x imaging T advancedx-ray tomographic xTmedica.fisica.edu.uy/docs/IS/Day 2 Mammo and tomo.pdf ·...

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9/5/2017

Fundamentos físicos de la mamografía y tomosintesisIoannis 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 BREAST CANCER IMAGING

BREAST CANCER IMAGING

MicrocalcificationsMasses Architectural Dist.

Tx 3 Courtesy of Dr. Carl J. D’Orsi

Clinical Application ‐ Screening

ScreeningScreening

Diagnostic work‐up

Biopsy

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Clinical Application ‐ Concern

Di iDiagnostic work‐up

Biopsy

Mammographic Screening ViewsCranio Caudal (CC) view Medio‐Lateral Oblique (MLO) view

Mammographic Work‐up ViewsMagnificationMagnificationSpot compressionRollsLateral (90°)

Ultrasound

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BI‐RADS® ‐ Breast Imaging Reporting and Data System

gnostic

work‐up

Diag THE MAMMOGRAPHY SYSTEM

THE MAMMOGRAPHY SYSTEM

A typical mammography system

Tx © Bushberg, Seibert, Leidholdt and Boone

A typical mammography system

Tx 12 Courtesy GE Medical Systems

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Why a dedicated machine?

MAMMOGRAPHY SPECTRA

What is needed for lower energy?

Lower tube voltage (kVp)Lower tube voltage (kVp)Different target material?Higher tube current‐exposure time product (mAs) (why?)

Higher quantum efficiency (why?)

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Optimal energies

Monochromatic energy between 15 and 25 keV.

Drawbacks of using low energy

Low energy Higher doseLow energy Higher dose

Low energy Longer exposuresLow energy Longer exposures

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Molybdenum

Melting point: 2896 K

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Rhodium

Tx By Alchemist‐hp (talk) www.pse‐mendelejew.dederivative work: Purpy Pupple (talk) ‐ Own work, CC BY‐SA 3.0 de, https://commons.wikimedia.org/w/index.php?curid=7636785

Rhodium

Melting point: 2237 K

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Add filtration

Inherent tube filtration

Exit port:Exit port: ~0.8 mm Beryllium (Z=4)

No oil

Ideal choice for added filtration?Ideal choice for added filtration?

Mo and Rh Linear Attenuation Coefficients

Mo Characteristic Energies

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Mo and Rh FilteringMolybdenum Target Rhodium Target

0.030 mm (30 µm) is the thickness of Molybdenum filtration used.0.025 mm (25 µm) is the thickness of Rhodium filtration used.

Target‐Filter MixingRh filters can be used with Mo targets.

Target‐Filter MixingMo filters can NOT be used with Rh

targets!!targets!!

TungstenMore bremsstrahlung x‐raysMore bremsstrahlung x rays Z is higherLower exposure times

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TungstenNo characteristic emissionsNo characteristic emissionsRh, Al, Ag filters used to shape

W Spectra – Rh Filter

W Spectra – Al Filter

HALF VALUE LAYERS

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Half Value Layers

Increases:Increases: Z of target Z of filters T b lt

Tube voltage

Half Value Layers ‐ Examples

Mo/Mo 25 kVp: 0.322 mm AlRh/Rh 35 kVp: 0.509 mm AlW/Rh 35 kVp: 0.575 mm Al

Tissue HVLE.g. Tissue HVL of 1.5 cm:E.g. Tissue HVL of 1.5 cm:Only half the x‐rays make it through the first 1.5 cm of breast.

After a 6 cm breast (4 HVL), only ~6% of x‐rays exit the breast.

y FIELD GEOMETRY

FIELD GEOMETRY

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Why half‐field geometry?

Tx Yaffe et al, Radiology 1995.

Breast positioning and the heel effect

BREAST COMPRESSION

Why breast compression?Reduce:M tiMotionDoseSuperpositionGeometric unsharpnessX‐ray scatter.

Pull breast tissueIncrease exposure uniformity

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Scatter Reduction

Exposure uniformity

Spot compression

Spot compression confirms there is no mass…

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SPATIAL RESOLUTION

Why high resolution?

Tx Courtesy of Dr. Carl J. D’Orsi

What is needed for high resolution?Small focal spotSmall focal spotThin scintillating screensSmall pixels in digital detectorsFast acquisition

Two Focal Spots

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Anode Angle –Effective Focal Spot

Tx 57 © Bushberg, Seibert, Leidholdt and Boone

Scintillating Screen in Screen‐Film Mammography

Screen

…so in screen‐film mammography we use only one screen under the film.

