juga telahmencoba untuk mengevaluasiuse in optical imaging [13]. digunakan dalam pencitraan optik [13]. There are actually effortsto Sebenarnya ada upaya untukcommercialize some of the optical imaging methods described mengkomersialkan beberapa

pencitraan optik metode yang dijelaskanabove [14]. di atas [14].Although, in our research group, we have also investigated Meskipun, dalam kelompok risetkami, kami juga menelitithe use of short laser pulses [15] and photon density waves, penggunaan laser pendek pulsa[15] dan kerapatan foton gelombang,

1077260X/99$10.00 1999 IEEE 1077-260X/99 $ 10,00 1999 IEEE

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JOURNAL OF DIPILIH Forum di QUANTUM ELECTRONICS, VOL. 5, NO. 5, NO. 4,JULY/AUGUST 1999 4, Juli / Agustus 1999


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[16], [17], in medical imaging, we have decided to do our [16], [17], dalam pencitraan medis,kami telah memutuskan untuk melakukan yanginitial clinical trials with continuous wave (CW) laser sources uji klinis awal dengangelombang kontinu (CW) laser sumber[18]. [18]. Our method uses many source and detector fiber probes Metode kami

menggunakan banyak sumber dan detektor serat probeattached solidly on the inner surface of a cup which is placed terpasang kokoh pada

permukaan bagian dalam sebuah cangkir yang ditempatkanaround the patients breast. di sekitar payudara pasien. This approach provides a morePendekatan ini memberikan tampilan yang lebih

practical and reliable hardware setup which is suitable for praktis dan dapat diandalkan setuphardware yang cocok untukclinical trials. uji klinis. We have actually built a clinical prototype Kita sebenarnya telahmembangun sebuah prototipe klinisfor optical mammography and have been testing it clinically untuk optik mamografi dan telahmengujinya secara klinis

during the past couple of years. selama beberapa tahun. We have also reported some of Kamijuga telah melaporkan beberapaour initial results previously [19], [20]. hasil awal kami sebelumnya [19], [20]. In this paper,we would Dalam makalah ini, kami akanlike to present a more complete description of our experiments seperti untuk menyajikangambaran yang lebih lengkap eksperimen kamiand results and also discuss future possibilities of research dan hasil dan juga mendiskusikankemungkinan masa depan penelitianwith this approach. dengan pendekatan ini.II. II. T TISSUE ISSUEO OPTICS PTICSIn this section, we will give a brief review on the basic Dalam bagian ini, kami akanmemberikan ulasan singkat mengenai dasarcomponents of healthy and diseased tissue, and their main komponen jaringan sehat dansakit, dan utama merekaoptical properties. optiknya. Biological tissue is made up of a large Jaringan biologis terdiridari besarnumber of molecules consisting of primarily carbon, hydrogen, jumlah molekul terutamaterdiri dari karbon, hidrogen,

oxygen, and nitrogen atoms [21], [22]. oksigen, dan nitrogen atom [21], [22]. These atomsare bound Atom ini terikatinto a vast variety of small and large molecules, up to menjadi luas berbagai molekul besardan kecil, hinggatimes kalithe weight of an H atom. berat atom H. This large variety of molecules form Besar ini

berbagai bentuk molekulthe cells of a biological organizm. sel-sel biologis organizm. Cells contain 70%80% Selmengandung 70% -80%water, and 1020% of lipids, fatty molecules which form the air, dan 10-20% lemak, molekullemak yang membentuk

cell membranes. membran sel. The interior of cells can contain particles Interior sel dapatmengandung partikel


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and macromolecules of highly varied shapes and dimensions dan makromolekul yang sangatbervariasi bentuk dan dimensiranging from 100 s of angstroms to 100 s of micrometers. mulai dari 100 s dari angstromsampai 100 s dari mikrometer.These include large molecules such as proteins, amino acids, Ini termasuk molekul-molekul

besar seperti protein, asam amino,nucleic acids (DNA), and polysaccharides. asam nukleat (DNA), dan polisakarida. Cells,depending Sel, tergantungon the different organs of a human, can have many different pada organ-organ yang berbedamanusia, dapat mempunyai banyak berbedashapes and sizes varying from 10100 m. bentuk dan ukuran yang bervariasi 10-100 m.Due to the refractive index variations in the length scales Karena variasi indeks bias dalamskala panjangdescribed above, the propagation of light in tissue has a diffuse dijelaskan di atas, propagasicahaya dalam jaringan memiliki difusicharacter. karakter. Structural fibers and nuclei Struktural serat dan nuklei

1.45) in -1,45) Dia background of cytoplasm latar belakang sitoplasmaand extracellular dan ekstraselularfluid fluidaare the origin for the main part of the adalah asal untuk bagian utama dariindex variations [23]. indeks variasi [23]. Light absorption occurs primarily on Cahaya

penyerapan terjadi terutama padadiscrete portions of the cells known as chromophores, such diskrit bagian dari sel-sel yangdikenal sebagai chromophores, sepertias chromatin, cytochrome, haemoglobin and myoglobin. sebagai kromatin, sitokrom,hemoglobin dan mioglobin. The Ituthree last pigments change their optical characteristics as a tiga pigmen terakhir mengubahkarakteristik optik sebagaifunction of the metabolism, whether the pigment is oxidized or fungsi metabolisme, apakah

pigmen teroksidasi ataureduced [5]. dikurangi [5]. Obviously living tissue is also a dynamic system. Jelas jaringanhidup juga merupakan sistem dinamik.It changes properties and shape with, again, highly varying It perubahan sifat dan bentukdengan, sekali lagi, sangat bervariasitime scales. skala waktu. For example, heart beat, with about 1/80 of a Sebagai contoh,

jantung berdetak, dengan sekitar 1 / 80 dari sebuah

minute of period, changes the shape of the veins, the organs periode menit, perubahan bentukpembuluh darah, organ-organand the oxygenation state of many molecules contained in dan keadaan oksigenasi banyakmolekul yang terkandung dalamthem. mereka. There are many molecules in motion in the blood stream, Ada banyak molekuldalam gerakan dalam aliran darah,and they result in Doppler broadening of the scattered light dan mereka menghasilkanDoppler perluasan dari cahaya yang tersebarwith time scales in the order of sub milliseconds. dengan skala waktu dalam urutan submilidetik. Due to all Karena semuathese reasons, it is very difficult to obtain clear optical images alasan ini, sangat sulit untuk

mendapatkan gambar yang jelas optik


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of the interior of the biological tissue by direct methods. dari bagian dalam jaringan biologismetode langsung.Furthermore, because of the same effects, the biological tissue Lebih jauh lagi, karena efekyang sama, jaringan biologisusually responds to optical excitation in a very indistinct way, biasanya merespons eksitasi

optik dalam cara yang sangat tidak jelas,making the spectroscopic identification of different tissue types membuat identifikasispektroskopi jenis jaringan yang berbedadifficult. sulit.Despite these difficulties, due to the expected safety and Meskipun kesulitan-kesulitan ini,karena diharapkan keselamatan daneasiness of optical imaging methods, there have been numer- optik pencitraan kemudahanmetode, ada numer -ous studies to determine the optical properties of tissue. ous studi untuk menentukan sifatoptik jaringan. To UntukFig. Gambar. 1. 1. Relative transmission of the most relevant absorbing compounds in Relatif

transmisi yang paling relevan dalam menyerap senyawabiological tissues in the visible and NIR region (adapted from [24]). biologis jaringan diwilayah terlihat dan NIR (diadaptasi dari [24]). Water Air(OH), fat (CH) and hemoglobin (Hb,HbO) are the most important absorbers (OH), lemak(CH) dan hemoglobin (Hb, HBO) adalah yang paling penting absorbersin tissue. dalam jaringan. The vertical lines indicate the laser wavelengths used in our studyGaris vertikal menunjukkan panjang gelombang laser yang digunakan dalam penelitian

presented here. disajikan di sini.Fig. Gambar. 2. 2. Pathological slide for an intraductal carcinoma [27], emphasizing thePatologis slide untuk intraductal karsinoma [27], yang menekankanhigh heterogeneity of the breast tissue. heterogenitas yang tinggi dari jaringan payudara. Themalignant cells are confined to Sel-sel yang ganas terbatas padathe ducts (1). saluran (1). There is a region of degenerating (necrotic) cells (2). Ada wilayahmemburuk (nekrotik) sel-sel (2). Normal Normallobules (3), fibrous stroma (4) and fat (5) regions are also shown. lobulus (3), stroma fibrosa(4) dan lemak (5) daerah juga ditampilkan. Sketch in Sketsathe inset shows the vascularization of the cancerous region. insetnya menunjukkanvascularization dari daerah kanker. Due to this and Karena ini danalso associated hemorrhages, these regions result in higher optical absorption juga

berhubungan perdarahan, daerah ini menghasilkan penyerapan optik yang lebih tingginear Hb bands indicated in Fig. Hb dekat band ditunjukkan pada Gambar. 1. 1.

summarize some of these, we first give the relative trans- merangkum beberapa di antaranya,pertama-tama kita memberikan relatif trans -mission spectra of the most relevant absorbing compounds in spektrum misi yang palingrelevan dalam menyerap senyawatissues in Fig. jaringan dalam Gambar. 1. 1. Water, fat and hemoglobin are most importantAir, lemak dan hemoglobin adalah yang paling pentingabsorbers in tissue [24]. absorber dalam jaringan [24]. This set of curves has sufficient detailSet kurva ini telah cukup detailto label the major features in a full transmission spectra ofin untuk label fitur-fitur utamadalam transmisi spektrum penuh dalamvivo breast, as given previously [24]. vivo payudara, seperti yang diberikan sebelumnya [24].

