Monte Carlo calculations of electron beam quality conversion factors for several ion chamber types

Abstract

These results will prove useful as electron beam reference dosimetry protocols are being updated. The analysis of this work indicates that cylindrical ion chambers may be appropriate for use in low-energy electron beams but measurements are required to characterize their use in these beams.

Electron beam water calorimetry measurements to obtain beam quality conversion factors

“…Two recent publications provide Monte Carlo calculated k Q factors in electron beams using the same method and the same Monte Carlo code system . Muir and Rogers compared their calculated values to those of Zink and Wulff and found very good agreement. Therefore, we only compare the measured results obtained here to the more extensive set of calculations of Muir and Rogers.…”

“…Zink and Wulff used Monte Carlo calculations to determine k Q factors for four plane‐parallel ion chamber types (PTW Roos, PTW Markus, PTW Advanced Markus and IBA NACP‐02). Muir and Rogers used similar Monte Carlo calculations to provide k Q factors for several plane‐parallel and cylindrical ion chamber types and there is substantial overlap with the chambers investigated here. A comparison among results from different studies is difficult because of the various approaches used to define the point of measurement and the differences in beam qualities for the beams investigated in each publication.…”

“…For plane‐parallel chambers, we use a water‐equivalent scaling of the chambers' front face to position chambers at the point of measurement whereas TG‐51 values are for plane‐parallel chambers positioned with the inside of their front face at the reference depth. As noted in the Monte Carlo study by Muir and Rogers and the TRS‐398 protocol, this small difference in positioning has little impact on k Q or k ecal factors for high‐energy electron beams so no adjustment is made for this difference in point of measurement for comparison of results. To obtain the k ecal factor for plane‐parallel chambers calibrated directly against the primary standard calorimeter, interpolation of the results in the 18 MeV and 22 MeV beams is used to get the value of k ecal with = 7.5 cm.…”

Use of parallel‐plate ionization chambers in reference dosimetry of NOVAC and LIAC® mobile electron linear accelerators for intraoperative radiotherapy: a multi‐center survey

“…The results are in excellent agreement with the tables reported by the manufacturer . Finally, the PPC40 chamber has the same k Q,Qo,TRS398 as the PTW 34001 (Roos) chamber within 0.2%, as verifiable by means of the above references . k Q,Qo,TRS398 factors were used as k Q,Qo in Eq.…”

“…37 Finally, the PPC40 chamber has the same k Q,Qo,TRS398 as the PTW 34001 (Roos) chamber within 0.2%, as verifiable by means of the above references. [35][36][37][38] k Q,Qo, TRS398 factors were used as k Q,Qo in Eq. (1) by centers that performed reference dosimetry at z ref .…”