Introduction to Tomosynthesis - AMOS...
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Introduction to Tomosynthesis
Ioannis Sechopoulos, Ph.D., DABR Diagnostic Medical Physics Laboratory
Department of Radiology and Imaging Sciences & Winship Cancer Institute
Emory University Atlanta, Georgia
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Disclosure
• Institutional Research Collaborations:
– Barco
– Hologic
• Consultant:
– Fuji Medical Systems USA
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Learning Objectives
• To understand the fundamental principles behind tomosynthesis
• To explain the possible different system designs
• To explain the determinants of image quality
• To list the factors that affect radiation dose
• To understand the common artifacts in tomosynthesis
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Outline
Motivation
Introduction
System Design and Design Considerations
Image Reconstruction
Radiation Dose
X-Ray Scatter
Artifacts
Synthetic Mammograms
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MOTIVATION
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0.16 lesion
localization
fraction
8 Vikgren et al, Radiology 249(3), 1034-1041 (2008).
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9 Vikgren et al, Radiology 249(3), 1034-1041 (2008).
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29% of missed cancers were missed due to being “obscured by overlying tissue”
13 Birdwell et al, Radiology 219, 192-202 (2001).
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17 Courtesy GE Medical Systems
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Computed Tomography
More expensive Higher radiation dose 100x chest CT over chest radiograph 2-5x breast CT over mammography Metal problematic Slower to read (?) ….otherwise, fantastic!
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Is there a halfway??
(can we get the best of both worlds?)
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Linear Tomography
22 Bushberg et al, The Essential Physics of Medical Imaging, 2nd edition.
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Towards Tomographic Imaging
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Standard
Transmission
Imaging
Stereoscopic
Imaging
Digital
Tomosynthesis
Computed Tomography
2+ D 2.2 D 2 D 3 D
(If your optical system can handle it!)
(Is more always
better?)
Linear
Tomography
2.1 D
(If you plan ahead!)
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DIGITAL TOMOSYNTHESIS
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25
Detector
Translated X-ray source
X-ray beam
Lesions of Interest
This information is used to reconstruct the volume
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Shift correlates with vertical location
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Recall
Courtesy of Hologic Inc. 27
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CC view .IDC
Courtesy of Hologic Inc. 28
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Courtesy of Hologic Inc. 29
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Benefits
Similar to Radiography/Mammography System
Workflow
Interpretation
Dose
…but with some discrimination of vertical position!
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SYSTEM DESIGN AND DESIGN CONSIDERATIONS
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FFDM System Breast Tomo System
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33 Courtesy Joseph Lo (via youtube)
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34 https://www.youtube.com/watch?v=g9AjqhQJwAs
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35 Courtesy of Philips Digital Mammography AB
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System
Fuji
AMULET
Innovality
GE Essential
Hologic
Selenia
Dimensions
IMS Giotto
TOMO
Philips
MicroDose
Planmed
Nuance Excel
DBT
Siemens
MAMMOMAT
Inspiration
Detector Type
Full field -
Direct (a-Se)
(Hexagonal
pixels)
Full field -
Indirect
Full field -
Direct (a-Se)
Full field -
Direct (a-Se)
Linear Slit Scan
– Spectral
Photon
Counting (Si)
Full field -
Direct (a-Se)
Full field -
Direct (a-Se)
Detector
Motion Static Static Rotating Static
Continuous Slit
Scan
Rotating during
exposure Static
X-Ray Tube
Motion Continuous Step-and-Shoot Continuous Step-and-Shoot Continuous Continuous Continuous
Detector to
Center of
Rotation
Distance (cm)
4 4 0 2 -40 4.37 4.7
Angular Range 15 25 15 40 11 30 50
Number of
Projections 15 9 15 13 21 15 25
Scan Time (sec) 4 7 3.7 12 3 – 10 20 25
Reconstruction
Method
Modified
FBP Iterative FBP
Iterative with
Total Variation
Regularization
Iterative Iterative FBP
Development
Stage
Commercial
System**
Commercial
System
Commercial
System
Commercial
System** Prototype Prototype
Commercial
System
36 **Currently not approved for clinical use in the U.S. by the Food and Drug Administration (FDA)
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37 http://2014.bhpa.eu/wp-content/uploads/formidable/Marshall_Nicolas.pdf
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38 Courtesy of Otto Zhou, Applied Nanotechnology Laboratory, University of North Carolina at Chapel Hill
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CNT s-DBT