We also observe that, Kami juga mengamati bahwa,


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there is a window from 650 to 900 nm, where the lowest ada jendela 650-900 nm, di manaterendah

percentage of light is absorbed. persentase cahaya yang diserap. From these one expects that,it Dari seorang pun mengharapkan bahwa, halshould still be possible to identify the weak absorption peaks seharusnya masih dapat dibuat

untuk mengidentifikasi puncak penyerapan lemahcoming from haemoglobin, fat and water. berasal dari hemoglobin, lemak dan air. Forexample, one Sebagai contoh, satucan deduce that a wavelength at 780 nm should show the dapat menyimpulkan bahwa

panjang gelombang pada 780 nm harus menunjukkanstrongly blood perfused parts of the breast as a shadow as perfused darah kuat bagian

payudara sebagai bayangan sebagaicompared to other tissues containing more water, for example. dibandingkan dengan jaringanlain yang mengandung lebih banyak air, misalnya.In cancer, the regular cellular growth cycle of cells changes Pada kanker, sel biasa siklus

pertumbuhan sel perubahan

due to the mutations in the DNA, resulting in variations in karena mutasi pada DNA,menyebabkan variasi dalamthe cell cycle times [25]. siklus sel kali [25]. Most carcinomas in the breast arise Kebanyakankarsinoma pada payudara timbulin the epithelial lining of the milk glands and ducts [26]. dalam lapisan epitel kelenjar susudan saluran [26].Different components of breast cancer and surrounding tissues Komponen yang berbedakanker payudara dan jaringan sekitarnyaare shown in the pathological slide in Fig. akan ditampilkan dalam slide patologis dalamGambar. 2. 2. In the avascular Dalam avascular

phase the initial clump of malignant cells can remain as a rumpun fase awal dari sel-sel ganasdapat tetap sebagai

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COLAKet al. : CLINICAL OPTICAL TOMOGRAPHY AND NIR SPECTROSCOPY FORBREAST CANCER DETECTION COLAKet al.: KLINIS OPTIK spektroskopi NIRtomography DAN UNTUK KANKER PAYUDARA DETECTION1145 1145Fig. Gambar. 3. 3. The optical mammo prototype system. Mammo optik sistem prototipe.The arrow near the cup area Panah di dekat daerah cangkirtoward the computer monitor indicates the reference point where the images ke arah monitor

komputer menunjukkan titik acuan di mana gambardiscussed in the text are registered. dibahas dalam teks terdaftar.harmless in situ carcinoma for many years at a size of about 1 in situ karsinoma tidak

berbahaya selama bertahun-tahun di ukuran sekitar 1mm. mm. Further growth requires vascularization, where the nearby Vascularizationmembutuhkan pertumbuhan lebih lanjut, di mana di dekatnya

blood vessels send out capillaries into the tumor. pembuluh darah kapiler mengirimkan ketumor. This leads Ini mengarahto a vascularized lump with irregular and diffuse boundaries ke vascularized benjolan dengan

batas-batas yang tidak teratur dan baur[28] as shown schematically in Fig. [28] seperti yang ditunjukkan secara skematik pada

Gambar. 2 as inset. 2 sebagai inset. Due to this Karena ini


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rapid vascularization, tumors have high internal pressure and vascularization cepat, tumormemiliki tekanan internal yang tinggi danresult in hemorrhages [29]. mengakibatkan perdarahan [29]. These regions are irrigatedheavily Irigasi wilayah ini sangatin hypoxic blood, showing up as highly absorbing regions in di hipoksia darah, muncul

sebagai sangat menyerap daerah dioptical transmission. transmisi optik.In order to utilize the optical techniques in diagnosis ef- Dalam rangka untuk menggunakanteknik-teknik optik diagnosis ef -fectively, we must characterize the biological tissue with its fectively, kita harus ciri jaringan

biologis denganmost important parameters. parameter yang paling penting. Spectroscopic analysis of suchAnalisis spektroskopi seperti

parameters can lead to differentiation of the phenomena such parameter dapat menyebabkandiferensiasi dari fenomena tersebutas vascularization in cancer core as well as the molecular sebagai inti kanker vascularization

serta molekulerdifferences in the same region, leading to the detection and perbedaan-perbedaan di daerahyang sama, yang mengarah ke deteksi danassessment of cancer. penilaian kanker. Such spectral differences have been Seperti telah

perbedaan spektralreported in measurements for the absorption, fluorescence, dilaporkan dalam pengukuranuntuk penyerapan, fluoresensi,light diffusion, Raman scattering, etc. [30]. cahaya difusi, hamburan Raman, dll [30]. Itshould be Harusrealized, however, that the cancerous tissue has a rather menyadari, bagaimanapun, bahwa

jaringan kanker telah agakdiffusive boundary, and the appearance and the molecular difusif batas, dan penampilan danmolekuler

properties of cancerous tissue of various kinds of tumors sifat jaringan kanker berbagai jenistumordiffer greatly. berbeda jauh. Despite this variations, biological tissue has Meskipun variasiini, memiliki jaringan biologis

been characterized mainly by a few parameters depending terutama dicirikan oleh beberapaparameter tergantungon the diffusion properties of the light within it. pada sifat difusi cahaya di dalamnya. Most ofSebagian

such collected data are normally presented as absorption, mengumpulkan data seperti itubiasanya disajikan sebagai penyerapan,, and scattering , Dan menyebarkancoefficients, usually given in units of koefisien, biasanya diberikan dalam satuan(1/m) or (1/mm). (1 / m) atau (1/mm). Numerical values of these optical parameters Nilainumerik parameter optik iniwithin 700900 nm range for breast tissue, which are around dalam rentang 700-900 nm

jaringan payudara, yang sekitar1/mm for 1/mm untukand 0.05/mm for dan 0.05/mm untuk, have been reported in , Telah dilaporkan

previous studies [31][34]. penelitian sebelumnya [31] - [34]. Note that the attenuationconstant Perhatikan bahwa pelemahan konstan


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values discussed later, are related to these parameters by nilai dibahas kemudian, berkaitandengan parameter ini denganIII. III. O OPTICAL PTICALM M

AMMO AmunisiP PROTOTYPE ROTOTYPEIn order to be able to do clinical optical imaging for breast Untuk dapat melakukan pencitraanoptik klinis payudaracancer we have built an optical mammography prototype kanker kami telah membangun

prototipe mamografi optiksystem. sistem. A photo of this system is shown in Fig. Sebuah foto dari sistem iniditunjukkan pada Gambar. 3. 3. Its most PalingFig. Gambar. 4. 4. The close up photo of the cup region of the prototype. Foto yang dekatdari daerah cangkir prototipe. Tips of some Tips dari beberapa

of the source and detector fibers are seen within the cup. dari sumber dan detektor seratterlihat dalam cangkir. The red diverging Divergen merahlight is from one of the source fibers emitting at around 670 nm. cahaya dari salah satusumber memancarkan serat sekitar 670 nm.important element is the cup region shown in the following elemen penting adalah wilayahcangkir ditunjukkan pada berikutFig. Gambar. 4, where the transmission of the breast is measured over 4, di mana transmisi

payudara diukur atasa conical surface. permukaan berbentuk kerucut. On the boundary of the cup 255 optical Di

batas cangkir optik 255fibers are mounted that lead to one detector each. serat dipasang yang mengarah ke satudetektor masing-masing. Interleaved, Interleaved,255 fibers are mounted that can be selected sequentially to 255 serat dipasang yang dapatdipilih secara berurutan untukreceive the light of one of the three continuous-wave diode menerima cahaya dari salah satudari tiga gelombang kontinu diodalasers that are operating at different wavelengths in the NIR. laser yang beroperasi pada

panjang gelombang yang berbeda di NIR.All detectors measure simultaneously so that one complete Semua detektor mengukur secarasimultan sehingga satu lengkapmeasurement for one wavelength takes less than 2 min. pengukuran untuk satu panjang

