ESTRO 2025 - Abstract Book

S2603

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

Results indicated that testicular shielding significantly reduced the radiation dose. During the CT scan, the dose to the testicles dropped from 18.81 mGy without shielding to 0.17 mGy with shielding. Similarly, CBCT imaging showed a 97% dose reduction, from 5.94 mGy without shielding to 0.15 mGy with shielding. During the treatment phase, a rectal cancer radiation plan delivering 2 Gy per fraction resulted in a 59.7% reduction in the testicular dose—from 28.57 mGy without shielding to 11.51 mGy with shielding (Table 1). For a typical treatment course of 25 fractions (2 Gy each), without shielding, the cumulative testicular dose would amount to 881.56 mGy, including contributions from CT and CBCT imaging, which would exceed the recommendations. With shielding, this dose is reduced to 291.67 mGy, representing a 66.9% overall reduction.

Conclusion:

Although the lead shielding introduced imaging artifacts that degraded image quality, the planning CT remained adequate for delineation and the CBCT images remained adequate for bone matching (Figure 1), which is critical in rectal cancer treatment planning. The significant reduction in testicular dose demonstrates that testicular shielding is effective and could be recommended to preserve fertility in male patients undergoing radiation therapy for rectal cancer, despite the impact on image quality. Further measures, such as dedicated planning to reduce testicular exposure, may lead to even greater dose reductions.

Keywords: Fertility, shielding, reduction