Inverse treatment planning based on MRI for HDR prostate brachytherapy.
OBJECTIVE
To develop and optimize a technique for inverse treatment planning based solely on magnetic resonance imaging (MRI) during high-dose-rate brachytherapy for prostate cancer.


METHODS
Phantom studies were performed to verify the spatial integrity of treatment planning based on MRI. Data were evaluated from 10 patients with clinically localized prostate cancer who had undergone two high-dose-rate prostate brachytherapy boosts under MRI guidance before and after pelvic radiotherapy. Treatment planning MRI scans were systematically evaluated to derive a class solution for inverse planning constraints that would reproducibly result in acceptable target and normal tissue dosimetry.


RESULTS
We verified the spatial integrity of MRI for treatment planning. MRI anatomic evaluation revealed no significant displacement of the prostate in the left lateral decubitus position, a mean distance of 14.47 mm from the prostatic apex to the penile bulb, and clear demarcation of the neurovascular bundles on postcontrast imaging. Derivation of a class solution for inverse planning constraints resulted in a mean target volume receiving 100% of the prescribed dose of 95.69%, while maintaining a rectal volume receiving 75% of the prescribed dose of <5% (mean 1.36%) and urethral volume receiving 125% of the prescribed dose of <2% (mean 0.54%).


CONCLUSIONS
Systematic evaluation of image spatial integrity, delineation uncertainty, and inverse planning constraints in our procedure reduced uncertainty in planning and treatment.
Citrin
Deborah
D
Radiation Oncology Branch, CCR, NCI, National Institutes of Health, Department of Health and Human Services, Bldg. 10, Rm. B3B69, 9000 Rockville Pike, Bethesda, MD 20892, USA. citrind@mail.nih.gov
Ning
Holly
H
Guion
Peter
P
Li
Guang
G
Susil
Robert C
RC
Miller
Robert W
RW
Lessard
Etienne
E
Pouliot
Jean
J
Huchen
Xie
X
Capala
Jacek
J
Coleman
C Norman
CN
Camphausen
Kevin
K
Ménard
Cynthia
C
D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D019047:Phantoms, Imaging; D010865:Pilot Projects; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*