gelombang memakan waktu kurang dari 2 menit. The Ituconical cup geometry and the CW operation, in our prototype, cangkir berbentuk kerucutgeometri dan operasi CW, dalam prototipe kami,were chosen as a result of our conclusions from previous dipilih sebagai hasil darikesimpulan dari sebelumnyastudies with phantoms [16][18]. penelitian dengan hantu [16] - [18].Although the photo of the cup shown in Fig. Meskipun foto cangkir yang ditunjukkan padaGambar. 4 indicates 4 menunjukkanthat the boundary of the cup is black, most of our clinical bahwa batas cangkir hitam,sebagian besar klinismeasurements were done by using a reflecting surface for pengukuran dilakukan dengan

menggunakan permukaan untuk mencerminkan


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the cup. cangkir. The reasons are as follows. Alasannya adalah sebagai berikut. During ourstudies we Selama kajian-kajian kami kitafound that the main difficulty in reconstructing an image is the menemukan bahwa kesulitanutama dalam membangun kembali gambar adalahinfluence of the boundary on the observability of small objects pengaruh batas pada benda

kecil observabilityinside the medium. dalam medium. In a continuous-wave (CW) technique, a Dalamgelombang kontinu (CW) teknik, sebuahreflecting boundary enhances the detectibility as compared to meningkatkan batasmencerminkan detectibility dibandingkan dengana black boundary. batas hitam. However, a reflecting boundary reduces the Namun,mengurangi batas mencerminkanimage resolution, but only marginally. resolusi gambar, tetapi hanya sedikit. This medium isthe Media ini adalah

breast in our case, which has a attenuation constant of about payudara dalam kasus kami,yang memiliki konstanta pelemahan tentang

mm. mm. We used a reflecting cup, with an optical Kami menggunakan cangkirmencerminkan, dengan optikcoefficient providing an effective loss that is about the same koefisien memberikan kerugianyang efektif adalah samaas the sebagaiof average breast, so the resolution is affected very payudara rata-rata, sehingga resolusisangat dipengaruhilittle. kecil. As a result however, the light levels increase. Namun Akibatnya, tingkat cahayameningkat. Moreover, Terlebih lagi,the system resembles an infinite medium better, resulting in menyerupai sistem media yangtak terbatas lebih baik, sehinggaeasier and faster computations for the image reconstruction. perhitungan lebih mudah danlebih cepat untuk gambar rekonstruksi.The transmission spectra and the optical diffusion parame- Spektrum transmisi dan difusioptik parameter -ters of the in vivo breast tissue was discussed in the previous Ters dari dalam jaringan

payudara vivo telah dibahas di sebelumnyasection. bagian. From there and also from the discussion given in the Dari sana dan juga daridiskusi yang diberikan dalam

previous paragraph, we know that the attenuation in breast paragraf sebelumnya, kita tahubahwa pelemahan di payudara

tissue in its most transparent region is in the order of 100150 jaringan di wilayah yangpaling transparan dalam urutan 100-150m . m. Of all the methods considered and discussed in the Dari semua metode yangdipertimbangkan dan dibahas dalamintroduction, only continuous wave (CW) transillumination pengenalan, hanya gelombangkontinu (CW) transillumination

provides the dynamic range of about 4 10 to allow mea- menyediakan dinamis jarak sekitar 410 untuk membolehkan mea -

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1146 1146


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IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. IEEEJOURNAL OF DIPILIH Forum di QUANTUM ELECTRONICS, VOL. 5, NO. 5, NO. 4,JULY/AUGUST 1999 4, Juli / Agustus 1999Fig. Gambar. 5. 5. The operation of the mechanical switch which is designed to choosePengoperasian saklar mekanis yang dirancang untuk memilih

the laser wavelength for the source fiber set is shown here. panjang gelombang laser untuksumber serat set yang ditampilkan di sini. This operation is Operasi inicontrolled fully automatically by a PC. dikontrol sepenuhnya secara otomatis oleh PC.Fig. Gambar. 6. 6. The results of measurements testing the reproducibility of the me- Hasil

pengujian pengukuran reproduktifitas dari saya -chanical fiber switch. serat chanical saklar. The error is within 5 mV, which corresponds toabout Kesalahan adalah dalam waktu 5 mV, yang sesuai dengan tentang0.1% of the full scale signal of about 5 V shown in the plotted results. 0,1% dari sinyal skala

penuh sekitar 5 V ditampilkan dalam hasil diplot.surements over all source detector distances of 5130 mm for surements atas semua detektorsumber jarak 5-130 mm untuk

the cup region of our prototype. daerah cangkir prototipe kami. Therefore, we have chosenOleh karena itu, kita telah memilihto work with CW diode lasers operating in the near infrared. untuk bekerja dengan dioda laserCW beroperasi di dekat inframerah.For the main portion of our clinical trials, the wavelengths we Untuk bagian utama kami ujiklinis, panjang gelombang kamihave chosen are 660, 780, and 920 nm. telah memilih adalah 660, 780, dan 920 nm.However, during these Namun, selama initrials, we have noted too much noise with the measurements cobaan, kami telah mencatatterlalu berisik dengan pengukuranwith the laser at the longest wavelength of 920 nm due to the dengan laser pada panjanggelombang terpanjang 920 nm karenalow transmission of tissue. jaringan transmisi rendah. Therefore, we decided to switch Olehkarena itu, kami memutuskan untuk beralihthis laser with a new laser operating at a wavelength of 870 laser ini dengan laser baru

beroperasi pada panjang gelombang 870nm to decrease some of the noise in these measurements. nm untuk menurunkan beberapakebisingan dalam pengukuran ini.During the measurements, the laser wavelengths are selected Selama pengukuran, panjanggelombang laser dipilihsequentially and automatically with a mechanical switch as secara berurutan dan secara

otomatis dengan saklar mekanisshown in Fig. ditunjukkan pada Gambar. 5. 5. Actually, the only mechanical selectionSebenarnya, satu-satunya pilihan mekanisinvolved in our measurements is this laser source switching terlibat dalam pengukuran adalahsumber laser ini switchingto the source fibers. ke sumber serat. The reproducibility of the switch was Thereproduktifitas dari saklar initested by measuring the coupled output power to a reference diuji dengan mengukur outputdigabungkan kekuatan untuk referensidetector. detektor. The results of this test are shown in Fig. Hasil tes ini diperlihatkan padaGambar. 6. 6. As Sebagai

seen the error introduced into the measurements due to this melihat kesalahan diperkenalkanke dalam pengukuran karena ini


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mechanical switch is about 0.1%. saklar mekanik sekitar 0,1%. The power output from theDaya output darilasers are about 50 mW. laser sekitar 50 mW. Some of this power gets lost in the Beberapakekuatan ini akan hilang dalamfibers and their connectors before reaching the cup. serat dan konektor sebelum mencapai

cangkir.Fig. Gambar. 7. 7. The measurement system of the cup area showing the laser light Sistem

pengukuran daerah cangkir menunjukkan sinar laserinjection, collection and the detection system. injeksi, koleksi dan sistem deteksi.Fig. Gambar. 8. 8. The histogram of the detector dark noise measured from the prototypeHistogram dari gelap detektor suara diukur dari prototipesystem. sistem. For the load resistor the mV figures translate to fW on the Untuk resistor

beban menerjemahkan angka-angka yang mV untuk FW dix xaxis. sumbu.The measurement system related to the cup area is schemat- Sistem pengukuran yang

berkaitan dengan daerah cangkir schemat -ically shown in Fig. ically ditunjukkan pada Gambar. 7. 7. The laser light, which isintroduced Sinar laser, yang diperkenalkanfrom the source fiber, diffuses around in the cup medium dari sumber serat, berdifusi didalam cangkir mediacontaining inhomogeneities and some of this light exits at the berisi inhomogeneities dan

beberapa cahaya ini keluar padadetector fiber. detektor serat. The fibers attached to the cup area are plastic Serat yangmelekat pada kawasan cangkir plastikand have a size of about a mm in diameter. dan memiliki ukuran tentang mm diameter. Theefficiency Efisiensiof the pin photo diode, at the other end of this fiber, is about dari dioda foto pin, di ujung laindari serat ini, adalah tentang0.6 A/W. 0,6 A / W. Although it is not shown explicitly, a number of Meskipun tidakditampilkan secara eksplisit, sejumlahload resistors present in the circuitry allows a large dynamic beban resistor hadir di sirkuitmemungkinkan dinamis besarrange by automatic selection of the appropriate load resistor. Rentang oleh seleksi otomatisresistor beban yang sesuai.This selection is achieved by special solenoid switches. Pilihan ini dicapai dengan switchsolenoida khusus. As a Sebagai

result, the detection system has a dynamic range of 4 10 Akibatnya, sistem deteksi memilikijangkauan dinamis 4 10and an NEP of 25 fW. dan NEP 25 FW. The dark noise from this system was Kebisingangelap dari sistem ini adalahmeasured and the results are plotted in Fig. diukur dan hasilnya diplot pada Gambar. 8. 8. Asseen, this Seperti yang terlihat, ini

