Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy

An intra- and interobserver study

Laurence E. Court, Lei Dong, Noah Taylor, Matthew Ballo, Kei Kitamura, Andrew K. Lee, Jennifer O'Daniel, R. Allen White, Rex Cheung, Deborah Kuban

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)412-418
Number of pages7
JournalInternational Journal of Radiation Oncology Biology Physics
Volume59
Issue number2
DOIs
StatePublished - Jun 1 2004
Externally publishedYes

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Prostate
radiation therapy
Radiotherapy
alignment
evaluation
scanning electron microscopy
Uncertainty
Observer Variation
Intensity-Modulated Radiotherapy
rectum
dosage
Particle Accelerators
analysis of variance
bladder
linear accelerators
radiation
Therapeutics
Rectum
confidence
Prostatic Neoplasms

All Science Journal Classification (ASJC) codes

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

Cite this

Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy : An intra- and interobserver study. / Court, Laurence E.; Dong, Lei; Taylor, Noah; Ballo, Matthew; Kitamura, Kei; Lee, Andrew K.; O'Daniel, Jennifer; White, R. Allen; Cheung, Rex; Kuban, Deborah.

In: International Journal of Radiation Oncology Biology Physics, Vol. 59, No. 2, 01.06.2004, p. 412-418.

Research output: Contribution to journalArticle

Court, Laurence E. ; Dong, Lei ; Taylor, Noah ; Ballo, Matthew ; Kitamura, Kei ; Lee, Andrew K. ; O'Daniel, Jennifer ; White, R. Allen ; Cheung, Rex ; Kuban, Deborah. / Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy : An intra- and interobserver study. In: International Journal of Radiation Oncology Biology Physics. 2004 ; Vol. 59, No. 2. pp. 412-418.
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abstract = "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.",
author = "Court, {Laurence E.} and Lei Dong and Noah Taylor and Matthew Ballo and Kei Kitamura and Lee, {Andrew K.} and Jennifer O'Daniel and White, {R. Allen} and Rex Cheung and Deborah Kuban",
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TY - JOUR

T1 - Evaluation of a contour-alignment technique for CT-guided prostate radiotherapy

T2 - An intra- and interobserver study

AU - Court, Laurence E.

AU - Dong, Lei

AU - Taylor, Noah

AU - Ballo, Matthew

AU - Kitamura, Kei

AU - Lee, Andrew K.

AU - O'Daniel, Jennifer

AU - White, R. Allen

AU - Cheung, Rex

AU - Kuban, Deborah

PY - 2004/6/1

Y1 - 2004/6/1

N2 - 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.

AB - 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.

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