Scintillating Screen in Digital Mammography X‐rays

Diffusing scintillations

CsI:Tl structured scintillator Detector

Microcolumnar CsI(Tl) film with a needle diameter of 3‐5 m.

Tx Courtesy of RMD Inc., Watertown, MA

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MTF Comparison

MTF Comparison79 µm (direct)

200 µm (indirect DR)

54 µm (scanning indirect)79 µm (direct)

100 µm (indirect)85 µm (direct)

µ ( )

Lazzari et al, Medical Physics, 2007.Granfors et al, Medical Physics, 2000.

X RAY SCATTER

X‐RAY SCATTER

X‐Ray Scatter in MammographyContrast is reduced by:Contrast is reduced by:

1CCSPR

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SPR as a function of compressed breast thickness and breast size

TxSPR doesn’t vary significantly with target/filter combination or tube voltage

Mammographic anti‐scatter grids

MAGNIFICATION VIEWS

What changes?0.1 mm focal spot

No scatter grid

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Why no anti‐scatter grid?

Focal Spot MTF Comparison

ARTIFACTS

Motion

Tx Ayyala R S et al. Radiographics 2008;28:1999-2008

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Antiperspirant

Ghosting

Collimator misalignment

Underexposure

Tx 76 Ayyala R S et al. Radiographics 2008;28:1999-2008

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Grid Artifact

Detector Line Artifacts

Tx http://www.upstate.edu/radiology/education/rsna/mammography/artifact/

Static

?So?Tx

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Dutch Screening Performance

Cancer Detection Rate0.68%

Tx NETB Monitor 2014

< 20 mm:61.2%

Recall Rate2.54%

Tx NETB Monitor 2014 Tx

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Negative Recalls2.6 per positive recall

Program Sensitivity74.9%

Cancers Missed1 out of 4

Cancer Detection vs. Density14% 22% 30% 39%

86% 78% 70% 61%

30% 39%

VDG 1 VDG 2 VDG 3 VDG 4Screening Interval

Wanders et al, Breast Cancer Res Treat (2016)

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29% of missed cancers were missed due towere missed due to being “obscured by overlying tissue”

Tx 89 Birdwell et al, Radiology 219, 192‐202 (2001).

We needWe need tomographic i i !

imaging!

DIGITAL TOMOSYNTHESIS

Translated X‐ray source

X‐ray beam

Detector

Lesions of Interest

This information is used to reconstruct the volume

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Recall

TxCourtesy of Hologic Inc.

Recall

TxCourtesy of Hologic Inc.

CC view .IDC

Tx 95Courtesy of Hologic Inc. Tx 96Courtesy of Hologic Inc.

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BenefitsSimilar to Radiography/Mammographyg p y/ g p ySystemWorkflowInterpretationDose

…but with some discrimination of vertical position!

FFDM System Breast Tomo System

TxCourtesy Joseph Lo (via youtube) Tx

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Tx280 slices 72 slices

slice 140/280 slice 36/72

slice 7/14 = 5.46 mm thick slice 36/72

SYSTEM DESIGN

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Translated X‐ray source

X‐ray beam

Tx 105

Detector

Tx 106 Otto Zhou, Applied Nanotechnology Laboratory, UNC at Chapel Hill

Tx 107 Courtesy of Philips Digital Mammography AB TxXcounter AB

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Tx 109 Zhang and Yu, Medical Physics, 2010, 37(8), 4186–4192

FURTHER DESIGN CONSIDERATIONS

Acquisition GeometryMammography:

h f1 position, 1 shot, fast

CT:full revolution, 1000 shots, as fast as

possible

Tomosynthesis:???

Design decisions…Detector TypeypDetector MotionX‐Ray Tube MotionCenter of RotationAngular Range Number of Projections

Number of ProjectionsScan TimeReconstruction Method

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SystemFuji

AMULET Innovality

GE EssentialHologicSelenia

Dimensions

IMS Giotto TOMO

Philips MicroDose

Planmed Nuance Excel

Siemens MAMMOMAT Inspiration

Detector Motion

Static Static Rotating StaticContinuous Slit

ScanRotating during

exposureStatic

X‐Ray Tube Motion

Continuous Step‐and‐Shoot Continuous Step‐and‐Shoot Continuous Continuous Continuous

Tx Tx Zhao and Zhao, Medical Physics, 35(5), 2008

Tx 115 http://2014.bhpa.eu/wp‐content/uploads/formidable/Marshall_Nicolas.pdf

Total Angular Range ‐ Oblique Incidence

(20 deg)(20 deg)

Tx Acciavatti and Maidment, Medical Physics, 38(11), 2011

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Oblique Incidence – Direct Detectors

