Does Image Time Affect Semi-Quantitative Result of Gallium-67 Renal Scan?

Received 4/4/2001; revise 4/25/2001; accepted 5/17/2001. For correspondence or reprints contact: Wan-Yu Lin, M.D., Department of Nuclear Medicine, Taichung Veterans General Hospital, 160, Section 3, Taichung Harbor Road, Taichung 407, Taiwan. Tel: (886)4-23741349, Fax (886)4-23741348, E-mail: [email protected] Purpose: Gallium renal imaging has been reported to be useful in monitoring disease activity and predicting the response to therapy in lupus nephritis. Gallium imaging is usually performed 48-72 h following administration of the Ga-citrate. The aim of the present study was to determine whether the imaging time affects the semi-quantitative result of gallium renal scintigraphy. Methods: One hundred and twenty-two patients with lupus nephritis underwent gallium renal imaging at both 48 h and 72 h post injection of 111 MBq (3 mCi) Gacitrate. For semi-quantitative analysis of the gallium uptake in the kidneys, regions of interest (ROI) were drawn over the left kidney, the left forearm and the adjacent spine. The uptake ratios were calculated and expressed as “Kidney/Spine ratio (K/S ratio)” or “Kidney/Arm ratio (K/A ratio)”. Results: The correlation of both the left K/S ratios and the left K/A ratios from the 48-h and 72-h renal images was excellent. The mean left K/S ratio obtained from 48-h and 72-h images was 0.969 and 0.964 (P = 0.241). Whereas, the mean left K/A ratio from 48-h and 72-h images was 3.421 and 3.547 (P = 0.000043). Conclusions: There is no statistical difference of the left K/S ratios from 48-h and 72-h images. However, the left K/A ratio was significantly affected by the imaging time.