aQuantities and units are as given in the original publication of the data.

aQuantities and units are as given in the original publication of the data.

5.5 Summary

Table 5.4 lists steps for two dose-evaluation approaches. Approach I is employed for determining the mean glandular dose (Dg) delivered to a breast of reference composition by the equipment at a particular facility. This may then be compared to published national averages (Table 5.3). Approach II is required for determining Dg for a range of actual patients at a facility. The demographics for patient populations may differ greatly from one mammography facility to another.

Table 5.4—Dose-evaluation procedures (for Dg ). Approach I

1. Application: Comparing mean glandular dose (Dg ) from various techniques and comparing facility equipment performance to national averages.

2. Procedure:

a. Note tube target and filter materials, operating potential (kVp), and breast thickness b. Measure HVL (mm Al) _

c. Use these data to obtain DgN value from Table 5.2

d. Measure incident x-ray exposure rate (per mAs) (no phantom)

e. Determine required mAs for proper image density in radiographing standard phantom f. Calculate Xa as the product of results of_Steps_d and e.

g. Determine mean glandular dose using Dg = DgN Xa

Approach II

1. Application: Determination of the average value of Dg for a specific population of patients.

2. Procedure: Same as above, except Step e: mAs is instead determined from an average for a large representative sample of patients with varying compressed breast thicknesses.

Was this article helpful?

0 0

Post a comment