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COLAKet al. : CLINICAL OPTICAL TOMOGRAPHY AND NIR SPECTROSCOPY FORBREAST CANCER DETECTION COLAKet al.: KLINIS OPTIK spektroskopi NIRtomography DAN UNTUK KANKER PAYUDARA DETECTION

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Fig. Gambar. 9. 9. The prototype cup and the positioning of the patient's breast withinPrototipe cangkir dan posisi dada pasien dalamit during the measurement procedures. selama prosedur pengukuran.dark noise and the fluctuations due to the mechanical fiber kebisingan gelap dan fluktuasikarena serat mekanis

switch discussed above, are both well under the acceptable beralih dibahas di atas, keduanyabaik di bawah dapat diterimameasurement range of the detector system. rentang pengukuran sistem detektor. Furthermore,it Selain itu,should be stated that the bit noise due to AD conversion is harus dinyatakan bahwa sedikitkebisingan akibat konversi ADalso less than a millivolt. juga kurang dari millivolt. The drift in the measurement system,Arus di sistem pengukuran,due to the detector and source stability during a period of 30 karena detektor dan sumberstabilitas selama periode 30min, is about 5 mV, or 0.2%. min, adalah sekitar 5 mV, atau 0,2%. Note that, since our data is

based Perhatikan bahwa, karena data kami didasarkanto a reference measurement, the constant losses, such as the untuk referensi pengukuran,kerugian yang terus-menerus, sepertiones due to fiber input and propagation, is not expected to yang disebabkan oleh seratmasukan dan propagasi, tidak diharapkan untukintroduce errors in our imaging. memperkenalkan kesalahan dalam pencitraan kita.IV. IV. E EXPERIMENTS XPERIMENTSIn a normal measuring sequence, the prototype cup is Dalam urutan mengukur normal,cangkir prototipefilled with a matching fluid. diisi dengan cairan yang serasi. The subject has to lie downTopik ini telah untuk berbaringon the machine and let one of her breasts hang freely in pada mesin dan membiarkan salahsatu payudaranya menggantung bebas dithe cup containing the fluid. cangkir berisi cairan. The cup and the positioning Cangkir dan

posisiof the patients breast during the measurements are shown dada pasien selama pengukuranditampilkanin Fig. pada Gambar. 9. 9. The fluid is specially designed to match the mean Fluida dirancangkhusus agar sesuai dengan meanoptical properties of the breast. sifat optik payudara. It is kept at around 31 C Hal ini

disimpan di sekitar 31 Cfor comfort. untuk kenyamanan. The main function of this fluid is simply to Fungsi utamacairan ini hanya untukdecrease the unwanted contrast in the transmitted light due mengurangi kontras yang tidakdiinginkan dalam cahaya yang ditransmisikan karenato voids that would be present in the absence of this fluid. untuk void yang akan hadir dalamketiadaan cairan ini. As Sebagaidiscussed in the next section, this makes the computations for dibahas dalam bagian

berikutnya, hal ini membuat perhitungan untuktomographic image reconstruction more manageable. rekonstruksi citra tomografi lebihmudah dikelola. During a Selama

normal measurement, the signal for all detector positions are pengukuran normal, sinyaluntuk semua posisi detektor


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measured simultaneously, with all source positions addressed diukur secara bersamaan,dengan semua posisi sumber dialamatkanin sequence. berurutan. First, a reference measurement only with the Pertama, pengukuranreferensi hanya denganmatching liquid, without the breast, is made and stored for the pencocokan cair, tanpa

payudara, dibuat dan disimpan untukcalibration of the sources and detectors at a later step. kalibrasi dari sumber dan detektor padalangkah berikutnya. Then, Kemudian,immediately following the reference measurement, the same segera setelah referensi

pengukuran, yang samaset of measurements is performed for one breast and then the set pengukuran dilakukan untuksatu payudara dan kemudianother breast. payudara lain. Within each set, all of these are repeated three Dalam setiaprangkaian, semua ini diulang tigatimes corresponding to each of the three different wavelengths. kali sesuai dengan masing-masing dari tiga panjang gelombang yang berbeda.

This makes a total of nine measurements per patient. Hal ini membuat total sembilanpengukuran per pasien. After the Setelahdata collection, the reference measurement is used to calibrate pengumpulan data, referensi

pengukuran digunakan untuk kalibrasithe sources and the detectors. sumber dan detektor.Fig. Gambar. 10. 10. Difference in the transmitted test intensity with and without the 10Perbedaan dalam intensitas tes yang ditransmisikan dengan dan tanpa 10mm diameter black bead discussed in the text. mm diameter manik hitam yang dibahas dalamteks. The vertical axis on the surface Sumbu vertikal pada permukaan

plot on the right is the logarithmic difference intensity, plot di sebelah kanan adalahperbedaan logaritma intensitas,dI dI. . The horizontal axis Sumbu horizontallabeled berlabel "

k k represents the fiber ring layers in the cup. "Mewakili cincin serat lapisan dalam cangkir.

The other axis labeled Sumbu yang lain diberi label "

j j is for the number of detector fiber in a given ring. "Adalah untuk jumlah detektor serat

dalam suatu cincin. The transmission Transmisi

shadow of the bead appears as the black area centered at bayangan dari manik-manik munculsebagai daerah hitam berpusat di(k; j) = (7; 15) (k; j) = (7; 15). .Fig. Gambar. 11. 11. The cup geometry describing the indices for the difference intensityGeometri cangkir indeks untuk menggambarkan perbedaan intensitas

plots in Fig. plot pada Gambar. 10. 10. The arrow on the top right corner corresponds to thesame Panah di sudut kanan atas sesuai dengan yang samalocation in the prototype bed, in Fig. lokasi di tempat tidur prototipe, pada Gambar. 3, labeledas the reference point. 3, dilabeli sebagai titik acuan.In order to be able to test the prototype and determine its Dalam rangka untuk dapat menguji

dan menentukan prototipe


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limitations due to noise on image forming, we have made a keterbatasan akibat kebisinganpada gambar membentuk, kami telah membuatseries of initial experiments with simple phantoms consisting serangkaian percobaan awaldengan hantu sederhana yang terdiriof beads in a matching fluid. manik-manik dalam cairan yang serasi. For this, the matching

fluid Untuk ini, fluida yang cocokconsisted of 1% intralipid solution in water. terdiri dari 1% intralipid larutan dalam air. Theresults shown Hasil ditampilkanin Fig. pada Gambar. 10 are for a sapphire bead. 10 adalah untuk manik batu safir. The beadhas a 10 mm Manik-manik memiliki 10 mmdiameter and is painted black on its surface. diameter dan dicat hitam pada permukaannya.The results Hasil

plotted in Fig. diplot pada Gambar. 10 is the light intensity difference between the 10 adalahperbedaan intensitas cahaya antarameasurement in the presence of the bead and the reference pengukuran di hadapan manik-manik dan referensi

measurement where the bead was removed. pengukuran di mana manik telah dihapus. Thatis; Yaitu;(1) (1)where di manais the intensity difference between the measured test adalah intensitas diukur perbedaanantara tesdata intensity, data intensitasand the reference intensity, dan referensi intensitas,measured in diukurthe absence of the bead. adanya manik-manik. This transmitted light difference, is Cahayayang ditransmisikan perbedaan ini, adalahstudied over the inner surface of the cone with a geometry as belajar di atas permukaan batinkerucut dengan geometri sebagaidefined with the sketch in Fig. ditetapkan dengan sketsa pada Gambar. 11. 11. In this figure,Dalam gambar ini,represents mewakiliring index corresponding for the -axis of the conical cup. indeks cincin sesuai untuk sumbudari cangkir kerucut. This Inihas a maximum index of 10 corresponding to the different fiber memiliki indeks maksimumdari 10 yang sesuai dengan serat yang berbedaring numbers in the prototype cup. cincin angka dalam cangkir prototipe.

in Fig. pada Gambar. 11 represents 11 mewakilithe source or detector indices, respectively, within a given sumber atau detektor indeks,masing-masing, dalam suatufiber ring in the cup. cincin serat dalam cangkir. It corresponds to the horizontal axis with Inisesuai dengan sumbu horizontal denganan fiber number changing from 30 for the top ring to 21 for suatu jumlah serat berubah dari30 untuk cincin atas 21 untuk

