A Simple Diagnostic X-ray Shielding Overview

What report outlines guidelines for Structural shielding of medical x-ray imaging facilities

NCRP 147

With diagnostic energies how does the workload get calculated

It is very important to get the workload distribution versus kVp as the penetration power through shielding increases by about three orders of magnitude from 60-100 kVp and leakage increases by about eight orders of magnitude from 50-150 kVp (alternatively you could assume all images are taken using highest kVp).

With radiographic units, what is the maximum leakage?

1. Leakage is limited to 1 mSv/hr at 1 meter when the tube is run at its maximum permissible loading (highest kVp, as many pulses in 1 hour as the tube is rated for due to thermal concerns).

Typical shielding requirements for conventional simulator

1/32 in (0.8 mm) lead - but if operated in fluoro mode this increases a lot

What is of concern with a CT sim shielding

1. CT simulation units are usually accompanied with isodose curves from the manufacturer specifying dose at a certain distance from the unit per scan (or mA-min value).

2. Only secondary radiation is of concern (leakage and scattered) as all primary radiation is intercepted by the detectors.

How do you calculate barrier transmission on a CT sim?

B=P/WDT where D is the dose per scan (mA-min)

Along which axis is radiation the highest?

table axis

Typical shielding requirement for a CT simulator

1/16 inches (1.6mm)

Workload considerations for a PET/CT

1. W = the workload, must consider only the PET workload (number of patients, uptake, activity administered about 15 mCi, gamma factor F-18).

1. Consider the number of patients in 1 week (n).

2. Scan time (t) (usually about 1 hour).

3. The amount of activity administered per patient (A).

4. Gamma factor (GAMMA) of F-18 (5.29 mSv - cm² / mCi /hr).

1. 

Typical shielding requirements for a PET/CT

about 1 cm of lead.