Digital Mammography Update: Design and Characteristics of ... · AAPM 2008 Breast Imaging Course - Digital Mammography Update July 28, 2008 Kanal 6 Kanal 11 Various Approaches in

AAPM 2008 Breast Imaging Course -Digital Mammography Update

July 28, 2008

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Digital Mammography Update: Design Digital Mammography Update: Design and Characteristics of Current Systems and Characteristics of Current Systems

Kalpana M. Kanal, Ph.D., DABRKalpana M. Kanal, Ph.D., DABRAssistant ProfessorAssistant Professor

Department of RadiologyDepartment of RadiologyUniversity of WashingtonUniversity of Washington

Seattle, WashingtonSeattle, Washington

AAPM Annual Meeting 2008 AAPM Annual Meeting 2008 –– Houston, TXHouston, TX

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Educational ObjectivesEducational Objectives

Understand the physics of digital detector technologyUnderstand the physics of digital detector technologyRecognize that vendors use varying detector technology Recognize that vendors use varying detector technology in FFDM systemsin FFDM systemsAppreciate the advantages and disadvantages of digital Appreciate the advantages and disadvantages of digital mammography systems mammography systems Understand the image quality metrics such as DQE and Understand the image quality metrics such as DQE and MTFMTF


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ResourcesResourcesDoug PfeifferDoug Pfeiffer, MS, DABR, MS, DABRDigital Mammography: An Digital Mammography: An overview overview –– Dr. MaheshDr. Mahesh(Radiographics (Radiographics 2004;24:17472004;24:1747--1760)1760)Fundamentals of Digital Fundamentals of Digital

Mammography Primer Mammography Primer –– Dr. Dr. SmithSmith (Hologic Inc)(Hologic Inc)Digital Mammography Digital Mammography ––Pisano and YaffePisano and Yaffe (Radiology (Radiology 2005; 234:3532005; 234:353--262)262)Bloomquist and Yaffe Bloomquist and Yaffe –– Med Med Phys 33 (3), 2006Phys 33 (3), 2006

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FullFull--Field Digital Mammography (FFDM)Field Digital Mammography (FFDM)

c.f. www.gehealthcare.com/rad/xr/education/dig_xray_intro.htmlc.f. www.gehealthcare.com/rad/xr/education/dig_xray_intro.html


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Wide dynamic range Wide dynamic range (1000:1) compared with (1000:1) compared with SFM (40:1)SFM (40:1)Dynamic image Dynamic image manipulationmanipulationAbility to postAbility to post--processprocessSoftSoft--copy read copy read accompanied by accompanied by computercomputer--aidedaided--diagnosis (CAD)diagnosis (CAD)3D imaging3D imaging

Radiographics 2004:24,1749

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AdvantageAdvantageEach component of the mammographic process can Each component of the mammographic process can be optimized with digital mammographybe optimized with digital mammography



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SFM vs. FFDMSFM vs. FFDM

SFM: Half mAs, Automatic exposure control, Double mAs

FFDM: Same technique factors as SFM, W/L adjusted


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SFM vs. FFDMSFM vs. FFDM



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Technologies for FFDMTechnologies for FFDMIndirect CaptureIndirect Capture

a scintillator such as a scintillator such as cesium iodide (CsI) cesium iodide (CsI) absorbs xabsorbs x--rays and rays and generates a light generates a light scintillationscintillationdetected by an array of detected by an array of photodiodes or chargephotodiodes or charge--coupled devices (CCDs)coupled devices (CCDs)Resolution degradation Resolution degradation

http://www.hologic.com/wh/pdf/R-LM-016_Radiology_Management.pdf

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Technologies for FFDMTechnologies for FFDMDirect CaptureDirect Capture

XX--ray photons are directly ray photons are directly captured by a captured by a photoconductor such as photoconductor such as amorphous selenium (aamorphous selenium (a--Se), which converts the Se), which converts the absorbed xabsorbed x--rays directly to rays directly to a digital signala digital signalSpatial resolution limited Spatial resolution limited to pixel sizeto pixel size



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Various Approaches in development of Various Approaches in development of FFDM systemsFFDM systems

