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Title: An evaluation of the variability of tumor-shape definition derived by experienced observers from CT images of supraglottic carcinomas (ACRIN protocol 6658)

Abstract

Purpose: Accurate target definition is considered essential for sophisticated, image-guided radiation therapy; however, relatively little information has been reported that measures our ability to identify the precise shape of targets accurately. We decided to assess the manner in which eight 'experts' interpreted the size and shape of tumors based on 'real-life' contrast-enhanced computed tomographic (CT) scans. Methods and Materials: Four neuroradiologists and four radiation oncologists (the authors) with considerable experience and presumed expertise in treating head-and-neck tumors independently contoured, slice-by-slice, his/her interpretation of the precise gross tumor volume (GTV) on each of 20 sets of CT scans taken from 20 patients who previously were enrolled in Radiation Therapy Oncology Group protocol 91-11. Results: The average proportion of overlap (i.e., the degree of agreement) was 0.532 (95% confidence interval 0.457 to 0.606). There was a slight tendency for the proportion of overlap to increase with increasing average GTV. Conclusions: Our work suggests that estimation of tumor shape currently is imprecise, even for experienced physicians. In consequence, there appears to be a practical limit to the current trend of smaller fields and tighter margins.

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [10];  [11];  [4];  [4]
  1. Department of Radiation Oncology, Maimonides Medical Center, Brooklyn, NY (United States). E-mail: jcooper@maimonidesmed.org
  2. Department of Radiology, University of Michigan Health System, Ann Arbor, MI (United States)
  3. (United States)
  4. Center for Statistical Sciences, Brown University, Providence, RI (United States)
  5. Department of Radiology, State University of New York, Albany Medical School, Albany, NY (United States)
  6. Department of Radiology, University of Florida School of Medicine, Gainesville, FL (United States)
  7. Department of Radiation Oncology, University of Florida School of Medicine, Gainesville, FL (United States)
  8. Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, NC (United States)
  9. Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, PA (United States)
  10. Department of Radiology, Bryn Mawr Hospital, Bryn Mawr, PA (United States)
  11. Department of Radiation Oncology, M. D. Anderson Cancer Center, Houston, TX (United States)
Publication Date:
OSTI Identifier:
20944751
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 67; Journal Issue: 4; Other Information: DOI: 10.1016/j.ijrobp.2006.10.029; PII: S0360-3016(06)03344-X; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; CARCINOMAS; COMPUTERIZED TOMOGRAPHY; EVALUATION; HEAD; IMAGES; MEDICAL PERSONNEL; NECK; PATIENTS; RADIOTHERAPY

