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Interobserver variability leads to significant differences in quantifiers of prostate implant adequacy
W Robert Lee1, Mack Roach, Jeff Michalski
1Department of Radiation Oncology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1030, USA. wrlee@wfubmc.edu
International Journal of Radiation Oncology, Biology, Physics
|September 24, 2002
Summary
Interobserver variability in prostate brachytherapy CT imaging leads to significant differences in implant adequacy quantifiers. Improving agreement among reviewers is crucial for reliable post-implant dosimetry.
Area of Science:
- Medical Imaging
- Radiation Oncology
- Urological Surgery
Background:
- Prostate brachytherapy involves implanting radioactive seeds to treat prostate cancer.
- Post-implant imaging, typically CT, is used to assess treatment adequacy.
- Accurate prostate volume delineation is essential for dosimetric evaluation.
Purpose of the Study:
- To compare prostate gland volumes and implant adequacy quantifiers.
- To assess interobserver variability among brachytherapists using post-implant CT scans.
- To evaluate the impact of contouring differences on dosimetric outcomes.
Main Methods:
- Ten patients underwent post-implant CT scans 1 day after 125I prostate brachytherapy.
- Five brachytherapists independently contoured the prostate gland on CT images.
- Prostate volumes, V(100), and D(90) were calculated using treatment planning software.
Main Results:
- Significant interobserver differences were found in prostate volume measurements (p <0.0001).
- Substantial variations were observed in V(100) (p <0.0001) and D(90) (p <0.0001) among reviewers.
- Reproducibility was fair for prostate volume (ICC=0.639) but poor for dosimetric quantifiers (V(100) ICC=0.344, D(90) ICC=0.275).
Conclusions:
- Significant interobserver variability exists in prostate volume contouring on post-implant CT scans.
- This variability directly impacts the accuracy of commonly used dosimetric quantifiers.
- Standardization of contouring methods is necessary to improve interobserver agreement and ensure reliable dosimetry.