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the bottom ring. cincin bagian bawah. For Fig. Untuk Gambar. 10, this number gives thedetector 10, jumlah ini memberikan detektornumber nomorfor each ring number, . untuk setiap nomor cincin,.The intensity difference plots in Fig. Perbedaan intensitas plot pada Gambar. 10 are given on

a 10 adalah diberikan padalogarithmic scale for the intensity. skala logaritmik untuk intensitas. These clearly show theIni jelas menunjukkanshadow of the 10-mm diameter black bead as the dark area bayangan dari 10-mm diametermanik-manik hitam sebagai daerah gelapcentered at about berpusat di sekitar(seventh ring from the bottom) (tujuh cincin dari bawah)and dan(15th detector fiber from the reference arrow). (Ke-15 detektor serat dari referensi panah).Such shadows also appear in the data from the patients, but Bayangan seperti itu juga munculdalam data dari pasien, tetapi

with a much lower resolution and with more noise due to dengan resolusi yang jauh lebihrendah dan dengan lebih kebisingan akibattissue heterogeneity. heterogenitas jaringan. The area to the left of the shadow, with Area disebelah kiri bayangan, denganthe measured high intensity difference, in Fig. yang diukur perbedaan intensitas tinggi, padaGambar. 10 is one of 10 adalah salah satu darithe parasitic effects in our measurements coming from the efek parasit dalam pengukurankami yang berasal daritime dependent drifts in the properties of the matching fluid waktu tergantung hanyut dalamsifat-sifat fluida yang cocoksurrounding the phantom. seputar hantu. Although we try to subtract the Meskipun kamimencoba untuk mengurangimain contributions of this fluid by using the data of the kontribusi utama dari cairan inidengan menggunakan data darireference, the results are not perfect. referensi, hasilnya tidak sempurna. The time differencePerbedaan waktu

between the real measurement and the reference measurement antara yang nyata referensipengukuran dan pengukuranstill results in imperfect cancellations of the effects of the masih menghasilkan pembatalantidak sempurna efekaverage background medium, the matching fluid in this case. latar belakang rata-rata

menengah, yang cocok cairan dalam kasus ini.The shadow of the bead discussed in these figures will be Bayangan manik-manik yangdibahas dalam angka-angka ini akanused in our discussions section to introduce a new concept for digunakan dalam bagiandiskusi kita untuk memperkenalkan konsep baru untukdiffuse optical tomography based on the statistical properties baur tomografi optik

berdasarkan statistik sifatof such transmission projections in our cup. transmisi seperti proyeksi dalam cangkir.The matching fluid discussed above is chosen according to Fluida yang cocok dibahas di atasdipilih sesuaiactual measurements taken from volunteers. pengukuran aktual yang diambil dari

sukarelawan. Its optical prop- Its optik prop


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inhomogeneity, one needs to measure at the shortest distances inhomogeneity, orang perluuntuk mengukur pada jarak terpendekto the source and the inhomogeneity itself. ke sumber dan inhomogeneity itu sendiri. Thisgives the Ini memberikan

best sensitivity for detecting objects in this case. sensitivitas terbaik untuk mendeteksi benda-

benda dalam kasus ini. However, Akan tetapi,one should not forget that the returning original source signal orang tidak boleh lupa bahwasumber aslinya kembali sinyallevels from the shorter distances are also high. tingkat dari jarak pendek juga tinggi. At thishigh Pada tinggiintensity levels, the bit noise in our digitization circuitry limits tingkat intensitas, bitkebisingan di sirkuit digitalisasi kita batasthe signal. sinyal. In cases where we measure the relative change due Dalam kasus-kasus dimana kita mengukur perubahan relatif karenaFig. Gambar. 12. 12. Attenuation constant fit to the transmitted intensity data taken fromPelemahan terus-menerus sesuai dengan intensitas yang ditransmisikan data yang diambil

darithe breast of one of the volunteers at the laser wavelength of 870 nm. dada salah satusukarelawan pada panjang gelombang laser 870 nm. The Itufit indicates that the optical properties of the fluid surrounding the breast cocok menunjukkan

bahwa sifat optik dari fluida yang mengelilingi payudaraprovides a good optical match. menyediakan optik yang baik cocok.to the inhomogeneity, we need to still stay at the shortest ke inhomogeneity, kita perlu untuktetap tinggal di terpendekdistances to the inhomogeneity but remain as far away from jarak ke inhomogeneity tetapitetap sebagai jauh darithe source as possible. sumber mungkin. In this case, we measure low intensity Dalam kasusini, kita mengukur intensitas rendahlevels and the signal is limited by the statistical noise limit of tingkat dan sinyal dibatasi oleh

batas kebisingan statistikour detectors. detektor kita. Therefore, the optimization for the detection of Oleh karena itu,

pengoptimalan untuk mendeteksian inhomogeneity will actually take place in the measurement sebuah inhomogeneity akan

benar-benar terjadi pada pengukuranregion between these two limiting cases. wilayah antara kedua membatasi kasus. Mosttomography Kebanyakan tomographymethods which have been tried up to now, seem to ignore metode yang telah mencoba sampai

sekarang, tampaknya mengabaikanthis region. daerah ini. This data region has special emphasis within the Data ini wilayahmempunyai penekanan khusus dalamstatistical tomography method discussed later in the section statistik metode tomografidibahas kemudian dalam bagianon ongoing research. pada penelitian berkelanjutan.V. T V. TOMOGRAPHY OMOGRAPHYTo be able to probe an optically diffuse medium, the Untuk dapat menyelidiki menyebarsecara optikal media, yang

breast in our case, the measurements of the transmitted output payudara dalam kasus kami,

dengan pengukuran output yang ditransmisikan


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intensity are made at a specific set of detector positions intensitas yang dibuat pada settertentu detektor posisifollowing the scattering of light injected from another set of mengikuti penyebaran cahayadisuntikkan dari satu setsource positions posisi sumber

. . This tomographic measurement geometry Pengukuran tomografi ini geometriis shown schematically in Fig. diperlihatkan secara skematik pada Gambar. 13. 13. In order to

be able to Dalam rangka untuk bisaobtain a 3-D image showing the variation of tissue properties memperoleh gambar 3-Dmenunjukkan variasi jaringan propertiinside the breast, a reconstruction algorithm is required to deal di dalam dada, sebuahalgoritma rekonstruksi diperlukan untuk menanganiwith the very high turbidity of the breast tissue. dengan kekeruhan sangat tinggi dari jaringan

payudara. However, Akan tetapi,with the 65 000 data points from the source and detectors in dengan data 65 000 poin darisumber dan detektor di

our experimental system, and large number of corresponding sistem eksperimental kami, danjumlah besar sesuaivoxels in the image, the problem is not very trivial for voxels dalam gambar, masalahnyatidak terlalu sepele untukreal-time clinical applications. real-time aplikasi klinis. We have to actually devise Kita harus

benar-benar merancangrelatively simple tomographic methods to remain practical in metode tomografi relatifsederhana untuk tetap praktis dalamour computations. perhitungan kami. In our work, as described below, we have Dalam

pekerjaan kami, seperti yang dijelaskan di bawah ini, kami telahtried several such methods for reconstructing tomographic mencoba beberapa metode untukmerekonstruksi seperti tomografiimages. gambar. These methods are all based on the model where the Metode ini semuadidasarkan pada model di manatissue is represented simply by an isotropic diffuse medium. jaringan hanya diwakili oleh

baur isotropik medium.Therefore, before we describe the details of the tomography Oleh karena itu, sebelum kamimenjelaskan rincian tomographymethods employed in this study, we first outline the basics of metode yang digunakan dalamstudi ini, pertama-tama kita garis besar dasar-dasarthe diffuse medium model used in this study. menengah yang tersebar model yang digunakan

dalam studi ini.

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COLAKet al. : CLINICAL OPTICAL TOMOGRAPHY AND NIR SPECTROSCOPY FORBREAST CANCER DETECTION COLAKet al.: KLINIS OPTIK spektroskopi NIRtomography DAN UNTUK KANKER PAYUDARA DETECTION1149 1149Fig. Gambar. 13. 13. The geometry defining the light projections used for the tomo-Mendefinisikan geometri proyeksi cahaya yang digunakan untuk tomo -graphic image reconstructions. gambar grafik rekonstruksi.A diffuse medium can be characterized by a pair of parame- Sebuah media baur dapat

dicirikan oleh sepasang parameter -


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ters, called the scattering and absorption coefficients, Ters, yang disebut koefisien hamburandan penyerapan,and , dan,respectively, already discussed in the previous section. masing-masing, sudah dibahas pada

bagian sebelumnya. Using Menggunakan

this simple model in the diffusion equation in homogeneous model sederhana ini dalampersamaan difusi homogenmedium, we find that the output intensity, in phot/(s-cm menengah, kita menemukan bahwaintensitas output, dalam PHOT / (s-cmis adalahgiven by [35] diberikan oleh [35](3) (3)where di manais the distance from the source location, adalah jarak dari lokasi sumber,is the adalahsource term, in phot/s units, injecting photons into the medium, istilah sumber, di PHOT / s

unit, menyuntikkan foton ke dalam medium,is the photon diffusion coefficient (in adalah koefisien difusi foton (dalamcm) and cm) danis the attenuation constant. adalah pelemahan konstan.is a adalahdimensionless constant dependent on the collection geometry, konstan berdimensi koleksitergantung pada geometri,where we assumed that we have a certain collection area at the di mana kita beranggapan

bahwa kita memiliki koleksi tertentu daerah dioutput fiber, ignoring any corrections due to the detector solid keluaran serat, mengabaikansemua koreksi karena detektor padatangle. sudut. Since we obtain our images with respect to a reference, Karena kita memperolehgambaran kita terhadap referensi,this assumption is not expected to introduce large errors. asumsi ini tidak diharapkan untukmemperkenalkan kesalahan besar.Approaches of this sort has been found to describe the Pendekatan semacam ini telahditemukan untuk menggambarkandistribution of photons in highly scattering media, with a few distribusi sangat hamburanfoton dalam media, dengan beberapaheterogeneities, rather well [36][39]. heterogeneities, cukup baik [36] - [39]. However, itshould be Namun, itu harus

noted that its application to problems with real biological tissue mencatat bahwapenerapannya masalah dengan jaringan biologis nyatais still to be proven. masih harus dibuktikan. If one desires to have a solution to the Jika salahsatu keinginan untuk memiliki solusi untukdiffusion equation for general object shapes and strengths there persamaan difusi untuk objekumum bentuk dan kekuatan di sanaare also rigorous analytical and numerical techniques. juga ketat teknik analitis dan numerik.This Iniis not needed for our present study. tidak diperlukan untuk studi kita sekarang. It onlycomplicates the Hanya merumitkancomputations unnecessarily. perhitungan yang tidak perlu.

