Dosimetric comparison of modern radiotherapy techniques for gastric cancer after total gastrectomy.

PURPOSE: The purpose of this study is to investigate the optimal radiotherapy technique for postoperative irradiation of gastric cancer treated with total gastrectomy. MATERIALS AND METHODS: The database of ten patients was used for this study. Three-dimensional (3D) conformal radiotherapy, intensity-modulated therapy (IMRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) plans were created for each dataset. The prescription dose was 45 Gy in 25 fractions. Comparative analyses of the target volume coverage and the doses of organs at risk were performed. RESULTS: HT was significantly provided more homogeneity. The best conformal plans were achieved with VMAT. Both kidneys were better preserved with HT and VMAT. HT significantly lowered the V13 of the left kidney and VMAT significantly lowered V20. However, the mean left kidney doses were not statistically different. The lowest liver V30 was obtained with VMAT but not with statistically different than IMRT and HT. Mean liver doses were statistically inferior with 3D. The worst spinal cord doses were seen with 3D. The integral dose of the body did not differ among the techniques. CONCLUSION: In comparison of the four techniques, 3D seems to be the most unsuitable method regarding sparing the normal tissues. According to availability, HT and VMAT should be primarily preferred. IMRT can also be used with carefully paying attention to the clinical condition of the patient.

A Phantom Study on Fetal Dose Reducing Factors in Pregnant Patients with Breast Cancer during Radiotherapy Treatment.

PURPOSE: This study aims to investigate the factors that reduce fetal dose in pregnant patients with breast cancer throughout their radiation treatment. Two main factors in a standard radiation oncology center are considered as the treatment planning systems (TPSs) and simple shielding for intensity modulated radiation therapy technique. MATERIALS AND METHODS: TPS factor was evaluated with two different planning algorithms: Anisotropic analytical algorithm and Acuros XB (external beam). To evaluate the shielding factor, a standard radiological purpose lead apron was chosen. For both studies, thermoluminescence dosimeters were used to measure the point dose, and an Alderson RANDO-phantom was used to simulate a female pregnant patient in this study. Thirteen measurement points were chosen in the 32nd slice of the phantom to cover all possible locations of a fetus up to 8th week of gestation. RESULTS: The results show that both of the TPS algorithms are incapable of calculating the fetal doses, therefore, unable to reduce them at the planning stage. Shielding with a standard lead apron, however, showed a slight radiation protection (about 4.7%) to the fetus decreasing the mean fetal dose from 84.8 mGy to 80.8 mGy, which cannot be disregarded in case of fetal irradiation. CONCLUSIONS: Using a lead apron for shielding the abdominal region of a pregnant patient during breast irradiation showed a minor advantage; however, its possible side effects (i.e., increased scattered radiation and skin dose) should also be investigated further to solidify its benefits.