DBT
System MTF
~30% increase in system resolution for standard 15 degree, 15 view scan
A. Tucker, et al, Med Phys 2012
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S-DBT reconstructions above
Continuous motion DBT reconstructions
MC # 1 MC # 2 MC # 3 MC # 4 MC # 5 MC # 6
Micro-calcification visibility
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41 Shan et al, Phys. Med. Biol. 60, 81-101, 2015
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System
Fuji
AMULET
Innovality
GE Essential
Hologic
Selenia
Dimensions
IMS Giotto
TOMO
Philips
MicroDose
Planmed
Nuance Excel
DBT
Siemens
MAMMOMAT
Inspiration
Detector Type
Full field -
Direct (a-Se)
(Hexagonal
pixels)
Full field -
Indirect
Full field -
Direct (a-Se)
Full field -
Direct (a-Se)
Linear Slit Scan
– Spectral
Photon
Counting (Si)
Full field -
Direct (a-Se)
Full field -
Direct (a-Se)
Detector
Motion Static Static Rotating Static
Continuous Slit
Scan
Rotating during
exposure Static
X-Ray Tube
Motion Continuous Step-and-Shoot Continuous Step-and-Shoot Continuous Continuous Continuous
Detector to
Center of
Rotation
Distance (cm)
4 4 0 2 -40 4.37 4.7
Angular Range 15 25 15 40 11 30 50
Number of
Projections 15 9 15 13 21 15 25
Scan Time (sec) 4 7 3.7 12 3 – 10 20 25
Reconstruction
Method
Modified
FBP Iterative FBP
Iterative with
Total Variation
Regularization
Iterative Iterative FBP
Development
Stage
Commercial
System**
Commercial
System
Commercial
System
Commercial
System** Prototype Prototype
Commercial
System
42 **Currently not approved for clinical use in the U.S. by the Food and Drug Administration (FDA)
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Total Angular Range Oblique Incidence
43 Acciavatti and Maidment, Medical Physics, 38(11), 2011
(20 deg)
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Oblique Incidence – Direct Detectors
44 Zhao and Zhao, Medical Physics, 35(5), 2008
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Oblique Incidence – Indirect Detectors
45 Mainprize et al, Medical Physics, 33(9), 2006
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Acquisition Geometry
Radiography:
1 position, 1 shot
CT:
full revolution, 1000 shots
Tomosynthesis:
???
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Acquisition Geometry Optimization
Acquisition parameters:
Angular range
Number of projection angles
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48 Maidment et al, Proceedings of SPIE, 5745, 2005
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Artifact Spread Function
49
s BG
s 0 BG 0
I z -I zASF z =
I z -I z
Wu et al, Medical Physics, 31(9), 2004
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Angular Range
50 Hu et al, Medical Physics, 35(12), 2008
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Image Acquisition Optimization
Computer simulated breast volume and lesions
63 different acquisition geometries
In-plane quality and vertical resolution
51
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52 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199-1207.
(a) Mass
Masses: Increased in-plane quality with increased angular range, fewer projections
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53 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199-1207.
µCa: Increased in-plane quality with decreased angular range ( mammo), fewer projections (small effect)
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54 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199-1207.
Vertical resolution increases with angular range
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55 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199-1207.
Threshold number of projections to improve vertical resolution
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Acquisition Geometry and Vertical Resolution
56 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199-1207.
aSubstantial artifacts due to narrow angular range
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Subsequent studies:
Threshold number of projections for each angular range was confirmed by others
57
Tucker et al, Proc. SPIE 8313, 831307-831310 (2012) A. S. Chawla et al, Med. Phys. 36, 4859-4869 (2009) I. Reiser and R. M. Nishikawa, Med. Phys. 37, 1591-1600 (2010) Goodsitt et al, Phys. Med. Biol. 59 (2014) 5883
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Chest Tomosynthesis
58
No gain in increase in projections beyond a certain number
Söderman et al, Medical Physics, Vol. 42, No. 3, 2015
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Acquisition Geometry
↑ angular range ↑ vertical resolution
↑ # of projections ↑ vertical resolution up to a point
Have to consider:
scan time
anatomy
detector size
59
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ACQUISITION TECHNIQUE
60
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Tube Voltage Selection
Multiple studies reported higher kV than mammo optimal for tomo
One study reported lower energies beneficial
61
Ren et al, Proceedings of SPIE 5745, 550–561 (2005). Zhao et al, Proceedings of SPIE 5745, 1272–1281 (2005). Wu et al, Proceedings of SPIE 6142, 61425E (2006) Glick and Gong, Proceedings of SPIE 6142, 61421L–61429L (2006).