IndirectIndirectA single flatA single flat--panel scintillator and an amorphous silicon panel scintillator and an amorphous silicon (a(a--Si) diode array Si) diode array –– GE GE Slot scanning with scintillators and CCD arrays Slot scanning with scintillators and CCD arrays –– Fischer Fischer Imaging, now HologicImaging, now HologicPhotostimulable phosphor plates Photostimulable phosphor plates -- FujiFuji

DirectDirectA flatA flat--panel amorphous selenium (apanel amorphous selenium (a--Se) array Se) array –– Hologic, Hologic, SiemensSiemensTiled scintillators with fiberoptic tapers and mosaic CCD Tiled scintillators with fiberoptic tapers and mosaic CCD arrays arrays –– Hologic StereotacticHologic Stereotactic

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FDA and Digital MammographyFDA and Digital Mammography

Butler Butler -- http://www.acr.org/accreditation/mammography/rsna07presentationhttp://www.acr.org/accreditation/mammography/rsna07presentation.aspx.aspx


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MQSA ScorecardMQSA Scorecard

Certification statistics, as of July 1, 2008 Certification statistics, as of July 1, 2008 Total certified facilities / Total accredited unitsTotal certified facilities / Total accredited units

8,845 / 13,4508,845 / 13,450Certified facilities with FFDM units / Accredited FFDM Certified facilities with FFDM units / Accredited FFDM unitsunits

3,366 / 5,1193,366 / 5,11938%38% certified facilities with FFDM unitscertified facilities with FFDM units38%38% accredited FFDM unitsaccredited FFDM units

http://www.fda.gov/cdrh/mammography/scorecardhttp://www.fda.gov/cdrh/mammography/scorecard--statistics.htmlstatistics.html

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Technologies for FFDM Technologies for FFDM –– Indirect CaptureIndirect CaptureGEGE

GE Senographe Essential Full GE Senographe Essential Full Field Digital Mammography Field Digital Mammography (FFDM) System (FFDM) System -- 04/11/0604/11/06 (larger detector)

GE Senographe DS Full FieldGE Senographe DS Full FieldDigital Mammography (FFDM) Digital Mammography (FFDM) System System -- 02/19/0402/19/04

GE Senographe 2000D Full Field GE Senographe 2000D Full Field Digital Mammography System on Digital Mammography System on 01/28/0001/28/00

Fig. Ref: GE DS QC manualFig. Ref: GE DS QC manual


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In this system, the digital In this system, the digital detector array is constructed detector array is constructed from an afrom an a--Si thinSi thin--film transistor film transistor (TFT) matrix deposited on a (TFT) matrix deposited on a glass substrateglass substrateThe CsI scintillator is deposited The CsI scintillator is deposited on the aon the a--Si detectorSi detectorEach lightEach light--sensitive diode sensitive diode element is connected by TFTs element is connected by TFTs to a control and a data line so to a control and a data line so that charge produced in the that charge produced in the diode is read out in response to diode is read out in response to light emission from the scintillatorlight emission from the scintillator


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141414141414Bit DepthBit Depth

5 lp/cm5 lp/cm5 lp/cm5 lp/cm5 lp/cm5 lp/cmLimiting Limiting Spatial Spatial

ResolutionResolution2394 x 3062 2394 x 3062

pixels (14 MB)pixels (14 MB)1914 x 2294 1914 x 2294 pixels (9 MB)pixels (9 MB)

1914 x 2294 1914 x 2294 pixels (9 MB)pixels (9 MB)

Image sizeImage size

100 100 µµmm100 100 µµmm100 100 µµmmPixel sizePixel size

24.0 x 30.724.0 x 30.719.2 x 23.019.2 x 23.019.2 x 23.019.2 x 23.0Detector Detector sizesize

EssentialEssentialDSDS2000D2000D


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Technologies for FFDM Technologies for FFDM –– Indirect CaptureIndirect CaptureGE GE –– Advantages and DisadvantagesAdvantages and Disadvantages

Close bonding between CsI and aClose bonding between CsI and a--Si ensures minimal Si ensures minimal light losslight lossStrong signal from the Si diode array yields higher Strong signal from the Si diode array yields higher detective quantum efficiencydetective quantum efficiencyDetector is linear over a wide range (10Detector is linear over a wide range (1055))

