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Abstract
PURPOSE:
To investigate interobserver variation in target volume delineations for prostate cancer salvage radiotherapy using planning computed tomography (CT) versus combined planning CT and magnetic resonance imaging (MRI).

MATERIALS AND METHODS:
Ten radiation oncologists independently delineated a target volume on the planning CT scans of five cases with different pathological status after radical prostatectomy. Two weeks later, this was repeated with the addition of planning MRI. The volumes obtained with CT only and combined CT and MRI were compared, and the effect of the addition of planning MRI on interobserver variability was assessed.

RESULTS:
There were large differences in clinical target volume (CTV) delineated by each observer, regardless of the addition of planning MRI (9.44-139.27 cm3 in CT only and 7.77-122.83 cm3 in CT plus MRI) and no significant differences in the mean and standard deviation of CTV. However, there were decreases in mean volume and standard deviation as a result of using the planning MRI.

CONCLUSION:
This study showed substantial interobserver variation in target volume delineation for salvage radiotherapy. The combination of planning MRI with CT tended to decrease the target volume and the variation.

Author information

Lee E1, Park W1, Ahn SH1, Cho JH2, Kim JH3, Cho KH4, Choi YM5, Kim JS6, Kim JH7, Jang HS8, Kim YS9, Nam TK10.
1
Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
2
Department of Radiation Oncology, Yonsei University College of Medicine, Severance Hospital, Seoul, Korea.
3
Department of Radiation Oncology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea.
4
Proton Therapy Center, National Cancer Center, Goyang, Korea.
5
Department of Radiation Oncology, Dong-A University College of Medicine, Busan, Korea.
6
Department of Radiation Oncology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
7
Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea.
8
Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
9
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
10
Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea.