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Improving calibration accuracy in gel dosimetry.

Publication ,  Journal Article
Oldham, M; McJury, M; Baustert, IB; Webb, S; Leach, MO
Published in: Phys Med Biol
October 1998

A new method of calibrating gel dosimeters (applicable to both Fricke and polyacrylamide gels) is presented which has intrinsically higher accuracy than current methods, and requires less gel. Two test-tubes of gel (inner diameter 2.5 cm, length 20 cm) are irradiated separately with a 10 x 10 cm2 field end-on in a water bath, such that the characteristic depth-dose curve is recorded in the gel. The calibration is then determined by fitting the depth-dose measured in water, against the measured change in relaxivity with depth in the gel. Increased accuracy is achieved in this simple depth-dose geometry by averaging the relaxivity at each depth. A large number of calibration data points, each with relatively high accuracy, are obtained. Calibration data over the full range of dose (1.6-10 Gy) is obtained by irradiating one test-tube to 10 Gy at dose maximum (Dmax), and the other to 4.5 Gy at Dmax. The new calibration method is compared with a 'standard method' where five identical test-tubes of gel were irradiated to different known doses between 2 and 10 Gy. The percentage uncertainties in the slope and intercept of the calibration fit are found to be lower with the new method by a factor of about 4 and 10 respectively, when compared with the standard method and with published values. The gel was found to respond linearly within the error bars up to doses of 7 Gy, with a slope of 0.233 +/- 0.001 s(-1) Gy(-1) and an intercept of 1.106 +/- 0.005 Gy. For higher doses, nonlinear behaviour was observed.

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Published In

Phys Med Biol

DOI

ISSN

0031-9155

Publication Date

October 1998

Volume

43

Issue

10

Start / End Page

2709 / 2720

Location

England

Related Subject Headings

  • Radiotherapy
  • Radiometry
  • Polymers
  • Nuclear Medicine & Medical Imaging
  • Magnetic Resonance Spectroscopy
  • Gels
  • Gelatin
  • Calibration
  • Brachytherapy
  • Acrylamides
 

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Oldham, M., McJury, M., Baustert, I. B., Webb, S., & Leach, M. O. (1998). Improving calibration accuracy in gel dosimetry. Phys Med Biol, 43(10), 2709–2720. https://doi.org/10.1088/0031-9155/43/10/002
Oldham, M., M. McJury, I. B. Baustert, S. Webb, and M. O. Leach. “Improving calibration accuracy in gel dosimetry.Phys Med Biol 43, no. 10 (October 1998): 2709–20. https://doi.org/10.1088/0031-9155/43/10/002.
Oldham M, McJury M, Baustert IB, Webb S, Leach MO. Improving calibration accuracy in gel dosimetry. Phys Med Biol. 1998 Oct;43(10):2709–20.
Oldham, M., et al. “Improving calibration accuracy in gel dosimetry.Phys Med Biol, vol. 43, no. 10, Oct. 1998, pp. 2709–20. Pubmed, doi:10.1088/0031-9155/43/10/002.
Oldham M, McJury M, Baustert IB, Webb S, Leach MO. Improving calibration accuracy in gel dosimetry. Phys Med Biol. 1998 Oct;43(10):2709–2720.
Journal cover image

Published In

Phys Med Biol

DOI

ISSN

0031-9155

Publication Date

October 1998

Volume

43

Issue

10

Start / End Page

2709 / 2720

Location

England

Related Subject Headings

  • Radiotherapy
  • Radiometry
  • Polymers
  • Nuclear Medicine & Medical Imaging
  • Magnetic Resonance Spectroscopy
  • Gels
  • Gelatin
  • Calibration
  • Brachytherapy
  • Acrylamides