The output intensity equation discussed above, does not Persamaan intensitas output yangdibahas di atas, tidak


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provide a direct assignment of the value of the transmitted memberikan penugasan langsungdari nilai yang ditransmisikanintensity back to the object's real space in the medium. intensitas kembali ke objek ruangnyata dalam medium. For that Untukwe study the photon path distributions which are given by the kita mempelajari jalur

distribusi foton yang diberikan olehresponse of the system to a point perturbation in the medium. respon dari sistem ke sebuahtitik kekacauan dalam medium.To be able to find the functional form of this distribution, Untuk dapat menemukan bentukfungsional distribusi ini,we consider a single source-detector pair and assume that we kami mempertimbangkansumber-detektor tunggal pasangan dan menganggap bahwa kitahave an absorbing point object at a position memiliki titik menyerap objek pada posisiwithin the dalamscattering medium. media penyebaran. The total photon density at a position Foton totaldensitas pada posisi

elsewhere in the medium changes due to the presence of this di tempat lain dalam perubahanmedia karena keberadaan

point perturbation by a banana-like function [38], [39]. titik Usikan oleh seperti pisang-fungsi[38], [39]. The Itusimplified form for this perturbation function bentuk yang disederhanakan untuk fungsiUsikanfor an untukabsorbing point is shown in Fig. titik menyerap ditunjukkan pada Gambar. 14 with a surface

plot. 14 dengan plot permukaan. Fig. Gambar. 14 14is only an example given for source and detector positions hanyalah sebuah contoh yangdiberikan untuk posisi sumber dan detektorat diand danwhere the parameters mana parametermm and mm/mm are used. / mm digunakan. Furthermore, this Lebih jauh lagi, ini

plot represents the perturbation function only in the plot mewakili fungsi Usikan hanya dalamFig. Gambar. 14. 14. Perturbation function Gangguan fungsiP (r; r1) P (r; r1)defining the region of highest sen- mendefinisikan wilayah tertinggi sen -sitivity to a point object between the source and the detector. sitivity ke objek titik antara

sumber dan detektor. The parameters Parameterto obtain this example are discussed in the text. untuk memperoleh contoh ini dibahas dalamteks.

plane, and the actual 3-D shape of this function pesawat, dan 3-D sebenarnya bentuk fungsiinican dapat

be obtained by rotating the shape around the dapat diperoleh dengan memutar bentuk diaxis. sumbu. Further Lebih jauhdiscussion on this function can be found in [35]. pembahasan mengenai fungsi ini dapatditemukan di [35].The meaning of the perturbation function Arti dari gangguan fungsi

discussed dibahas


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above can be explained as follows. di atas dapat dijelaskan sebagai berikut. If in a diffuseoptical Apabila dalam suatu baur optiktomography experiment, an intensity (or photon density) mea- tomography percobaan,intensitas (atau kerapatan foton) mea -surement differs from an expected value, then the cause of this surement berbeda dari nilai

yang diharapkan, maka penyebab inidifference can be assigned to any point in the object space Perbedaan tersebut dapatditetapkan untuk setiap titik dalam ruang obyekaccording to the strength of the perturbation function. sesuai dengan kekuatan fungsigangguan. In fact, Bahkan,the strength of the perturbation causing the observed difference kekuatan Usikanmenyebabkan perbedaan yang diamatiis inversely proportional to the value of berbanding terbalik dengan nilai. . Needless to Perlusay, in a highly heterogeneous medium, such regions can have mengatakan, dalam mediayang sangat heterogen, daerah tersebut dapat memiliki

complicated shapes. rumit bentuk. Nevertheless, for a medium consisting of Namundemikian, untuk media yang terdiri dariweak inhomogeneities, this perturbation function introduces inhomogeneities lemah, fungsiUsikan ini memperkenalkanthe notion of the highest probability light paths in such a pengertian tentang jalan cahaya

probabilitas tertinggi sedemikiandiffuse medium. baur media. As we will discuss below, this notion can Seperti yang akan kita

bahas di bawah ini, pengertian ini dapatbe utilized to obtain a practical algorithm for our image dimanfaatkan untuk mendapatkanalgoritma praktis untuk foto kamireconstruction problem. masalah rekonstruksi.It is clear that the resolution of imaging in diffusive media Jelas bahwa resolusi dari

pencitraan di media difusifdepends on the width of these banana shaped perturbation tergantung pada lebar pisang ini

berbentuk Usikanregions, regardless of how distorted they may be. daerah, terlepas dari bagaimana terdistorsimereka mungkin. As implied Seperti yang tersiratin this discussion, the projections of the objects embedded dalam diskusi ini, proyeksi dari

benda tertanamin diffusive media will be blurred. dalam difusif media akan menjadi buram. Comparing thesimplified Membandingkan disederhanakan

form for the perturbation function, with the straight line for formulir untuk fungsi Usikan,dengan garis lurus untukthe X-Ray projections, we see that in optical tomography, X-Ray proyeksi, kita melihat

bahwa dalam tomografi optik,what we effectively get is that, the line integral for the X-Ray absorption is replaced by the volume integral for the

diffuse optical attenuation. This volume is actually definedwithin the volume of the banana of the perturbation function.Within this assumption of the banana shape path, we find thatthe full width at half maximum broadening for a point objectis approximately sekitar

. . If the distance between thesource and detector is taken to be 10 cm, then an attenuation


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constant of/m yields a broadening of 3.6 cm,and dan/m reduces this width to 3.1 cm. Choosing a Memilihwavelength such that

is further increased would enhance theresolution, but this will also require an even larger dynamicalrange for the detector in our system.

Page 8Halaman 8

1150 1150IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 5, NO.5, NO. 4, JULY/AUGUST 1999After defining these light paths in the diffuse medium, wenow have to make a decision on the quantity to be plotted inthe images. gambar. There are many possible quantities which could

be used as the imaged quantity in optical tomography indiffuse media. These possibilities are: the attenuation coef-ficient, absorption/scattering coefficients, diffusion coefficient,the perturbation parameters, the differences of such parametersat two wavelengths, their time dependencies/constants etc. Inour work we choose the attenuation coefficientto be the menjadi

preferred quantity to represent our images in. This quantitycan be easily computed by using different source detectordistances as done in the previous section. Furthermore, since

we have a set of reference measurements available, we canalso obtain differences in the attenuation coefficientsby comparing the real measurements to this reference set.This is also advantageous for noise considerations in the fan

beam geometry, because of the high intensity contrast comingfrom the large variation in the source and detector distances.In summary, due to these arguments, we choose to presentthe results of our measurements in terms of the attenuationcoefficient koefisienin units of m . For images we usethe itu

difference between the attenuation coefficientof the tissue dari jaringanand danof the homogeneous reference medium.As emphasized at the beginning of this section, in order todeal with 65 000 data points and a large number of voxelsin practical manner, we first devised a simple backprojectionmethod based on the X-Ray tomography principles [40], [41].The main difference in this approach as compared to the con-ventional X-Ray tomography is that we replace the projectionlines with the banana perturbation paths described above. In Di

this paper, we only give a brief description of this methodbecause the details were presented earlier [35]. Basically, in


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this approach, we first obtain an average attenuation constantfrom the measurements in order to be able to define a bananawidth. lebar. This width is then used to spread the effects of a

perturbation, given in terms of the difference in the attenuationcoefficient, back to the image space. This procedure is repeated Prosedur ini diulang

for all source detector positions. Since in our geometry thefiltering by thefilter [40] is not straightforward, weignore it. mengabaikannya. Actually, the broadening due to thiseffect is Efekignorable as compared to the blurring due to optical diffusioneffects. efek. It should be noted that, within this simple approach,we also ignored all the refraction effects present in optical

projections. proyeksi. This would be important if we were dealing withmuch stronger inhomogeneities in the scattering medium ascompared to the tenuous biological tissue.

