Inverse planning simulated annealing for magnetic resonance imaging-based intracavitary high-dose-rate brachytherapy for cervical cancer.
OBJECTIVE
To develop a technique using exclusively magnetic resonance imaging (MRI) to perform dwell position identification, targets and organs at risk delineation, and to apply inverse planning dose optimization to high-dose-rate brachytherapy for cervical cancer.


METHODS
We included 15 consecutive women treated with high-dose-rate (HDR) brachytherapy for cervical cancer. All patients underwent MRI after placement of tandem and ring applicator containing a gadodiamide-filled dummy marker. This technique allowed direct visualization of the source pathway and precise definition of the intra-applicator source positions. For each patient, we delineated gross target volume (GTV), high-risk clinical target volume (HR-CTV), and organs at risk on MRI, according to the European Gynecological GEC-ESTRO Working Group definitions. We performed inverse planning simulated annealing (IPSA) and analyzed the dose-volume histograms with the following endpoints: D(90), D(100), and V(100) for GTV and HR-CTV; D0.1 cc, D1 cc, D2 cc for bladder, rectum, and bowel; and dose at Point A.


RESULTS
The intra-applicator source pathway was easily visualized on MRI using the gadodiamide-filled marker. IPSA provided excellent target coverage. The mean D(90) and V(100) for HR-CTV were 103+/-5% and 92+/-3%, respectively. IPSA provided excellent bladder sparing. D1 cc and D2 cc of bladder were 73+/-10% and 67+/-10%, respectively.


CONCLUSIONS
We developed a novel technique that allows direct visualization of the intra-applicator source pathway on MRI. Using this technique, we successfully performed inverse planning directly from MRI.
Kubicky
Charlotte Dai
CD
Department of Radiation Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA. charlottedai@gmail.com
Yeh
Benjamin M
BM
Lessard
Etienne
E
Joe
Bonnie N
BN
Speight
Joycelyn L
JL
Pouliot
Jean
J
Hsu
I-Chow
IC
D001918:Brachytherapy / Q000379:methods*; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012007:Rectum / Q000528:radiation effects; D012016:Reference Values; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA