Temperature-Controlled Immobilization for Testicular Irradiation: A Technical Report of a Single Case.

Background

Testicular irradiation presents technical challenges due to the temperature-dependent cremasteric reflex causing positional variability, yet detailed immobilization protocols addressing this issue and cone-beam computed tomography (CBCT)-based setup data remain lacking. This formative and preliminary single-patient descriptive technical report describes a temperature-controlled immobilization technique and reports preliminary setup observations from its clinical application.

Methods

A 74-year-old male with primary testicular diffuse large B-cell lymphoma (DLBCL) received prophylactic contralateral testicular irradiation. The immobilization protocol combined a custom thermoplastic device with infrared warming to maintain the scrotal surface temperature at 36-36.5 °C, intended to facilitate a relaxed scrotal position prior to and during each fraction under temperature-controlled conditions. Treatment was delivered using a three-field three-dimensional conformal radiotherapy (3D-CRT) technique (30.6 Gy in 17 fractions), and seven CBCT scans were used to document interfraction setup measurements.

Results

The treatment was completed as planned with adequate target coverage (clinical target volume [CTV] D97% = 100%) and minimal organ-at-risk (OAR) doses. Setup measurements showed a CTV root-mean-square displacement (RMS) of 3.8 mm and a mean Dice similarity coefficient (DSC) of 0.85, while the testis alone showed an RMS of 5.2 mm and a mean DSC of 0.73.

Conclusions

The temperature-controlled immobilization technique was feasibly implemented, and the setup measurements observed during its application showed a CTV RMS of 3.8 mm and a mean DSC of 0.85. These findings may provide a practical reference for institutions encountering this rare clinical scenario.