PURPOSE: S-[(11)C]-methyl-L-cysteine ([(11)C]MCYS) has been claimed to offer higher tumor selectivity than L-[methyl- (11)C]methionine ([(11)C]MET). We examined this claim in animal models.
PROCEDURES: Rats with implanted untreated (n = 10) or irradiated (n = 7, 1 × 25 Gy, on day 8) orthotopic gliomas were scanned after 6, 9, and 12 days, using positron emission tomography. Rats with striatal injections of saline (n = 9) or bacterial lipopolysaccharide (n = 9) were scanned after 3 days.
RESULTS: Uptake of the two tracers in untreated gliomas was similar. [(11)C]MCYS was not accumulated in salivary glands, nasal epithelium, and healing wounds, in contrast to [(11)C]MET, but showed 40 % higher accumulation in the healthy brain. Both tracers showed a reduced tumor uptake 4 days after irradiation and minor accumulation in inflamed striatum. [(11)C]MCYS indicated higher lesion volumes than [(11)C]MET (untreated tumor + 47 %; irradiated tumor up to + 500 %; LPS-inflamed striatum + 240 %).
CONCLUSIONS: [(11)C]MCYS was less accumulated in some non-tumor tissues than [(11)C]MET, but showed lower tumor-to-brain contrast.
- Amino acids
- Brain tumors
- Positron emission tomography
- Small animal imaging