Due to the high cost and low availability, PET is not accessible to many patients. Labelled 99mTc agents to be used with SPECT could be an alternative to 18FDG-PET. Glucosamine (G) is a six-carbon amino sugar, enters the cells by a glucose transporter system and by phosphate and glycolitic pathways forms glucosamine-6-phosphate. Reacting G with cysteine (C) and label with 99mTc (99mTcCG) could be used with SPECT to show hypermetabolic lesions similar to 18FDG-PET imaging. The aim of this study was to evaluate scintigraphy with 99mTc-CG in detecting tumors and correlate them with histopathology.
Material and Methods: Labelling of 99mTc-CG was done by adding (C), (G), N-hydroxysuccinimide, carbodiimide, and stannous chloride to the 99mTc.
Patients: 35 patients ( 23 F, 12 M, range age 7-79, average 52 ) with histopathology diagnosis by biopsy or surgery, were referred for scintigraphy with 99mTc-CG.
Imaging: Patients fasted for 12 hr, and 1–4 hrs after the i.v. injection of 920-1088 MBq of 99mTc-CG, underwent 1) whole body scan, 2) SPECT images (reconstructed with OSEM algorithm) on the field of view of the lesion. To eliminate the intravascular and interstitial activity of the 99mTc-CG imaging, patients were given 737 MBq of 99mTc human serum albumin(99mTc-HSA) and other SPECT was done. Both SPECT images were normalizad and subsequently the 99mTc-HSA image was subtracted from the 99mTc-CG image. Images were visually analysed according to the following criteria, a) normal: homogeneous uptake, b) abnormal: focal asymetric uptake of 99mTc-CG.
Results: 32 lesions were malignant (breast (5), colon (8), lung (9), Hodgkin’s disease(6), thyroid(1), bladder (1), melanoma (1), ependimoma (1), and 3 were benign (brain radiation necrosis, breast inflamation and inespecific peritoneal granuloma). 99mTc-CG show abnormal focal uptake in all malignant lesions (sensitivity=100%) as well as in two bening lesion (false positive). Accuracy of 99mTcC-G in patients with malign tumors was 94%. SPECT images defined the tumor uptake better than planar imaging. Imagen sustraction (99mTc-CG minus 99mTc-HAS) highlighted the 99mTc-CG abnormal uptake by eliminating the non-tumoral uptake.
Conclusion: Our preliminary study showed that 99mTc-CG is a useful tool for metabolic imaging with SPECT, and might be a good alternative when 18FDG-PET is not available. Image subtraction is helpful in highlight tumor uptake.
