Breast imaging tomosynthesis l rotenberg

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  • 1. H o n g K o n g 1 2th e d i t i o n D r L i l i a n L . Y. L E O N G - Hong Kong President Pr Gilbert FERRETTI - Prsident Franais Pr Jean Michel TUBIANA - Prsident dHonneur 7 t o t h 1 0 K O W L O O N 6 K ! 4 o M o w d l y R o o a o d n , N o v t h 2 0 1 3 S H A N G R I - L A T , s i H m S o h n a T g s u K i E o a s n t , g
  • 2. DIGITAL BREAST TOMOSYNTHESIS (DBT) Luc Rotenberg, Jean Guigui, Gregory Lenczner ISHH RPO Clinique Hartmann Ambroise Par Neuilly Sur Seine - France #drrotenberg dr.rotenberg@radiologieparisouest.com H o n g 12 ! th K o n g edition
  • 3. WHY TOMOSYNTHESIS? FFDM WAS NOT ENOUGH? After more than 10 years from its introduction, FFDM has almost totally replaced the analogue mammography (SFM). Its superior diagnostic performances have been demonstrated by a large scale multicenter study: the DMIST ! GE HOLOGIC SIEMENS SECTRA IMS GIOTTO FISCHER
  • 4. DMIST Clinical trial made in2004 2006 in North America 50.000 women enrolled made both exams (FFDM/SFM) Preliminary results published starting from 2006 RESULTS For women 50 years old and/or dense breast Sensitivity goes from 51% (SFM) to 70 - 78% (FFDM) Visualized almost 28% more breast cancers More than 1 over 4 cancers were not recognized: false negatives DMIST Results : Technologic or Observer Variability? Daniel B. Kopans Radiology 2008, Vol.248: 703-704 Diagnostic Accuracy of Digital versus Film Mammography: Exploratory Analysis of Selected Population Subgroups in DMIST Etta D. Pisano & coll, Radiology, 2008, Vol.246: 376-383 THE SUPERIORITY OF FFDM VS. SFM HAS BEEN PROVEN! !
  • 5. FFDM: SUPERIOR TECHNIQUE, BUT NOT PERFECT As a matter of fact we know: Breast screening target is EARLY DIAGNOSIS OF BREAST CANCER In most of the cases Screening reaches the goal almost 10 15% of the found late cancers is originated in regularly screened women FFDM is blind under some particular circumstances : dense breasts dense tissues overlapping lesions !
  • 6. Pooled BI-RADSbased ROC curves for diagnostic assessment of conventional diagnostic views and tomosynthesis views Zuley M L et al. Radiology 2013;266:89-95, Pittsburgh !
  • 7. DBT ROC curves for average probability of malignancy as assessed by using conventional supplemental diagnostic views and tomosynthesis views. Zuley M L et al. Radiology 2013;266:89-95 !
  • 8. Pooled ROC curves for reader studies 1 and 2 using probability of malignancy scores; curves represent average ROC performance for 12 readers in study 1 and 15 in study 2. Rafferty E A et al. Radiology 2013;266:104-113 !
  • 9. Assessing Radiologist Performance Using Combined Digital Mammography and Breast Tomosynthesis Compared with Digital Mammography Alone: Results of a Multicenter, Multireader Trial Diagnostic Sensitivity, Specificity, and Positive and Negative Predictive Values Rafferty E A et al. Radiology 2013;266:104-113, Boston !
  • 10. The challenge of tomosynthesis An efficient DBT system should accomplish some basic requirements: The total released dose should be lower than the one released during an FFDM exam and the closest possible to a 2-D FFDM projection The image quality should be same as the 2D, but it has to provide much more clinical information. The exam has to be the shortest possible (fast scan). The scan angle should be large enough to provide an adequate depth (3-D) resolution. ! DOSE 3-D circa = DOSE 2-D
  • 11. DBT : PARAMETERS AFFECTING THE IMAGE QUALITY The quality of the DBT images depends on several parameters, often in contrast each other Scan Angle: a wide angle causes high depth resolution (the ideal angle is 360!). Dose released to the patient: it must be the lowest possible. Number of projections: the smallest possible to decrease the time of exam. Pixel dimension/ Binning: smaller the pixel higher the spatial resolution and visibility of details Tube movement: shooting while tube moves or stop at each exposure (Step & Shoot) 3-D Reconstruction Algorithm: Better if dedicated to the specific DBT geometry. !
  • 12. SCAN ANGLE PROS & CONS Wide angle: + It provides superior depth resolution: ideal 360 (CT) - It causes mechanical movement complexities - It causes longer scan time 40 50 (GE Essential-Siemens Inspiration) GIOTTO: 40 Small angle: + More simple design / construction mechanics + Shorter scan time - Lower Depth resolution. Loss of details perception ! 15 (7,5) (Hologic Dimensions)
  • 13. NUMBER OF PROJECTIONS PROS & CONS Large Number: + Better reconstruction because more data to the 3D algorithm - Lower S/N per projection because the total dose is unchanged = Low Image Quality - Longer scan time Small Number: - Less data for the 3-D algorithm + Higher S/N per projection = Improved I.Q. + Faster scan ! Hologic Dimensions: 15 exp. GE Essential: 9 exp (or 15?) Siemens Inspiration: 25 exp. Giotto Tomo: 13 exp with variable angles
  • 14. STEP & SHOOT The tube moves rapidly along an arc stopping at each exposure for a fraction of a second The images are shown as 1mm slices or more (slab) -20 +20 Compression plate Breast Digital detector Giotto:13 Projections !
  • 15. CONTINUOUS AND STEPPING MOVEMENT: PROS & CONS Continuous + It is faster = Faster scan time + Much simpler mechanics to design and to build - The exposures during the tubes movement create anyway a blurring effect so causing the loss of crispy contours of the details, especially of the tiny microcalcifications Step & Shoot: - More complex mechanics to avoid vibrations due to variations of speed + The images made in frozen conditions are clear and crispy. No detail is lost. !
  • 16. PIXEL DIMENSION/ BINNING Binning: Virtual combination of two or more pixels of the detector matrix. Usually 4. + The total number of pixel decreases 75% shortening the detector reading, decreasing the weight of the file and the 3-D recon time - The spatial resolution decreases dramatically with loss of details that, if simultaneously the tube movement is continuous, causes an important decrease of micro calcifications visibility. !
  • 17. 3-D RECONSTRUCTION ALGORITHM The classic 3-D Algorithms are those created in the last 30 years for CT scanners or forMRI (FBP o SART) They have the advantage to be well known and tested, but also the defect to be designed for a different geometry: source and detectors rotating 360 around the object. The DBT geometry is by far different: it can go from a minimum of 15 (Hologic) to a maximum of 50 (Siemens) Adapting these algorithms to the DBT geometry causes streaking artifacts and worsensthe image quality. The Iterative algorithm is much more fit for DBT, but it is heavier and causes longer reconstruction time (to a maximum of 4 min). !
  • 18. ADVANCED 3-D ITERATIVE ALGORITHM Non CT style, but DBT dedicated Low number of artifacts Better micro calcifications visualization Better visualization of the skin line Better S/N ratio It requires less projections The projections can be further apart !
  • 19. GIOTTO TOMO: ADVANCED 3-D ITERATIVE ALGORITHM ALL PARAMETERS OPTIMIZED Wide scan angle, 40 Only 13 exposures Step & Shoot 3-D Iterative Algorithm RESULTS: Increased S/N rat