Transcript Mammography

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.
B.
C.
D.
E.
Reduced patient motion blur.
Reduced geometric blur.
Reduced scatter.
Reduced average glandular dose.
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.