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9/6/2017
1
Dosimetría en imagenologíade la mamaIoannis Sechopoulos, PhD, DABRAssociate ProfessorAdvanced X‐Ray Tomographic Imaging (AXTI) LaboratoryDepartment of Radiology and Nuclear MedicineRadboud University Medical CenterandDutch Reference Center for Screening (LRCB)Nijmegen the Netherlands
Tx T advancedx-raytomographicimagingx
Nijmegen, the Netherlands
OutlineMotivationMotivationCurrent dosimetry modelTomo vs. mammo doseLimitationsLimitations
Tx
LimitationsLimitations Future dosimetry
Why studyWhy study dosimetry in breast imaging?
Tx
breast imaging?
Tx
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Average Glandular Dose
Energy deposited by x‐rays in glandular tissueMass of glandular tissue
Tx
What can we measure?
Tx
Average Glandular Dose
D Ai K (K) *D = Air Kerma (K) * g c s
Obtained with M t C l
Tx
Monte Carlo simulations
Monte Carlo SimulationsX‐Ray Source Emitted
X RayX‐Ray
Adipose Tissue
s At
tenu
atio
n C
oeffi
cien
t (cm
2 /g)
10-1
100
101
102
103
104
Photoelectric EffectCompton ScatterRayleigh Scatter
Compton Scatter
4e+0
6e+0
8e+0
30
60
90
120
150
Tx
Repeat 1 million times!
X-Ray Energy (keV)
0 20 40 60 80 100
Mas
s
10-3
10-2
0 2e+0 4e+0 6e+0 8e+00
2e+0
02e+04e+06e+08e+00
2e+0
4e+0
6e+0
8e+0
0180
210
240
270
300
330
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Need to define the breast model
Breasts vary in shape
Tx
Breast Shape ‐ CC View
Tx
Standard Breast Shape ‐ CC View
Tx
Boone, Med Phys, 2002; 29(5): 869‐875Dance, PMB, 1980; 25(1): 25‐37
Wu et al, Radiology, 1991; 179: 143‐148
Breast Shape – MLO View
Tx
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Standard Breast Shape ‐MLO View
1.9 * CN
DCND
Tx Sechopoulos et al, Med Phys, 2007; 3(1): 221‐232Sechopoulos et al, JACMP, 2008; 9(4): 161‐171
Glandular Tissue Varies
Tx
Dose variation with vertical positionDose variation with vertical position of glandular tissue:
68‐84%
Tx Boone JM, Radiology, Response to eLetter, 25 October 2000 TxHammerstein et al, Radiology, 1979; 130, 485–491.
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Standard Breast Model ‐ CC View
Tx Dance, PMB, 1990; 35(9): 1211‐1219
Conversion factors ‐ g
Tx Dance (1990 and 2000)
Glandular Density90
100
30
40
50
60
70
80
90
Gla
ndul
arity
(%)
Tx
0
10
20
10 20 30 40 50 60 70 80 90 100 110 120
Compressed breast thickness (mm)
40-4950-64
Dance, PMB, 2000, Vol 45, 3225.
Conversion factors ‐ c
Tx Dance (1990 and 2000)
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Conversion factors ‐ s
Tx Dance (1990 and 2000)
Mammography:g p y
Tomosynthesis:
MAMMOD Kgcs
Tx
TOMOD Kgcst
Tx Sechopoulos et al, Med Phys, 2007; 3(1): 221‐232 Tx Sechopoulos et al, Med Phys, 2007; 3(1): 221‐232
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Tx Sechopoulos et al, Med Phys, 2007; 3(1): 221‐232 Tx Sechopoulos et al, Med Phys, 2007; 3(1): 221‐232
Conversion factors ‐ t
Tx Dance (2011)
Conversion factors ‐ T
Tx Dance (2011)
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Different model in the USA
Tx Wu et al, Radiology, 1991; 179, 143‐148.
