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

Takayuki Nose, Masahiko Koizumi, Ken Yoshida, Kinji Nishiyama, Junichi Sasaki, Takeshi Ohnishi, Takuyo Kozuka, Kotaro Gomi, Masahiko Oguchi, Iori Sumida, Yutaka Takahashi, Akira Ito, Takashi Yamashita

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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.

Original languageEnglish (US)
Pages (from-to)626-633
Number of pages8
JournalInternational Journal of Radiation Oncology Biology Physics
Volume70
Issue number2
DOIs
StatePublished - Feb 1 2008

Keywords

  • Brachytherapy
  • High dose rate
  • In vivo dosimetry
  • Radiophotoluminescence glass dosimeter
  • Radiotherapy

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