Impact of detector thickness on imaging characteristics of the Siemens Biograph

DUO PET/CT with GATE

N. N. Chatzisavvasd, T. J. Sevvosd, Em. M. Vlamakisd, A. A. Fotopoulos d, X. A. Argyriou d X. Tsantilasb, S. Kottoub , P.H.Yannakopoulosd, A. Louizib , I. Kandarakisc, J. Malamitsib and D. Nikolopoulosa

a Department of Physics, Chemistry and Material Science, Technological Educational Institute (TEI) of Piraeus, Petrou Ralli & Thivon 250, 122 44,Aigaleo,Athens,Greece

b Medical Physics Department, Medical School, University of Athens, Mikras Asias 75, 11527, Athens, Greece

c Department of Medical Instruments Technology, Technological Educational Institution of Athens, Ag. Spyridonos, Aigaleo, 122 10 Athens, Greece

d Department of Engineering of Electronic and Computer Systems,Technological Educational Institute (TEI) of Piraeus, Petrou Ralli & Thivon 250, 122

44,Aigaleo,Athens,Greece

International Scientific Conference eRA-7

The present paper is a Monte Carlo study of a Siemens Biograph DUO PET/CT with GATE,with emphasis given on PET imaging and, especially, to changes caused by changing the thickness of the LSO detector of a PET/CT.

AIM

International Scientific Conference eRA-7

Introduction 1/3

Positron emission tomography - computed tomography PET-CT is a medical imaging technique using a device which combines system both a Positron Emission Tomography (PET) and an x-ray Computed Tomography.

International Scientific Conference eRA-7

Introduction 2/3

Scintillation is a process of emitted characteristic light spectrum when a scintillator is absorbing ionising radiation.

LSO Scintillator :

International Scientific Conference eRA-7

Introduction 3/3

GATE is an advanced open source software , combines the advantages of the GEANT4 simulation toolkit, dedicated to numerical simulations in medical imaging and radiotherapy written in C/C++

International Scientific Conference eRA-7

Materials and Methods

Simulation with Gate-Geant of the PET/CT Siemens Biograph DUO

GATE codes for (building the simulation):

(a) the entire PET detector arrangement (b) the light guides, photomultiplier tubes and related

electronics (c) the digitizer (d) the shielding between PET and CT (e) the coincidence circuits and processors (f) the time-delay of PET (g) the data processing systems (h) the examination bed (i) the PET and CT gantry (j) the PET motions (gantry, bed) (k) the shielding of the room (l) the CT image reconstruction chain .

International Scientific Conference eRA-7

Materials and Methods Software phantoms (inside the simulation): (a) a cylindrical source phantom of radius 1 mm and height 15

cm filled with F-18 FDG (b) human body phantom :

◦ (b-i) an ellipsoid of 8 cm minimum and 15 cm maximum radius mimicking the human main body.

◦ (b-ii) two cylinders of radius 5 cm and height 30 cm mimicking the human

hands. ◦ (b-iii) a sphere of 14 cm radius mimicking the human head. ◦ (b-iii) A cylindrical F-18 FDG source of 0.5 cm radius and 5 cm height .

International Scientific Conference eRA-7

Materials and Methods

Interaction phenomena :

i) Crystal energy blurring: resolution of 0.25 at 511keV.

(ii) Detector characteristics: quantum detection

efficiency of 0.98 , light output of 30000 photons/MeV, intrinsic resolution of 0.088 and transfer efficiency coefficient of 0.28.

(iii) Energy window: between 250 and 650 keV (iv) Time Resolution: coincidence window of 120

ns, dead time window of 120 ns and dead time offset of 700 ns.

(v) F-18 FDG source half life of 6586.2 s (vi) Slice time of 1 s and acquisition time of 10s.

