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. 2009;164(2009):12058.
doi: 10.1088/1742-6596/164/1/012058.

Investigating the Feasibility of 3D Dosimetry in the RPC IMRT H&N Phantom

Hs Sakhalkar  1 , D Sterling, J Adamovics, G Ibbott, M Oldham
Affiliations

Investigating the Feasibility of 3D Dosimetry in the RPC IMRT H&N Phantom

Hs Sakhalkar et al. J Phys Conf Ser. 2009.

Abstract

An urgent requirement for 3D dosimetry has been recognized because of high failure rate (~25%) in RPC credentialing, which relies on point and 2D dose measurements. Comprehensive 3D dosimetry is likely to resolve more errors and improve IMRT quality assurance. This work presents an investigation of the feasibility of PRESAGE/optical-CT 3D dosimetry in the Radiologic Physics Center (RPC) IMRT H&N phantom. The RPC H&N phantom (with standard and PRESAGE dosimetry inserts alternately) was irradiated with the same IMRT plan. The TLD and EBT film measurement data from standard insert irradiation was provided by RPC. The 3D dose measurement data from PRESAGE insert irradiation was readout using the OCTOPUS™ 5X optical-CT scanner at Duke. TLD, EBT and PRESAGE dose measurements were inter-compared with Eclipse calculations to evaluate consistency of planning and delivery. Results showed that the TLD point dose measurements agreed with Eclipse calculations to within 5% dose-difference. Relative dose comparison between Eclipse dose, EBT dose and PRESAGE dose was conducted using profiles and gamma comparisons (4% dose-difference and 4 mm distance-to-agreement). Profiles showed good agreement between measurement and calculation except along steep dose gradient regions where Eclipse modelling might be inaccurate. Gamma comparisons showed that the measurement and calculation showed good agreement (>96%) if edge artefacts in measurements are ignored. In conclusion, the PRESAGE/optical-CT dosimetry system was found to be feasible as an independent dosimetry tool in the RPC IMRT H&N phantom.

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Figures

Fig 1
Fig 1. RPC H&N phantom and inserts
A picture of the phantom with insert is shown in A. The central cross-section of the standard RPC insert is shown in B. The PRESAGE insert is shown in C.
Fig 2
Fig 2. Reduction in prescription dose did not change relative dose distribution in RPC insert and PRESAGE insert
Fig 3
Fig 3. PRESAGE dose measurement
A) Central slice. B) Dose profiles along dotted lines in A show reduced noise and edge artefact.
Fig 4
Fig 4. Profile (A) and gamma comparison (B) between PRESAGE dose, EBT dose and Eclipse dose
See this image and copyright information in PMC

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