Accumulation of 99mTc-Cysteine in experimental inflammatory lesions in comparison to 99mTc-glutamine and 99mTc-HIG.

AIM

The aim of this experimental work was to investigate the efficacy of 99mTc-L-Cysteine (Cys) in scintigraphic visualization of inflammatory lesions in comparison to 99mTc-L-glutamine (G), and 99mTc-HIG.

METHODS

In mice abscesses were induced by intramuscular injection of turpentine. Six days later mice were injected with 3.7 MBq of each agent and sacrificed in groups of three at 1, 3, 6 and 24 h. Scintigrams were obtained with a gamma camera. The organs, some blood, abscesses, some muscle and urine were removed, weighed and counted in a gamma counter. Percentage of uptake by organs and per gram tissues and abscess/normal tissue concentration ratios were calculated. Experimental arthritis was produced in 6 New Zealand rabbits by intraarticular injection of ovalbumin. Four days later 37 MBq of 99mTc-Cys and 99mTc-HIG were each i.v. administered to 3 rabbits. Scintigrams obtained at 1, 3, 6, and 24 h demonstrated the arthritic joints very well. ROI's over arthritic joints were compared to contralateral normal joints (A/C).

RESULTS

In mice the abscesses were well visualized on all scintigrams. The maximum abscess/muscle ratios were 5.21 +/- 1.09 (6 h), 3.73 +/- 0.81 (3 h) and 5.98 +/- 1.17 (24 h) and the maximum abscess/blood ratios were 3.46 +/- 1.33 (24 h), 1.81 +/- 0.10 (6 h) and 0.914 +/- 0.351 (24 h) for 99mTc-Cys, 99mTc-G, and 99mTc-HIG, respectively. In rabbits the maximum A/C ratios were 2.61 +/- 0.53 (3 h) and 2.92 +/- 0.99 (24 h) for 99mTc-Cys and 99mTc-HIG, respectively.

CONCLUSION

Our results indicate that 99mTc-Cys is a promising agent for imaging inflammatory lesions. It is preferred to 99mTc-HIG, because of higher concentration ratios attained earlier, lower blood background, lower cost and a simpler in-house preparation method.