….for both viewsThickness Spectrum MLO View CC View
Glandularity (%) Glandularity (%)1 25 50 75 100 1 25 50 75 100
2 Mo/Mo 25 2.33 2.19 2.05 1.92 1.80 2.59 2.43 2.28 2.13 2.00Mo/Mo 26 2.44 2.29 2.14 2.01 1.89 2.70 2.54 2.38 2.23 2.09Mo/Mo 27 2.53 2.38 2.23 2.10 1.97 2.81 2.64 2.48 2.33 2.18Mo/Rh 27 3.03 2.86 2.69 2.54 2.40 3.34 3.16 2.98 2.81 2.65Mo/Rh 29 3.19 3.02 2.85 2.69 2.54 3.52 3.34 3.15 2.97 2.81Rh/Rh 29 3.24 3.07 2.91 2.76 2.61 3.57 3.39 3.21 3.04 2.88
(cm)p
(Target/Filter/kVp) Glandularity (%) Glandularity (%)
Tx Sechopoulos et al, Med Phys, 2007; 3(1): 221‐232
Rh/Rh 31 3.45 3.28 3.11 2.95 2.80 3.79 3.61 3.42 3.25 3.09Rh/Rh 33 3.62 3.45 3.28 3.12 2.97 3.98 3.80 3.61 3.43 3.27Rh/Rh 35 3.78 3.60 3.43 3.26 3.11 4.15 3.96 3.77 3.59 3.42
3 Mo/Mo 25 1.81 1.65 1.50 1.37 1.25 2.01 1.83 1.66 1.51 1.38Mo/Mo 26 1.90 1.73 1.58 1.44 1.32 2.11 1.92 1.75 1.59 1.46
Tx AAPM TG 223 Report, Med Phys, 2014; 41(9): 091501
Philips MicroDose – Slot Scan
Tx AAPM TG 223 Report, Med Phys, 2014; 41(9): 091501
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Conversion factors ‐ TS
Tx Dance (2011)
Average Glandular Dose
D Ai K (K) * tD = Air Kerma (K) * g c s t
Obtained with M t C l
Tx
Monte Carlo simulations
PhantomPhantom (Prospective)Dosimetry
Tx
y
Cheap phantoms
Tx Feng and Sechopoulos, Radiology, 2012, 263(1): 35‐42
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Dose vs. Breast Thickness
Tx Feng and Sechopoulos, Radiology, 2012, 263(1): 35‐42
MammographyMean Glandular Dose (mGy)Breast Thickness 14 3% Density 50% DensityBreast Thickness
(cm)14.3% Density 50% Density
2 0.313 0.3765 0.775 1.208 1.66 2.28
Tx Feng and Sechopoulos, Radiology, 2012, 263(1): 35‐42
TomosynthesisMean Glandular Dose (mGy)Breast Thickness 14 3% Density 50% DensityBreast Thickness
(cm)14.3% Density 50% Density
2 0.735 0.6705 1.48 1.308 3.07 2.64
Tx Feng and Sechopoulos, Radiology, 2012, 263(1): 35‐42
Tomosynthesis / MammoMGD RatioBreast Thickness 14 3% Density 50% DensityBreast Thickness
(cm)14.3% Density 50% Density
2 2.34 1.785 1.90 1.088 1.85 1.16
Tx Feng and Sechopoulos, Radiology, 2012, 263(1): 35‐42
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PMMA
Tx EUREF Guidelines, 4th edition
PMMA to model breast conversionPMMA thickness
(mm)Equivalent breast thickness (mm)
Glandularity of equivalent breast (%)
20 21 97
30 32 67
40 45 41
45 53 29
50 60 20
Tx
50 60 20
60 75 9
70 90 4
80 103 3
EUREF Guidelines, 4th edition
Air Kerma
Tx EUREF Guidelines, 4th edition
Apply the conversion…Mammography:Mammography:
Tomosynthesis:
MAMMOD Kgcs
D K t
Tx
TOMOD Kgcst
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Tx EUREF Guidelines, 4th edition Tx
PatientPatient (Retrospective)Dosimetry
Tx
os et y
DICOM Header
Tx
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System I Ratio DBT/DM:Mean = 1.08 (0.54 – 1.81)
Tx Bouwman et al, Phys. Med. Biol. 60 (2015) 7893Hendrick et al, AJR. 194 (2010) 362
System I Ratio DBT/DM:Mean = 1.08 (0.54 – 1.81)
Tx Bouwman et al, Phys. Med. Biol. 60 (2015) 7893
System II (DBT CC only)7
8
clinical DM
Ratio DBT / DM:Mean = 1.62 (unpaired)
2
3
4
5
6
AGD (m
Gy)
clinical DM
clinical DBT
Tx Bouwman et al, Phys. Med. Biol. 60 (2015) 7893Hendrick et al, AJR. 194 (2010) 362
0
1
0 20 40 60 80 100Breast thickness (mm)
System IV Ratio DBT‐ST / DM:Mean = 1.48 (unpaired)
Tx Bouwman et al, Phys. Med. Biol. 60 (2015) 7893Hendrick et al, AJR. 194 (2010) 362
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System V Ratio DBT / DM:Mean = 0.90 (!) (unpaired)
Tx Bouwman et al, Phys. Med. Biol. 60 (2015) 7893Hendrick et al, AJR. 194 (2010) 362
Mean AGD [mGy]GE SenoClaire EssentialBreast Thickness N Mammo Tomo
All 236 1.62 1.49<40 mm 28 1.13 1.1441‐50 mm 46 1.34 1.3351‐60 mm 74 1.48 1.4161‐70 mm 55 1.82 1.62>70 mm 33 2.39 1.98
Tx 58Paulis et al, Investigative Radiology, online ahead of print
Are these final?
