Monte Carlo simulated beam quality and perturbation correction factors for ionization chambers in monoenergetic proton beams

Kretschmer, Jana; Dulkys, A.; Brodbek, Leonie; Stelljes, Tenzin Sonam; Looe, Hui Khee; Poppe, B

doi:10.1002/mp.14499

Cited by 16 publications

(36 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The physics parameters in GATE/Geant4 used in this work were selected based on previous publications (Wulff et al, 2018;Simiele and DeWerd, 2018;Kretschmer et al, 2020). The settings are summarized in the table S1 provided as supplementary material following the…”

Section: Monte Carlo Simulation Settingsmentioning

confidence: 99%

Investigating the lateral dose response functions of point detectors in proton beams

Kretschmer¹,

Brodbek²,

Looe³

et al. 2022

Phys. Med. Biol.

Self Cite

View full text Add to dashboard Cite

Objective Point detector measurements in proton fields are perturbed by the volume effect originating from geometrical volume-averaging within the extended detector’s sensitive volume and density perturbations by non-water equivalent detector components. Detector specific lateral dose response functions K(x) can be used to characterize the volume effect within the framework of a mathematical convolution model, where K(x) is the convolution kernel transforming the true dose profile D(x) into the measured signal profile of a detector M(x). The aim of this work is to investigate K(x) for detectors in proton beams. Approach The K(x) for five detectors were determined by iterative deconvolution of measurements of D(x) and M(x) profiles at 2 cm water equivalent depth of a narrow 150 MeV proton beam. Monte Carlo simulations were carried out for two selected detectors to investigate a potential energy dependence, and to study the contribution of volume-averaging and density perturbation to the volume effect. Main results The Monte Carlo simulated and experimentally determined K(x) agree within 2.1% of the maximum value. Further simulations demonstrate that the main contribution to the volume effect is volume-averaging. The results indicate that an energy or depth dependence of K(x) is almost negligible in proton beams. While the signal reduction from a Semiflex 3D ionization chamber in the center of a gaussian shaped field with 2 mm sigma is 32% for photons, it is 15% for protons. When measuring the field with a microDiamond the trend is less pronounced and reversed with a signal reduction for protons of 3.9% and photons of 1.9%. Significance The determined K(x) can be applied to characterize the influence of the volume effect on detectors measured signal profiles at all clinical proton energies and measurement depths. The functions can be used to derive the actual dose distribution from point detector measurements.

show abstract

Section: Monte Carlo Simulation Settingsmentioning

confidence: 99%

Investigating the lateral dose response functions of point detectors in proton beams

Kretschmer¹,

Brodbek²,

Looe³

et al. 2022

Phys. Med. Biol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…For cylindrical ICs, a p dis correction of up to 4.5%, at lower proton energies, has been previously found for farmer type ICs, which reduced to 2.0% for cylindrical ICs with smaller sensitive volumes. 11,50 Therefore, parallel-plate ICs are recommended for lower proton energies. The largest displacement correction for carbon ion beams in this work was calculated to be 1.70% and is expected to increase for carbon ion energies smaller than the lowest energy beam investigated in this work, that is, 150 MeV/u.…”

Section: Perturbation Correction Factormentioning

confidence: 99%

“…9 Several studies have shown a non-negligible perturbation correction for both photon and proton beams in the past. 10,11 The extent of the perturbation effect in carbon ion beams has yet to be investigated and is expected to be non-negligible.…”

Section: Introductionmentioning

confidence: 99%

“…Monte Carlo (MC) methods can be employed to calculate the k Q correction factor. 10,11,[16][17][18] Previously, MC-derived f Q correction factors were reported in pristine carbon ion beams in the 150-450 MeV/u energy range for a cylindrical and a parallel-plate IC. 19 A nonnegligible perturbation effect was observed; however, the magnitude of the perturbation correction due to the specific IC subcomponents was not included.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the perturbation effect and LET dependence of beam quality correction factors in carbon ion beams

et al. 2022

View full text Add to dashboard Cite

Background: In a recent study, we reported beam quality correction factors, f Q , in carbon ion beams using Monte Carlo (MC) methods for a cylindrical and a parallel-plate ionization chamber (IC). A non-negligible perturbation effect was observed; however, the magnitude of the perturbation correction due to the specific IC subcomponents was not included. Furthermore, the stopping power data presented in the International Commission on Radiation Units and Measurements (ICRU) report 73 were used, whereas the latest stopping power data have been reported in the ICRU report 90. Purpose: The aim of this study was to extend our previous work by computing f Q correction factors using the ICRU 90 stopping power data and by reporting ICspecific perturbation correction factors.Possible energy or linear energy transfer (LET) dependence of the f Q correction factor was investigated by simulating both pristine beams and spread-out Bragg peaks (SOBPs). Methods: The TOol for PArticle Simulation (TOPAS)/GEANT4 MC code was used in this study. A 30 × 30 × 50 cm 3 water phantom was simulated with a uniform 10 × 10 cm 2 parallel beam incident on the surface. A Farmer-type cylindrical IC (Exradin A12) and two parallel-plate ICs (Exradin P11 and A11) were simulated in TOPAS using the manufacturer-provided geometrical drawings. The f Q correction factor was calculated in pristine carbon ion beams in the 150-450 MeV/u energy range at 2 cm depth and in the middle of the flat region of four SOBPs. The k Q correction factor was calculated by simulating the f Qo correction factor in a 60 Co beam at 5 cm depth. The perturbation correction factors due to the presence of the individual IC subcomponents, such as the displacement effect in the air cavity, collecting electrode, chamber wall, and chamber stem, were calculated at 2 cm depth for monoenergetic beams only. Additionally, the mean dose-averaged and track-averaged LET was calculated at the depths at which the f Q was calculated. Results: The ICRU 90 f Q correction factors were reported. The p dis correction factor was found to be significant for the cylindrical IC with magnitudes up to 1.70%. The individual perturbation corrections for the parallel-plate ICs were <1.0% except for the A11 p cel correction at the lowest energy. The f Q correction for the P11 IC exhibited an energy dependence of >1.00% and displayed differences up to 0.87% between pristine beams and SOBPs. Conversely, the f Q for A11 and A12 displayed a minimal energy dependence of <0.50%. The energy dependence was found to manifest in the LET dependence for the P11 IC. A statistically significant LET dependence was found only for the P11 IC in pristine beams only with a magnitude of <1.10%.

show abstract

“…The article by Kretschmer et al 1 has been published with incomplete Table 3. Due to a technical error, the last 17 of rows in Table 3 were omitted from the published article.…”

Section: Item Name Description Referencesmentioning

confidence: 99%

Erratum: "Monte Carlo simulated beam quality and perturbation correction factors for ionization chambers in monoenergetic proton beams" [Med. Phys. 47, 5890–5905 (2020)]

2021

Medical Physics

View full text Add to dashboard Cite

Monte Carlo simulated beam quality and perturbation correction factors for ionization chambers in monoenergetic proton beams

Cited by 16 publications

References 38 publications

Investigating the lateral dose response functions of point detectors in proton beams

Investigating the lateral dose response functions of point detectors in proton beams

On the perturbation effect and LET dependence of beam quality correction factors in carbon ion beams

Erratum: "Monte Carlo simulated beam quality and perturbation correction factors for ionization chambers in monoenergetic proton beams" [Med. Phys. 47, 5890–5905 (2020)]

Contact Info

Product

Resources

About