Tx 117 Zhao and Zhao, Medical Physics, 35(5), 2008

Oblique Incidence – Indirect Detectors

Tx 118Mainprize et al, Medical Physics, 33(9), 2006

Oblique Incidence

Tx 119

Image Acquisition OptimizationAcquisition parameters:q p

Angular rangeNumber of projection anglesTube voltageTube current‐exposure time productSource to object distance (SOD)

Prior knowledge

Source to object distance (SOD)Source to imager distance (SID)

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A priori thoughts:

↑ angular range ↑ vertical resolution

↑ ver cal resolu on↑ # of projections ↓ exposure per proj

↑ # of projections ↓ exposure per proj.↑ scan me

121 Tx 122Maidment et al, Proceedings of SPIE, 5745, 2005

Artifact Spread Function

s 0 BG 0

I z -I zASF z =

I z -I z

Tx 123Wu et al, Medical Physics, 31(9), 2004 Tx 124 Hu et al, Medical Physics, 35(12), 2008

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Image Acquisition OptimizationComputer simulated breast volumeComputer simulated breast volume and lesions

63 different acquisition geometries

In‐plane quality and vertical resolution

125Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207. Tx

Realistic mammogramIdeal 0° projection

126 Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207.

0° tomosynthesis proj.Acquisition: 13 proj. over 60°

angular range.

0° tomosynthesis proj.Acquisition: 41 proj. over 60°

angular range.

Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207. Tx

Central reconstructed sliceAcquisition: 13 proj. over 60°

angular range.

Central reconstructed sliceAcquisition: 41 proj. over 60°

angular range.

Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207.

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Tx 129

(a) Mass

Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207. Tx 130Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207.

Tx 131Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207. Tx 132Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207.

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Tx 133

aSubstantial artifacts due to narrow angular range

Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207.

Summary Metric

Tx 134Sechopoulos and Ghetti, Medical Physics 2009, 36, 1199‐1207.

SystemFuji

AMULET Innovality

GE EssentialHologic Selenia

Dimensions

IMS Giotto TOMO

Philips MicroDose

Angular Range 15 25 15 40 11 30 50Number of Projections

15 9 15 13 21 15 25

Does the exposure distribution have to be uniform?

x mAs x mAs x mAs

X‐ray beam

Tx 137

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How about:x mAs

x mAs y mAs x mAs

X‐ray beam y < x ?

y > x ?

Tx 138

Or even:x mAs

x mAsy mAs

x mAsx mAs

X‐ray beam y < x ?

y > x ?

Tx 139

Mammo Tomo Proposal

Tx 140 Nishikawa, Reiser et al, Proceedings of SPIE 6510, 65103C–65108C (2007).

μCa detectability: center projection < single center slicecenter projection < single center slice

of reconstruction

Mass detectability: no statistically significant difference

no statistically significant difference

Das et al, Medical Physics 2009, 36(6), 2009

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IMS GiottoVariable dose and angles

Tx 142 http://www.tomosynthesis‐giotto.com/3/technical‐specifications

What if??Improved

lx kVp

y kVp x kVp y kVp

image quality?Dose reduction?Single‐pass

contrast enhanced imaging?

ACQUISITION TECHNIQUE

Tube Voltage SelectionMultiple studies reported higher kV than mammo optimal for tomo

One study reported lower energies beneficial

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)

One study reported lower energies beneficial

Glick and Gong, Proceedings of SPIE 6142, 61421L–61429L (2006).

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Technique and Dosimetric Characterization of a Clinical System

Tx 146

Feng and Sechopoulos, Radiology, 2012; 263(3): 35‐42

Breast

Thickness Filter

Voltage 1st HVL

(mm Al)Filter

Voltage

1st HVL

(mm Al)

Tomosynthesis Mammography

Rh 25 0.453

Rh 26 0.494

Rh 28 0.517

Rh 29 0.551

(kVp)Al)

Al 26 0.441

Al 28 0.476

Al 29 0.490

Al 31 0.541

Rh 31 0.567

Ag 30 0.586

Ag 32 0.611

Al 33 0.572

Al 35 0.600

Al 38 0.660

Feng and Sechopoulos, Radiology, 2012; 263(3): 35‐42

TOMOSYNTHESIS RECONSTRUCTION

SystemFuji

AMULET Innovality

GE EssentialHologic Selenia

Dimensions

IMS Giotto TOMO

Philips MicroDose

Reconstruction Method

Modified FBP

Iterative FBPIterative with Total Variation Regularization

Iterative Iterative FBP

Tx 149

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BACKPROJECTION

Projection Acquisition

1 1 1 1 1

1 1 10 1 1

1 1 1 1 1

1 1 10 1 1

1 1 1 1 1

5 5 14 5 5

1 1 1 1 1

1 1 10 1 1

1 1 1 1 1

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Projection Acquisition5 5 14 5 5

