Quantitative ionization chamber alignment to a water surface: Theory and simulation

Siebers, Jeffrey V.; Ververs, James D.; Tessier, Frédéric

doi:10.1002/mp.12319

Cited by 3 publications

(11 citation statements)

References 26 publications

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“…This effect persists, although it is moderated, when the water surface tension is reduced. This finding confirms the recommendations of AAPM TG‐106 and others that PDD scans should be performed from depth in water toward the water surface. The reduction in water surface tension via the addition of dishwashing detergent or other chemical to the water is not recommended for standard clinical water tank usage.…”

Section: Scans and Resultssupporting

confidence: 89%

“…Noise can be further reduced by acquiring data at slower speeds for a continuously moving IC or sampling for longer times at each individual depth (recommended). Fitting of these measurements analogous to the work done in the companion paper confirms the gCAP locations, as shown in Data .…”

Section: Scans and Resultssupporting

confidence: 72%

“…Fitting of these measurements analogous to the work done in the companion paper generally confirms the gCAP locations, as shown in the Data , although use of different fitting forms can produce notably different results, particularly for small‐ and large‐volume ICs as compared with typical scanning IC volumes. The Exradin A2 also appears to be an outlier for the 6 MV measurements, but the large diameter of this IC impacts the magnitude of the derivative and therefore the sensitivity of the gCAP .…”

Section: Scans and Resultssupporting

confidence: 70%

“…Figure (b) shows the difference between the measured gCAP and the IC OR for each IC. Based on the theory, the gCAP should be equal to the IC OR. For nine of the 12 ICs, this is the case within the 0.1 mm level of accuracy of the data.…”

Section: Scans and Resultsmentioning

confidence: 99%

“…This study expands upon the initial and companion studies by experimentally validating the gCAP method for photon depth‐ionization measurements taken with a variety of ICs. The twenty‐two IC models tested include commonly used scanning ICs, Farmer models, micro‐ICs, and parallel‐plate designs.…”

Section: Introductionmentioning

confidence: 84%

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

2017

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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.

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Section: Scans and Resultssupporting

confidence: 89%

Section: Scans and Resultssupporting

confidence: 72%

Section: Scans and Resultssupporting

confidence: 70%

Section: Scans and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 84%

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

2017

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The effective point of measurement for depth‐dose measurements in small MV photon beams with different detectors

Wegener

Sauer

2019

Medical Physics

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Purpose: The effective point of measurement (EPOM) of cylindrical ionization chambers differs from their geometric center. The exact shift depends on chamber construction details, above all the chamber size, and to some degree on the field-size and beam quality. It generally decreases as the chamber dimensions get smaller. In this work, effective points of measurement in small photon fields of a range of cylindrical chambers of different sizes are investigated, including small chambers that have not been studied previously. Methods: In this investigation, effective points of measurement for different ionization chambers (Farmer type, scanning chambers, micro-ionization chambers) and solid state detectors were determined by measuring depth-ionization curves in a 6 MV beam in field sizes between 2 9 2 cm 2 and 10 9 10 cm 2 and comparing those curves with curves measured with plane-parallel chambers. Results: It was possible to average the results to one shift per detector, as the results were sufficiently independent of the studied field sizes. For cylindrical ion chambers, shifts of the EPOM were determined to be between 0.49 and 0.30 times the inner chamber radius from the reference point. Conclusions:We experimentally confirmed the previously reported decrease of the EPOM shift with decreasing detector size. Highly accurate data for a large range of detectors, including new very small ones, were determined. Thus, small chambers noticeably differ from the 0.5-times to 0.6-times the inner chamber radius recommendations in current dosimetry protocols. The detector-individual EPOMs need to be considered for measurements of depth-dose curves.

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Development of a device to improve the precision of water surface identification for MeV electron beam dosimetry

Okky Agassy,

Park,

Kim

2024

Nuclear Engineering and Technology

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Quantitative ionization chamber alignment to a water surface: Theory and simulation

Cited by 3 publications

References 26 publications

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

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

The effective point of measurement for depth‐dose measurements in small MV photon beams with different detectors

Development of a device to improve the precision of water surface identification for MeV electron beam dosimetry

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