Tx
System III Ratio DBT / DM:Mean = 2.00 (!)
Tx
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System III Ratio DBT / DM:Mean = 2.00 (!)
Tx
After software upgrade…
Tx
System III Ratio DBT / DM:Mean = 1.90 (1.51 – 2.74)
Tx
System III Ratio DBT / DM:Mean = 1.90 (1.51 – 2.74)
Tx
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AEC settings…
Tx
In addition…
Tx
What is a tomo exam?
Tx
Ratios Dose DBT/DM from Clinical Studies
1‐view DBT vs DM = 0.34 – 1.02‐view DBT vs DM = 0.68 – 1.17
1‐view DBT + DM vs DM = 1.03 – 1.50
Tx
2‐view DBT + DM vs DM = 2.0 – 2.23
Svahn et al, The Breast, 24 (2015) 93‐99
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Synthetic (?)
1‐view DBT vs DM = 0.34 – 1.02‐view DBT vs DM = 0.68 – 1.17
Tx Svahn et al, The Breast, 24 (2015) 93‐99
DBT implementation is still in flux
Tx
DBT + DM ≥ 2*dose of DMDBT + DM ≥ 2*dose of DM(minus reduced recalls!)
Tx
1 DBT alone co ld1v DBT alone could be lower dose
Tx
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Developing Technology
Tx
X i f DBTX‐views of DBT + Y‐views of DM
Tx
S th tiSynthetic
Tx
Ratios Dose DBT/DM from Clinical Studies
1‐view DBT (+ Synth) vs DM = 0.34 – 1.02‐view DBT (+ Synth) vs DM = 0.68 – 1.17
1‐view DBT + DM vs DM = 1.03 – 1.502 i DBT DM DM 2 0 2 23
Tx
2‐view DBT + DM vs DM = 2.0 – 2.23
Svahn et al, The Breast, 24 (2015) 93‐99
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Tx
Let’s be happy, dose is/will be low!
Tx
Wait, that’s not it…
Let’s celebrate for the correct reason!
Tx Tx
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Breast density???Breast density???
Tx
Low dose is easyLow dose is easy…
Tx
Phantom Patients?
Tx
Patient to phantom MGD ratio
Tx Bouwman et al, PMB, 60 (2015) 7893
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Not good enough anymore…
Tx Bouwman et al, PMB, 60 (2015) 7893
bCan we be more objective?
Tx
Tx
Standard Breast Shape ‐ CC View
Tx
Boone, Med Phys, 2002; 29(5): 869‐875Dance, PMB, 1980; 25(1): 25‐37
Wu et al, Radiology, 1991; 179: 143‐148
9/6/2017
24
Standard Breast Shape ‐MLO View
1.9 * CN
DCND
Tx Sechopoulos et al, Med Phys, 2007; 3(1): 221‐232Sechopoulos et al, JACMP, 2008; 9(4): 161‐171 Tx Rodriguez‐Ruiz et al, Medical Physics, in press
Examples…
Tx Rodriguez‐Ruiz et al, Medical Physics, in press
Principal Component Analysis
Tx
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Average distance error
Tx Rodriguez‐Ruiz et al, Medical Physics, in press
191 ‐> 210 cm2
144 ‐> 155 cm2
Boone 2000: 157 cm2
Tx Rodriguez‐Ruiz et al, Medical Physics, in press
Tx Rodriguez‐Ruiz et al, Medical Physics, in press Tx Rodriguez‐Ruiz et al, Medical Physics, in press
9/6/2017
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Tx Rodriguez‐Ruiz et al, Medical Physics, in press
How about the 3rd dimension?