The application of the simple tomography method describedabove to our experiments is demonstrated in Fig. 15. 15. The Itumultiplanar optical tomography pictures shown in this figureare obtained from a phantom prepared by placing a 10-mmdiameter sapphire bead in a tissue-like scattering fluid. This Inifluid was composed of a 1% intralipid solution in water. The Itusapphire bead was painted black on its surface and the testwas done by using a 780-nm laser. The definition of the Definisi

planar images are shown in Fig. 16, where different axis givethe normal directions to each planar image. Specifically, the Khusus,circular cross sectional image, in Fig. 15, is at a horizontal

plane normal to the axis of the cup. The conical cross

Fig. Gambar. 15. 15. The multiplanar tomography images, at 780 nm, of a 10-mmdiameter black bead in a tissue-like scattering fluid of 1% intralipid solutionin water. dalam air. Red regions indicate high attenuation, and point to the location ofthe bead placed in the intralipid correctly.Fig. Gambar. 16. 16. The definition of the planes used in images shown in Fig. 15. 15.Different axes shown here define the normal directions to each planar imagein Fig. pada Gambar. 15 as described in the text.section images on the right side and below this circularimage are the vertical planes normal to the and axes,

respectively. masing-masing. The right side of this circular cross sectionalimage corresponds to the reference point in our prototype cupas indicated in Fig. 16 with a thick horizontal arrow at therim of the cup. The red areas in these images are the areasof highest attenuation within the cup. These areas point tothe known location of the black bead placed in the intralipidcorrectly. benar. As discussed before, these optical tomographicimages in Fig. 15 show the degree of optical blurring clearly.Some of our present efforts are directed toward adapting ouralgorithms to apply Fourier deconvolution methods to sharpenthese images as was described for simpler geometries before

[35]. [35]. Some of our preliminary results in this direction will bediscussed later in this paper. dibahas kemudian dalam makalah ini.


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Page 9Halaman 9

COLAKet al. : CLINICAL OPTICAL TOMOGRAPHY AND NIR SPECTROSCOPY FORBREAST CANCER DETECTION1151

TABLE I TABEL IR RESULTS FROMC CLINICAL LINICALT TRIALS RealThe simple backprojection method described above is suc-cessful in obtaining images of acceptable resolution up to alimited degree. In some instances, the inhomogeneities can

be missed with this method. In order to improve the qualityof the resultant images, we have developed a tomographyalgorithm based on the algebraic reconstruction technique(ART), capable of generating quantitative reconstructions fromthe data relative to the homogeneous reference measurementsdescribe above. This approach is based on a perturbativeapproach [42], and a brief description was presented earlier[19]. [19]. In this technique, the perturbation is spread back to theimage space in a similar fashion as described in the bananamethod described above. metode yang dijelaskan di atas. Except that, in ART, the image isupdated, or corrected, after each iteration. The corrections at

each step are determined by the difference of the measureddata from a set of computed data found from the imagereconstructed in the previous iteration. These iterations arerepeated till an error measure is minimized as common toother ART-based approaches [43].VI. VI. C CLINICAL LINICALR RESULTS ESULTSA summary of the results from our clinical trials is presentedin Table I. During this first trial phase we have tested 14

patients with the detectability of the inhomogeneities as ourmain focus. In this procedure, the information from X-Rayand ultrasound images were available to us prior to our opticalmeasurements. pengukuran. Our goal was to check if the inhomogeneitiesdiagnosed by standard clinical methods could also be detectedin our optical images. As Table I shows, our detection rate ofthe inhomogeneities is about 90%. The measurements doneon patients which are not reported in the table failed dueto experimental malfunction before imaging phase could bereached. tercapai. In the following paragraphs in this section, we willfocus on a few of the cases from Table I and describe what

we mean by the phrase visible in the table.azm01: Medullar Carcinoma


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The carcinoma of this patient was in the inner side of herright breast. The most straightforward result from this patientis the raw optical transmission image corresponding to thegeometry described in Figs. 10 and 11. 10 dan 11. This result is shown inFig. Gambar. 17 as a color coded projection image on the cone surface.

The cancerous area, as determined from the X-ray images fromthe patient, appears as a red, high attenuation, area in the topcenter of the optical image. This red part has a quantitativevalue of 0.15/mm for the attenuation constant, and some ofthe deeper blue parts corresponds to 0.09/mm attenuation. This Ini

projection image was taken by a 780-nm laser light.The two X-Ray mammography pictures shown in Fig. 18 18are taken from the right (R) breast of the same patient (azm01)with a breast cancer. In both the CC (top to down) and theMLO (right to left) views, a large dense mass in the orderof 12 cm is clearly visible. The images are flipped around

in order to make it easier to compare with the correspondingoptical images discussed below.The tomographic multiplanar images in Fig. 19 show howthis tumor appears in the optical mammograms obtained

by our optical mammography prototype system from theright breast of the patient azm01. The reconstruction wasdone by the simple backprojection method based on the

banana perturbation function described in the previous section.These images use the color coding normalized between 0(blue) and 1 (red), corresponding to the lowest and highestabsorptive perturbations in the transmitted intensity throughthe breast. payudara. This is shown as the local difference betweenthe attenuation coefficient of the tissue and the homogeneousreference medium obtained both at a wavelength of 786nm. nm. As in the previous image, the red region indicates thestrongest parts of the inhomogeneities. Clearly visible is theabsorbing structure in the breast. Histological examination Pemeriksaan histologisdetermined this to be a medullar carcinoma, with a size ofabout two centimeters. Its location agrees reasonably well withthe location of the cancerous lesion observed in the X-raymammograms. As mentioned before, the optical tomographic

images show a large degree of optical blurring. At the present Saat initime, we are adapting our algorithms and using other newmethods to reduce the effects of this blurring.The image in Fig. Gambar pada Gambar. 20 shows the 3-D view of the recon-structed image of the cancer in the same right breast. This Iniimage is also obtained at a laser wavelength of 780 nm.The isocontour of the inhomogeneity on the left is obtainedat normalized 0.9 value and, as indicated above, its locationagrees well with the location which can be deduced from theX-ray mammo pictures given above. The cone like surface is

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IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 5, NO.5, NO. 4, JULY/AUGUST 1999Fig. Gambar. 17. 17. The transmitted light through the right breast of the patient azm01when illuminated from a source fiber from the reference direction at 780nm. nm. This is a raw projection indicating the attenuation coefficient through

the breast toward the detectors. The cancerous area, appears as a red, highattenuation, area in the top center of the image.Fig. Gambar. 18. 18. X-Ray mammogram images from the right breast of patient azm01.shown only to indicate the boundaries of the cup. Right sideof this cup corresponds to the position of the right arm of the

patient as the data was being taken. This is the side labeledas the reference point in the photo of our prototype systemin Fig. pada Gambar. 3. 3.azm05: CystThis patient was suspected of having a large cyst on theouter part of her left breast. It is worthwhile to emphasize that,

in most cases involving a cyst, the X-ray mammograms do notgive clear evidence on the presence of such inhomogeneitiesin the breast. In such cases, ultrasound images are obtained.Such an image corresponding to the left breast of this patientis shown in Fig. ditunjukkan pada Gambar. 21. 21. This ultrasound image clearly shows alarge region with no sound reflections. Having a postfocusingeffect below this region indicates that the inhomogeneity is acyst rather than a tumor.Multiplanar cross section optical tomography images of theleft breast of this patient is given in Fig. 22. 22. The reconstructionwas done by the iterative ART method described in the

previous section. bagian sebelumnya. This figure shows the local difference inattenuation constant between the attenuation coefficient ofthe tissue and the homogeneous reference medium, bothobtained at a wavelength of 658 nm. Clearly visible is aless absorbing structure (dark blue area) in the breast. As Sebagaimentioned above, the histological examination determined thisFig. Gambar. 19. 19. Multiplanar cross section optical tomography images of the right

breast of patient azm01. The sketch on the right indicate the location of thecancerous lesion which corresponds to the location of the high attenuation,red, are in the images.

Fig. Gambar. 20. 20. The 3-D isocontour view of the reconstructed image of the cancerin the right breast of azm01. The isocontour of the inhomogeneity on the leftis obtained at normalized 0.9 value.to be a cyst, with a size of about 3 cm. The location of thisdark blue area in these images correlates well with the known

position of the cyst in patient's left breast. The low attenuationblue regions correspond to an attenuation constant of about, while the surrounding red areas representan attenuation constant around 125 m . These red areas inthese images are believed to correspond to high density areasof the patients breast. It should be noted that in the absence

of prior information about the patient, such distinctions fromcancerous areas, could not be made unambiguously.


