7 t h t o 1 0 t h N o v 2 0 1 3 KOWLOON SHANGRI-LA 6 4 M o d y R o a d , T s i m S h a T s u i E a s t , K o w l o o n , H o n g K o n g Dr Lilian L.Y. LEONG - Hong Kong President Pr Gilbert FERRETTI - Président Français Pr Jean Michel TUBIANA - Président d’Honneur H o n g K o n g 12 th edition
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
!
7 t h t o 1 0 t h N o v 2 0 1 3
K O W L O O N S H A N G R I - L A 6 4 M o d y R o a d , T s i m S h a T s u i E a s t , K o w l o o n , H o n g K o n g
D r L i l i a n L . Y . L E O N G - H o n g K o n g P r e s i d e n t P r G i l b e r t F E R R E T T I - P r é s i d e n t F r a n ç a i s P r J e a n M i c h e l T U B I A N A - P r é s i d e n t d ’ H o n n e u r
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 multi-center study: the DMIST
GE SIEMENS SECTRA FISCHER
HOLOGIC IMS GIOTTO
!
THE SUPERIORITY OF FFDM VS. SFM HAS BEEN PROVEN!
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
!
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
Pooled BI-RADS–based ROC curves for diagnostic assessment of conventional diagnostic views and tomosynthesis views
Zuley M L et al. Radiology 2013;266:89-95, Pittsburgh
!
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
!
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
!
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
!
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 2-D, 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
!
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.
!
SCAN ANGLE– PROS & CONS
Wide angle:
+ It provides superior depth resolution: ideal 360° (CT) - It causes mechanical movement complexities - It causes longer scan time
Small angle:
+ More simple design / construction mechanics + Shorter scan time - Lower Depth resolution. Loss of details perception
15° (±7,5°)
(Hologic Dimensions)
40° 50°
(GE Essential-Siemens Inspiration)
GIOTTO: 40°
!
NUMBER OF PROJECTIONS PROS & CONS
Large Number:
+ Better reconstruction because more data to the 3-D algorithm
- Lower S/N per projection because the total dose is unchanged = Low Image Quality
� 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)
Giotto:13 Projections
STEP & SHOOT
!
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 tube’s 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.
!
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.
!
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).
!
• 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
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 ratio • Visibility of tiny microcalcs • Visibility of the skin line • Contrast and contours of the tissues
are clear and crispy
GIOTTO TOMO: ADVANCED 3-D ITERATIVE ALGORITHM
!
S Angiomammography (CEDM) based on the Dual Energy principle.