title: Dose error from deviation of dwell time and source position for high dose-rate 192Ir in remote afterloading system.
abstract: The influence of deviations in dwell times and source positions for (192)Ir HDR-RALS was investigated. The potential dose errors for various kinds of brachytherapy procedures were evaluated. The deviations of dwell time ΔT of a (192)Ir HDR source for the various dwell times were measured with a well-type ionization chamber. The deviations of source position ΔP were measured with two methods. One is to measure actual source position using a check ruler device. The other is to analyze peak distances from radiographic film irradiated with 20 mm gap between the dwell positions. The composite dose errors were calculated using Gaussian distribution with ΔT and ΔP as 1σ of the measurements. Dose errors depend on dwell time and distance from the point of interest to the dwell position. To evaluate the dose error in clinical practice, dwell times and point of interest distances were obtained from actual treatment plans involving cylinder, tandem-ovoid, tandem-ovoid with interstitial needles, multiple interstitial needles, and surface-mold applicators. The ΔT and ΔP were 32 ms (maximum for various dwell times) and 0.12 mm (ruler), 0.11 mm (radiographic film). The multiple interstitial needles represent the highest dose error of 2%, while the others represent less than approximately 1%. Potential dose error due to dwell time and source position deviation can depend on kinds of brachytherapy techniques. In all cases, the multiple interstitial needles is most susceptible.
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okamoto
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Ako
authors.initials: A
authors.lastname: Aikawa
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Akihisa
authors.initials: A
authors.lastname: Wakita
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Yoshio
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Murakami
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Hamada
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Abe
authors.affiliation: Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Itami
mesh_terms: D001918:Brachytherapy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007496:Iridium Radioisotopes / Q000008:administration & dosage*; D009369:Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000706:statistics & numerical data; D061106:Radiotherapy Setup Errors / Q000517:prevention & control / Q000706:statistics & numerical data
chemical_list: D007496:Iridium Radioisotopes
keywords: 192Ir; RALS; dose error; dwell time; source position