Lead-rubber shielding effect on radiation dose to the gonads from a bilateral hand X-ray examination

Introduction
Recent guidance from the British Institute of Radiology (BIR) and the American Association of Physicists in Medicine (AAPM) focuses on cessation of patient Lead-rubber (Pb) shielding placed within the Field of View (FOV) that may influence image exposure or quality. Furthermore, the BIR assert shielding organs greater than 5 cm from the primary X-ray beam will have a negligible effect to the received radiation dose. Bilateral hand X-rays are frequently and repeatedly requested for the diagnosis and ongoing management of arthritic conditions. There is a lack of literature regarding the effect of Pb shielding during bilateral hand X-ray examinations. This research aimed to investigate the scattered secondary radiation dose to the gonads during a bilateral hand X-ray, with and without the use of Pb shielding outside the FOV at a greater distance than 5 cm from the primary beam.

Methods
Using an anthropomorphic phantom and constructed upper limbs, radiation was recorded to the male and female gonads. Thermoluminescent dosimeters (TLD's) (⅛" x ⅛" x 0.15″ TLD-100H) were placed in groups of three upon the testes and within the left and right ovary to record the ionising radiation dose. Three collimated exposures were completed using a standard clinical practice hand X-ray protocol of 60 kVp and 2.5 mAs with a source to image distance (SID) of 100 cm. The mean and standard deviation of the radiation dose was calculated for both with and without Pb shielding. A paired two-sample t-test was conducted to determine statistical significance (p ≤ 0.05).

Results
Data analysis demonstrated dose measured to the testes of 5.3 μGy (SD 0.8) without Pb shielding and 2.3 μGy (SD 0.2) with Pb (reduction of 3 μGy; 56.6%). Left ovary doses measured 40.6 μGy (SD 1.2) without Pb shielding and 28.8 μGy (SD 1.7) with Pb (reduction of 11.9 μGy; 29.2%) and right ovary doses measured 39.5 μGy (SD 1.9) without Pb shielding and 26.6 μGy (SD 1.0) with Pb (reduction of 12.8 μGy; 32.4%). The paired two-sample t-test presented a statistically significant dose reduction (p = 0.0039).

Conclusion
The study demonstrated dose limitation from scattered secondary radiation to the gonads when Pb shielding was used during a bilateral hand X-ray at distances greater than 5 cm from the primary X-ray beam on anatomy outside the FOV.

Implications for practice
The use of Pb shielding over the gonad area during a bilateral hand X-ray examination aligns to ALARP best practice and provides prospects for patient (male and female) dose reduction.