International Scientific Conference eRA-7

Results and Discussion

i) Diagram with Characteristics of the Biograph DUO PET/CT (black line) and estimation from Gate Simulation (blue)

ii) Diagram Number of

counts – Energy Mev (2 picks at 0.2 MeV and 0.511 MeV)

International Scientific Conference eRA-7

Results and Discussion

iii)Number of Counts –

Energy (MeV) ( pick at 0.25 MeV)

ii)Diagram Number of counts

– Energy Mev (2 picks at 0.2 MeV and 0.511 MeV) (± 1 deg)

International Scientific Conference eRA-7

Results and Discussion

Root Mean Square (RMS) energy is 99.06 keV

Mean energy is 407.5 keV

FWHM of energy and RER are 0.6 and 6% for the peak near 0.511 MeV

As thickness increases, FWHM, RER and SNR increase

International Scientific Conference eRA-7

Results and Discussion

Energy Resolution Of System ◦ A) 2 cm LSO thickness

◦ B) 3 cm LSO thickness

The peak of the 3.0 cm thick

crystals is sharper , more wide and has more counts than the one of the 2.0 cm thickness. This attributes to the higher detection efficiency of the thicker LSO detectors at 0.511 MeV

International Scientific Conference eRA-7

Results and Discussion

As detector thickness increases, the axial distribution sensitivity of the number of counted photons is enhanced at the centre, viz. the energy distribution is sharper.

International Scientific Conference eRA-7

Results and Discussion

The increase with thickness of the photon detection sensitivity of a block of 64 LSO crystals points in another way that blocks of thicker crystals detect and count more photons.

International Scientific Conference eRA-7

Conclusions

Non-significant changes were observed for: ◦ positron kinetic energy spectrum

◦ interactions of positrons with matter

◦ positron annihilation distance

◦ number of annihilation processes

◦ gamma ray production

◦ distribution and scattering of gamma-rays

The detector absorption efficiency is strongly affected by the scintillator thickness.

Possible use of 3.0 cm thick LSO crystals will increase detection efficiency of the system, RER and SNR

But will delay signal process and increase the construction cost and may be accompanied by paralax effects .

International Scientific Conference eRA-7

Thank You !

http://env-hum-comp-res.teipir.gr/

International Scientific Conference eRA-7

References:

Bailey,D.L., Meikle, S.R. 1994. A Convolution-Subtraction scatter correction method for 3D PET, Phys. Med. Biol. 39, 411-424

Beutel, J., Kundel, H.L., Van Metter, R.L., 2000. SPIE Press, Bellingham, Washington.

Blasse, G., Grabmaier, B.C., 1994. Luminescent Materials, Springer, Heidelberg, Berlin.

Bonifacio, D.A.B., Belcari, N., Moehrs, S., Moralles, M., Rosso, V., Vecchio, S. Del Guerra, A., 2010. A Time Efficient Optical Model for GATE Simulation of a LYSO Scintillation Matrix Used in PET Applications, IEEE Trans. Nucl. Sci. 57(5), 2483-2489.

Brownell, G.L., Correia, J.A., Zamenhof, R.G., 1978. Positron instrumentation, Recent Advances in Nuclear Medicine 5, New York.

Chen, J., Zhang, L. Zhu, R.Y., 2007. Large size LSO and LYSO crystal scintillators for future high-energy physics and nuclear physics experiments, Nucl. Instrum. Meth. A 572,218-224.

Cherry, S.R., 2004. In vivo molecular and genomic imaging: new challenges for imaging physics, Phys. Med. Biol. 49, R13–R48.

El Fakhri, G., Surti, S., Trott, C.M., Scheuermann, J., Karp, J.S., 2011. Improvement in lesion detection with whole-body oncologic time-of-flight PET, J. Nucl. Med. 52, 347–353.

Hejazi, S., Tauernicht, D.P., 1997. System considerations in CCD-based x-ray imaging for digital chest radiography and digital mammography, Med. Phys. 24 , 287-297.

Jakoby, B. W., Bercier, Y., Conti, M., Casey, M. E., Bendriem, B., Townsend, B. W., 2011. Physical and clinical performance of the mCT time-of-flight PET/CT scanner, Phys. Med. Biol. 56, 2375–2389.

