On the wall perturbation correction for a parallel‐plate NACP‐02 chamber in clinical electron beams

Zink, Klemens; Wulff, Jörg

doi:10.1118/1.3544660

Cited by 16 publications

(12 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The model used in that work is based on the publication of Chin et al 22 who suggested that the mass thickness of the front wall of the NACP-02 chamber should be increased by about 50%. The result of Zink and Wulff 34 is similar to the corresponding value of 0.71 mm in Table II although the results of the present work also account for the effect of the air cavity on the electron fluence.…”

Section: B2 Comparison To Previous Calculationssupporting

confidence: 85%

“…In what follows, we compare the calculated EPOM shifts obtained here with those obtained by other authors using Monte Carlo simulations of ion chamber response in electron beams. [32][33][34] Since the results of this work and all previous Monte Carlo calculated EPOM shifts used the EGSnrc code system, there is some correlation among the results discussed in this comparison.…”

Section: B2 Comparison To Previous Calculationsmentioning

confidence: 84%

“…Their results amount to 1.48 ± 0.03, 1.51 ± 0.05 and 1.51 ± 0.05 mm in 6, 11, and 21 MeV beams, respectively, in good agreement with the 1.55 mm value in Table II. In the same publication, Zink and Wulff 33 studied the variation of the wall correction factor for the PTW Roos chamber with depth and observed that a beam energy independent EPOM shift into the chamber cavity by 0.17 mm minimizes the variation of P wall with depth which compares to our value of 0.42 mm in Table II. In a subsequent publication, 34 the same authors found that the use of an EPOM shift of 0.58 mm from the inside of the front face into the NACP-02 chamber cavity minimizes the variation of P wall with depth. The model used in that work is based on the publication of Chin et al 22 who suggested that the mass thickness of the front wall of the NACP-02 chamber should be increased by about 50%.…”

Section: B2 Comparison To Previous Calculationsmentioning

confidence: 93%

See 2 more Smart Citations

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

Muir

Rogers

2014

Medical Physics

View full text Add to dashboard Cite

show abstract

Section: B2 Comparison To Previous Calculationssupporting

confidence: 85%

Section: B2 Comparison To Previous Calculationsmentioning

confidence: 84%

Section: B2 Comparison To Previous Calculationsmentioning

confidence: 93%

See 1 more Smart Citation

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

Muir

Rogers

2014

Medical Physics

View full text Add to dashboard Cite

show abstract

“…A bigger challenge for parallel-plate ICs is defining the EPOM once the position of the outer wall is determined. A number of recent publications [13][14][15][16][17][18] have indicated that this is not necessarily congruent with the inside entrance window of the IC.…”

Section: Discussionmentioning

confidence: 98%

Quantitative ionization chamber alignment to a water surface: Performance of multiple chambers

2017

View full text Add to dashboard Cite

The water-to-air scanning method coupled with gCAP analysis identifies the alignment of the IC OR to the water surface within the scanning resolution for all ICs studied. The gCAP method can precisely and reproducibly align the physical center of a given cylindrical IC with the water surface, be applied prospectively or retrospectively, and provides the prospect for automated water surface identification for scanning systems. The gCAP method eliminates the visual subjectivity inherent to current IC-to-water surface alignment techniques, has been validated with a wide variety of commercially available ICs, and should be independent of the scanning system used for data acquisition.

show abstract

“…14, 15 The results will be applicable not only to the Markus chamber but also to the more recent designs of flat ionization chambers for electron beam dosimetry such as the Roos, Exradin A10, and the Advanced Markus chamber. Similarly to the experimental study performed by Johansson,8 we only consider wall-less cavities, i.e., the impact of the chamber wall always present in real ionization chambers will not be investigated.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo study of the depth‐dependent fluence perturbation in parallel‐plate ionization chambers in electron beams

Zink

Czarnecki²,

Looe

et al. 2014

Medical Physics

Self Cite

View full text Add to dashboard Cite

Purpose:The electron fluence inside a parallel-plate ionization chamber positioned in a water phantom and exposed to a clinical electron beam deviates from the unperturbed fluence in water in absence of the chamber. One reason for the fluence perturbation is the well-known "inscattering effect," whose physical cause is the lack of electron scattering in the gas-filled cavity. Correction factors determined to correct for this effect have long been recommended. However, more recent Monte Carlo calculations have led to some doubt about the range of validity of these corrections. Therefore, the aim of the present study is to reanalyze the development of the fluence perturbation with depth and to review the function of the guard rings. Methods: Spatially resolved Monte Carlo simulations of the dose profiles within gas-filled cavities with various radii in clinical electron beams have been performed in order to determine the radial variation of the fluence perturbation in a coin-shaped cavity, to study the influences of the radius of the collecting electrode and of the width of the guard ring upon the indicated value of the ionization chamber formed by the cavity, and to investigate the development of the perturbation as a function of the depth in an electron-irradiated phantom. The simulations were performed for a primary electron energy of 6 MeV. Results: The Monte Carlo simulations clearly demonstrated a surprisingly large in-and outward electron transport across the lateral cavity boundary. This results in a strong influence of the depth-dependent development of the electron field in the surrounding medium upon the chamber reading. In the buildup region of the depth-dose curve, the in-out balance of the electron fluence is positive and shows the well-known dose oscillation near the cavity/water boundary. At the depth of the dose maximum the in-out balance is equilibrated, and in the falling part of the depth-dose curve it is negative, as shown here the first time. The influences of both the collecting electrode radius and the width of the guard ring are reflecting the deep radial penetration of the electron transport processes into the gas-filled cavities and the need for appropriate corrections of the chamber reading. New values for these corrections have been established in two forms, one converting the indicated value into the absorbed dose to water in the front plane of the chamber, the other converting it into the absorbed dose to water at the depth of the effective point of measurement of the chamber. In the Appendix, the in-out imbalance of electron transport across the lateral cavity boundary is demonstrated in the approximation of classical small-angle multiple scattering theory. Conclusions: The in-out electron transport imbalance at the lateral boundaries of parallel-plate chambers in electron beams has been studied with Monte Carlo simulation over a range of depth in water, and new correction factors, covering all depths and implementing the effective point of measurement concept, have been developed. C

show abstract

On the wall perturbation correction for a parallel‐plate NACP‐02 chamber in clinical electron beams

Cited by 16 publications

References 38 publications

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

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

Quantitative ionization chamber alignment to a water surface: Performance of multiple chambers

Monte Carlo study of the depth‐dependent fluence perturbation in parallel‐plate ionization chambers in electron beams

Contact Info

Product

Resources

About