Abstract During irradiation sessions for brain tumors or head and neck cancers, some patients experience abnormal olfactory sensations. To date, the frequency of such sensations during these treatment sessions has not been investigated. We analyzed abnormal olfactory sensations in patients who underwent radiation therapy at our institution for primary brain tumors, excluding malignant lymphoma, between January 2009 and January 2018. A total of 191 patients who were awake during radiation treatment and capable of communicating were analyzed in this retrospective medical study. Of these patients, 7 were aware of olfactory sensations during irradiation. The median age of these 7 patients was 13 (range 8–47) years, Six were <20 years of age, accounting for 10% of the total population of similar age (n = 60). However, only 1 of 131 patients aged ≥20 years complained of strange olfactory sensations. Four of seven patients had germ cell tumors, but none had a medulloblastoma. We investigated patients who experienced light sensation, as an internal standard to ascertain the accuracy of this study. Only 10 patients experienced light sensation during their irradiation sessions. This suggests that the frequency of these sensations was possibly underestimated in our study. In conclusion, a considerable number of patients experienced unusual olfactory sensations during radiation treatment. Further prospective studies on abnormal olfactory sensations during irradiation are needed to clarify the underlying mechanism of this sensation.

The purpose of this study was to test the superiority of a soft tissue‐based setup using cone‐beam computed tomography (CBCT) to a bony structure‐based setup using the ExacTrac system in intensity‐modulated radiotherapy (IMRT) for prostate cancer. We studied 20 patients with localized prostate cancer who received IMRT between November 2010 and February 2012. After the initial setup, the pelvic bony structure‐based setup and ExacTrac system were applied. After that, CBCT and a soft tissue‐based setup were used. A shift in the isocenter between the ExacTrac‐based and CBCT‐based setup was recorded in the anterior–posterior (AP), superior–inferior (SI), and left–right (LR) axes. The shift was considered an interfractional prostate shift. Post‐treatment CBCT was also taken once a week to measure the intrafractional prostate shift, based on the coordinates of the isocenter between pre‐ and post‐treatment CBCT. The planning target volume (PTV) margins were determined using van Herk's method. We measured the elapsed time required for soft tissue matching and the entire treatment time using CBCT. The means±standard deviationfalse(SDfalse) of the inter‐ and intrafractional shifts were 0.9±2.8 mm and −0.3±1.4 mm in the AP, 0.9±2.2 mm and −0.1±1.2 mm in the SI, and 0.1±0.7 mm and −0.1±0.7 mm in the LR directions. The PTV margins in the cases of bony structure‐based and soft tissue‐based setups were 7.3 mm and 2.7 mm in the AP, 5.8 mm and 2.3 mm in the SI, and 1.9 mm and 1.2 mm in the LR directions. Even though the median elapsed time using CBCT was expanded in 5.9 min, the PTV margins were significantly reduced. We found the calculated PTV margins in the soft tissue‐based setup using CBCT were small, and this arrangement was superior to the bony structure‐based setup in prostate IMRT.PACS numbers: 87.19.ru, 87.55.T‐