The Vienna applicator for combined intracavitary and interstitial brachytherapy of cervical cancer:: Design, application, treatment planning, and dosimetric results

Purpose: To present a combined intracavitary and interstitial dedicated applicator and magnetic resonance imaging (MRI) treatment planning for cervical cancer brachytherapy. Methods and Materials: A modified ring applicator allows interstitial needles to be implanted in parallel to the intrauterine tandem. MRI treatment planning based on a standard loading pattern with stepwise dwell weight adaptation and needle loading is performed to achieve optimal dose coverage and sparing of organs at risk. Dose constraints are applied for dose-volume histogram parameters. Results: The use of additional interstitial needles provides prescription dose up to 15 mm lateral to point A. Twenty-two patients with high-risk clinical target volumes of mean 44 cm(3) were treated with a mean prescribed total dose of 85 Gy (biologically equivalent to 2 Gy fractionation, alpha/beta = 10 Gy) and 93% coverage (V100). The dose to organs at risk was within standard limits for intracavitary brachytherapy alone. Conclusions: A combined interstitial-intracavitary applicator results in reproducible implants for cervical cancer brachytherapy. MRI-based treatment planning based on a target concept, dose-volume constraints, and limitations for the relative dwell weight allows for an increase in target coverage, treated volume, and total dose without increasing the dose to critical structures. (c) 2006 Elsevier Inc.