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Evolution of Analog Mammography Machines: From Quality Concerns to Modern Features

Explore the brief history and quality concerns of analog mammography machines and films. Learn about the features of mammography machines, including the control panel and generator ripple. Discover the importance of breast compression and magnification for improved contrast and resolution. Understand the impact of film and processing conditions, and explore the role of CAD in mammography.

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Evolution of Analog Mammography Machines: From Quality Concerns to Modern Features

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  1. CHAPTER 11 Analog Mammography Machines, Processors, and Films

  2. A BRIEF HISTORY

  3. QUALITY OF X-RAYS QUESTIONED: NEXT

  4. QUALITY OF MAMMOGRAMS QUESTIONED • Breast Evaluation Nationwide Trends (BENT)

  5. BENT • 1986 Philadelphia: Gawkin et al. • 41% unacceptable processor variations • Radiation dose ranged from 26–260 millirads per film

  6. 1992 MQSA SIGNED INTO LAW • Regulates: • Mammography machines • Processor performance • Phantom image • Clinical images • Dose

  7. ANALOG MAMMOGRAPHY MACHINE • Dedicated screen-film mammographic unit

  8. MAMMOGRAPHY MACHINE FEATURES • Face shield • Foot pedals • 2 sizes of IRSD • Compression device

  9. CONTROL PANEL • Photo timing • Density selection • Technique selection

  10. GENERATOR RIPPLE DETERMINES kVp • kVp determines contrast. • Tube current and x-ray intensity diagrams. Steady x-ray intensity results from the constant potential system. Today’s machines incorporate this technology.

  11. POWER VARIATIONS IN MAMMOGRAPHY UNITS

  12. PHOTOELECTRIC EFFECT • Electron from cathode strikes the target and removes tightly bound inner shell electron (photoelectron). Original electron disappears. Hole created by ejected photoelectron filled by outer orbit electron. Characteristic radiation emitted as outer-shell electron gives up energy to move closer to nucleus.

  13. CHARACTERISTIC WAVEFORM MOLYBDENUM • Typical Mo x-ray emission spectra for analog mammography

  14. CHARACTERISTIC PEAKS

  15. MOLYBDENUM VERSUS RHODIUM • Mo image has higher contrast but higher dose. Rh penetrates better but has lower contrast. A. Mo; B. Rh

  16. “SOFT” GRIDS USED IN MAMMOGRAPHY • Grid ratios of 4:1 or 5:1 • Grids increase contrast by reducing scatter.

  17. BREAST COMPRESSION INCREASES CONTRAST • A thinner object results in less scatter. Less scatter results in higher contrast.

  18. 7 REASONS FOR COMPRESSION • Decrease motion unsharpness • Decrease geometric unsharpness • Increase contrast • Separate glandular tissue • Reduce dose • More uniform density • Assess density of masses

  19. MAGNIFICATION • Range: 1.4–2× • “Sweet spot” 4 cm away from chest wall edge

  20. RESOLUTION VERSUS MAGNIFICATION FACTOR • 1.5× magnification results in a smaller image with better resolution. With 2× magnification, the image is larger but has less resolution.

  21. HEEL EFFECT IN MAMMOGRAPHY • From chest wall (cathode) to nipple (anode) • Heel effect is used in mammography. It is oriented from chest wall to nipple, rather than left to right as in diagnostic radiology.

  22. FILM AND PROCESSING CONDITIONS

  23. SINGLE-EMULSION FILM • Single-emulsion film produces a more resolute image. Double-emulsion film contends with the parallax effect.

  24. GREEN LIGHT SAFELIGHT IN DARKROOM • Mammography film is green light sensitive; diagnostic x-ray film is blue light sensitive.

  25. PROCESS IN STANDARD 90-SECOND PROCESSOR A. 3D silver halide crystal emulsion. Low average gradient so processor had to be optimized to artificially enhance film contrast. C. Cubic grain technology solved the contrast dilemma. Standard processing okay to use.

  26. OPTIMAL FILM PROCESSING • Check average gradient • AG = (2.0+BF) – (0.25+BF) LOG2 – LOG E1

  27. AVERAGE GRADIENT • Film A is faster and higher in contrast.

  28. CAD (COMPUTER-AIDED DETECTION) • Acts like a spell checker in a computer • CAD display of ROI marked for radiologist review. Radiologist may/may not agree with computer’s findings.

  29. ANALOG CAD • Film placed into digitizer • Computer analysis • Technologist hangs films on viewbox

  30. DIGITAL CAD • No action required by technologist • CAD just another computer in the room • Results display on MD monitor

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