Mammo Quiz

What structures are required to be included in a mammo image? Why?

Pectoralis and Nipple. To Measure PNL

Why is breast compression necessary?

Push glandular tissue aside

→ reduce scatter and overlapping. Improves contrast

What is primary goal of mammo?

Early detection: looking for signs of development

Why are axillary nodes imaged?

IF a tumor is present, need to image for axillary nodes where cancer is spreading

difference between Axillary node and primary breast images?

Breast images are “soft” x-rays (~26-35 kV)

Axillary is “medium” (45-49 kV)

How to achieve sharp skin line?

Increase kV: more penetrating, less scatter

What type of grid is used in mammo? Why?

Reciprocating. Reduces scatter because low kV. Removes grid lines in images. More efficient

T/F. Spatial resolution is lost in the transition from film to digital systems. (And whats the difference in resolution?)

Film ~1 micron…. Digital ~ 50 microns

Resolution is NOT lost! (Effective resolution is not lost) Because digital allows for higher contrast, which is related to spatial res… so ultimately spatial res is not lost even though digital systems have less physical resolution

Why does mammo necessitate low kV?

Increased contrast. Differences in attenuation coefficients between materials increases with decreasing kV

What contrast is mammo imaging?

Subject, NOT image contrast. Subject contrast is difference between attenuation coefficients of materials. Because the lienar attenuation between tissues in the breast are so close, subject contrast needs to be maximized

What type of contrast in mammo, and how to improve it?

Subject contrast. use “soft” x-rays (26-35 kV), and small focal spot (0.1-0.3 mm compared to ~0.9)

What are 3 signs of developing disease in breast imaging?

1. Fibers

2. Microcalcifications

3. Skin Line

What is the mamography phantom? (equivalence)

4.5 cm compressed breast, 50/50 glandular to adipose tissue

Compare k-edge of Molybdenum and Rhodium filters

K-edge of Moly < Rhodium → better contrast because lower E_AVG of spectrum

How to find HVL? Where does Al go?

place increasing thicknesses of Aluminum to find what thickness gives 50% radiation compared to 0mm Al

Al is some distance upstream of detector to exclude scatter

What is HVL needed for? max value?

HVL, and kV, are used to convert mR detector reading into mGy for AGD (Average Glandular Dose)

AGD < 3 mGy

Difference between spatial resolution and contrast?

Spatial allows detection of fine objects, those with very different attenuation coefficients

Contrast allows detections of faint objects, those with very similar coefficients

What limits digital system contrast?

Noise