SU-E-T-463: Impact to Total Scatter Factors On the Calculated Dose Distribution in Radiosurgery

Journal Article · Mon Jun 15 04:00:00 EDT 2015 · Medical Physics

DOI:https://doi.org/10.1118/1.4924825· OSTI ID:22548505

Garcia, O; Larraga-Gutierrez, J ^[1]

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1. National Institute of Neurology and Neurosurgery, Mexico, D.F. (Mexico)

Purpose: To assess the impact of relative measurements: off axis ratios (OAR), tissue phantom ratios (TPR) and especially total scatter factor (TSF) on the calculated dose distribution in stereotactic radiosurgery with circular cones. Methods: Six detectors were employed to characterize circular collimated photon beams of 6 MV: three diodes (SFD, E, SRS), one ionization chamber (CC01) and two radiochromic films (EBT, EBT2). The relative measurements were incorporated in the treatment planning system (TPS) in order to compare and analyze the calculated dose distributions (DD). Each dose distribution was re-scaled by the TSF to observe its effect in the final dose distribution. The comparison was performed by using the gamma index. A Monte Carlo generated dosimetry was used as reference. Results: The results showed that in terms of relative dosimetry all the detectors have a good agreement within 2%, with the exception of the CC01 and EBT2 film. However, the analysis performed with the dose distributions re-scaled relative to the TSF for each detector showed that the impact it was not only to the isocenter dose. The dose to the PTV and normal tissue showed differences up to 13% depending of the dosimeter used for TSF measurements. Conclusion: With the exception of the CC01 ionization chamber and EBT2 radiochromic film, all the studied dosimeters were adequate for the measurement of OAR and TPR. However, attention must be put in the measurement of TSF. The use of the wrong detector does not only affect the isocenter dose, it may have an impact in the PTV and normal tissue dose.

• OSTI ID: 22548505
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 6 Vol. 42; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
61 RADIATION PROTECTION AND DOSIMETRY
ANIMAL TISSUES
FILM DOSIMETRY
IONIZATION CHAMBERS
MONTE CARLO METHOD
PHANTOMS
PHOTOGRAPHIC FILM DOSEMETERS
PHOTON BEAMS
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOTHERAPY
SURGERY