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Elizabeth Krupinski, PhD Hans Roehrig, PhD University of Arizona William Schempp, PhD

Physical & Psychophysical Evaluation of a New Digital Specimen Radiography System for Use in Mammography. Elizabeth Krupinski, PhD Hans Roehrig, PhD University of Arizona William Schempp, PhD MedOptics Corporation. Rationale.

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Elizabeth Krupinski, PhD Hans Roehrig, PhD University of Arizona William Schempp, PhD

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  1. Physical & Psychophysical Evaluation of a New Digital Specimen Radiography System for Use in Mammography Elizabeth Krupinski, PhD Hans Roehrig, PhD University of Arizona William Schempp, PhD MedOptics Corporation

  2. Rationale • Specimen radiography of excised breast tissue is critical to ensure that an appropriate tissue sample has been obtained or that complete removal of the lesion has been successful.

  3. Objectives • To physically characterize the new high-resolution digital specimen radiography system from MedOptics Corporation. • To evaluate human observer detection performance using images acquired with the new system.

  4. The Digital System • Camera • 1024 x 1024, 1” x 1” large area high-res CCD • 2:1 fiber optic taper bonded to CCD (2”x2” FOV) • standard Lanex Regular screen coupled to large end of taper • image data digitized at 500 Kpix/sec, 12-bits • Faxitron MICRO 50 x-ray source • 15-50 kVp range • 1-90 sec time selection • SID = 50 cm

  5. Faxitron HVL & Eeff

  6. Camera X-radiation Response Camera Response (Mean and Stdv (rms) in Digital 10000.00 Units [ADU]) to X-radiation (mR) 25 kVp 30 kVp 20 kVp Corrected Mean 1000.00 Curve Fit for 30 kVp ] log(Y) = 1.04655*log(X) + 1.7888 U D ] A U [ n D a A e [ M S 100.00 M d e R t c r e o r 25 kVp r o 20 kVp C Corrected RMS Curve Fit for 30 kVp log(Y) = 0.50577*log(X) - 0.291 10.00 30 kVp 1.00 1.00 10.00 100.00 1000.00 Exposure [mR]

  7. Camera Dark Signal & Noise 1000.00 Uncorrected Dark-Signal and Dark-Noise of Uncooled CCD as Function of Time Dark Signal 100.00 ] L G [ v e d t S r o Dark Noise n a e M 10.00 1.00 0.01 0.10 1.00 10.00 100.00 Time [sec]

  8. Noise Power Spectrum 25 kVp 100.00 Noise Power Spectra for Exposures at 25 kVp 10.00 ) Exposure Time 4 sec 2 ^ m m ( r e w 1.00 o P e s i o N Exposure Time 1 sec 0.10 0.01 0.00 2.00 4.00 6.00 8.00 10.00 Spatial Frequency (lp/mm)

  9. Noise Power Spectrum 30 kVp 10.00 Noise Power Spectra for Exposures at 30 kVp Exposure Time 3 sec ) 2 ^ m m ( r e w 1.00 o P e s i o N Exposure Time 1 sec 0.10 0.00 2.00 4.00 6.00 8.00 10.00 Spatial Frequency (lp/mm)

  10. Comparison NPS & Square MTF 100.00 Noise Power Spectrum and MTF for Specimen Radiography System 10.00 2 ^ Noise Power Spectrum F T 25 kVp, 4 sec M r o 1.00 ) 2 ^ m m ( r e w 0.10 o Scaled MTF^2 P from Curve Fit e s i o N 0.01 0.00 0.00 2.00 4.00 6.00 8.00 10.00 Spatial Frequency (lp/mm)

  11. MTF 1.00 MTF of the CCD-based Camera of the MedOptics Specimen Radiography System; derived from the Fourier Transform of profiles of x-ray images of a 10 micron wide x-ray slit ("Line-Spread-Function") 0.80 ) s t 0.60 i Dashed Line 25 kVp n U Solid Line 30 kVp . l e r ( F T 0.40 M 0.20 Polynomial Coefficients Curve Fit: Polynomial of degree 2 Degree 0: 0.997419 Degree 1: -0.220671 Degree 2: 0.0125387 0.00 0.00 2.00 4.00 6.00 8.00 10.00 Spatial Frequency (lp/mm)

  12. MTF from Square Wave Response 1.00 MTF of the CCD-based Camera of the MedOptics Specimen Radiography System; derived from the Fourier Transform of x-ray images of a lead-bar pattern ("Squarewave Response") 0.80 ) s t 0.60 i Dashed Line 25 kVp n U Solid Line 30 kVp . l e r ( F T 0.40 M 0.20 0.00 0.00 2.00 4.00 6.00 8.00 10.00 Spatial Frequency (lp/mm)

  13. Observer Performance Study • 2 CDMAM contrast-detail phantoms • Commercially available large version • Small experimental version • Imaging conditions • Traditional plain film • Fuji Computed Radiography (CR) • MedOptics Digital System • 25 kV & 30 kV @ High (3600 GL), medium (2400 GL) & low (1200 GL) exposures

  14. Film Image Optical Densities

  15. Viewing Conditions • Traditional film & Fuji CR film • standard viewbox @ 1100 ft-L • extraneous light masked • Fuji CR digital & MedOptics Digital • DataRay DR110 • 1728 x 2304 • 140 ft-L • Perceptually linearized with Barten curve

  16. Observers & Task • 10 undergrad students in each condition • On outline of phantom indicate location of all disks visible in the phantom(s) • Window/Level & zoom available on monitor • Ambient lights turned off in all conditions

  17. Large Phantom Results F = 68.44, p < 0.0001

  18. Small Phantom Results F = 52.62, p < 0.0001

  19. Performance Summary • Increases monotonically low to high exposures • 25 kV > 30 kV • MedOptics Digital System Best • Traditional plain film worst • Fuji CR monitor & film in middle • Minor differences between phantoms

  20. Conclusions • MedOptics Digital Biopsy System yields high detection performance • Currently mammographers image core biopsy samples with either traditional systems or stereotactic units • Traditional takes too long • Stereotactic requires patient to get out of unit to image sample • Digital avoids these problems & is fast

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