MRI-based preplanning in low-dose-rate prostate brachytherapy.
OBJECTIVE
To compare the dosimetric results between MRI-based and TRUS-based preplanning in permanent prostate brachytherapy, and to estimate the accuracy of MRI-based preplanning by comparing with CT/MRI fusion-based postimplant dosimetry.


METHODS
Twenty-one patients were entered in this prospective study with written informed consent. MRI-based and TRUS-based preplanning were performed. The seed and needle locations were identical according to MRI-based and TRUS-based preplanning. MRI-based and TRUS-based preplanning were compared using DVH-related parameters. Following brachytherapy, the accuracy of the MRI-based preplanning was evaluated by comparing it with CT/MRI fusion-based postimplant dosimetry.


RESULTS
Mean MRI-based prostate volume was slightly underestimated (0.73 cc in mean volume) in comparison to TRUS-based volume. There were no significant differences in the mean DVH-related parameters except with rectal V(100)(cc) between TRUS-based and MRI-based preplanning. Mean rectal V(100)(cc) was 0.74 cc in TRUS-based and 0.29 cc in MRI-based preplanning, respectively, and the values demonstrated a statistical difference. There was no statistical difference in mean rectal V(150)(cc), and rectal V(100)(cc) between MRI-based preplanning and CT/MRI fusion-based postimplant dosimetry.


CONCLUSIONS
Prostate volume estimation and DVH-related parameters in MRI-based preplanning were almost identical to TRUS-based preplanning. From the results of CT/MRI fusion-based postimplant dosimetry, MRI-based preplanning was therefore found to be a reliable and useful modality, as well as being helpful for TRUS-based preplanning. MRI-based preplanning can more accurately predict postimplant rectal dose than TRUS-based preplanning.
Tanaka
Osamu
O
Department of Radiology, Gifu University School of Medicine, Japan. osa-mu@umin.ac.jp
Hayashi
Shinya
S
Matsuo
Masayuki
M
Nakano
Masahiro
M
Kubota
Yasuaki
Y
Maeda
Sunaho
S
Ohtakara
Kazuhiro
K
Deguchi
Takashi
T
Hoshi
Hiroaki
H
D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D015641:Radiography, Interventional; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D018084:Ultrasonography, Interventional