A novel device for intravaginal electronic brachytherapy.
OBJECTIVE
Postoperative intravaginal brachytherapy for endometrial carcinoma is usually performed with (192)Ir high-dose rate (HDR) afterloading. A potential alternative is treatment with a broadband 50kV X-ray point source, the advantage being its low energy and the consequential steep dose gradient. The aim of this study was to create and evaluate a homogeneous cylindrical energy deposition around a newly designed vaginal applicator.


METHODS
To create constant isodose layers along the cylindrical plastic vaginal applicator, the source (INTRABEAM system) was moved in steps of 17-19.5 mm outward from the tip of the applicator. Irradiation for a predetermined time was performed at each position. The axial shift was established by a stepping mechanism that was mounted on a table support. The total dose/dose distribution was determined using film dosimetry (Gafchromic EBT) in a "solid water" phantom. The films were evaluated with Mathematica 5.2 and OmniPro-I'mRT 1.6. The results (dose D0/D5/D10 in 0/5/10 mm tissue depth) were compared with an (192)Ir HDR afterloading plan for multiple sampling points around the applicator.


RESULTS
Three different dose distributions with lengths of 3.9-7.3 cm were created. The irradiation time based on the delivery of 5/7 Gy to a 5 mm tissue depth was 19/26 min to 27/38 min. D0/D5/D10 was 150%/100%/67% for electronic brachytherapy and 140%/100%/74% for the afterloading technique. The deviation for repeated measurements in the phantom was <7%.


CONCLUSIONS
It is possible to create a homogeneous cylindrical dose distribution, similar to (192)Ir HDR afterloading, through the superimposition of multiple spherical dose distributions by stepping a kilovolt point source.
Schneider
Frank
F
Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany. frank.schneider@umm.de
Fuchs
Holger
H
Lorenz
Friedlieb
F
Steil
Volker
V
Ziglio
Francesco
F
Kraus-Tiefenbacher
Uta
U
Lohr
Frank
F
Wenz
Frederik
F
D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D016889:Endometrial Neoplasms / Q000532:radiotherapy*; D004867:Equipment Design; D005260:Female; D005373:Film Dosimetry; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D011879:Radiotherapy Dosage
D007496:Iridium Radioisotopes