The effect of out of field scattering radiation dose on testicle in radiotheraphy applications in rectum cancer

Objective: The aim of this study was Investigation of the effect of out of field scattering radiation dose on testicle in radiotheraphy applications in rectum cancer. Method: The testis structure was created for the human-like phantom to be used in the study. This testis structure was fixed on the phantom. Human-like phantom cross-sectional images were obtained with a computerized tomography device for treatment planning. A 28-fraction three-dimensional conformal radiotherapy plan was designed with 180 cGy daily treatment dose using 18MV energy on the Precise treatment planning system for a human-like phantom patient to be treated with rectal cancer. Peripheral radiation dose taken by the testes outside the treatment area during the treatment were measured by placing and certain points on the testis structure These dosing procedures were repeated and statistical evaluation was performed on the data of different dosimetric instruments. Results: In the testis-like structure placed on the human-like phantom, the point that is the closest to the edge of the field is 206 cGy and the farthest point is 82 cGy. Again, the difference of the TPS doses of these points with the measurement dose was found to be -0.6% and -17.5%, respectively. The end result of EBT3 films is different from TPS and TLD measurements. Conclusion: With the measurements it was concluded that the testes that are out of the field need to be determined in advance and that the TPS data may contain high degree of uncertainty, thus the uncertainties in the determination of these doses may be uncertain. When determining out-of-field doses depending on treatment energy and field sizes used in rectum radiotheraphy by going out of the way, protocols should be prepared for the measurements to be taken for regions outside the treatment area to be performed before and doses of testis should be predicted. If necessary, the testes should be protected using the testis shielding. Key words: Peripheral radiation dose; TLD; gafcromic films; conformal