Citation Formats

Cooper, Jay S., Mukherji, Suresh K., Department of Otolaryngology Head Neck Surgery, University of Michigan Health System, Ann Arbor, MI, Toledano, Alicia Y., Beldon, Clifford, Schmalfuss, Ilona M., Amdur, Robert, Sailer, Scott, Loevner, Laurie A., Kousouboris, Phil, Ang, K. Kian, Cormack, Jean, and Sicks, JoRean M.S. An evaluation of the variability of tumor-shape definition derived by experienced observers from CT images of supraglottic carcinomas (ACRIN protocol 6658). United States: N. p., 2007. Web. doi:10.1016/j.ijrobp.2006.10.029.
Cooper, Jay S., Mukherji, Suresh K., Department of Otolaryngology Head Neck Surgery, University of Michigan Health System, Ann Arbor, MI, Toledano, Alicia Y., Beldon, Clifford, Schmalfuss, Ilona M., Amdur, Robert, Sailer, Scott, Loevner, Laurie A., Kousouboris, Phil, Ang, K. Kian, Cormack, Jean, & Sicks, JoRean M.S. An evaluation of the variability of tumor-shape definition derived by experienced observers from CT images of supraglottic carcinomas (ACRIN protocol 6658). United States. doi:10.1016/j.ijrobp.2006.10.029.
Cooper, Jay S., Mukherji, Suresh K., Department of Otolaryngology Head Neck Surgery, University of Michigan Health System, Ann Arbor, MI, Toledano, Alicia Y., Beldon, Clifford, Schmalfuss, Ilona M., Amdur, Robert, Sailer, Scott, Loevner, Laurie A., Kousouboris, Phil, Ang, K. Kian, Cormack, Jean, and Sicks, JoRean M.S. Thu . "An evaluation of the variability of tumor-shape definition derived by experienced observers from CT images of supraglottic carcinomas (ACRIN protocol 6658)". United States. doi:10.1016/j.ijrobp.2006.10.029.
@article{osti_20944751,
title = {An evaluation of the variability of tumor-shape definition derived by experienced observers from CT images of supraglottic carcinomas (ACRIN protocol 6658)},
author = {Cooper, Jay S. and Mukherji, Suresh K. and Department of Otolaryngology Head Neck Surgery, University of Michigan Health System, Ann Arbor, MI and Toledano, Alicia Y. and Beldon, Clifford and Schmalfuss, Ilona M. and Amdur, Robert and Sailer, Scott and Loevner, Laurie A. and Kousouboris, Phil and Ang, K. Kian and Cormack, Jean and Sicks, JoRean M.S.},
abstractNote = {Purpose: Accurate target definition is considered essential for sophisticated, image-guided radiation therapy; however, relatively little information has been reported that measures our ability to identify the precise shape of targets accurately. We decided to assess the manner in which eight 'experts' interpreted the size and shape of tumors based on 'real-life' contrast-enhanced computed tomographic (CT) scans. Methods and Materials: Four neuroradiologists and four radiation oncologists (the authors) with considerable experience and presumed expertise in treating head-and-neck tumors independently contoured, slice-by-slice, his/her interpretation of the precise gross tumor volume (GTV) on each of 20 sets of CT scans taken from 20 patients who previously were enrolled in Radiation Therapy Oncology Group protocol 91-11. Results: The average proportion of overlap (i.e., the degree of agreement) was 0.532 (95% confidence interval 0.457 to 0.606). There was a slight tendency for the proportion of overlap to increase with increasing average GTV. Conclusions: Our work suggests that estimation of tumor shape currently is imprecise, even for experienced physicians. In consequence, there appears to be a practical limit to the current trend of smaller fields and tighter margins.},
doi = {10.1016/j.ijrobp.2006.10.029},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 4,
volume = 67,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Purpose: To determine required PTV margins for ≤1% loss in mean population TCP using systematic (Σ) and random (σ) errors calculated from daily cone-beam CT (CBCT) images of head and neck patients. Methods: Daily CBCT images were acquired for 50 head and neck patients. The CBCT image sets acquired at each fraction were registered with planning CT to obtain positional errors for each patient for each fraction. Systematic and random errors were calculated from data collected for 50 patients as described in IPEM On Target report. CTV delineation uncertainty of 2mm is added quadratically to systematic error. Assuming a sphericalmore » target volume, the dose in each voxel of target volume is summed for each fraction in the treatment by shifting the dose grid to calculate mean population TCP inclusive of geometric uncertainties using a Monte Carlo method. These simulations were repeated for the set of Σ and σ in each axis for different PTV margins and drop in TCP for each margin are obtained. In order to study the effect of dose-response curve on PTV margins, two different σα of 0.048 Gy-1 and 0.218 Gy-1 representing steep and shallow dose-response curves are studied. Σ were 2.5, 2.5, 2.1 mm and σ were 0.3, 0.3 0.2 mm respectively in x, y and z axis respectively. Results: PTV margins based on tumor radiobiological characteristics are 4.8, 4.8 and 4 mm in x, y and z axis assuming 25 treatment fractions for σα 0.048 Gy-1 (steep) and 4.2,4.2 and 2.2 for σα of 0.218 Gy-1 (shallow). While the TCP-based margins did not differ much in x and y axis, it is considerably smaller in z axis for shallow DRC. Conclusion: TCP based margins are substantially smaller than physical dose-based margin recipes. This study also demonstrates the importance of considering tumor radiobiological characteristics while deriving margins.« less
  • Purpose: Recently, task-based assessment of diagnostic CT systems has attracted much attention. Detection task performance can be estimated using human observers, or mathematical observer models. While most models are well established, considerable bias can be introduced when performance is estimated from a limited number of image samples. Thus, the purpose of this work was to assess the effect of sample size on bias and uncertainty of two channelized Hotelling observers and a template-matching observer. Methods: The image data used for this study consisted of 100 signal-present and 100 signal-absent regions-of-interest, which were extracted from CT slices. The experimental conditions includedmore » two signal sizes and five different x-ray beam current settings (mAs). Human observer performance for these images was determined in 2-alternative forced choice experiments. These data were provided by the Mayo clinic in Rochester, MN. Detection performance was estimated from three observer models, including channelized Hotelling observers (CHO) with Gabor or Laguerre-Gauss (LG) channels, and a template-matching observer (TM). Different sample sizes were generated by randomly selecting a subset of image pairs, (N=20,40,60,80). Observer performance was quantified as proportion of correct responses (PC). Bias was quantified as the relative difference of PC for 20 and 80 image pairs. Results: For n=100, all observer models predicted human performance across mAs and signal sizes. Bias was 23% for CHO (Gabor), 7% for CHO (LG), and 3% for TM. The relative standard deviation, σ(PC)/PC at N=20 was highest for the TM observer (11%) and lowest for the CHO (Gabor) observer (5%). Conclusion: In order to make image quality assessment feasible in the clinical practice, a statistically efficient observer model, that can predict performance from few samples, is needed. Our results identified two observer models that may be suited for this task.« less
  • The purpose of this study was to assess the efficacy of a gross tumor volume (GTV) contouring protocol on interobserver variability between 4 physicians in positron emission therapy/computed tomography (PET/CT) treatment planning of head-and-neck cancer. A GTV contouring protocol for PET/CT treatment planning was developed utilizing 4 stages: Preliminary contouring on CT alone, determination of appropriate PET windowing, accurate image registration, and modification of CT contouring with correctly formatted PET/CT display and rules for modality disagreement. Two neuroradiologists and 2 radiation oncologists (designated as A, B, C, and D, respectively) were given a tutorial of PET/CT coregistered imaging individualized tomore » their skill level, which included a step-by-step explanation of the protocol with clinical examples. Opportunities for questions and hands-on practice were given. The physicians were asked to re-contour 16 head-and-neck patients from Part I on PET/CT fusion imaging. Differences in volume magnitude were analyzed for statistical significance by analysis of variance (ANOVA) and paired t-tests ({alpha} < 0.05). Volume overlap was analyzed for statistical significance using Wilcoxon signed-rank tests ({alpha} < 0.05). Volume overlap increased significantly from Part I to Part II (p < 0.05). One previously significant difference between physicians disappeared with the protocol in place. The mean fusion volume of Physician C, however, remained significantly larger than that of Physician D (p < 0.01). This result is unchanged from Part I. The multidisciplinary contouring protocol significantly improved the coincidence of GTVs contoured by multiple physicians. The magnitudes of the volumes showed marginal improvement in consistency. Developing an institutional contouring protocol for PET/CT treatment planning is highly recommended to reduce interobserver variability.« less
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