Jan, S., Comtat, C., Strul, D., Santin, G., Trbossen, R., 2005. Monte Carlo simulation for the ECAT EXACT HR+ system using GATE IEEE Trans. Nucl. Sci. 52 627–33

Geramifar, P., Ay, M.R., Shamsaie Zafarghandi, M., Sarkar, S., Loudos, G., Rahmim, A., 2011. Investigation of time-of-flight benefits in an LYSO-based PET/CT scanner:A Monte Carlo study using GATE, Nucl. Instrum. Meth. A, 641, 121–127.

Gonias, P., Bertsekas, N., Karakatsanis, N.A., Saatsakis, G., Nikolopoulos, D., Tsantilas, X., Loudos, G., N., Sakellios, N., Gaitanis, A., Papaspyrou, L., Daskalakis, A., Liaparinos, P., Cavouras, D., Kandarakis, I., Panayiotakis, G.S., 2007. Validation of a GATE model for the simulation of the Siemens PET/CT Biograph 6 scanner, Nucl. Instrum. Meth. A 571, 263-266.

Karakatsanis, N., Sakellios, N., Tsantilas, N.X., Dikaios, N., Tsoumpas, C., Lazaro, D., Loudos, G., Schmidtlein, C.R., Louizi, K., Valais J., Nikolopoulos, D., Malamitsi, J., Kandarakis, J., Nikita, K.. 2006. Comparative evaluation of two commercial PET scanners, ECAT EXACT HR+ and Biograph 2, using GATE. Nucl. Instr. Meth. A 571, 368-372.

Karimian, A. R., Thompson, C. J.,2008.Assessment of a new scintillation crystal (LaBr3) in PET scanners using Monte Carlo method, NUKLEONIKA 53(1), 3−6.

Karp, J.S., Surti, S., Daube-Witherspoon, M.E., Muehllehner, G., 2008. Benefit of time-of-flight in PET: experimental and clinical results, J. Nucl. Med. 49, 462–470.

Knoll, G. F., 1979. Radiation detection and measurement, John Wiley & Sons, New York.

Lartizien ,C., Kuntne, C., Goertzen, A .L. , Evans, A. C., Reilhac, A., 2007. Validation of PET-SORTEO Monte Carlo simulations for the geometries of the MicroPET R4 and Focus 220 PET scanners, Phys. Med. Biol. 52, 4845–4862.

Lewellen, T.K., 2008. Recent developments in PET detector technology, Phys. Med. Biol. 53, R287–R317.

Lewellen, T.K., 2010.The Challenge of Detector Designs for PET , AJR 195, 301–309 .

Merheb, C., Petegnief, Y., Talbot, J. N., 2007. Full modelling of the MOSAIC animal PET system based on the GATE Monte Carlo simulation code, Phys. Med. Biol. 52, 563–576.

International Scientific Conference eRA-7

Michel, C., Eriksson, L., Rothfuss, H., Bendriem, B., 2006. Influence of crystal material on the performance of the HiRez 3D PET scanner: a Monte Carlo study, IEEE Nuclear Science Symp. Conf., 2528–31

Nakamori,T., Kato, T.Kataoka, J., Miura, T., Matsuda, H., Sato, K. Ishikawa, Y. Yamamura, K., Kawabata, N., Ikeda, H., Satoc, G., Kamadad, K. 2012.Development of a gamma-ray imager using a large area monolithic 4×4 MPPC array for a future PET scanner, JINST 7, C01083, 1-13.

Nassalski,A., 2007. Comparative study of scintillators for PET/CT detectors, IEEE T. Nucl. Sci. 54, 3-10.

Nikl,M., 2006. Scintillation detectors for X-rays, Meas. Sci. Technol. 17, R37-R54.

Nikolopoulos, D., Kandarakis, I., Cavouras, D., Louizi, A., Nomicos, C., 2006a. Investigation of radiation absorption and x-ray fluorescence of medical imaging scintillators by Monte Carlo Methods, Nucl.Instr.Method.(A) 565, 821-832

Nikolopoulos, D., Kandarakis, I., Tsantilas, X., Valais, I., Cavouras, D., Louizi A., 2006b. Comparative study of the radiation detection efficiency of LSO, LuAP, GSO and YAP scintillators for use in positron emission imaging (PET) via Monte-Carlo Methods, Nucl.Instr.Method.(A) 569, 350-354.

