In the treatment of seminoma, an external testicular shield should be used for the remaining testicle because the TD 5/5 for the testis is as low as:

In the context of seminoma treatment, the use of an external testicular shield for the remaining testicle is essential due to the relatively low tolerance dose that the testis can safely absorb before experiencing adverse effects. The TD 5/5, which stands for the "tolerance dose" at which there is an estimated 5% risk of complication within 5 years of treatment, is indeed as low as 1 Gy for the testis.

This low tolerance underscores the critical importance of protecting the testis during radiation therapy, particularly since testicular tissue is highly sensitive to radiation exposure, which can result in effects such as infertility or hormonal disturbances. By applying a shielding device during treatment, radiation oncologists effectively minimize the risk of damage to the remaining testicle, preserving its function and overall reproductive health for the patient.

The tolerance dose of the testes being as low as 1 Gy signifies that even minimal exposure can lead to serious complications, making it imperative to implement strategies like the use of protective shields to ensure patient safety during the course of seminoma treatment.