1 1 1 1 1

1 1 10 1 1

1 1 1 1 1

5 5 14 5 5

1 1 1 1 1

1 1 10 1 1

1 1 1 1 1

Backprojection

5 5 14 5 5

Backprojection

10 10 19 10 10

19 19 28 19 19

10 10 19 10 10

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Backprojection5 5 14 5 5

15 15 33 15 15

24 24 42 24 24

15 15 33 15 15

Backprojection

20 20 38 20 20

38 38 56 38 38

20 20 38 20 20

BackprojectionDividing all pixels by 4 to compute the average

5 5 9.5 5 5

9.5 9.5 14 9.5 9.5

5 5 9.5 5 5

Acquisition

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Backprojection

TxTomosynthesis

Backprojection

Tx 165

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FILTERED BACKPROJECTION

1/r Blurring

Filtered Backprojection

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(really) Filtered Back ProjectionHfilter (ωy, ωz) = Hspectrum(ωy) ⋅ Hprofile(ωz) ⋅ Hinverse(ωy, ωz)filter y z spectrum y profile z inverse y z

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)

Tx Mertelmeier et al, SPIE 6142, 61420F (2006) Tx 173Mertelmeier et al, SPIE 6142, 61420F (2006)

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Tx Zhou et al, Medical Physics, Vol. 34, No. 3, March 2007

FBP w/ramp only + Hanning & thickness filter + Hanning & thickness filter 2

Tx Zhou et al, Medical Physics, Vol. 34, No. 3, March 2007

+ modified ramp SBP Iterative

ITERATIVE RECONSTRUCTION

Guess the reconstructed

volumeAdjust guess

iv vp p

Simulate the projections that would result from the guessed volume

N=N0e‐ΣµTAcquired projections

Simulated projections of guessed volume

Compare

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Other Reconstruction MethodsSIRTSARTARTMLEM

178 Tx 179 Van de Sompel et al, Medical Image Analysis 2011, 15, 53–70

Comparison of ReconstructionsOptimal acquisition might differ forOptimal acquisition might differ for different recons

Challenging for a single group to implement and optimize all recons

implement and optimize all recons

Most appropriate metric(s)?

m‐1)

W/Al 32 kVp

W/Al 32 kVp + 6 cm of breast tissue

µ Breast Tissue (cm^‐1)µ = 25.2 keV

ar Atten

uation

fficient (cm

Normalized

µ = 21.7 keV

0 5 10 15 20 25 30 35 40

X‐Ray Energy (keV)

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Homogeneous Phantom + MassesFBP MLEM Spectral

0% 80%

60% 40% 20%

0% 80%

60% 40% 20%

0% 80%

60% 40% 20%

Tx 182

100% 100% 100%

Spectral

0 20 40 60 80 100

Lesion Glandular Density (%)

Homogeneous Phantom + Microcalcifications

FBP Spectral

Tx 184

Homogeneous Phantom + Microcalcifications

FBP Spectral

Tx 185

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Dual Spectrum Single Pass Tomo

AEC kVp

49 kVp + Cu AEC kVp 49 kVp + Cu

AEC kVp

Tx Sechopoulos et al, European Congress of Radiology, 2015

8 cm Homogeneous Phantom + Masses

AEC (38 kVp, 84 mAs) AEC + 49 kVp/0.254 mm Cu

Tx 187 Sechopoulos et al, European Congress of Radiology, 2015

p = 0.412826

p = 0.232631

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8 cm Homogeneous Phantom + MassesAEC (38 kVp, 84 mAs) AEC + 49 kVp/0.254 mm Cu

80% 40%

AGD = 1.43 mGy AGD = 1.03 mGy

Tx 190

Sechopoulos et al, European Congress of Radiology, 2015

ResultsThickness SDNR Difference Dose

5 cm ‐16.0 ± 9.25% (p>0.08)

‐48%

8 cm ‐3.2 ± 19.9% (p>0.41)

‐28%

BREAST COMPRESSION

Why compress the breast?Reduce:Tissue superpositionX‐ray scatterMotionGeometric distortionRadiation dose

Increase: Tissue coverageImage homogeneity

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Monte Carlo study with phantomsDetectability of lesions at full andDetectability of lesions at full and reduced compression

