Mammography Questions and Answers Roland Wong, Sc.M., D.A.B.M.P.

RAPHEX Diagnostic Question 2001 D17: Which of the following is not an advantage of good compression in mammography? A. Reduced patient motion blur. B. Reduced geometric blur. C. Reduced scatter. D. Reduced average glandular dose. E. Increased magnification.

RAPHEX Answer to 2001 Question D17 E. A-D are advantages of good compression, bur magnification decreases since patient to image receptor distance decreases.

RAPHEX Diagnostic Question 2001 D18: The main reason the kVp in mammography is increased for thicker breasts is to: Reduce average glandular dose B. Improve contrast C. Reduce scatter D. Reduce exposure time E. Reduce focal spot size

RAPHEX Answer to 2001 Question D18 D. Reduce exposure time. Although the AGD is decreased by raising the kVp, the main reason for increasing kVp is to reduce exposure time, and hence motion blurring. The rule of thumb is to try to keep the exposure time between 1 and 2 sec.

RAPHEX Diagnostic Question 2001 D19: Ideally, the AEC (phototimer) sensor in mammography should placed: A. As close to the chest wall as possible B. Under the densest portion of the breast C. Under the least dense portion of the breast D. Under the most anterior portion of the breast E. In the center of the breast

RAPHEX Answer to 2001 Question D19 B. Under the densest portion of the breast. Placing the AEC sensor under the densest portion will reduce problems with underpenetration. All portions of the image should have an OD above 1.0. Reviewing previous films helps to position the sensor.

RAPHEX Diagnostic Question 2001 D20: Subject contrast in mammography is affected by: A. Beam filter choice B. Focal spot size C. AEC density setting D. Exposure time E. Film processing conditions

RAPHEX Answer for 2001 Question D20 A. Beam filter choice Only changes in x-ray beam and scatter affect subject contrast. The other items affect film contrast. Focal spot size has no effect on contrast.

RAPHEX Diagnostic Question 2002 D29: Which of the following is NOT true? Vigorous compression in mammography reduces: A. Patient dose B. Scatter C. Motion unsharpness D. Subject contrast

RAPHEX Answer for 2002 Question D29 D. Subject contrast Compression improves subject contrast by reducing scatter.

RAPHEX Diagnostic Question 2002 D30: The filtration in mammography units primarily transmits the characteristic x-rays. It is desired to filter out the very low-energy bremsstrahlung x-rays because they contribute to _____, and it is desired that the higher energy bremsstrahlung x-rays be filtered because they contribute to ______. A. tube heating, off-focus radiation B. heel effect, focal spot blooming C. radiation dose, loss of contrast D. grid cut-off, septal penetration E. coherent scatter, K-edge photons

RAPHEX Answer for 2002 Question D30 C. radiation dose, loss of contrast Most low-energy x-rays do not reach the film, and only contribute to absorbed dose. Therefore, we wish to fllter these x-rays out before they reach the breast. The higher energy x-rays are less likely to undergo photoelectric interactions which are the source of the image contrast, while Compton scattering (which reduces contrast) remains the same. In mammography, the x-ray beam filtration is usually the same material as the anode, with the highest attenuation occurring just above the energy of the K-characteristic x-rays. Thus, x-rays (bremsstrahlung) above this energy are selectively absorbed.

RAPHEX Diagnostic Question 2003 D32: Calcifications are seen In mammograms because of their ________. A. Atomic number B. Density C. Electrons/gram D. Size E. Location

RAPHEX Answer for 2003 Question D32 A. Atomic number. At the low x-ray energy used in mammography, the interactions are predominantly photoelectric. Thus attenuation (and hence contrast) is proportional to Z3. The Z of calcium is 20, while the effective Z of fat and breast tissue is between 6 and 8.

RAPHEX Diagnostic Question 2003 D31: In mammography, average glandular tissue dose depends on: A. Breast compression B. Breast thickness C. kVp D. mAs E. All of the above

RAPHEX Answer for 2003 Question D31 E. All of the above. Average dose of the glandular tissue is an indicator of the risk of carcinogenesis. The dose depends on the energy distribution in the incident x-ray beam (kVp, HVL), mAs, and compressed breast thickness.

RAPHEX Diagnostic Question 2003 D33: In mammography the ACR recommends a compression force of 25-40 pounds. This will result in: A. Reduced geometric unsharpness B. Contrast improvement C. Reduced radiation dose E. All of the above

RAPHEX Answer for 2003 Question D33 E. All of the above. Good compression moves the breast tissue closer to the film, reducing geometric unsharpness from the focal spot. It also reduces the breast thickness near the chest wall, resulting in less scatter and better contrast, and a lower radiation dose. Compression also prevents movement, reducing motion unsharpness.

RAPHEX Diagnostic Question 2002 D28: Which grid would be the best choice for use as a stationary grid in mammography? A. 44 line/cm, 5:1 ratio B. 44 line/cm, 12:1 ratio C. 80 line/cm, 5:1 ratio D. 80 line/cm, 12:1 ratio E. Any of the above, as long as they are made of carbon fiber

RAPHEX Answer for 2002 Question D28 C. High line/cm are needed for the stationary grid so the grid lines are not visible. A 5:1 grid ratio is appropriate for mammography because thesmall scattering volume and low kVp cause relatively little scatter. Carbon fiber is a good material with low attenuation for grid covers and interspacing. However, there are also good mammographic grids that use other types of fiber or wood.

RAPHEX Diagnostic Question 2003 D34: In order to limit the loss of spatial resolution due to geometric unsharpness, the measured focal spot size for screening mammography should be less than _____ mm. A. 2.0 B. 1.0 C. 0.6 D. 0.3 E. 0.15

RAPHEX Answer for 2003 Question D34 C. 0.6 See NCRP Report 85: “Mammography – A User’s Guide”

RAPHEX Diagnostic Question 2003 D29: The following film processor parameters all affect mammography image quality EXCEPT: A. Nitrate depletion B. Developer concentration C. Developer temperature D. Replenishment rates E. Developer immersion time

RAPHEX Answer to 2003 Question D29 A. Nitrate depletion B-E directly influence the density and speed of the various film/screen systems. Although bromine concentration in the developer affects both speed and contrast, nitrate depletion has no effect on the development of mammography films.