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CT-based dosimetry for transperineal I-125 prostate brachytherapy
1Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
International Journal of Radiation Oncology, Biology, Physics
|October 6, 1997
Summary
This study evaluated CT-based target coverage in prostate brachytherapy, finding that achieving 80% or more coverage of the prostate target volume with the prescribed radiation dose is likely adequate for effective treatment.
Area of Science:
- Radiation Oncology
- Medical Imaging
- Urologic Oncology
Background:
- Brachytherapy is a key treatment for localized prostate cancer.
- Accurate dose delivery and target coverage are crucial for treatment efficacy.
- CT-based dosimetry allows for precise evaluation of brachytherapy implants.
Purpose of the Study:
- To assess CT-based target volume coverage achieved by an experienced brachytherapy team.
- To establish a benchmark for evaluating technical results of prostate brachytherapy implants.
- To correlate dose coverage with treatment outcomes.
Main Methods:
- CT scans of the pelvis were obtained 2-4 hours post-implantation in 20 patients with T1/T2 prostate cancer.
- Prostate and rectal margins were delineated on 3-mm CT slices.
- Transperineal I-125 implants were analyzed, with a prescribed minimum peripheral prostate dose of 140 Gy.
Main Results:
- An average of 84% of the target volume was covered by the 140 Gy isodose line.
- An average of 90% of the target volume was covered by the 120 Gy isodose line.
- The average minimum target dose was 57 Gy, with a loose correlation (r=0.33) to target coverage.
Conclusions:
- CT-based evaluation suggests that achieving 80% or more target volume coverage by the prescription dose is likely adequate.
- Accurate evaluation is challenging due to difficulties in target identification and post-implant volume changes.
- These findings provide a reference for other brachytherapy teams to evaluate their technical performance.