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Technique and Dosimetric Characterization of a Clinical System
62 Feng and Sechopoulos, Radiology, 2012; 263(3): 35-42
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Breast
Thickness
(cm)
2
3
4
5
6
7
8
Filter
Tube
Voltage
(kVp)
1st HVL
(mm Al)
Rh 25 0.453
Rh 26 0.494
Rh 28 0.517
Rh 29 0.551
Rh 31 0.567
Ag 30 0.586
Ag 32 0.611
63
Filter
Tube
Voltage
(kVp)
1st HVL
(mm Al)
Al 26 0.441
Al 28 0.476
Al 29 0.490
Al 31 0.541
Al 33 0.572
Al 35 0.600
Al 38 0.660
Tomosynthesis Mammography
Feng and Sechopoulos, Radiology, 2012; 263(3): 35-42
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TOMOSYNTHESIS RECONSTRUCTION
64
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System
Fuji
AMULET
Innovality
GE Essential
Hologic
Selenia
Dimensions
IMS Giotto
TOMO
Philips
MicroDose
Planmed
Nuance Excel
DBT
Siemens
MAMMOMAT
Inspiration
Detector Type
Full field -
Direct (a-Se)
(Hexagonal
pixels)
Full field -
Indirect
Full field -
Direct (a-Se)
Full field -
Direct (a-Se)
Linear Slit Scan
– Spectral
Photon
Counting (Si)
Full field -
Direct (a-Se)
Full field -
Direct (a-Se)
Detector
Motion Static Static Rotating Static
Continuous Slit
Scan
Rotating during
exposure Static
X-Ray Tube
Motion Continuous Step-and-Shoot Continuous Step-and-Shoot Continuous Continuous Continuous
Detector to
Center of
Rotation
Distance (cm)
4 4 0 2 -40 4.37 4.7
Angular Range 15 25 15 40 11 30 50
Number of
Projections 15 9 15 13 21 15 25
Scan Time (sec) 4 7 3.7 12 3 – 10 20 25
Reconstruction
Method
Modified
FBP Iterative FBP
Iterative with
Total Variation
Regularization
Iterative Iterative FBP
Development
Stage
Commercial
System**
Commercial
System
Commercial
System
Commercial
System** Prototype Prototype
Commercial
System
65 **Currently not approved for clinical use in the U.S. by the Food and Drug Administration (FDA)
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(really) Filtered Back Projection
66
Hfilter (ωy, ωz) = Hspectrum(ωy) ⋅ Hprofile(ωz) ⋅ Hinverse(ωy, ωz)
Hspectrum(ωy): Hanning filter to control noise
Hinverse(ωy, ωz): Ramp-type filter
Hprofile(ωz): Slice profile filter for constant depth resolution
Mertelmeier et al, SPIE 6142, 61420F (2006)
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67 Mertelmeier et al, SPIE 6142, 61420F (2006)
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68 Mertelmeier et al, SPIE 6142, 61420F (2006)
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69 Zhou et al, Medical Physics, Vol. 34, No. 3, March 2007
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70 Zhou et al, Medical Physics, Vol. 34, No. 3, March 2007
FBP w/ramp only + Hanning & thickness filter + Hanning & thickness filter 2
+ modified ramp SBP Iterative
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Iterative Reconstruction Methods
71
Guess the reconstructed
volume
Simulate the projections that would result from the guessed volume
N=N0e-ΣµT
Simulated projections of
guessed volume
Acquired projections
Compare
Adjust guess
1
i
v vp p
pi i
v v
vp
p
l E Y
l R E
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Other Reconstruction Methods
SIRT
SART
ART
MLEM
TVR
72
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73 Van de Sompel et al, Medical Image Analysis 2011, 15, 53–70
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Comparison of Reconstructions
Optimal acquisition might differ for different recons
Challenging for a single group to implement and optimize all recons
Most appropriate metric(s)?
