The Vienna applicator for combined intracavitary and interstitial brachytherapy of cervical cancer: design, application, treatment planning, and dosimetric results.
OBJECTIVE
To present a combined intracavitary and interstitial dedicated applicator and magnetic resonance imaging (MRI) treatment planning for cervical cancer brachytherapy.


METHODS
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.
Kirisits
Christian
C
Department of Radiotherapy and Radiobiology, Medical University of Vienna, Vienna, Austria. Kirisits@meduniwien.ac.at
Lang
Stefan
S
Dimopoulos
Johannes
J
Berger
Daniel
D
Georg
Dietmar
D
Pötter
Richard
R
D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*