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X-ray surface dose measurements using TLD extrapolation

Journal Article


Abstract


  • Surface dose measurements in therapeutic x-ray beams are of importance in determining the dose to the skin of patients undergoing radiotherapy. Measurements were performed in the 6-MV beam of a medical linear accelerator with LiF thermoluminescence dosimeters (TLD) using a solid water phantom. TLD chips (surface area 3.17x3.17 cm2) of three different thicknesses (0.230, 0.099, and 0.038 g/cm2) were used to extrapolate dose readings to an infinitesimally thin layer of LiF. This surface dose was measured for field sizes ranging from 1X 1 cm2 to 40 x 40 cm2. The surface dose relative to maximum dose was found to be 10.0% for a field size of 5X5 cm2, 16.3% for 10x10 cm2, and 26.9% for 20x20 cm2. Using a 6-mm Perspex block tray in the beam increased the surface dose in these fields to 10.7%, 17.7%, and 34.2% respectively. Due to the small size of the TLD chips, TLD extrapolation is applicable also for intracavity and exit dose determinations. The technique used for in vivo dosimetry could provide clinicians information about the build up of dose up to 1-mm depth in addition to an extrapolated surface dose measurement. © 1993, American Association of Physicists in Medicine. All rights reserved.

Publication Date


  • 1993

Citation


  • Kron, T., Showell, G., & Clubb, B. (1993). X-ray surface dose measurements using TLD extrapolation. Medical Physics, 20(3), 703-711. doi:10.1118/1.597019

Scopus Eid


  • 2-s2.0-0027172666

Start Page


  • 703

End Page


  • 711

Volume


  • 20

Issue


  • 3

Abstract


  • Surface dose measurements in therapeutic x-ray beams are of importance in determining the dose to the skin of patients undergoing radiotherapy. Measurements were performed in the 6-MV beam of a medical linear accelerator with LiF thermoluminescence dosimeters (TLD) using a solid water phantom. TLD chips (surface area 3.17x3.17 cm2) of three different thicknesses (0.230, 0.099, and 0.038 g/cm2) were used to extrapolate dose readings to an infinitesimally thin layer of LiF. This surface dose was measured for field sizes ranging from 1X 1 cm2 to 40 x 40 cm2. The surface dose relative to maximum dose was found to be 10.0% for a field size of 5X5 cm2, 16.3% for 10x10 cm2, and 26.9% for 20x20 cm2. Using a 6-mm Perspex block tray in the beam increased the surface dose in these fields to 10.7%, 17.7%, and 34.2% respectively. Due to the small size of the TLD chips, TLD extrapolation is applicable also for intracavity and exit dose determinations. The technique used for in vivo dosimetry could provide clinicians information about the build up of dose up to 1-mm depth in addition to an extrapolated surface dose measurement. © 1993, American Association of Physicists in Medicine. All rights reserved.

Publication Date


  • 1993

Citation


  • Kron, T., Showell, G., & Clubb, B. (1993). X-ray surface dose measurements using TLD extrapolation. Medical Physics, 20(3), 703-711. doi:10.1118/1.597019

Scopus Eid


  • 2-s2.0-0027172666

Start Page


  • 703

End Page


  • 711

Volume


  • 20

Issue


  • 3