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Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy: an intra- and interobserver study.

Publication ,  Journal Article
Court, LE; Dong, L; Taylor, N; Ballo, M; Kitamura, K; Lee, AK; O'Daniel, J; White, RA; Cheung, R; Kuban, D
Published in: Int J Radiat Oncol Biol Phys
June 1, 2004

PURPOSE: The recent introduction of integrated CT/linear accelerator systems may mean that daily CT localization can become a reality in the clinic, possibly allowing further dose escalation to the prostate while limiting unwanted doses to the rectum and bladder. However, the implementation of CT localization is currently impeded by the lack of precise and robust techniques to align the treatment plan with the daily CT images. The purpose of this study was to evaluate a manual alignment technique, in which the gross target volume contours are overlaid on the daily CT images and then shifted to match the structures visible in the images. METHODS AND MATERIALS: A total of 28 CT image sets were taken before the standard delivery of intensity-modulated radiotherapy for prostate cancer for 2 patients. Seven observers (four radiation oncologists and three medical physicists) manually shifted the gross target volume contours from the treatment plan to best match the daily CT images. One observer repeated the process 1 week later to evaluate intraobserver variations. The experiment was then repeated, but the CT images from the original treatment plan were used as a reference to reduce interobserver uncertainty when aligning the contours. The shifts in prostate position found by different observers, both with and without reference data, were evaluated using a factorial analysis of variance to determine the standard errors of measurement for the intra- and interobserver uncertainty (SEM(intra) and SEM(inter), respectively). The differences in the SEM for the two groups of observers (radiation oncologists and medical physicists), the two alignment techniques (with and without reference information), and the two patients were evaluated using the t test at 90% confidence levels. RESULTS: With no reference information, the SEM(inter) using one patient data set (Patient 1) was 0.8 mm, 2.0 mm, and 2.2 mm in the right-left (RL), anterior-posterior (AP), and superior-inferior (SI) directions, respectively. The use of the treatment plan as a reference reduced the SEM(inter) to 0.7 mm, 1.0 mm, and 1.6 mm in the RL, AP, and SI directions, respectively. In Patient 2, localization of the prostate was more difficult; the best SEM(inter) achieved with this patient was 0.8 mm, 1.9 mm, and 2.0 mm in the RL, AP, and SI directions, respectively. The SEM(intra) values with Patient 1 were also slightly better than with Patient 2. When reference data were used, the SEM(intra) value was 0.5 mm, 0.7 mm, and 0.5 mm for Patient 1 and 0.6 mm, 1.0 mm, and 0.7 mm for Patient 2 in the RL, AP, and SI directions, respectively. Despite the larger than expected interobserver variation reported here, the SEM(inter) was smaller than the typical day-to-day variation in prostate position. The contour alignment technique may still be useful to aid daily prostate localization or in a correction scheme to minimize the effect of target positional error. CONCLUSION: The interobserver uncertainties associated with aligning the gross target volume contours with daily CT images were sufficiently small that this method may be used for daily CT localization of the prostate. The use of a reference image is important to improve the consistency among different users in this technique.

Duke Scholars

Published In

Int J Radiat Oncol Biol Phys

DOI

ISSN

0360-3016

Publication Date

June 1, 2004

Volume

59

Issue

2

Start / End Page

412 / 418

Location

United States

Related Subject Headings

  • Tomography, X-Ray Computed
  • Radiotherapy, Conformal
  • Prostatic Neoplasms
  • Prostate
  • Oncology & Carcinogenesis
  • Observer Variation
  • Male
  • Humans
  • Analysis of Variance
  • 5105 Medical and biological physics
 

Citation

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Chicago
ICMJE
MLA
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Court, L. E., Dong, L., Taylor, N., Ballo, M., Kitamura, K., Lee, A. K., … Kuban, D. (2004). Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy: an intra- and interobserver study. Int J Radiat Oncol Biol Phys, 59(2), 412–418. https://doi.org/10.1016/j.ijrobp.2003.10.023
Court, Laurence E., Lei Dong, Noah Taylor, Matthew Ballo, Kei Kitamura, Andrew K. Lee, Jennifer O’Daniel, R Allen White, Rex Cheung, and Deborah Kuban. “Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy: an intra- and interobserver study.Int J Radiat Oncol Biol Phys 59, no. 2 (June 1, 2004): 412–18. https://doi.org/10.1016/j.ijrobp.2003.10.023.
Court LE, Dong L, Taylor N, Ballo M, Kitamura K, Lee AK, et al. Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy: an intra- and interobserver study. Int J Radiat Oncol Biol Phys. 2004 Jun 1;59(2):412–8.
Court, Laurence E., et al. “Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy: an intra- and interobserver study.Int J Radiat Oncol Biol Phys, vol. 59, no. 2, June 2004, pp. 412–18. Pubmed, doi:10.1016/j.ijrobp.2003.10.023.
Court LE, Dong L, Taylor N, Ballo M, Kitamura K, Lee AK, O’Daniel J, White RA, Cheung R, Kuban D. Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy: an intra- and interobserver study. Int J Radiat Oncol Biol Phys. 2004 Jun 1;59(2):412–418.
Journal cover image

Published In

Int J Radiat Oncol Biol Phys

DOI

ISSN

0360-3016

Publication Date

June 1, 2004

Volume

59

Issue

2

Start / End Page

412 / 418

Location

United States

Related Subject Headings

  • Tomography, X-Ray Computed
  • Radiotherapy, Conformal
  • Prostatic Neoplasms
  • Prostate
  • Oncology & Carcinogenesis
  • Observer Variation
  • Male
  • Humans
  • Analysis of Variance
  • 5105 Medical and biological physics