A procedure to determine the planar integral spot dose values of proton pencil beam spotsa)
Comparison of: (a) ion chamber measured and Monte Carlo simulated cross-line relative dose profiles at two depths for 72.5 MeV PPBS and (b) ion Chamber measured and Monte Carlo simulated cross-line relative dose profiles at three different depths for 221.8 MeV PPBS.
Comparison of in-line and cross-line lateral relative dose profiles for 72.5 MeV PPBS and 221.8 MeV PPBS at 2 cm depth measured using ion chamber.
Comparison between the ion chamber and film measured lateral relative dose profiles of 146.9 MeV PPBS at a 2 cm water equivalent depth.
In-line lateral dose (cGy/MU) profiles of PPBSs of different energies measured at 2 cm depth.
Peak spot dose in cGy/MU at different depths for PPBSs of five different energies measured by ion chamber (IC) by placing it both at the peak of the single PPBS and the center of a 10 × 10 cm2 broad field. Spot spacing of 5 mm was used in creating the broad field. The nominal range corresponds to the depth of 90% Bragg peak dose location.
Limited dose averaging factor (LDAF) obtained from the ratio of the average PISD calculated using PPBS lateral relative dose profiles along the two principal axes and those at different angles measured using Kodak XV film at 2 cm depth.
Comparison of PISD values from the present area integration of planar PPBS dose method (PISDfull and PISDRBPC) with those from measurement with BPC (PISDBPC). All PISD values are in units of Gy mm2/MU. The PISDfull is calculated by setting the upper limit of integration for radius in Eq. (2) to a value where the relative dose value is less than the 0.1% of the PPBS peak dose. The upper limit in Eq. (2) was set to 4.08 cm, which corresponds to the radius of BPC, to calculate the PISDRBPC.
Calculated LTDCF from the present area integration of planar PPBS dose method and comparison with Monte Carlo simulated values for a virtual chamber of 9 cm radius.
Comparison of calculated PISD values (PISDfull) in (Gy mm2/MU) from the present area integration of planar PPBS dose method with the currently commissioned values in Eclipse TPS at PTCH at 2 cm depths in water. PISD full values are obtained by setting the limit of integration to an off-axis distance in the PPBS profile where the relative dose value is 0.1% of its peak value in Eq. (2), and the TPS PISD values were obtained from Monte Carlo simulation for a 20 cm radius virtual chamber.
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