In vivo dosimetry of high-dose-rate interstitial brachytherapy in the pelvic region: use of a radiophotoluminescence glass dosimeter for measurement of 1004 points in 66 patients with pelvic malignancy

Int J Radiat Oncol Biol Phys. 2008 Feb 1;70(2):626-33. doi: 10.1016/j.ijrobp.2007.09.053. Epub 2007 Dec 31.

Abstract

Purpose: To perform the largest in vivo dosimetry study for interstitial brachytherapy yet to be undertaken using a new radiophotoluminescence glass dosimeter (RPLGD) in patients with pelvic malignancy and to study the limits of contemporary planning software based on the results.

Patients and methods: Sixty-six patients with pelvic malignancy were treated with high-dose-rate interstitial brachytherapy, including prostate (n = 26), gynecological (n = 35), and miscellaneous (n = 5). Doses for a total of 1004 points were measured by RPLGDs and calculated with planning software in the following locations: rectum (n = 549), urethra (n = 415), vagina (n = 25), and perineum (n = 15). Compatibility (measured dose/calculated dose) was analyzed according to dosimeter location.

Results: The compatibility for all dosimeters was 0.98 +/- 0.23, stratified by location: rectum, 0.99 +/- 0.20; urethra, 0.96 +/- 0.26; vagina, 0.91 +/- 0.08; and perineum, 1.25 +/- 0.32.

Conclusions: Deviations between measured and calculated doses for the rectum and urethra were greater than 20%, which is attributable to the independent movements of these organs and the applicators. Missing corrections for inhomogeneity are responsible for the 9% negative shift near the vaginal cylinder (specific gravity = 1.24), whereas neglect of transit dose contributes to the 25% positive shift in the perineal dose. Dose deviation of >20% for nontarget organs should be taken into account in the planning process. Further development of planning software and a real-time dosimetry system are necessary to use the current findings and to achieve adaptive dose delivery.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Brachytherapy / instrumentation
  • Brachytherapy / methods*
  • Female
  • Genital Neoplasms, Female / radiotherapy
  • Humans
  • Luminescence
  • Male
  • Middle Aged
  • Pelvic Neoplasms / radiotherapy*
  • Perineum
  • Prostatic Neoplasms / radiotherapy
  • Radiation Monitoring / instrumentation*
  • Radiation Monitoring / methods
  • Radiotherapy Dosage
  • Rectum
  • Urethra
  • Vagina