Monte Carlo-calculated beam quality and perturbation correction factors validated against experiments for Farmer and Markus type ionization chambers in therapeutic carbon-ion beams.

. In current dosimetry protocols, the estimated uncertainty of the measured absorbed dose to waterin carbon-ion beams is approximately 3%. This large uncertainty is mainly contributed by the standard uncertainty of the beam quality correction factor.

Investigation of Halcyon multi-leaf collimator model in Eclipse treatment planning system: A focus on the VMAT dose calculation with the Acuros XB algorithm.

Purpose: The dual-layer multi-leaf collimator (MLC) in Halcyon involves further complexities in the dose calculation process, because the leaf-tip transmission varies according to the leaf trailing pattern. For the volumetric modulated arc therapy (VMAT) treatment, the prescribed dose for the target volume can be sensitive to the leaf-tip transmission change. This report evaluates the dosimetric consequence due to the uncertainty of the dual-layer MLC model in Eclipse through the dose verifications for clinical VMAT.

Survey on utilization of flattening filter-free photon beams in Japan.

To understand the current state of flattening filter-free (FFF) beam implementation in C-arm linear accelerators (LINAC) in Japan, the quality assurance (QA)/quality control (QC) 2018-2019 Committee of the Japan Society of Medical Physics (JSMP) conducted a 37-question survey, designed to investigate facility information and specifications regarding FFF beam adoption and usage. The survey comprised six sections: facility information, devices, clinical usage, standard calibration protocols, modeling for treatment planning (TPS) systems and commissioning and QA/QC. A web-based questionnaire was developed.

Estimation of the cable effect in megavoltage photon beam by measurement and Monte Carlo simulation.

Purpose: Ionization chambers are widely used for dosimetry with megavoltage photon beams. Several properties of ionization chambers, including the cable effect, polarity effect, and ion recombination loss, are described in standard dosimetry protocols. The cable effect is categorized as the leakage current and Compton current, and careful consideration of these factors has been described not only in reference dosimetry but also in large fields.

Effect of ICRU report 90 recommendations on Monte Carlo calculated k for ionization chambers listed in the Addendum to AAPM's TG-51 protocol.

Purpose: The ICRU has published new recommendations for ionizing radiation dosimetry. In this work, the effect of recommendations on the water-to-air and graphite-to-air restricted mass electronic stopping power ratios (s and s ) and the individual perturbation correction factors P was calculated. The effect on the beam quality conversion factors k for reference dosimetry of high-energy photon beams was estimated for all ionization chambers listed in the Addendum to AAPM's TG-51 protocol.

Evaluation of gantry angle during respiratory-gated VMAT using triggered kilovoltage x-ray image.

Respiratory-gated volumetric modulated arc therapy (gated VMAT) involves further complexities to the dose delivery process because the gantry rotation must repeatedly stop and restart according to the gating signals. In previous studies, the gantry rotation performances were evaluated by the difference between the plan and the machine log. However, several reports pointed out that log analysis does not sufficiently replicate the machine performance.

Field-size correction factors of a radiophotoluminescent glass dosimeter for small-field and intensity-modulated radiation therapy beams.

Purpose: We evaluated the energy responses of a radiophotoluminescent glass dosimeter (RPLD) to variations in small-field and intensity-modulated radiation therapy (IMRT) conditions using experimental measurements and Monte Carlo simulation.

Methods: Several sizes of the jaw and multileaf collimator fields and various plan-class IMRT-beam measurements were performed using the RPLD and an ionization chamber. The field-size correction factor for the RPLD was determined for 6- and 10-MV x rays.

Correction of stopping power and LET quenching for radiophotoluminescent glass dosimetry in a therapeutic proton beam.

To measure the absorbed dose to water D in proton beams using a radiophotoluminescent glass dosimeter (RGD), a method with the correction for the change of the mass stopping power ratio (SPR) and the linear energy transfer (LET) dependence of radiophotoluminescent efficiency [Formula: see text] is proposed. The calibration coefficient in terms of D for RGDs (GD-302M, Asahi Techno Glass) was obtained using a Co γ-ray. The SPR of water to the RGD was calculated by Monte Carlo simulation, and [Formula: see text] was investigated experimentally using a 70 MeV proton beam.

Changes in deviation of absorbed dose to water among users by chamber calibration shift.

Purpose: The JSMP01 dosimetry protocol had adopted the provisional Co calibration coefficient [Formula: see text], namely, the product of exposure calibration coefficient N and conversion coefficient k . After that, the absorbed dose to water D  standard was established, and the JSMP12 protocol adopted the [Formula: see text] calibration. In this study, the influence of the calibration shift on the measurement of D among users was analyzed.

[A Proposal for the Absorbed Dose to Water Dosimetry for Flattening Filter-free Beams].

Flattening filter-free (FFF) beams generated by linear accelerators have been widely adopted in many hospitals recently for radiation therapy. FFF technology can provide higher dose rates so that shortening of the treatment time and less intra-fraction motion error are expected.In Japan, the current way of determining absorbed dose to water for FFF beams is to follow the Standard Dosimetry 12 protocol which was developed for flattened beams.

Application of a radiophotoluminescent glass dosimeter to nonreference condition dosimetry in the postal dose audit system.

Purpose: The purpose of this study was to obtain a set of correction factors of the radiophotoluminescent glass dosimeter (RGD) output for field size changes and wedge insertions.

Methods: Several linear accelerators were used for irradiation of the RGDs. The field sizes were changed from 5 × 5 cm to 25 × 25 cm for 4, 6, 10, and 15 MV x-ray beams.

[Beam quality conversion factor].

This report describes the update of the beam quality conversion factor k(Q,Q0) of the standard dosimetry protocol in Japan. The k(Q,Q0) corrects for the difference between the response of an ionization chamber in the reference beam quality Q0 used for calibrating the chamber and in the actual user beam quality Q. All changes of k(Q,Q0) were caused by the perturbation correction factors which were recalculated by Monte Carlo simulation.

Evaluation of beam hardening and photon scatter by brass compensator for IMRT.

When a brass compensator is set in a treatment beam, beam hardening may take place. This variation of the energy spectrum may affect the accuracy of dose calculation by a treatment planning system and the results of dose measurement of brass compensator intensity modulated radiation therapy (IMRT). In addition, when X-rays pass the compensator, scattered photons are generated within the compensator.

[Discrepancy between the intended isocenter and that from orthogonal linacgrams in the treatment of CT-guided stereotactic body radiotherapy(SBRT)].

Purpose: In our institution a CT scanner was installed in the same room as the linear accelerator. In stereotactic body radiotherapy (SBRT) we confirmed the isocenter position by serial thin-slice and long-scan-time CT images before every treatment as well as in planning. In planning we constructed digitally reconstructed radiography (DRR) of both the anterior and lateral views.

Reference dosimetry condition and beam quality correction factor for CyberKnife beam.

This article is intended to improve the certainty of the absorbed dose determination for reference dosimetry in CyberKnife beams. The CyberKnife beams do not satisfy some conditions of the standard reference dosimetry protocols because of its unique treatment head structure and beam collimating system. Under the present state of affairs, the reference dosimetry has not been performed under uniform conditions and the beam quality correction factor kQ for an ordinary 6 MV linear accelerator has been temporally substituted for the kQ of the CyberKnife in many sites.