Intra-reader reliability of FDG PET volumetric tumor parameters: effects of primary tumor size and segmentation methods.
OBJECTIVE
To establish the effects of size and segmentation methods on intra-reader reliability of primary tumor metabolic tumor volume (MTV) and total glycolytic activity (TGA) in human solid tumors.


METHODS
This is a retrospective study of 121 patients who had a baseline FDG PET/CT scan for oncologic staging. Volumetric parameter readings were performed in random order on two separate occasions, 12 weeks apart, by the same reader. The MTV and TGA were segmented using gradient and fixed maximum standardized uptake value (SUVmax) threshold methods. Intra-reader reliability was established by the intraclass correlation coefficient (ICC) and Bland-Altman analysis.


RESULTS
The biases for MTV were 2.95, 14.76 and 11.13% for gradient segmentation, 38 and 50% SUVmax fixed threshold segmentations, respectively (p < 0.0001). For TGA, the corresponding biases were 0.76, 10.36 and 7.46% (p < 0.0001). There were no statistically significant differences in the biases between the first and second reads for MTV segmented for small and large volume tumors by the gradient method (p < 0.34) or 50% SUVmax threshold segmentation (p < 0.08). However, there were statistically significant differences in the corresponding biases for the 38% SUVmax threshold segmentation (p < 0.04). There were no statistically significant differences in the biases between the first and second reads for TGA segmented for small and large volume tumors (p < 0.98).


CONCLUSIONS
Intra-reader reliability for primary tumor FDG MTV and TGA is affected by the tumor size and segmentation methods. The segmentation bias was smaller for gradient method than percentage fixed threshold method for MTV. The segmentation biases were smaller for TGA than MTV.
Department of Radiology, Boston University School of Medicine, Boston, MA, USA.
B
B
Shah
N
N
Srivastava
A E
AE
Hirsch
G
G
Mercier
R M
RM
Subramaniam
D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D047368:Tumor Burden
D019788:Fluorodeoxyglucose F18