74
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Tomosynthesis Reconstruction
Mono-energetic Assumption Or constant spectral beam
No explicit definition
Same case with CT reconstruction algorithms
75
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Standard Tomosynthesis Spectrum
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0 5 10 15 20 25 30 35 40
Lin
ear
Att
en
uat
ion
Co
eff
icie
nt
(cm
-1)
No
rmal
ize
d S
pe
ctru
m
X-Ray Energy (keV)
W/Al 32 kVp
W/Al 32 kVp + 6 cm of breast tissue
µ Breast Tissue (cm^-1)
µ = 21.7 keV
µ = 25.2 keV
76
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Breast Tomosynthesis Acquisition Model
biθ acquired signal at pixel i for projection θ
ψ(ε) incident energy fluence at energy ε
µ(x,ε) linear attenuation coefficient of voxel x at energy ε
L θ,i line from source to pixel i for projection θ
,
,
L i
x dl
ib e d
77
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Breast Tomosynthesis Acquisition Model
Minimize Poisson likelihood :
Using iterative gradient descent optimization method
arg min
log
MLE
i i i
L
L b b b
X X
X
78 Sechopoulos et al, European Congress of Radiology, 2013
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Homogeneous Phantom + Masses
79
0% 80%
60% 40% 20%
100%
0% 80%
60% 40% 20%
100%
0% 80%
60% 40% 20%
100%
FBP MLEM Spectral
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Homogeneous Phantom + Masses
80
-2
0
2
4
6
8
10
12
14
0 20 40 60 80 100
SDN
R
Lesion Glandular Density (%)
Spectral
MLEM
FBP
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Homogeneous Phantom + Microcalcifications
81
FBP Spectral
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Homogeneous Phantom + Microcalcifications
82
FBP Spectral
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RADIATION DOSE
83
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Breast Tomosynthesis Dosimetry Model
• Mammography:
• Tomosynthesis:
84
MAMMO g MAMMOAGD D N AK
MAX
MIN
TOMO g MAMMO
RGD
AGD D N AKN
AAPM Task Group Report 234
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Projection Angle (deg)
-30 -20 -10 0 10 20 30
RG
D(
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1%
25%
50%
75%
100%
Projection Angle (deg)
-30 -20 -10 0 10 20 30
RG
D(
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Mo/Mo 25 kVp
Mo/Mo 27 kVp
Mo/Rh 29 kVp
Rh/Rh 31 kVp
Rh/Rh 35 kVp(a) (b)
Projection Angle (deg)
-30 -20 -10 0 10 20 30
RG
D(
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
7 cm
10 cm
13 cm
16 cm
19 cm
Projection Angle (deg)
-30 -20 -10 0 10 20 30
RG
D(
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
2 cm
3 cm
4 cm
5 cm
6 cm
7 cm
8 cm(c) (d)
(a) Glandular fraction (d) X-ray spectrum
(c) Chest wall to nipple distance
(b) Thickness
Relative Glandular Dose
85 Sechopoulos et al, Med Phys, 2007; 3(1): 221-232
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Mammography and Tomosynthesis Dose
86 Feng and Sechopoulos, Radiology, 2012, 263(1): 35-42
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AGD Ratio of Tomo / Mammo
Breast Thickness
(cm)
Glandular Density (%)
1 14.3 25 50 2 2.47 2.34 1.87 1.78 3 2.40 1.94 1.49 1.39 4 2.66 2.11 1.84 1.28 5 2.37 1.90 1.53 1.08 6 1.91 1.83 1.94 1.25 7 2.26 1.75 1.38 1.12 8 2.13 1.85 1.46 1.16
87 Feng and Sechopoulos, Radiology, 2012, 263(1): 35-42
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Mean AGD [mGy] GE SenoClaire Essential
Breast Thickness N Mammo Tomo
All 236 1.62 1.49
<40 mm 28 1.13 1.14
41-50 mm 46 1.34 1.33
51-60 mm 74 1.48 1.41
61-70 mm 55 1.82 1.62
>70 mm 33 2.39 1.98
88 Paulis et al, Investigative Radiology, online ahead of print
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Chest Imaging Effective Dose [mSv]
2-View CXR Chest Tomo Chest CT
0.056 0.124 7
89 Sabol, Medical Physics, Vol. 36, No. 12, 2009
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90 Detector
X-ray beam
x mAs
x mAs x mAs x mAs
x mAs
Does the exposure distribution have to be uniform?
