An Introduction to Multiplanar
Reconstructions in Digital Breast
Tomosynthesis
Senior Thesis Defense
Trevor L. Vent
Advisors: Ryan Nielson, Andrew D. A. Maidment
Breast Cancer
• Breast cancer is the 2nd
most diagnosed cancer in
women.
• 40,290 women are
expected to die this year
from breast cancer alone.
• It is second only to lung
cancer in mortality rate
[8].
CT Scanner
Image obtained from:
http://www.medgadget.com/wpcontent/uploads/2014/06/Toshiba-PET-CT.jpg
Carotid artery CT scan
Axial plane
E.S. Bartlett et al. AJNR 2006;27:13-19
Sagittal plane
3D Reconstruction
Digital Breast Tomosynthesis
Acciavatti, Raymond J. et al, (2013) Med Phys. 40
Motivation
• The purpose of this study was to quantify the
ability of tomosynthesis to support
multiplanar reconstructions (MPR).
• Experiments were performed over a range of
obliquities to determine the impact on spatial
resolution and contrast.
Multiplanar reconstructions in
tomosynthesis
Dome Phantom
• 15° longitudinal & latitudinal lines
• The dome phantom was built to house a test
object in the shallow cavity of the middle
figure.
Phantom Design
• Two dome
hemispheres with
cylindrical
encasement
• ABS Plus
Filament
• Print Resolution
of 0.25 mm
0° orientation
90° orientation
Star Pattern
0° & 90° Phantom
orientations
45° & 135° Phantom
orientations
Image Acquisition
• Hologic DBT
System
• 140𝜇m detector
• Aliasing frequency
is 3.6 line
pairs/mm
Real Time Tomography (RTT)
The star pattern is tilted at 30°. The multiplanar reconstruction
(MPR) plane of the RTT software matches the plane of the star
pattern orientation.
RTT MPR reconstruction plane
Dome 0°
Dome 90°
Visual calculation of resolution
Contrast
Dome rotation of 0°
Axis of rotation is the y-axis perpendicular to the
plane of source motion.
0° orientation
Resolution
Tilt 0°
Tilt 45°
Tilt 60°
Dome rotation of 0°
Resolution as a function of tilt
Contrast as a function of tilt
0.05
0.045
5
0.04
0.035
4
Contrast
Resolution (line pairs/mm)
6
3
0.03
0.025
0.02
2
0.015
0.01
1
0.005
Phantom: 0
0
0
20
40
Dome: 0
60
80
Phantom: 0
100
120
Tilt Angle (deg)
140
160
180
0
0
20
40
Dome: 0
60
80
100
120
140
160
Tilt Angle (deg)
The phantom rotation of 0° shows super resolution up
to a 60° tilt.
180
Raw projection vs. reconstruction
Raw
Reconstruction
The arrow indicates the maximum resolution.
45° tilt angle
Raw
Reconstruction
The arrow indicates the maximum resolution.
Phantom orientation of 90°
Same reconstruction plane, but different
orientation of frequency.
Addition of phantom rotation of 90°
Contrast as a function of tilt
Resolution as a function of tilt
6
0.05
5
0.04
0.035
4
Contrast
Resolution (line pairs/mm)
0.045
3
0.03
0.025
0.02
2
0.015
0.01
1
0
Phantom: 0 Dome: 0
Phantom: 90 Dome: 0
Aliasing threshold
0
20
40
60
Phantom: 0 Dome: 0
Phantom: 90 Dome: 0
0.005
0
80
100
Tilt Angle (deg)
120
140
160
180
0
20
40
60
80
100
120
Tilt Angle (deg)
Resolution is degraded along the direction perpendicular to
source motion, and super-resolution is not achieved.
140
160
180
90° orientation
Dome rotation: 90°, Phantom rotation: 0°
For this dome rotation the y’ axis is now aligned with the x axis.
Phantom orientation of 0°
Contrast as a function of tilt
Resolution as a function of tilt
0.05
6
5
0.04
0.035
4
Contrast
Resolution (line pairs/mm)
0.045
3
0.03
0.025
0.02
2
0.015
0.01
1
0
Phantom: 0
Dome: 0
Phantom: 0
Dome: 90
Phantom: 90
Dome: 0
Aliasing Frequency
0
20
40
60
Phantom: 0
Phantom: 0
Phantom: 90
0.005
80
100
Tilt Angle (deg)
120
140
160
180
0
0
20
40
Dome: 0
Dome: 90
Dome: 0
60
80
100
Tilt Angle (deg)
120
140
160
180
Phantom orientation of 90°
Reconstruction plane is oblique, but frequency is not oblique
Phantom orientation of 90°
Resolution as a function of tilt
Contrast as a function of tilt
6
0.05
5
0.04
0.035
4
Contrast
Resolution (line pairs/mm)
0.045
3
0.03
0.025
0.02
2
0.015
Phantom: 0
Dome: 0
Phantom: 0
Dome: 90
Phantom: 90
Dome: 0
Phantom: 90
Dome: 90
Aliasing Frequency
1
0
0
20
40
60
80
0.01
Phantom: 0
Phantom: 0
Phantom: 90
Phantom: 90
0.005
100
120
Tilt Angle (deg)
140
160
180
0
0
20
40
Dome: 0
Dome: 90
Dome: 0
Dome: 90
60
80
100
120
140
Tilt Angle (deg)
Of the four approaches super-resolution is achieved
over the broadest range of tilt angles.
