High Precision in Dose Delivery: Routine Use of a Microcomputer

Awschalom, M.; Goodwin, R.W.; Grumboski, L.; Rosenberg, Ivan; Shea, Megyn

doi:10.2172/1156175

Cited by 1 publication

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“…In the absence of a standard neutron source, a cesium-137 source was chosen as a reference standard. To facilitate frequent quality assurance measurements, a computerized data collection system was devised (1) . This system has been in use for nearly thirty years and has enabled acquisition of data on the long-term behavior of TE ionization chambers.…”

Section: Introductionmentioning

confidence: 99%

Stability of A-150 plastic ionisation chamber response over a 30-y period

Kroc

Lennox

2007

Radiation Protection Dosimetry

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At the Northern Illinois University Institute for Neutron Therapy at Fermilab, the clinical tissue-equivalent ionisation chamber response is measured every treatment day using a cesium source that was configured to match readings obtained at the National Bureau of Standards. Daily measurements are performed in air using the air-to-tissue dose conversion factors given in AAPM Report #7. The measured exposure calibration factors have been tabulated and graphed as a function of time from 1978 to present. For A-150 plastic ionisation chambers, these factors exhibit a sinusoidal variation with a period of approximately 1 y and amplitude of +/- 1%. This variation, attributable to the hygroscopic nature of A-150 plastic, is correlated with the relative humidity of the facility, and is greater than the humidity corrections for gas described in the literature. The data suggest that chamber calibration should be performed at least weekly to accommodate these variations.

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Section: Introductionmentioning

confidence: 99%