This document discusses the effects of slice thickness filters in breast tomosynthesis reconstruction using filtered back projection. It summarizes a study that used simulations to analyze how filters impact impulse responses and the reconstruction of single and overlapping objects. The results showed that using a profile filter enhances sharpness, reduces ringing artifacts, and allows reconstructed objects to spread out more uniformly along depth, reducing mutual interference between neighboring slices. In conclusion, profile filters improve the quality of breast tomosynthesis reconstructions.

1. Effects of Slice Thickness Filter in
Breast Tomosynthesis Filtered
Back Projection Reconstruction
Linlin Cong 1, Weihua Zhou 2, *Ying Chen 1,2
1Biomedical Engineering Graduate Program
2Department of Electrical and Computer Engineering, Southern
Illinois University, Carbondale, IL 62901
(* Corresponding Author)
IEEE GENSIPS 2011
Medical Imaging Laboratory
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2. OUTLINE
 Introductions
 Breast Tomosynthesis Imaging System
 Tomosynthesis Image Reconstruction
and Simulation
 Results
 Conclusions
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3. Introduction
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4. Breast Cancer
 Breast Cancer:
• Most common cancer among women
worldwide;
• Second leading cause of cancer related death
among women.
 Symptoms:
• No symptom in the early stage, regular breast
exams are important;
• Breast lump or lump in the armpit, change in
the size, shape, fluid from the nipple.
• Once the patient is diagnosed with breast
cancer, next step is staging (Grade:
0, I, II, III, IV). Higher the grade is, poorer the 4

5. Mammography
 Traditional mammography:
• Currently, a standard and important clinical
screening and diagnosis for early detection of
breast cancer;
• Cheap, low radiation dosage.
 Limitations of traditional mammography:
• 20% false negative rate, many call backs from
screening;
• low positive predictive value, about 30% of breast
cancers are still missed in mammography;
• 2D imaging system, difficult to distinguish a
cancer from overlapped breast tissues. 5

6. Breast Tomosynthesis
3D slice images provide depth information
 Improve conspicuity of structure by removing
the visual clutter associated with overlying
anatomy
 Promising to reduce recall rates, and to
increase cancer detection accuracy.
 Low dosage; relatively cheap
 Extensive attentions from academic
communities and industrial vendors have been
paid to this promising field.
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7. Breast Tomosynthesis
Imaging System
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8.  Examples of current commercial breast
tomosynthesis prototype systems :
Siemens
Mammomat
IMS GIOTTO Hologic Selenia Dimensions
GE
Inspiration
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9.  Most of these systems
re-utilize the traditional partial
isocentric mammography
design.
 X-ray tube moves in an arc across the breast
 Series of low dosage images are acquired at
different angles
 Limitation is X-ray tube’s movement may introduce
motion blur and cause patients’ discomfort.
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10. A Novel Nanotechnology Enabled Digital
Breast Tomosynthesis Prototype System
 Invented by our collaborators at the University of
North Carolina Chapel Hill
 Built up with fixed multi-beam field-emission X-
ray sources, no movement of X-ray tubes;
 Total scanning time: about 11.2 seconds for
typical 25 projection views
 Advantages:
• No motion blur
• Less scanning time, so decreasing the waiting
time
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11. • Fixed multi-beam field-
emission x-ray (MBFEX)
sources based on unique
properties of carbon
nanotube electron emitters.
• The total scan time for a
A novel multi-beam x-ray source
typical 25 views is about
developed by Zhou Lu et al.
11.2 seconds.
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12. Tomosynthesis Image
Reconstruction and
Simulation
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13. BREAST TOMOSYNTHESIS
IMAGING SYSTEM SIMULATION
 The image acquisition system we used to get the
projection images was simulated based on the
parallel imaging system.
• 25 X-ray sources.
• The path of tubes is parallel to the plane of
detector.
• Two sets of data were simulated to investigate
the filter effects:
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14.  The image acquisition system:
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15. IMAGING SYSTEM: Data 1
 One Sphere:
• placed at 30mm above the detector
• radius = 5mm.
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16. IMAGING SYSTEM: Data 2
 Two overlapping spheres were simulated.
• Sphere 1: height = 20mm above detector,
radius = 5mm
• Sphere 2: height = 40mm above detector,
radius = 10mm
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17. Reconstruction Algorithm
• Mathematic Reconstruction Methods:
 Shift and Add (SAA)
 Backprojection(BP)
• Filter-based Reconstruction Methods:
 Filtered Backprojection(FBP)
 Matrix Inversion Tomosynthesis (MITS)
• Statistical Reconstruction Methods:
 Maximum Likelihood Expectation
Maximization(MLEM)
• Algebraic Reconstruction Methods:
 Simultaneous Algebraic Reconstruction
Technique (SART)
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18. Reconstruction Algorithm
• Mathematic Reconstruction Methods:
 Shift and Add (SAA)
 Backprojection(BP)
• Filter-based Reconstruction Methods:
 Filtered Backprojection(FBP)
 Matrix Inversion Tomosynthesis (MITS)
• Statistical Reconstruction Methods:
 Maximum Likelihood Expectation
Maximization(MLEM)
• Algebraic Reconstruction Methods:
 Simultaneous Algebraic Reconstruction
Technique (SART)
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19. Filtered Back Projection (FBP)
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20. FBP: Profile Filter
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21. Results
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22. Impulse Responses Analysis
a) Impulse response without b) Impulse response
profile filter with profile filter
c) Intensity profiles of figure (a) d) Intensity profiles of figure (b)
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23. Single Sphere Data
a) Reconstructed b) Vertical plane of c) Reconstructed d) Vertical plane of
image of 30mm the object along image of 30mm the object along Z-
plane without Z-direction without plane with direction with
profile filter profile filter profile filter profile filter
e) Intensity profiles of figure (a) f) Intensity profiles of figure (b)
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24. Two Overlapping Sphere Data
a) Reconstructed b) Reconstructed c) Reconstructed d) Reconstructed
image of 20mm image of 40mm image of 20mm image of 40mm
plane without plane without plane with plane with
profile filter profile filter profile filter profile filter
e) Vertical plane of objects f) Vertical plane of objects
along Z-direction without along Z-direction with profile
profile filter filter
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25. CONCLUSIONS
 Effects of Profile Filter:
• Enhance the sharpness
• Reduce the ringing artifacts
• Make the reconstructed objects spread out
more uniformly along the depth (z) direction
• Reduce the mutual interference between
objects located on the neighboring slices
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26. ACKNOWLEDGMENT
• We thank our collaborators at The University of
North Carolina at Chapel Hill (UNC) and group
members at Southern Illinois University (SIU).
• The related work has been supported by
Southern Illinois University and U.S. National
Institutes of Health (NIH/NCI R01 CA134598-
01A1).
Medical Imaging Laboratory
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