160
180
Star Pattern
0° & 90° Phantom
orientations
45° & 135° Phantom
orientations
Additional phantom angles
Raw projections
45°
0°
The arrow indicates the maximum resolution.
Aliasing frequency
Addition
phantom rotations: 45° & 135°
for
45° andof
135°
Resolution as a function of tilt
Contrast as a function of tilt
phantom
orientations.
6
0.05
5
0.04
0.035
4
Contrast
Resolution (line pairs/mm)
0.045
3
0.03
Aliasing frequency
for 0° and 90°
phantom
orientations.
0.025
0.02
2
0.015
Phantom: 0
Phantom: 45
Phantom: 90
Phantom: 135
1
0
0
20
40
0.01
Dome: 0
Dome: 0
Dome: 0
Dome: 0
60
Phantom: 0
Phantom: 45
Phantom: 90
Phantom: 135
0.005
80
100
120
Tilt Angle (deg)
140
160
180
0
0
20
40
Dome: 0
Dome: 0
Dome: 0
Dome: 0
60
80
100
120
Tilt Angle (deg)
Resolution is the same for the 45° and 135°
orientations.
140
160
180
Phantom rotations: 45, 135 degrees
Dome rotation: 90 degrees
Dome rotation of 90°
Resolution as a function of tilt
Contrast as a function of tilt
6
0.05
0.04
0.035
4
Contrast
Resolution (line pairs/mm)
0.045
5
3
0.03
0.025
0.02
2
0.015
0.01
Phantom: 0
Phantom: 45
Phantom: 90
Phantom: 135
1
0
0
20
40
Dome: 90
Dome: 90
Dome: 90
Dome: 90
60
80
Phantom: 0
Phantom: 45
Phantom: 90
Phantom: 135
0.005
100
120
Tilt Angle (deg)
140
160
180
0
0
20
40
Dome: 90
Dome: 90
Dome: 90
Dome: 90
60
80
100
120
140
160
Tilt Angle (deg)
Super-resolution is achieved to a smaller tilt angle.
180
Summary - 1
• We have shown that tomosynthesis supports
oblique reconstructions over a broad range of
obliquities.
• We have quantified the quality of oblique
reconstructions in terms of low-frequency
contrast and limiting spatial resolution.
• Low-frequency contrast is nearly constant over a
broad range of obliquities
• Contrast does drop to near zero at high
obliquities.
Summary - 2
• Limiting resolution decreases with increasing
obliquity.
• Super-resolution is achieved for frequencies
aligned with the x-ray source motion.
• Super-resolution is not achieved for frequencies
perpendicular to the x-ray source motion
• Super-resolution and the alias frequency vary
with phantom angle.
• Limiting resolution varies with obliquity
Limitations & Future Directions
• Artifacts from the Dome MPR Phantom limited
the calculation of contrast and gave high
uncertainties.
• Many more oblique orientations should be
analyzed.
• The dependence of resolution and contrast with
respect to position of the dome phantom on the
breast support should also be analyzed.
• The analysis of Gaussian distribution for the
representative error will be analyzed.
Acknowledgements
• My Family, especially my darling wife, Tara
Mae.
• Dr. Andrew D. A. Maidment
• BYUI Physics faculty
• American Association of Physicists in
Medicine (AAPM)
• Real Time Tomography
• Perelman Center for Advanced Medicine
• Penn’s Biomedical Library
• Komen Foundation
References
Dome rotation of 90°
Resolution as a function of tilt
Contrast as a function of tilt
6
0.05
0.04
0.035
4
Contrast
Resolution (line pairs/mm)
0.045
5
3
0.03
0.025
0.02
2
0.015
0.01
Phantom: 0
Phantom: 45
Phantom: 90
Phantom: 135
1
0
0
20
40
Dome: 90
Dome: 90
Dome: 90
Dome: 90
60
80
Phantom: 0
Phantom: 45
Phantom: 90
Phantom: 135
0.005
100
120
Tilt Angle (deg)
140
160
180
0
0
20
40
Dome: 90
Dome: 90
Dome: 90
Dome: 90
60
80
100
120
140
160
Tilt Angle (deg)
Super-resolution is achieved to a smaller tilt angle.
180
Resolution
Tilt 0°
Tilt 45°
Tilt 60°