Zhang H, Inoue T, Alyafei S, Tian M, Oriuchi N, Endo K.

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

The purpose of this study was to investigate the detectability of small hot lesions in 2-dimensional transmission+emission (2D T/E), 2-dimensional simultaneous transmission+emission (2D simultaneous T/E) and 3-dimensional transmission+emission (3D T/E) acquisition modes in an 18F-fluorodeoxyglucose positron emission tomography (FDG PET) scan. The correlation between target detectability, target size, target to non-target uptake ratio (T/N ratio), and standardized uptake value (SUV) were studied. Small hot lesions ranging from 4.4 mm to 36.9 mm in diameter were set in a cylindrical phantom. The images of phantoms with T/N ratios of 2.0, 4.0, 6.0, 8.0, 9.6, 13.2, 17.5, 23.8 and 30.3 were obtained in 2D T/E, 2D simultaneous T/E and 3D T/E scans. Tumour uptake of 2-[18F]fluoro-2-deoxy-d-glucose (FDG) in a rabbit bearing VX-2 tumours was also studied in 2D T/E, 2D simultaneous T/E and 3D T/E scans. The target with a diameter > 10.6 mm and an actual T/N ratio from 6.0 to 30.3 could be identified on the images obtained with all the 2D T/E, 2D simultaneous T/E and 3D T/E acquisition modes. The detectability efficiency of a small hot target was found to be 77.8% in 2D T/E and 3D T/E, but 75.9% in 2D simultaneous T/E. The T/N ratio and recovery coefficient (RC) of the target from the 2D simultaneous T/E image was very similar to that from 2D T/E, and the SUV of the target from the 2D T/E image was almost the same as that from the 2D simultaneous T/E and 3D T/E images. This study indicated that 2D simultaneous T/E scanning and 3D T/E had similar abilities for detecting the tumour as did 2D T/E scanning. 2D T/E, 2D simultaneous T/E and 3D T/E scanning had the same feasibility for semi-quantitative analysis using SUV, as well as using the T/N ratios for 2D T/E and 2D simultaneous T/E. In contrast, the use of the T/N ratio in 3D T/E scanning gave an inferior result in semi-quantative analysis, although there might have been an improvement if a scatter correction had been performed.
PMID: 11314763