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

摘要

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 cm3 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.