Limiting factor is the large pixel size (100 Limiting factor is the large pixel size (100 μμm)m)Smaller pixel sizes improve spatial resolution but at the Smaller pixel sizes improve spatial resolution but at the cost of increased image noise and decreased SNR for cost of increased image noise and decreased SNR for the same breast dosethe same breast dosePossibility of ghosting in imagesPossibility of ghosting in images


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PSP PSP

Base supportBase support

plate exposure:plate exposure:create latent imagecreate latent image

xx--ray exposureray exposure

Technologies for FFDM Technologies for FFDM –– Indirect CaptureIndirect CaptureComputed Radiography Computed Radiography –– Fuji (7/10/2006)Fuji (7/10/2006)

(Barium fluorobromide)(Barium fluorobromide)

Technology introduced in 1981Technology introduced in 1981

Pfeiffer


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plate erasure:plate erasure:remove residual signalremove residual signal

light erasurelight erasure

plate readout:plate readout:extract latent imageextract latent image

laser beam scanlaser beam scan

Technologies for FFDM Technologies for FFDM –– Indirect CaptureIndirect CaptureComputed Radiography Computed Radiography –– FujiFuji

Technology introduced in 1981Technology introduced in 1981

Pfeiffer

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Technologies for FFDM Technologies for FFDM –– Indirect CaptureIndirect CaptureComputed Radiography Computed Radiography –– FujiFuji

Fuji FCRm, Dual-side reader

10 lp/mm10 lp/mmSpatial Spatial ResolutionResolution

14 bits14 bitsDynamic Dynamic RangeRange

3328 x 4096 3328 x 4096 pixels (24 MB)pixels (24 MB)Image sizeImage size

50 50 µµmmPixel sizePixel size

18 x 2418 x 2424 x 3024 x 30

Detector Detector sizesize

http://www.fujimed.com/


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Fuji Fuji -- Dual Side ReadoutDual Side Readout

laser beamlaser beam

mirrormirror

Protective Protective layerlayer

photodetectorphotodetector

photodetectorphotodetector

opticalopticalguideguide

TransparentTransparentsupport support

PhosphorPhosphorlayerlayer

emissionemission

opticalopticalguideguide

Pfeiffer

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Technologies for FFDM Technologies for FFDM –– Indirect CaptureIndirect CaptureFuji Fuji –– Advantages and DisadvantagesAdvantages and Disadvantages

Advantage of the CR mammo system is that filmAdvantage of the CR mammo system is that film--screen screen cassettes can be replaced by CR cassettes without replacing cassettes can be replaced by CR cassettes without replacing the entire systemthe entire systemBoth small and large cassettes can be accommodated by the Both small and large cassettes can be accommodated by the readerreaderDual side reader, 50 Dual side reader, 50 μμm pixel sizem pixel size

Disadvantage Disadvantage -- Effective pixel size influenced by phosphor Effective pixel size influenced by phosphor thickness, light diffusion within phosphor, laser light scatter thickness, light diffusion within phosphor, laser light scatter & & diameter of laser beamdiameter of laser beamTechnologist time on processing of imagesTechnologist time on processing of imagesNoise associated with the low collection efficiency of emitted Noise associated with the low collection efficiency of emitted lightlight


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Technologies for FFDM Technologies for FFDM –– Indirect CaptureIndirect Capture

A narrow slotA narrow slot--detector and detector and a narrow fan beam of xa narrow fan beam of x--rays are scanned rays are scanned synchronously across the synchronously across the full field of view to cover full field of view to cover the entire breastthe entire breastSystem consists of System consists of phosphor (thalliumphosphor (thallium--activated CsI) with a activated CsI) with a fiberoptic coupling to a fiberoptic coupling to a CCDCCD

SenoScanSenoScan; Fischer Imaging ; Fischer Imaging –– 9/25/019/25/01


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Seibert, AAPM Meeting Handout

SenoScanSenoScan; Fischer Imaging (now ; Fischer Imaging (now HologicHologic))


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Compact detector that is less expensive compared to Compact detector that is less expensive compared to othersothersExcellent scatter rejection due to small volume of breast Excellent scatter rejection due to small volume of breast exposed at any timeexposed at any timeNo grid needed therefore less doseNo grid needed therefore less doseLonger compression since scan times are longer Longer compression since scan times are longer (approx. 6 sec)(approx. 6 sec)Powerful tubes, elaborate signal readout and image Powerful tubes, elaborate signal readout and image reconstruction requiredreconstruction required

