RSNA November 2000

INTEGRATED ALGORITHM WITH PET WORKSTATION FOR THE CORRECTION OF THE PARTIAL VOLUME EFFECT (PVE) IN SIMULTANEOUS TRANSMISSION EMISSION (STE) SCAN

Saleh Alyafei, Tomio Inoue, Hong Zhang, Nasim Khan, Noboru Oriuchi, Noriko Sato, Keiko Koyama, Tomohiko Sato, Ichikawa Akihiro, Keigo Endo

Department of Nuclear Medicine and Diagnostic Radiology, Gunma University School of Medicine, Maebashi, Japan.

PURPOSE: The quantitative analysis of positron emission tomography (PET) is highly desirable in differentiating benign from malignant nodules. However, the small volume of the studied object compared to the limited spatial resolution of PET result in partial volume effect (PVE) on quantitative analysis. A semi-automated correction model was developed for standardized uptake value (SUV) of small nodules in reference to PVE in STE scan. METHOD / MATERIALS: A phantom study of six spheres with various sizes was used to calculate the recovery coefficient (RC) of different volumes in respect to scatter and T/N ratio in STE scan. A program for RC correction written in C++ language was combined with the program of SUV calculation. These programs were installed in the PET workstation for clinical routine work. Clinical studies of 24 patients with total of 26 small lesions were also conducted to evaluate the usefulness of the developed algorithm. Diagnostic sensitivity and specificity for malignant tumors using the SUV estimation were measured before and after the PVE correction. RESULTS: The corrected SUV value of diameter of 10.6, 14.4, 16.9, 20.6, 28.1 and 39.4mm was almost 4.2, 3.0, 2.2, 1.6, 1.2, and 1.04 times higher, respectively, than the uncorrected SUV. The diagnostic sensitivity increased from 54% to 85%, before and after the correction, respectively. Whereas, specificity remained unchanged at 69%. CONCLUSIONS: This model is convenient and useful in quantitative method to correct for PVE in specified clinical situations, especially for the evaluation of FDG uptake in small pulmonary nodule and lymph node metastasis.