Effectiveness of abdominal shields in chest radiography: a Monte Carlo evaluation.

OBJECTIVE

The aims of this study were to assess the effectiveness of abdominal shields in reducing the dose to shielded organs during posteroanterior (PA) chest radiographic examinations, to evaluate the various factors contributing to the dose under the shield and to address the concern that internal scatter from the shield may lead to a dose increase to shielded organs.

METHODS

Monte Carlo simulations of radiographic exposures to a soft-tissue "patient" phantom of 80 × 34 × 24 cm were performed at the peak X-ray tube voltage of 100 kV. The abdominal shield was simulated as 0.5-mm lead with/without a 0.2-mm-thick plastic film cover. The shield-to-phantom spacing varied from 0 to 40 cm.

RESULTS

The dose to the phantom at different phantom depths and distances from the X-ray field edge was recorded. At the level of the uterus and ovaries (approximately 8-cm deep and 15 cm from the field of view), the dose reduction was approximately 0.035 µGy or 4%. A small dose increase (maximum: 0.4 µGy) to the phantom surface layer was also observed.

CONCLUSION

In general, there was a small dose reduction in regions protected by the shield. However, the overall risk benefit to a patient would be negligible.

ADVANCES IN KNOWLEDGE

Abdominal shields used during PA chest radiography provide a small dose reduction to organs at depth by removing the primary X-ray beam photons that are scattered in air, while giving a small increase in skin dose due to X-rays scattered from the abdominal shield internal surface.