Can we
Tx
Can we characterize this?
Acquisition of 3‐D breast shapeCompression
Projector
Camera3‐D scanner
Compression paddle
Tx
Support paddle
Agasthya et al, AAPM 2015
3‐D scanner
Tx Agasthya et al, AAPM 2015
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Tx http://www.david‐3d.com/?section=Gallery Tx Agasthya et al, AAPM 2015
Tx Rodriguez‐Ruiz et al, Radiology, under review Tx Rodriguez‐Ruiz et al, Radiology, under review
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Tx Rodriguez‐Ruiz et al, Radiology, under review Tx Rodriguez‐Ruiz et al, Radiology, under review
Tx Rodriguez‐Ruiz et al, Radiology, under review
3D Model
Tx Rodriguez‐Ruiz et al, Radiology, under review
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3D Model
Tx
Principal component analysis again
Rodriguez‐Ruiz et al, Radiology, under review Tx Rodriguez‐Ruiz et al, Radiology, under review
Tx Rodriguez‐Ruiz et al, Radiology, under review
Breast model
Tx Rodriguez‐Ruiz et al, Radiology, under review
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How about the interior?
Tx
Glandular Density
90
100
30
40
50
60
70
80
90
Gla
ndul
arity
(%)
Tx
0
10
20
10 20 30 40 50 60 70 80 90 100 110 120
Compressed breast thickness (mm)
40-49
50-64
Dance, PMB, 2000, Vol 45, 3225.
Glandular Density
= 14.3 %
Tx Yaffe et al, Med Phys, 2009, Vol 36, 5437
Skin Thickness
= 1.45 mm
Tx Huang et al, Med Phys, 2008, Vol 35, 1199
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The (near) future in breast dosimetry…
Tx
Improved Dosimetry Model
Universal (!)Universal (!)MammographyTomosynthesisContrast enhanced mammo
Tx
Improved Dosimetry Model
CC and MLO viewsCC and MLO viewsSpot and magnification views
Tx
Improved Dosimetry Model
QA/QC – Phantom dosimetryQA/QC Phantom dosimetryPatient model dosimetry
Tx
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Improved Dosimetry ModelAppropriate phantom for AECAppropriate phantom for AECMore accurate breast model No biasSoftware (!)
Tx
Joint AAPM/EFOMP Task
But what do absolute values of AGD mean?
Tx
TxHammerstein et al, Radiology, 1979; 130, 485–491.
Tx
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So…“detailed information will have to be obtained on the amount and distribution of gland tissue in many individual cases” before individual risk estimates can be made.
Hammerstein et al, Radiology, 1979
Tx
Homogeneous breast dose modelGood for relative comparisons of doseTechnique optimizationSystem comparisonModality comparison (?)Quality control
Tx
But of course…A. Berrington de Gonzalez and G. Reeves, “Mammographic screening before age 50 years in the UK: Comparison of the radiation risks with be o e age 50 yea s t e U Co pa so o t e ad at o s s tthe mortality benefits,” Br. J. Cancer 93, 590–596 (2005).A. Berrington de Gonzalez, C. D. Berg, K. Visvanathan, and M. Robson, “Estimated risk of radiation‐induced breast cancer from mammographic screening for young BRCA mutation carriers,” J. Natl. Cancer Inst. 101, 205–209 (2009).R. E. Hendrick, “Radiation doses and cancer risks from breast imaging studies,” Radiology 257, 246–253 (2010).
Tx
M. J. Yaffe and J. G. Mainprize, “Risk of radiation‐induced breast cancer from mammographic screening,” Radiology 258, 98–105 (2011).E. Warner, “Breast‐cancer screening,” N. Engl. J. Med. 365, 1025–1032 (2011).