(SenoScan; Fischer Imaging (now Hologic))(SenoScan; Fischer Imaging (now Hologic))Advantages and DisadvantagesAdvantages and Disadvantages

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Comparison Comparison –– Indirect CaptureIndirect Capture

Fuji Fuji FCRFCRmm

3328 x 4096 3328 x 4096 pixels (24 pixels (24 MB)MB)

PSP platePSP plate

10 lp/mm10 lp/mm

50 50 µµmm

18 x 2418 x 2424 x 3024 x 30


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Technologies for FFDM Technologies for FFDM –– Direct CaptureDirect Capture

aa--Se, a good photoconductor Se, a good photoconductor is deposited directly onto the is deposited directly onto the aa--Si TFT substrate enabling Si TFT substrate enabling direct capturedirect captureThe aThe a--Se detector directly Se detector directly converts xconverts x--rays to electronrays to electron--hole pairs hole pairs The aThe a--Si TFT converts the Si TFT converts the electronelectron--hole pairs to hole pairs to electronic signalelectronic signal

aa--Se Array (Selenia, Se Array (Selenia, HologicHologic) ) –– 10/2/0110/2/01

http://www.hologic.com/wh/digisel.htm

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Technologies for FFDM Technologies for FFDM –– Direct CaptureDirect CaptureFlatFlat--Panel aPanel a--Se Array (Selenia, Hologic)Se Array (Selenia, Hologic)

http://www.hologic.com/wh/digisel.htm

> 7 lp/cm> 7 lp/cmSpatial Spatial ResolutionResolution



70 70 µµmmPixel sizePixel size24.0 x 29.024.0 x 29.0Detector sizeDetector size


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Technologies for FFDM Technologies for FFDM –– Direct CaptureDirect Capture

Advantage is that the detector response function Advantage is that the detector response function maintains its sharpness even with increasing thicknessmaintains its sharpness even with increasing thicknessHigh MTF and DQE can be achievedHigh MTF and DQE can be achieved

Potential weaknesses are the need for high biasing Potential weaknesses are the need for high biasing voltage, drifting of the dark signal and cost of detectorvoltage, drifting of the dark signal and cost of detectorInherent sharpness of detector may also increase the Inherent sharpness of detector may also increase the severity of aliasing artifacts associated with severity of aliasing artifacts associated with undersampling on any digital detectorundersampling on any digital detector

FlatFlat--Panel aPanel a--Se Array (Selenia, Hologic)Se Array (Selenia, Hologic)Advantages and DisadvantagesAdvantages and Disadvantages

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Technologies for FFDM Technologies for FFDM –– Direct CaptureDirect Captureaa--Se Array (Mammomat Novation, Siemens Se Array (Mammomat Novation, Siemens –– 8/20/04)8/20/04)

http://www.medical.siemens.com

> 7 lp/mm> 7 lp/mmSpatial Spatial ResolutionResolution

70 70 µµmm

24.0 x 29.024.0 x 29.0



Pixel sizePixel size

Detector sizeDetector size


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Comparison Comparison –– Direct CaptureDirect Capture

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Technologies for FFDMTechnologies for FFDM

http://www.hologic.com/oem/pdf/DROverviewR-007_Nov2000.pdf

Fuji/Kodak/Fuji/Kodak/

Agfa/PhilipsAgfa/Philips

Fischer Fischer (Hologic)(Hologic)

GEGE HologicHologic

SiemensSiemens


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MTFMTFMTF is a measure of signal transfer over a range of MTF is a measure of signal transfer over a range of frequencies and quantifies spatial resolutionfrequencies and quantifies spatial resolution

Yaffe - Radiology 2005:234,353

Type 1 Type 1 –– CsI (TFT)CsI (TFT)

Type 2 Type 2 –– CsI (CCD)CsI (CCD)

Type 3 Type 3 –– CRCR

Type 4 Type 4 –– aa--SeSe


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MTFMTFBloomquist et al Bloomquist et al -- DMIST trialDMIST trial

