Bladder and rectal doses from external-beam boosts after gynecologic brachytherapy

Joseph Y. Ting, Aaron H. Wolfson, Xiaodong Wu, Jeffrey A. Fiedler, May Abdel-Wahab, Ching Chong Yang, Marcia Watzich, Arnold M. Markoe

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

PURPOSE: To establish a typical value for radiation doses under pelvic midline shields. MATERIALS AND METHODS: Three methods were used to determine bladder and rectal doses under 5- or 6-half-value layer (HVL) shields for 10- and 24-MV external beams. First, dose was computed with a standard irregular field routine in 25 consecutive patients (aged 35-70 years) with stage IIB or IIIB disease treated with cesium-137 brachytherapy followed by a parametrial external-beam boost. Second, in vivo measurements with a solid-state probe were recorded during the first boost after completion of brachytherapy in each patient. Third, measurements obtained with an ionization chamber in a solid phantom (water-equivalent material) were compared with computed and in vivo results. RESULTS: All three dosimetric methods yielded bladder and rectal doses higher than the commonly assumed 5% of the unshielded primary beam dose. Doses within the shielded volume may be as high as 15% of the unshielded dose. Doses are similar under 5- and 6-HVL midline shields. Often, the actual bladder and rectal doses exceeded the planned dose limits and their corresponding maximum radiation dose tolerance levels. CONCLUSION: Bladder and rectal doses are higher than previously understood. Parametrial boosts may contribute as much as 3.0 Gy to the bladder and rectal doses.

Original languageEnglish (US)
Pages (from-to)825-830
Number of pages6
JournalRadiology
Volume209
Issue number3
DOIs
StatePublished - Dec 1998

Keywords

  • Dosimetry
  • Radiations, injurious effects, complications of therapeutic radiology
  • Radiations, measurement
  • Radiations, protective and therapeutic agents and devices
  • Uterine neoplasms, therapeutic radiology

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology

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