Various conditions: iso‐dose, iso‐SNR, iso mAs

iso‐mAs

194Saunders et al, Radiology, 251(3), 2009 Tx 195 Saunders et al, Radiology, 251(3), 2009

Assumed iso‐dose and:4 cm 4.5 cm6 cm 6.75 cm

Patient Study (N = 46)Mean Breast

Thickness (mm)Range (mm)

Thickness (mm)Full compression 45.4 23‐83Half compression 51.3 28‐92

Tx Fornvik et al, Radiation Protection Dosimetry (2010), Vol. 139, No. 1–3, pp. 118–123

Full Compression Rated Superior

Tx 197

glandular tissue and fibrous strands (n=15)

Fornvik et al, Radiation Protection Dosimetry (2010), Vol. 139, No. 1–3, pp. 118–123

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Patient Study at EmoryBreast thicknessBreast thicknessTissue coverageCompression forcePerceived pain

Tx Agasthya et al, AJR, in press

P 1Part 1

Tx 199

Tx 200Agasthya et al, AJR, in press Tx 201Agasthya et al, AJR, in press

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Tx 202Agasthya et al, AJR, in press

P 2Part 2

Tx 203

Tx 204Agasthya et al, AJR, in press Tx 205Agasthya et al, AJR, in press

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Tx 206Agasthya et al, AJR, in press

MLO Tomosynthesis

Blurring Tissue Coverage

Yes with Yes with MLO Tomosynthesis images No

Blurringadequate

diagnostic quality

poor diagnostic

quality

Adequate Inadequate

Radiologist 1

SC 22 21 8 47 4RC 18 26 7 49 2

Radiologist 2

SC 20 20 11 32 19RC 22 19 10 32 19

Radiologist 3

SC 14 24 13 48 3RC 8 23 20 47 4

Agasthya et al, AJR, in press

TOMOSYNTHESIS ARTIFACTS

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High contrast off‐plane objects introduce artifacts

“Voting” strategy to identify projections inidentify projections in which appropriate information is included, others ignored

Especially important for acquisitions with low

Tx 210 Wu et al, Medical Physics. 33(7), 2461–2471 (2006).

acquisitions with low number of projections

Breast tissue

Breast tissue outside reconstructed volume but that contributes to

attenuation

Tx 211

Breast tissue outside wide projection FOV

Reconstructed volume

Sechopoulos, Medical Physics, Vol. 40, No. 1, 2013

“Mask” to reconstruct only inside the breastonly inside the breast

Faster reconstruction

Avoids artifacts outside breast

Tx 212Zhang et al, Med. Phys. 34(9), 3603–3613 (2007) Tx 213 Zhang et al, J. Comput. Assist. Tomogr. 33(3), 426–435 (2009).

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Uncorrected Previous Improved

Tx 214 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

SYNTHETIC MAMMOGRAMS

What is a iscreening

mammographic

exam?216

What is a iscreening

tomosynthesis

exam?217

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Mammogram Orig. Synthetic Tomo Slice

Tx 218 Gur et al, Academic Radiology, Vol 19, No 2, 2012

Recall Rates

DBT + FFDM DBT + SyntheticNegativeor Benign

High Risk or Malignant

Negativeor Benign

High Risk or Malignant

Average 29.8 82.6 29.7 77.2

Tx 219Gur et al, Academic Radiology, Vol 19, No 2, 2012

DBT + Improved (current) synthetic (3Ds) vs. FFDM

Tx 220 Hologic Selenia Dimensions FDA Executive Summary September 2012

Recall RatesDBT + 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

Tx 221Skaane et al, Radiology, Vol 271(3), 2014

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Synthetic MammogramsCurrent synthetic 2D image can replaceCurrent synthetic 2D image can replace FFDM in combination with DBT

Included in various commercial systems

systems

CLINICAL PERFORMANCE

(Some) Screening Trials

i l N C ll ∆Trial N Cancer DetRate ∆

Recall Rate ∆

STORM‐2 9,672 DM: +35%Synth: +40%

DM: +16%Synth: +30%

OSLO 25,547 +30% ‐13%

MALMÖ 14,848 +30% +43%

Remaining questions in DBT

Patient throughput

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Reconstruction time

Reading time

DM + DBT or DBT (+ synth) alone?

How many views?

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Synthetic 2D or DM?

What after a tomo screen?

Current ResearchCADe and CADx for tomosynthesisy

Need to lower reading timeContrast enhanced tomosynthesisPhase contrast tomosynthesisTomosynthesis elastography

Tx 232

Multimodality ImagingTomosynthesisTomosynthesis

+ US+ SPECT+ Electrical Impedance+ Optical

+ Optical

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