Real-time computed tomography dosimetry during ultrasound-guided brachytherapy for prostate cancer

Kaplan, Irving D.; Meskell, Paul; Oldenburg, Nicklas E.; Saltzman, Brian; Kearney, Gary P.; Holupka, Edward J.

doi:10.1016/j.brachy.2006.03.001

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Volume 5, Issue 3 , Pages 147-151, July 2006

Real-time computed tomography dosimetry during ultrasound-guided brachytherapy for prostate cancer

Irving D. Kaplan
- Department of Radiation Therapy, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
- Corresponding author. Beth Israel Deaconess Medical Center, Department of Radiation Oncology, 330 Brookline Avenue, 5th floor, Boston, MA 02215. Tel.: +1-617-667-2345; fax: +1-617-667-9599.
Paul Meskell
- Department of Radiation Therapy, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
Nicklas E. Oldenburg
- Radiation Oncology Associates, Providence, RI
Brian Saltzman
- Department of Urology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
Gary P. Kearney
- Department of Urology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
Edward J. Holupka
- Department of Radiation Therapy, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA

Received 8 December 2005; received in revised form 28 February 2006; accepted 10 March 2006.

Abstract

Purpose

Ultrasound-guided implantation of permanent radioactive seeds is a treatment option for localized prostate cancer. Several techniques have been described for the optimal placement of the seeds in the prostate during this procedure. Postimplantation dosimetric calculations are performed after the implant. Areas of underdosing can only be corrected with either an external beam boost or by performing a second implant. We demonstrate the feasibility of performing computed tomography (CT)-based postplanning during the ultrasound-guided implant and subsequently correcting for underdosed areas.

Methods and materials

Ultrasound-guided brachytherapy is performed on a modified CT table with general anesthesia. The postplanning CT scan is performed after the implant, while the patient is still under anesthesia. Additional seeds are implanted into “cold spots,” and the resultant dosimetry confirmed with CT.

Results

Intraoperative postplanning was successfully performed. Dose–volume histograms demonstrated adequate dose coverage during the initial implant, but on detailed analysis, for some patients, areas of underdosing were observed either at the apex or the peripheral zone. Additional seeds were implanted to bring these areas to prescription dose.

Conclusion

Intraoperative postplanning is feasible during ultrasound-guided brachytherapy for prostate cancer. Although the postimplant dose-volume histograms for all patients, before the implantation of additional seeds, were adequate according to the American Brachytherapy Society criteria, specific critical areas can be underdosed. Additional seeds can then be implanted to optimize the dosimetry and reduce the risk of underdosing areas of cancer.

Keywords: Prostate Cancer, Brachytherapy, Dosimetry