title: Utility of Smart Arc CDR for intensity-modulated radiation therapy for prostate cancer.
abstract: Volumetric-modulated arc therapy (VMAT) is a widespread intensity-modulated radiation therapy (IMRT) method, however, VMAT requires adaptation of the radiation treatment planning system (RTPS) and linear accelerator (linac); these upgrades are quite expensive. The Smart Arc of Pinnacle(3) (Philips), which is the software used in VMAT calculations, can select constant dose rate (CDR) mode. This approach has a low initial cost because the linac upgrade is not required. The objective of this study was to clarify the utility of CDR mode for prostate IMRT. Pinnacle(3) and Clinac 21EX linac (Varian, 10 MV X-rays) were used for planning. The plans were created for 28 patients using a fixed multi-field IMRT (f-IMRT), VMAT and CDR techniques. The dose distribution results were classified into three groups: optimal, suboptimal and reject. For the f-IMRT, VMAT and CDR results, 25, 26 and 21 patients were classified as 'optimal', respectively. Our results show a significant reduction in the achievement rate of 'optimal' for a CDR when the bladder volume is <100 cm(3). The total numbers of monitoring units (MUs) (average ± 1σ) were 469 ± 53, 357 ± 35 and 365 ± 33; the average optimization times were ∼50 min, 2 h and 2 h 40 min, and the irradiation times were ∼280 s, 60 s and 110 s, respectively. CDR can reduce the total MUs and irradiation time compared with f-IMRT, and CDR has a lower initial cost compared with VMAT. Thus, for institutions that do not currently perform VMAT, CDR is a useful option. Additionally, in the context of patient identification, bladder volume may be useful.
authors: Kanagawa Cancer Center, 2-3-2, Nakao, Asahi-Ku, Yokohama City, Kanagawa, 241-8515, Japan hata19840928@gmail.com.
authors: Shogo
authors: S
authors: Hatanaka
authors: Rikkyo University, 3-34-1, Nishi-ikebukuro Toshima-Ku, Tokyo, 171-0021, Japan St Luke's International Hospital, 9-1, Akashi-Cho, Chuo-Ku, Tokyo, 104-8560, Japan.
authors: Seiichi
authors: S
authors: Tamaki
authors: St Luke's International Hospital, 9-1, Akashi-Cho, Chuo-Ku, Tokyo, 104-8560, Japan.
authors: Haruna
authors: H
authors: Endo
authors: St Luke's International Hospital, 9-1, Akashi-Cho, Chuo-Ku, Tokyo, 104-8560, Japan.
authors: Norifumi
authors: N
authors: Mizuno
authors: St Luke's International Hospital, 9-1, Akashi-Cho, Chuo-Ku, Tokyo, 104-8560, Japan.
authors: Naoki
authors: N
authors: Nakamura
mesh_terms: D006801:Humans; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D012984:Software; D001743:Urinary Bladder / Q000528:radiation effects
keywords: Smart Arc CDR; constant dose rate; intensity-modulated radiation therapy; prostate cancer; volumetric-modulated arc therapy