Paweł Wołowiec1, Paweł Kukołowicz2, Krzysztof Lis1. 1. Medical Physics Department, Holycross Cancer Centre, Kielce, Poland. 2. Medical Physics Department, Holycross Cancer Centre, Kielce, Poland ; The Jan Kochanowski University of Humanities and Sciences, Kielce, Poland.
Abstract
AIM: To validate a pretreatment verification method of dose calculation and dose delivery based on measurements with Metaplex PTW phantom. BACKGROUND: The dose-response relationships for local tumor control and radiosensitive tissue complications are strong. It is widely accepted that an accuracy of dose delivery of about 3.5% (one standard deviation) is required in modern radiotherapy. This goal is difficult to achieve. This paper describes our experience with the control of dose delivery and calculations at the ICRU reference point. MATERIALS AND METHODS: The calculations of dose at the ICRU reference point performed with the treatment planning system CMS XiO were checked by measurements carried out in the PLEXITOM™ phantom. All measurements were performed with the ion chamber positioned in the phantom, at the central axis of the beam, at depth equivalent to the radiological depth (at gantry zero position). The source-to-phantom surface distance was always set to keep the source-to-detector distance equal to the reference point depth defined in the ICRU Report 50 (generally, 100 cm). The dose was measured according to IAEA TRS 398 report for measurements in solid phantoms. The measurement results were corrected with the actual accelerator's output factor and for the non-full scatter conditions. Measurements were made for 111 patients and 327 fields. RESULTS: The average differences between measurements and calculations were 0.03% (SD = 1.4%), 0.3% (SD = 1.0%), 0.1% (SD = 1.1%), 0.6% (SD = 1.8%), 0.3% (SD = 1.5%) for all measurements, for total dose, for pelvis, thorax and H&N patients, respectively. Only in 15 cases (4.6%), the difference between the measured and the calculated dose was greater than 3%. For these fields, a detailed analysis was undertaken. CONCLUSION: The verification method provides an instantaneous verification of dose calculations before the beginning of a patient's treatment. It allows to detect differences smaller than 3.5%.
AIM: To validate a pretreatment verification method of dose calculation and dose delivery based on measurements with Metaplex PTW phantom. BACKGROUND: The dose-response relationships for local tumor control and radiosensitive tissue complications are strong. It is widely accepted that an accuracy of dose delivery of about 3.5% (one standard deviation) is required in modern radiotherapy. This goal is difficult to achieve. This paper describes our experience with the control of dose delivery and calculations at the ICRU reference point. MATERIALS AND METHODS: The calculations of dose at the ICRU reference point performed with the treatment planning system CMS XiO were checked by measurements carried out in the PLEXITOM™ phantom. All measurements were performed with the ion chamber positioned in the phantom, at the central axis of the beam, at depth equivalent to the radiological depth (at gantry zero position). The source-to-phantom surface distance was always set to keep the source-to-detector distance equal to the reference point depth defined in the ICRU Report 50 (generally, 100 cm). The dose was measured according to IAEA TRS 398 report for measurements in solid phantoms. The measurement results were corrected with the actual accelerator's output factor and for the non-full scatter conditions. Measurements were made for 111 patients and 327 fields. RESULTS: The average differences between measurements and calculations were 0.03% (SD = 1.4%), 0.3% (SD = 1.0%), 0.1% (SD = 1.1%), 0.6% (SD = 1.8%), 0.3% (SD = 1.5%) for all measurements, for total dose, for pelvis, thorax and H&N patients, respectively. Only in 15 cases (4.6%), the difference between the measured and the calculated dose was greater than 3%. For these fields, a detailed analysis was undertaken. CONCLUSION: The verification method provides an instantaneous verification of dose calculations before the beginning of a patient's treatment. It allows to detect differences smaller than 3.5%.
Entities:
Keywords:
PLEXITOM™; Quality control; Radiotherapy; Treatment plan verification
Authors: Maurizio Portaluri; Fulvio I M Fucilli; Santa Bambace; Roberta Castagna; Maria Chiara De Luca; Giorgio Pili; Vittorio Didonna; Francesco Tramacere; Maria Carmen Francavilla; Angela Leone; Maria Grazia Leo Journal: Ann Ist Super Sanita Date: 2009 Impact factor: 1.663
Authors: B A Fraass; K L Lash; G M Matrone; S K Volkman; D L McShan; M L Kessler; A S Lichter Journal: Int J Radiat Oncol Biol Phys Date: 1998-10-01 Impact factor: 7.038