Effect of topical agents on skin surface dose in volumetric modulated arc therapy for head and neck cancer.

In volumetric modulated arc therapy (VMAT), the effect of an increase in skin surface dose due to topical agents might be negligible. We investigated the bolus effects of three types of topical agents in VMAT for head and neck cancer (HNC). Topical agents of different thicknesses (0.1, 0.5 and 2 mm) were prepared. When each topical agent was set, the surface doses were measured for the anterior static field and VMAT, with and without a thermoplastic mask. No significant differences were observed among the three topical agents. For topical agent thicknesses of 0.1, 0.5 and 2 mm, the increases in surface dose for the anterior static field without the thermoplastic mask were 7-9, 30-31 and 81-84%, respectively. With the thermoplastic mask, the corresponding increases were 5, 12-15 and 41-43%, respectively. The increases in surface dose for VMAT without the thermoplastic mask were 5-8, 16-19 and 36-39%, respectively, and those with the thermoplastic mask were 4, 7-10 and 15-19%, respectively. The rate of increase in surface dose with the thermoplastic mask was smaller than that without the thermoplastic mask. The increase in surface dose with topical agents of clinical standard thickness (0.02 mm) was estimated to be 2% with the thermoplastic mask. The increase in surface dose with topical agents in dosimetric simulation, compared with control situation, is not significant in clinical conditions for HNC patients.

[New Attempt of Radiation Oncology Section to Radiotherapy for Head and Neck Cancer].

Oral care is important for patients with head and neck cancer who undergo radiotherapy because these patients encounter various symptoms, which decrease their quality of life(QOL). Oral mucositis is considered the major side effect of radiation, and the dose-volume parameters can serve as predictors of the occurrence of severe oral mucositis. Therefore, understanding radiation treatment planning(e. g., prescription dose and irradiated volumes of the organs at risk)and providing oral healthcare before, during, and after radiotherapy are essential for maintaining patients' QOL. METHODS: An RT viewer (Climb Medical Systems) was installed into the inhouse hospital information system to provide education regarding radiation treatment planning to medical staff members (dentists and nurses) by medical physicists. RESULTS: Patients can undertake appropriate oral care before radiotherapy, and this intervention has potential for reducing the radiation-related side effect. CONCLUSION: Education regarding radiation treatment planning by medical physicists using the RT viewer could improve the knowledge of medical staffs regarding the predictors of radiation-induced side effects for. By introducing the appropriate intervention of oral care before radiotherapy, it may be feasible to maintain patients' QOL.

Improvement in bladder volume reproducibility using A-mode portable ultrasound bladder scanner in moderate-hypofractionated volumetric modulated arc therapy for prostate cancer patients.

PURPOSE: This study introduced an A-mode portable ultrasound bladder scanner, the Lilium® α-200 (here after Lilium; Lilium Otsuka, Kanagawa, Japan), for the treatment of prostate cancer patients with hypofractionated volumetric modulated arc therapy to improve the reproducibility of bladder volume (BV). MATERIALS AND METHODS: Thirty patients were advised to maintain full BV prior to computed tomography (CT) simulation and daily treatment. Among these, the BV of 15 patients was measured using Lilium until a BV of 80% in the simulation was achieved (with the Lilium group). Daily cone-beam CT (CBCT) was performed for treatment. The correlation between BV measured by CBCT and Lilium was assessed. The differences in the BV and dosimetric parameters of the bladder in the CBCT versus planning CT were compared between the groups with and without Lilium. RESULTS: There was a significantly strong relationship (r = 0.796, p < 0.05) between the BVs measured using CBCT and Lilium. The relative BV ratios to simulation CT < 0.5 and > 2 were observed in 10.3% and 12.7%, respectively, of treatment sessions without Lilium group, while these ratios were 1% and 2.8%, respectively, in the Lilium group. The mean absolute difference in the range of V30Gy to V40Gy without Lilium sessions was significantly larger (p < 0.05) than that in the Lilium group. CONCLUSION: The use of the A-mode portable ultrasound bladder scanner significantly improved the reproducibility of the BV, resulting in few variations in the dosimetric parameters for the bladder.