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91 Detector
X-ray beam
x mAs
x mAs y mAs x mAs
x mAs
How about:
y < x ? y > x ?
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92 Detector
X-ray beam
x mAs x mAs
y mAs x mAs
x mAs
Or even:
y < x ? y > x ?
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93 Nishikawa, Reiser et al, Proceedings of SPIE 6510, 65103C–65108C (2007).
Mammo Tomo Proposal
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μCa detectability: center projection < single center slice of reconstruction
Mass detectability: no statistically significant difference
94 Das et al, Medical Physics 2009, 36(6), 2009
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95
Standard Tomo Variable 7 central / 18 total proj
Variable 5 central / 20 total proj
Hu and Zhao, Med. Phys. 38(5), 2455–2466 (2011).
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Uneven distribution of exposure and non-uniform angular sampling used by one commercial manufacturer in systems outside the US.
96
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What if??
Improved image quality?
Dose reduction?
Single-pass contrast enhanced imaging?
97
x kVp
y kVp x kVp y kVp
x kVp
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Dual Spectrum Single Pass Tomo
98
AEC kVp
49 kVp + Cu AEC kVp 49 kVp + Cu
AEC kVp
Sechopoulos et al, European Congress of Radiology, 2015
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8 cm Homogeneous Phantom + Masses
AEC (38 kVp, 84 mAs) AEC + 49 kVp/0.254 mm Cu
99 Sechopoulos et al, European Congress of Radiology, 2015
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100
p = 0.412826
Sechopoulos et al, European Congress of Radiology, 2015
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101
p = 0.232631
Sechopoulos et al, European Congress of Radiology, 2015
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Results
Thickness SDNR Difference Dose
5 cm -16.0 ± 9.25% (p>0.08)
-48%
8 cm -3.2 ± 19.9% (p>0.41)
-28%
102 Sechopoulos et al, European Congress of Radiology, 2015
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X-RAY SCATTER
103
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Effect of Scatter in Tomosynthesis
104 Wu et al, Proc SPIE, 2007
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Linear Grid
Cellular Grid
Radio-transparent
Material
Radio-opaque Material
Radio-opaque Material
Air
Incident x-rays
Imaged object
Scattered x-rays
Scatter grid
Primary-only x-rays
Detector
How is Scatter Normally Dealt With?
105
A clinical grid transmits ~80% of primary and ~20% of scatter x-rays
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Grids in Tomosynthesis
Cut-off at higher projection angles
Primary photon absorption
Prone to image artifacts
106
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GE SenoClaire Essential
Uses anti-scatter grid for DBT acquisition
Septa perpendicular to standard position
High number of lines per unit length
107
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Alternatives
Post-acquisition processing
Correction during reconstruction
108
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TOMOSYNTHESIS ARTIFACTS
109
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110 Wu et al, Medical Physics. 33(7), 2461–2471 (2006).
High contrast off-plane objects introduce artifacts “Voting” strategy to identify projections in which appropriate information is included, others ignored Especially important for acquisitions with low number of projections
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111 Zhang et al, Med. Phys. 34(9), 3603–3613 (2007)
“Mask” to reconstruct only inside the breast Faster reconstruction Avoids artifacts outside breast
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112
Breast tissue outside wide projection FOV
Breast tissue outside reconstructed volume
but that contributes to attenuation
Reconstructed volume
Sechopoulos, Medical Physics, Vol. 40, No. 1, 2013
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113 Zhang et al, J. Comput. Assist. Tomogr. 33(3), 426–435 (2009).
Varying number of projections contributes to the volume update, introducing discontinuities: introduced equalization using neighbor values updated by previous projection Bright artifact due to tissue attenuation outside volume: assume extension of “average” breast tissue outside of field of view to avoid bright artifact
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114
Uncorrected Previous Improved
Lu et al, Proceedings of the 11th IWDM 2012, pp. 745–752.
