Correlation of PET standard uptake value and CT window-level thresholds for target delineation in CT-based radiation treatment planning
- Department of Radiation Oncology, Nuclear Medicine Division, Loyola University Medical Center, Maywood, IL (United States)
- Department of Radiology, Nuclear Medicine Division, Loyola University Medical Center, Maywood, IL (United States)
Purpose: To develop standardized correlates of [{sup 18}F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) standard uptake value (SUV) to computed tomography (CT)-based window and levels. Methods and Materials: Nineteen patients with non-small-cell lung cancer who underwent imaging with positron emission tomography (PET) and CT were selected. A method of standardizing SUV within CT planning software was developed. A scale factor, determined by a sensitivity calibration of the PET scanner, converts voxel counts to activity per gram in tissue, allowing SUVs to be correlated to CT window and levels. A method of limiting interobserver variations was devised to enhance 'edges' of regions of interest based on SUV thresholds. The difference in gross tumor volumes (GTVs) based on CT, PET SUV {>=} 2.5, and regions of 40% maximum SUV were analyzed. Results: The mean SUV was 9.3. Mean GTV volumes were 253 cc for CT, 221 cc for SUV {>=} 2.5, and 97 cc for SUV40%Max. Average volume difference was -259% between {>=}2.5 SUV and CT and -162% between SUV40%Max and CT. Percent difference between GTV {>=} 2.5 SUV and SUV40%Max remained constant beyond SUV > 7. For SUVs 4-6, best correlation among SUV thresholds occurred at volumes near 90 cc. Mean percent change from GTVs contoured according to CT (GTV CT) was -260% for GTV2.5 and -162% for GTV40%Max. Using the SUV40%Max threshold resulted in a significant alteration of volume in 98% of patients, while the SUV2.5 threshold resulted in an alteration of volume in 58% of patients. Conclusions: Our method of correlating SUV to W/L thresholds permits accurate displaying of SUV in coregistered PET/CT studies. The optimal SUV thresholds to contour GTV depend on maximum tumor SUV and volume. Best correlation occurs with SUVs >6 and small volumes <100 cc. At SUVs >7, differences between the SUV threshold filters remain constant. Because of variability in volumes obtained by using SUV40%Max, we recommend using SUV {>=} 2.5 for radiotherapy planning in non-small-cell lung cancer.
- OSTI ID:
- 20944721
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 67, Issue 3; Other Information: DOI: 10.1016/j.ijrobp.2006.09.039; PII: S0360-3016(06)03130-0; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
Similar Records
Increasing the Accuracy of Volume and ADC Delineation for Heterogeneous Tumor on Diffusion-Weighted MRI: Correlation with PET/CT
Comparison of Tumor Volumes as Determined by Pathologic Examination and FDG-PET/CT Images of Non-Small-Cell Lung Cancer: A Pilot Study