O Mineev, Y. Kudenko, Y. Musienko, I. Polyansky, Yershov, N. 2011. Scintillator detectors with long WLS fibers and mulit-pixel photodiodes, JINST 6, P012004, 1-9.

Lipeng, P., Jianfeng, H., Lei, M., 2010. An initial simulation study of PET imaging by GATE, 978-1-4244-7618 IEEE.

Poon, J.K.,Dahlbom, M.L., Moses, W.W.,Balakrishnan, K.,Wang, W.,Cherry, S.R.,Badawi, R.D., 2012. Optimal whole-body PET scanner configurations for different volumes of LSO scintillator: A simulation study, Phys. Med. Biol. 57(13), 4077-4094

Shimizu, S., Pepin, C.M., Lecomte, R., 2010. Assessment of Lu1:8Gd0:2SiO5 (LGSO) Scintillators with APD Readout for PET/SPECT/CT Detectors, IEEE T. Nucl. Sci., 57(3), 1512-1517.

Schmidtlein, C.R., 2006. Validation of GATE Monte Carlo simulations of the GE advance/discovery LS PET scanners, Med. Phys. 33, 198–208.

Strother, S.C., Casey, M.E., Hoffman, E.J., 1990. Measuring PET scanner sensitivity: relating countrates to image signal-to-noise ratios using noise equivalent counts, IEEE Trans. Nucl. Sci. 37, 783–788.

Tavernier, S., Bruyndonckx, P., Leonard, S., Devroede, O., 2005. A high-resolution PET detector based on continuous scintillators, Nucl. Instrum. Methods A 537, 321–325.

Townsend, D. W., 2004. Physical Principles and Technology of Clinical PET Imaging, Ann. Acad. Med. 33:2, 133-145.

Townsend, D. W., Beyer, T., 2002. A combined PET/CT scanner: the path to true image fusion, Brit. J. Radiol. 75, S24-S30.

Tsantilas, X., Louizi, A., Valais, I., Nikolopoulos, D., Sakellios, N., Karakatsanis, N., Loudos, G., Nikita, K., Malamitsi, J., Kandarakis, I., 2005. Simulation of commercial PET scanners with GATE Monte-Carlo simulation package, Biomed. Tech. 50(Sup.1), 114-115.

Yong, C., Jin Ho, J., Yong Hyun, C., Devroede, O., Krieguer, M., Bruyndonckx, P., Tavernier, S., 2007. Optimization of LSO/LuYAP phoswich detector for small animal PET, Nucl. Instrum. Methods A 571, 669–675.

Yu, T., Sabol, J.M., Seibert, J.A., Boone,J.M.,Scintillating fiber optic screens: a comparison of MTF, light conversion efficiency, and emission angle with Gd2O2S:Tb screens, 1997. Med. Phys. 24, 279-285.

Vandenbroucke, A., Foudray, A.M.K., Olcott, P.D., Levin, C.S., 2011. Performance characterization of a new high resolution PET scintillation detector, Phys. Med. Biol. 56, 4135-4145.

Van der Laan, D.J, ,Schaart, D.R., Maas, M.C., Beekman, F.J., Bruyndonckx, P., Van Eijk, C.W.E., 2010. Optical simulation of monolithic scintillator detectors using GATE/GEANT4, Phys. Med. Biol. 59, 1659-1675.

Van Eijk,C.W.E., 2002, Inorganic scintillators in medical imaging, 2002. Phys. Med. Biol. 47 R85-R106.

Van Eijk,C.W.E., 2008. Radiation detector developments in medical applications: inorganic scintillators in positron emission tomography, Rad. Prot. Dosim. 129(1-3), 13-21.

Zeraatkar, N., Ay, M. R., Kamali-Asl, A. R., Zaidi, H., 2011. Accurate Monte Carlo modeling and performance assessment of the X-PET™ subsystem of the FLEX Triumph™ preclinical PET/CT scanner, Med. Phys. 38 (3),1217-1225

International Scientific Conference eRA-7