Improved estimation of x-ray path length in tissue outside field of view
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SYNTHETIC MAMMOGRAMS
115
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116
Mammogram Orig. Synthetic Tomo Slice
Gur et al, Academic Radiology, Vol 19, No 2, 2012
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Recall Rates
117
DBT + FFDM DBT + Synthetic
False Positive
Rate
% Detected Cancers
False Positive
Rate
% Detected Cancers
1st Generation 53.1 83.5 46.1 77.7
2nd Generation 45.6 87.3 45.2 85.5
Skaane et al, Radiology, Vol 271(3), 2014
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Synthetic Mammograms
Included in various commercial systems
118
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Current Research
CADe and CADx for tomosynthesis
Need to lower reading time
Contrast enhanced tomosynthesis
Phase contrast tomosynthesis
Tomosynthesis elastography
119
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Multimodality Imaging
Tomosynthesis
+ US
+ SPECT
+ Electrical Impedance
+ Optical
120
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Summary
Fast digital detectors Advanced imaging
Need to lower anatomic noise
Tomosynthesis similar to planar radiography
System footprint
Workflow
Image interpretation
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Summary
Acquisition geometry large impact on image quality
Dosimetry > but similar to planar radiography
Ongoing research in:
Reconstruction algorithms
Other techniques (enhanced, phase, etc.)
Multimodality
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QUESTIONS
123
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In terms of image acquisition, what is the main difference between linear tomography and digital tomosynthesis?
1. Linear tomography acquisition takes substantially longer than digital tomosynthesis.
2. Linear tomography results in a single plane being in focus per acquisition while in digital tomosynthesis any number of planes can be reconstructed to be in focus.
3. Linear tomography results in circular images while digital tomosynthesis results in rectangular images.
4. In linear tomography the x-ray tube moves in a straight line while in digital tomosynthesis it moves in a circle.
1. 2. 3. 4.
0%
13%13%
75%
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In terms of image acquisition, what is the main difference between linear tomography and
digital tomosynthesis?
(2) In linear tomography, the in-focus plane has to be selected before acquisition, while in digital tomosynthesis, the reconstruction of the acquired projections results in many planes being in focus.
125
Bushberg et al, “The Essential Physics of Medical Imaging”, 3rd Edition
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How does increasing the angular range of the tomosynthesis scan affect the vertical resolution of the
reconstructed image?
1. Consistently decreases
2. Decreases up to a point, then remains constant
3. Vertical resolution does not increase with increasing angular range
4. Increases up to a point, then remains constant
5. Consistently increases 1. 2. 3. 4. 5.
50% 50%
0%0%0%
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How does increasing the angular range of the tomosynthesis scan affect the vertical resolution
of the reconstructed image?
(5) Increasing the angular range covered by the swing of the x-ray source consistently increases the vertical resolution of the reconstructed tomosynthesis image.
127 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199-1207.
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How does increasing the number of projections of the tomosynthesis scan affect the vertical resolution of the
reconstructed image?
1. Consistently decreases
2. Decreases up to a point, then remains constant
3. Vertical resolution does not increase with increasing number of projections
4. Increases up to a point, then remains constant
5. Consistently increases 10
1. 2. 3. 4. 5.
0% 0% 0%0%0%
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How does increasing the number of projections of the tomosynthesis scan affect the vertical
resolution of the reconstructed image?
(4) Increasing the number of projections during a tomosynthesis acquisition increases the vertical resolution up to a certain threshold, beyond which the resolution remains constant unless the angular range is increased.
129 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199-1207.
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Why is there a high interest in chest tomosynthesis?
10
0%
0%
0%
0%
0% 1. Much lower dose than chest radiography with out-of-plane blurring
2. Much lower dose than chest CT with out-of-plane blurring
3. Same vertical resolution as chest CT but lower dose
4. Improved vertical resolution as chest CT at same dose
5. Same vertical resolution and dose as chest CT, but considerably cheaper
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Why is there a high interest in chest tomosynthesis?
(2) Chest tomosynthesis involves, in general, higher dose than chest radiography, but considerably lower than chest CT. Although it doesn’t result in true tomographic images as chest CT, it provides enough vertical resolution to be superior to chest radiography and sufficient for some clinical applications.
131
Sabol, Medical Physics, Vol. 36, No. 12, 2009 Dobbins and McAdams, European Journal of Radiology 72 (2009) 244–251
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Introduction to Tomosynthesis
Ioannis Sechopoulos, Ph.D., DABR Diagnostic Medical Physics Laboratory
Department of Radiology and Imaging Sciences & Winship Cancer Institute
Emory University Atlanta, Georgia