Comparison of lesions in PET alone and PET/CT fusion image: the additional value of PET/CT

Objectives: The purpose of this study was to compare certainty of lesion location and characterization in PET alone and PET/CT fusion image. Methods: 17 patients (10 women, 7 men; mean age ±SD, 59.71±12.72 y) who applied for 18F-FDG PET/CT scan in our hospital and have positive lesions were analyzed in this study. The clinical diagnosis of these 17 patients were lung cancer (4), gastric carcinoma (3), colorectal cancer (2), bladder cancer (2), esophagus lymphoma (1), breast lobe hyperplasia (1), nasopharyngeal carcinoma (1), mediastinum mass (1), abdominal mass (1), fever of unknown (1). Four experienced physicians interpreted and scored the images independently. The physicians were first given none attenuation corrected and attenuation corrected PET image. After they scored the lesion location and malignant possibility, the CT images and PET/CT fused images were given, and the lesions are re-scored according to all the information. Certainty of lesion characterization was scored on a 3-point scale (0 = benign, 1 = probably malignant, 3 = definitely malignant). Lesion location was scored on a 3-point scale (0 = uncertain, 1 = probable, 2 = definite). Results: There are totally 52 lesions analyzed. After given the CT and image registration information, 45.7% lesions were changed its reported location or increased location probability scale (average from four doctors). 5.8% lesions were changed its malignance certainty. There is not very large interpret difference among the 4 doctors. In PET alone images, uncertain, probable and definite location lesions are 15.4%, 24.0% and 60.6% respectively. But in PET/CT images, lesions with definite location are increased to 95.2%. Uncertain and probable location lesions decreased to 0% and 4.8%. Conclusions: PET/CT fused imaging increases the accuracy and certainty of locating lesions. Fewer probable and uncertain lesions were identified with PET/CT than with PET alone. (authors)