Bloomquist – Medical Physics 2006:33 (3), 719


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DQEDQEDetective Quantum Efficiency (DQE) measures SNR Detective Quantum Efficiency (DQE) measures SNR transfer through the system as a function of spatial transfer through the system as a function of spatial frequency and is a good measure of dose efficiencyfrequency and is a good measure of dose efficiency


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FFDM FFDM –– Radiation DoseRadiation Dose

Bloomquist et al Bloomquist et al -- DMIST trialDMIST trial

Bloomquist – Medical Physics 2006:33 (3), 719


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Storage of Digital ImagesStorage of Digital Images


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Display of Digital ImagesDisplay of Digital Images



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Economics of FFDMEconomics of FFDM

SFM systems cost well under $100,000SFM systems cost well under $100,000FFDM systems cost in the range of $300,000 FFDM systems cost in the range of $300,000 -- $450,000$450,000One attractive reason for centers to One attractive reason for centers to ““go digitalgo digital”” is the is the higher reimbursement rates approved by Medicarehigher reimbursement rates approved by Medicare

Plain FilmPlain Film ScreeningScreening $83.03$83.03DigitalDigital ScreeningScreening $133.69$133.69

DiagnosticDiagnostic $151.21$151.21CADCAD $14.86$14.86

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Expected Benefits of FFDMExpected Benefits of FFDM

The costs of FFDM systems should be compared along The costs of FFDM systems should be compared along with the inherent benefits of the digital technology prior with the inherent benefits of the digital technology prior to the purchase:to the purchase:

Reduced recall ratesReduced recall ratesIncreased patient throughputIncreased patient throughputIncreased early detection of breast cancerIncreased early detection of breast cancerDecreased falseDecreased false--negative biopsy resultsnegative biopsy resultsDecreasing film and processing costsDecreasing film and processing costsIncreasing the caseload of each mammography roomIncreasing the caseload of each mammography room


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Clinical Trials and Phantom StudiesClinical Trials and Phantom StudiesLarger screening study screened 49,500 womenLarger screening study screened 49,500 womenDigital Mammographic Imaging Screening TrialDigital Mammographic Imaging Screening Trial (DMIST), (DMIST), funded by NCI and conducted by ACRIN funded by NCI and conducted by ACRIN (http://www.acrin.org/6652_protocol.html)(http://www.acrin.org/6652_protocol.html)

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Advantages and DisadvantagesAdvantages and Disadvantages

AdvantagesAdvantagesOptimize postOptimize post--processing of imagesprocessing of imagesPermit computerPermit computer--aided detection to improve the aided detection to improve the detection of lesionsdetection of lesionsStorage of images easierStorage of images easier

DisadvantagesDisadvantagesImage display and system costImage display and system costLimiting spatial resolution is inferior to film, 5Limiting spatial resolution is inferior to film, 5--13 13 lp/mm vs. 20 lp/mmlp/mm vs. 20 lp/mm


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Future DevelopmentsFuture Developments

Tomosynthesis Tomosynthesis Dual energyDual energyContrast enhanced digital mammographyContrast enhanced digital mammographyCAD integrationCAD integrationTelemammographyTelemammography

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Future DevelopmentsFuture DevelopmentsContrast Enhanced Digital MammographyContrast Enhanced Digital Mammography

Radiology 2005:234:353:362


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Future DevelopmentsFuture DevelopmentsTomosynthesisTomosynthesis

Radiology 2005:234:353:362

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TAKE HOME POINTSTAKE HOME POINTS

Different technologies exist for digital systems Different technologies exist for digital systems –– indirect and indirect and directdirectCommercially available FFDM systems vary in technologyCommercially available FFDM systems vary in technologyMany advantages exist for FFDM in comparison to FSMMany advantages exist for FFDM in comparison to FSMMTF and DQE are typically used to characterize FFDM MTF and DQE are typically used to characterize FFDM systemssystemsDose is lower with FFDM compared to FSMDose is lower with FFDM compared to FSMAdvanced applications of FFDM include tomosynthesis, Advanced applications of FFDM include tomosynthesis, contrast enhanced mammography etccontrast enhanced mammography etc


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THANK YOUTHANK YOU

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Digital Mammography Update: Design and Characteristics of ... · AAPM 2008 Breast Imaging Course - Digital Mammography Update July 28, 2008 Kanal 6 Kanal 11 Various Approaches in