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- Title
Measurement of Functional Tumor Volume for Fluorodeoxyglucose-Positive Primary and Metastatic Liver Tumors: Validation of Optimal Threshold Value Technique.
- Authors
Mesoloras, Geraldine; Sandison, George A.; Gulec, Seza A.
- Abstract
Background: Positron emission tomography-computed tomography (PET-CT) has proven to be an invaluable tool for disease assessment in oncology. The tumor standard uptake value (SUV), a measure of the fluorodeoxyglucose (FDG) uptake, is used as a clinical tool for determining disease prognosis, as a marker for tumor biology, and as an evaluation of treatment response. A more comprehensive approach involving the determination of functional tumor volume is needed to better define disease biology and express treatment-related changes. Methods: The relationship between functional and anatomic volume was evaluated using phantom and patient studies. Phantom studies were performed using a cylindrical phantom containing hollow spheres of volume ranging from 0.5 to 16.0 cc. Solutions with different concentrations of fluorine 18 FDG were added to the spheres and the phantom to provide different target to background ratios (TBRs). The phantom was imaged using a PET-CT scanner, and functional volumes were determined using the background maximum activity concentration as the threshold value (BTV). Next, the optimal threshold value (OTV) was determined to result in a measured functional volume equal to the known sphere volume. A threshold correction factor (TCF) was established to estimate the OTV. Functional tumor volumes were determined and compared with anatomic tumor volumes for patients with liver lesions. Functional tumor volumes were initially determined using the normal liver SUVmax as a threshold and then using the OTVs established using the phantom studies. Results: An increase in measured functional volume with TBRmax and sphere volume was observed in the phantom studies. When the liver SUVmax was used as the threshold in patient studies (BTV), a linear relationship was observed between the functional and the anatomic tumor volume. The use of the OTVs in the determination of functional tumor volume resulted in a reduction in percent error from 89% to 13%. A reduction in the variability about the best fit line was observed when comparing the BTV and OTV methods as expressed by an increase in R2 values from .80 to .94. Conclusion: The method proposed for measuring functional tumor volumes in PET-CT clinical liver studies is reproducible and accurate when compared with anatomic volumes assessed using contrast-enhanced CT scans.
- Publication
Journal of Interventional Oncology, 2009, Vol 2, Issue 2, p95
- ISSN
1916-0518
- Publication type
Academic Journal
- DOI
10.2310/6650.2009.00012