Time Sensitivity Factor of Single Pulmonary Nodule : A New Cancer Characteristic Metabolic Parameter by F18-FDG PET

Abstract EN

Objective.

To calculate the time sensitivity factor (S) for discriminating the solitary pulmonary nodule (SPN) by FDG PET at different time points.

Methods.

The multiple time-point FDG PET images from 41 patients for evaluating SPN seen on chest X-ray or CT were prospectively analyzed to calculate and evaluate S against the gold standard of tissue histology (n=38) or long term clinicoradiographic follow-up (n=3).

The maximal standardized uptake values (SUV) at the 3 hourly time points were measured.

The S was calculated using S=d{ln(SUV)}/d{ln(t)} at 3 different time intervals.

ROC analysis of the S parameters was performed to evaluate the optimal cut-off value and their accuracy in classifying the SPN.

Results.

The SUV in malignant SPN was higher than the corresponding value in benign lesions at all 3 hourly time points (P<0.003).

The S parameters using 3 different time intervals all significantly separated the two groups (P<0.0005) with an optimal cut-off point near the theoretical value of zero with a high sensitivity of 100% and specificity of 86%.

Conclusion.

The S can be calculated for SPNs using multiple time-point FDG PET, providing a tumor characteristic metabolic parameter with high discrimination power using a simple positive value representing malignancy.