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azm06: AdenocarcinomaThis patient had a tumor on the top outer side of her left

breast. Subsequent diagnosis identified this as an adenocarci-noma of about 1 cm size. Multiplanar cross-sectional opticaltomography images of the left breast of this patient is given

in Figs. pada Gambar. 23 and 24. The images in Fig. 23 were obtained

Page 11Page 11

COLAKet al. : CLINICAL OPTICAL TOMOGRAPHY AND NIR SPECTROSCOPY FORBREAST CANCER DETECTION1153 1153Fig. Gambar. 21. 21. Ultrasound reflection image from the left breast of patient azm05.The large black area, toward the top indicate the cyst region.Fig. Gambar. 22. 22. Multiplanar cross-sectional optical tomography images of the left

breast of the patient azm05 with a cyst. The dark blue area correlates wellwith the known position of the cyst. The image was taken at 658 nm.

by the backprojection method, and the ones in Fig. 24 wasobtained the iterative ART method, both described in the

previous section. bagian sebelumnya. Both approaches identify the approximatelocation of the adenocarcinoma correctly. Except that, due tothe instabilities involved in the iteration cycles of the ARTmethod, there are additional contrast features in the imageswhich introduces ambiguity.VII. VII. S SPECTROSCOPYFor optical transillumination to be successful in being

sensitive and specific for breast cancer detection, we need tobe able to distinguish different tissue characteristics from suchoptical measurements. It is therefore of critical importanceto know the variation in the attenuation constantsof dari

both the normal and the diseased tissue. Unfortunately, the Sayangnya,results related to the spectroscopy in our clinical studies wereFig. Gambar. 23. 23. Multiplanar cross-sectional optical tomography images of the left

breast of the patient azm06 with an adenocarcinoma. The red area toward theleft in the circular horizontal cross section correlates well with the known

position of the adenocarcinoma close to the left arm. The image was obtained

by our simple backprojection method described in the previous section.Fig. Gambar. 24. 24. Multiplanar cross-sectional optical tomography images of the left

breast of the patient azm06 with a adenocarcinoma. This set of images wasobtained by our ART technique. As indicated for the previous figure, the redarea toward the left in the circular horizontal cross section correlates wellwith the known position of the adenocarcinoma close to the left arm. Other Laininhomogeneities appearing blue for low attenuation areas are probably relatedto the iteration instabilities involved in this reconstruction technique.

probably the most dissapointing aspects of our work. Although Meskipunwe will try to summarize our results here briefly, overall,we must say that there were not sufficiently distinct features


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Page 12Page 12

1154 1154IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 5, NO.5, NO. 4, JULY/AUGUST 1999Fig. Gambar. 25. 25. Comparison at two (pairs) wavelengths of the mean attenuation

coefficient,K; K;for several volunteers. Correlation seems to be strong, indi-cating that the heterogeneity of the tissue overshadows any effects specificto inhomogeneities.which we were able to find in our imaging efforts. This Iniresult is probably related to the arguments we raised on theheterogeneity of the tissue in our tissue optics section.Prior to our clinical trial phase, we have measured theaverage attenuation coefficient of the uncompressed breasts of17 volunteers, aged between 28 and 58 at wavelengths of 660,780, and 920 nm. The results were fit to the output intensityexpression, described earlier, in order to obtain an averageattenuation constant at different wavelengths for differentvolunteers. sukarelawan. We found that for 920 nm, probing CH bonds(fat), the attenuation constant,is approximately 150 mfor most volunteers. We have also found values ranging in

between (80160) mfor 660 nm, and (70140) mfor untuk

780 nm. For some volunteers, the breasts were too opaque(greater than 160 mat the third laser wavelength, 920nm. nm. This is probably due to the added effects of the nearbywater absorption band at around 980 nm as discussed in thesection on tissue optics. Despite the high dynamic range of ourdetectors, we were not able to obtain images with sufficientlysmall noise content even at laser powers of 50 mW at thiswavelength. panjang gelombang. This is the reason why most of our measurementsfor the clinical trials were done by replacing this laser byanother one operating at 870 nm.

Although the measured values for these volunteers showeda large scatter, we have found that the correlation betweendifferent sets of wavelengths is very strong. For example, the Sebagai contoh,attenuation coefficient for different volunteers at 780 nm isclosely related to the ones at 660 nm. Specifically, we foundthat the attenuation constantsat 786 nm, is related tothose at 658 nm, simply byAs both Ketika keduaof these wavelengths are located on the falling edge of theHb absorption peak, this correlation should not come as a

surprise. The results of this study showing the correlationof the average attenuation constants at two different pairs of


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Fig. Gambar. 26. 26. Comparison at two (pairs) wavelengths of the local attenuationcoefficient koefisienK Kfor a given breast of the patient azm06. From this and alsofrom other measurements made on other patients, we conclude that these

types of plots also shows a high degree of correlation between different pairsof wavelengths. dari panjang gelombang. The gray scale indicates a range of 0500 countsfrom lightestto the darkest gray.laser wavelengths for different volunteers are summarized inFig. Gambar. 25. 25.We have repeated the types of study described above foreach individual patient but by focusing on finding any spectraldistinctions at different locations within that breast. As the Sebagaireconstruction algorithm for one of our methods, ART, israther quantitative with sharper features, we attempted to make

a histogram of the assignedvalues, at every individual

position in a given breast, to compare the behavior at twodifferent wavelengths. panjang gelombang yang berbeda. After this procedure, we usuallyfounda spread of about 40 mwithin each breast image. This Inivariation is less than the variation between different volun-teers, as discussed above. Nevertheless, given the correlation

between the measurements for the averageand dan, we Kamihave also investigated the correlation between them within a

breast. The results are quite noisy and not easily conclusive.However, we found that most reconstructed values followthe itudependence described above for the

behavior describing different patients. Fig. Gambar. 26 shows a typicalcorrelation plot for patient azm06 as an example.VIII. VIII. O O

NGOING

R RESEARCH ESEARCHFrom the two previous sections, it is clear that our clinicaltrials give sufficient hope for the detection of inhomogeneitiesin female breast by optical tomography. However, for correctdiagnosis, one has to also identify the nature of an inhomo-geneity. geneity. That is, one should be able to tell if a high attenuationarea is from a cancerous lesion or from the natural variationsin the density of the breast tissue. Considering the differencesin the properties of breast tissue in different individuals, somesort of optical signature for cancer is highly desirable. In Di

order to improve our optical method toward this direction,our present emphasis focuses on improving our reconstruction


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techniques for better resolution and also disentangling thescattering and absorption coefficients of the tissue from eachother. lain. As described earlier, the diffuse broadening on the sizeof an object, placed near the middle of the cup, is in theorder of a centimeter. Although we do not expect to compete

with the submillimeter resolution of X-ray imaging, it is stillhighly desirable to sharpen our optical images, to facilitatethe extraction of spectroscopic information. As discussed in Sebagaimana dibahas dalamthe previous section, the extraction of reliable spectroscopic

Page 13Halaman 13

COLAKet al. : CLINICAL OPTICAL TOMOGRAPHY AND NIR SPECTROSCOPY FORBREAST CANCER DETECTION1155 1155Fig. Gambar. 27. 27. The breast phantom constructed from delrin. The blackened part onthe small cylinder, appearing outside, represents a high-attenuation section tomimic a cancerous lesion to be imaged.information is quite difficult with the added diffuse blurringin the image features. In this section, we will describe ourongoing studies aimed toward improvements in these areas

briefly. sebentar.Deblurring: In a previous paper [35], we have described adeconvolution technique to sharpen images of objects embed-ded in diffuse media. Since the diffusion creates a spatiallydependent point spread function, this method works onlyin conjunction with spatially dependent deconvolution tech-

niques. niques. As we had described earlier [35], such approacheshave already been applied in image restoration, includingmedical images taken by computed tomography [44] andelectrical impedance tomography [45]. Without going intodetail, we would like to present a resulting image fromour studies done by using a phantom in our prototype. The Itu

phantom and the images before and after deblurring are shownin Figs. pada Gambar. 27 and 28. The deblurring for this case has beendone only for a single circular ring. The phantom, shownin Fig. pada Gambar. 27, represents the model of the female breast formedin delrin material containing a single inhomogeneity. The Itu

inhomogeneity itself is also delrin, except that it is blackenedby paint to have a higher attenuation constant in order torepresent a cancerous lesion. As seen from the tomographicimages given in Fig. 28, this small inhomogeneity is notobservable prior to the deconvolution of the image. The detailsof the deblurring technique is described in sufficient detail inour previous report [35] and will not be repeated here. We Kamihave tried to extend this approach to the full volume of the cupgeometry in our mammography prototype system. However, Akan tetapi,due to sharp cut off of the data at the rim of the cup, we didnot have success with real experimental data. At the present Saat ini

time, we are investigating the utilization of wavelet expansionmethods on our data to go around the difficulty due to the


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discontinuity at the rim of the cup described above.Scattering Versus Absorption: One of the difficulties in thetomographic methods we have employed in the present work isthe treatment of the data coming from scattering and

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