title: Evaluation of Dose Uncertainty to the Target Associated With Real-Time Tracking Intensity-Modulated Radiation Therapy Using the CyberKnife Synchrony System.
abstract: We investigated the dose uncertainty caused by errors in real-time tracking intensity-modulated radiation therapy (IMRT) using the CyberKnife Synchrony Respiratory Tracking System (SRTS). Twenty lung tumors that had been treated with non-IMRT real-time tracking using CyberKnife SRTS were used for this study. After validating the tracking error in each case, we did 40 IMRT planning using 8 different collimator sizes for the 20 patients. The collimator size was determined for each planning target volume (PTV); smaller ones were one-half, and larger ones three-quarters, of the PTV diameter. The planned dose was 45 Gy in 4 fractions prescribed at 95% volume border of the PTV. Thereafter, the tracking error in each case was substituted into calculation software developed in house and randomly added in the setting of each beam. The IMRT planning incorporating tracking errors was simulated 1000 times, and various dose data on the clinical target volume (CTV) were compared with the original data. The same simulation was carried out by changing the fraction number from 1 to 6 in each IMRT plan. Finally, a total of 240 000 plans were analyzed. With 4 fractions, the change in the CTV maximum and minimum doses was within 3.0% (median) for each collimator. The change in D99 and D95 was within 2.0%. With decreases in the fraction number, the CTV coverage rate and the minimum dose decreased and varied greatly. The accuracy of real-time tracking IMRT delivered in 4 fractions using CyberKnife SRTS was considered to be clinically acceptable.
authors.affiliation: Department of Radiation Oncology, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya, Aichi, Japan Department of Neurosurgery, Yokohama CyberKnife Center, Yokohama, Kanagawa, Japan h-iwa-ncu@nifty.com.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Iwata
authors.affiliation: Division of Quality Management with Radiation, Yokohama CyberKnife Center, Yokohama, Kanagawa, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Miyakojima IGRT Clinic, Miyakojima-ku, Osaka, Japan.
authors.forename: Hiroya
authors.initials: H
authors.lastname: Shiomi
authors.affiliation: Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Murai
authors.affiliation: Department of Neurosurgery, Yokohama CyberKnife Center, Yokohama, Kanagawa, Japan.
authors.forename: Koshi
authors.initials: K
authors.lastname: Tatewaki
authors.affiliation: Department of Neurosurgery, Yokohama CyberKnife Center, Yokohama, Kanagawa, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohta
authors.affiliation: Division of Quality Management with Radiation, Yokohama CyberKnife Center, Yokohama, Kanagawa, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Okawa
authors.affiliation: Department of Neurosurgery, Yokohama CyberKnife Center, Yokohama, Kanagawa, Japan Radiation Oncology Center, Suzukake Central Hospital, Hamamatsu, Shizuoka, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Yokota
authors.affiliation: Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Shibamoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D035501:Uncertainty
keywords: CyberKnife synchrony respiratory tracking system; real-time tracking IMRT; tracking error