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Source localization following permanent transperineal prostate interstitial brachytherapy using magnetic resonance
D F Dubois1, B R Prestidge, L A Hotchkiss
1Radiation Oncology Service, Wilford Hall Medical Center, Lackland AFB, TX, USA.
International Journal of Radiation Oncology, Biology, Physics
|December 10, 1997
Summary
Magnetic Resonance Imaging (MRI) can now reliably visualize radioactive sources used in prostate brachytherapy. This allows for more accurate dosimetry and improved patient treatment evaluation compared to CT scans.
Area of Science:
- Medical Imaging
- Radiation Oncology
- Prostate Cancer Treatment
Background:
- Accurate dosimetric evaluation of brachytherapy implants is essential for technique refinement and patient prognosis.
- Current methods like CT and radiographs poorly delineate the prostate gland, while MRI excels at gland definition but struggles with source visualization.
- Optimizing MRI for source visualization is key to improving prostate brachytherapy dosimetry.
Purpose of the Study:
- To optimize MRI techniques for visualizing radioactive sources used in prostate brachytherapy.
- To compare MRI-derived source localization with CT-derived localization.
- To assess the dosimetric accuracy of MRI-based evaluations.
Main Methods:
- Developed and optimized MRI sequences for simultaneous visualization of the prostate gland and implanted radioactive sources.
- Evaluated CT and MRI scans from 20 patients undergoing prostate brachytherapy (125Iodine or 103Palladium).
- Utilized an in-house dosimetry system to compare MRI-derived and CT-derived dose-volume histograms (DVHs).
Main Results:
- No statistically significant differences were found in isodose volumes between MRI and CT at the 95% confidence level.
- MRI-derived DVHs were statistically similar to CT-derived DVHs at the prescription dose for both 125Iodine (p < 0.01) and 103Palladium (p < 0.026) implants.
- The optimized MRI sequence allowed for visualization of both the prostate gland and implanted sources.
Conclusions:
- This study provides the first evidence that MRI can reliably identify permanently implanted 125Iodine and 103Palladium brachytherapy sources.
- MRI offers superior prostate gland delineation, enabling more accurate and anatomically relevant dosimetric analysis of prostate implants.
- The optimized MRI protocol is cost-comparable to CT scans, making post-implant MRI a valuable tool for clinical correlation and treatment evaluation.