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Dynamic intraoperative dosimetry for prostate brachytherapy using a nonisocentric C-arm
Danny Y Song1, Ameet K Jain, Zhe Zhang
1Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD 21231, USA. dsong2@jhmi.edu
Brachytherapy
|August 10, 2010
Summary
Registered ultrasound and fluoroscopy (RUF) offers dynamic intraoperative dosimetry for prostate brachytherapy, improving accuracy over ultrasound-based seed localization (USD) by identifying underdosage before Day 0 CT scans.
Area of Science:
- Medical Physics
- Radiology
- Oncology
Background:
- Prostate brachytherapy requires precise seed placement for effective radiation delivery.
- Intraoperative dosimetry aims to optimize seed distribution during the procedure.
- Current methods may lack real-time accuracy, necessitating post-implant verification.
Purpose of the Study:
- To evaluate a dynamic intraoperative dosimetry system using registered ultrasound and fluoroscopy (RUF).
- To compare the dosimetry accuracy of RUF and ultrasound-based seed localization (USD) against Day 0 CT scans.
- To assess the feasibility of using a nonisocentric C-arm for intraoperative dosimetry.
Main Methods:
- Seed positions were determined using RUF and USD independently.
- RUF employed a radio-opaque fiducial for registration with ultrasound and 3D fluoroscopic reconstruction.
- Paired t-tests and nonparametric approaches compared RUF and USD accuracy against postimplant CT.
Main Results:
- RUF identified intraoperative underdosage in all six patients, leading to the placement of additional seeds.
- RUF showed equal or closer correlation with CT dosimetry than USD in 40 of 42 measures.
- RUF demonstrated statistically significant variation from CT in only 1 of 7 parameters, compared to 6 of 7 for USD.
Conclusions:
- Dynamic intraoperative dosimetry is feasible with conventional nonisocentric C-arms.
- RUF-based dosimetry aligns more closely with immediate postimplant CT than USD.
- RUF effectively identifies underdosage missed by USD, enabling timely adjustments.