Tx
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What is the error introduced by the homogeneous tissue approximation in breast
Tx
approximation in breast dosimetry?
Heterogeneous Mammography DgN
Heterogeneous BCT DgN
Patient BCT Tissue Simulated
Monte Carlo Simulation Monte Carlo
Simulation
HomogenizationHomogenization
Imaging Classification Compression
Tx
Homogeneous Mammography
DgNHomogeneous BCT DgN
Monte Carlo Simulation
Monte Carlo Simulation
19 patients
Breast CT
300 projections300 projections10 seconds49 kVp, 16 – 200 mA8 ms0.273 mm voxel size20 patients
Tx
p
Courtesy of Koning Corp.
Automated Tissue Classification
Tx Yang et al, Medical Physics, 2012, 39(10), 6397‐6406.
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Breast CT image
Manual
Automated
Manual
TxDifference
Accuracy of Classification1
0.84
0.88
0.92
0.96
Percen
tage
Gland
Fat
Skin
Tx
0.81 2 3 4 5 6 7 8
Subject
34.4% 12.5% 8.5% 10.7% 11.1% 6.4% 8.9% 31.6%Gland tissue
Mechanical Breast Compression
Tx Zyganitidis et al, Med. Biol. Eng. Comput. 2007, 45, 661‐669.
Monte Carlo simulations
Tx
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mG
y)
0.3
0.4(a) Mammography
ogen
eous
DgN
(mG
y/m
0.1
0.2
TxHeterogeneous DgN (mGy / mGy)
0.0 0.1 0.2 0.3 0.4
Hom
o
0.0
Sechopoulos et al, Medical Physics, 2012, 39(8), 5050‐5059
gene
ous
DgN
1.8
2.0
2.290th percentile
75th percentilemean
median25th percentile
neou
s D
gN /
Het
erog
1.2
1.4
1.610th percentile
Tx
Mammography BCT 49 kVp BCT 80 kVp
Hom
ogen
0.8
1.0
Sechopoulos et al, Medical Physics, 2012, 39(8), 5050‐5059
Model‐based Confirmation (N=219)
Mo anode: −35.3% (SD = 4.1)W anode: −24.2% (SD = 3.0)
Tx Hernandez et al, Medical Physics, 2015, 42(11), 6337
10.3
Tx0.0
Sechopoulos et al, Medical Physics, 2012, 39(8), 5050‐5059
9/6/2017
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Internal Dose Distribution ‐Mammo
Tx Sechopoulos et al, Medical Physics, 2010; 37(8), 4110.
Internal Dose Distribution ‐ BCT
Tx Sechopoulos et al, Medical Physics, 2010; 37(8), 4110.
Tx
Homogeneous tissue gmixture approximation good enough for QA/QC.
Tx
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Patient‐Specific Breast Dosimetry
Tx
Patient‐Specific Breast Dosimetry
Need a tomosynthesis image classification algorithm
Tx
Representative Classification ‐ Fuji
Tx
Tomography ClassificationGold Standard
Representative Classification ‐ Phillips
Tx
Tomography ClassificationGold Standard
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Classification Validation – Physical phantoms
0 9
1.0 Philips Data Set (n=10)
Fuji Data Set (n=11)
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Performance
Fuji Data Set (n 11)
Siemens Data (n=10)
Tx
0.0
0.1
0.2
DSC Sensitivity Specificity
Evaluations for Glandular Tissue
Patient‐Specific Breast Dosimetry
Tx
Patient‐Specific Breast Dosimetry
Tx
Patient‐Specific Breast Dosimetry
4 j4‐year project funded by the Susan G. Komen Foundation for
Tx
the Cure
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In short…
Tx
Patient dose DBTPatient dose DBT~ 0.9 – 1.8 * DM
Tx
DBT + DM > 2*dose of DMDBT + DM > 2*dose of DM
(minus reduced work‐up dose!)
Tx
But…
Tx
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D l i t h lDeveloping technology
Tx
S th tiSynthetic
Tx
X i DBTX‐view DBT + Y‐view DM
Tx
Current breast dosimetryCurrent breast dosimetry has limitations
Tx
(the future one will too!)