Surface dose measurement using TLD powder extrapolation

Journal Article · Sun Oct 01 04:00:00 EDT 2006 · Medical Dosimetry

DOI:https://doi.org/10.1016/j.meddos.2006.02.003· OSTI ID:20858077

Rapley, P ^[1]

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1. Regional Cancer Care, Thunder Bay Regional Health Sciences Centre, Thunder Bay, Ontario (Canada)

Surface/near-surface dose measurements in therapeutic x-ray beams are important in determining the dose to the dermal and epidermal skin layers during radiation treatment. Accurate determination of the surface dose is a difficult but important task for proper treatment of patients. A new method of measuring surface dose in phantom through extrapolation of readings from various thicknesses of thermoluminescent dosimeter (TLD) powder has been developed and investigated. A device was designed, built, and tested that provides TLD powder thickness variation to a minimum thickness of 0.125 mm. Variations of the technique have been evaluated to optimize precision with consideration of procedural ease. Results of this study indicate that dose measurements (relative to D{sub max}) in regions of steep dose gradient in the beam axis direction are possible with a precision (2 standard deviations [SDs]) as good as {+-} 1.2% using the technique. The dosimeter was developed and evaluated using variation to the experimental method. A clinically practical procedure was determined, resulting in measured surface dose of 20.4 {+-} 2% of the D{sub max} dose for a 10 x 10 cm{sup 2}, 80-cm source-to-surface distance (SSD), Theratron 780 Cobalt-60 ({sup 60}C) beam. Results obtained with TLD powder extrapolation compare favorably to other methods presented in the literature. The TLD powder extrapolation tool has been used clinically at the Northwestern Ontario Regional Cancer Centre (NWORCC) to measure surface dose effects under a number of conditions. Results from these measurements are reported. The method appears to be a simple and economical tool for surface dose measurement, particularly for facilities with TLD powder measurement capabilities.

• OSTI ID: 20858077
• Journal Information: Medical Dosimetry, Journal Name: Medical Dosimetry Journal Issue: 3 Vol. 31; ISSN 0958-3947; ISSN MEDOEJ
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
ACCURACY
BEAMS
CALIBRATION STANDARDS
COBALT 60
EXTRAPOLATION
NEOPLASMS
PHANTOMS
RADIATION DOSES
SKIN
THERMOLUMINESCENT DOSEMETERS
THICKNESS
X RADIATION