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Characterization of the Two-Dimensional Liquid Field Ion Chamber Detector Array Used for the Verification of the Treatments in Radiation Therapy

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M Markovic

M Markovic1*, S Stathakis3, C Ha3, B Poppe2, A Gutierrez3, N Papanikolaou3, (1) University of Texas Health Science Center at San Antonio, San Antonio, TX, (2) Pius Hospital, Oldenburg,(3) Cancer Therapy and Research Center University of Texas Health Sciences Cent, San Antonio, TX

SU-E-T-323 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The aim for the study was to investigate characteristics of the OCTAVIUS Detector 1000 SRS, used for verification of the treatment plans in radiotherapy treatments of the small field sizes.

Methods:Reproducibility and dose linearity of the output of the detector has been checked. As well as radiation output as a function of the field size. The detectors sensitivity to positional changes of the collimation system and the perturbation effect of irradiated area has been investigated. Clinical dose maps were measured and the detectors performance has been investigated. Dose profiles of the open and wedge modulated fields for the different field sizes were measured. All the collected data has been analyzed and relevant comparisons were done.

Results:Reproducibility of the measurements within every batch showed superb agreement with the highest value of the standard deviation of the mean not exceeding 0.2%, which is an indicator of very short-term reproducibility performance. The standard deviation between the batches does not exceed 0.5%, which is an excellent indicator of the reproducibility with the longer period of time. The measured results of the central axis (CAX) ionization chamber showed that response is very linear with the dose. The output factors agreement between detector and the pinpoint chamber measured data set is very good as well as agreement with microLion chamber measured data set. Sensitivity measurement showed that the geometrical separation of the detectors does not contribute to the loss of the sensitivity and there is no noticeable perturbation effect of the irradiated area. Dose profiles measurement showed excellent agreement with data acquired with pinpoint chamber.

Conclusion:Broad range of tests performed in investigation showed that OCTAVIUS Detector 1000 SRS is a dosimetrically accurate and sensitive device and it can be used for quality assurance and verification of clinical radiotherapy beams.

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