Vol 5, No 2 (2002)
Published online: 2002-06-07
Comparison of99mTc-alafosfalin and 67Ga-citrate in a mouse model of bacterial infection
Nucl. Med. Rev 2002;5(2):93-97.
Abstract
BACKGROUND: The antibiotic-peptide 99mTc-alafosfalin was assessed as an infection imaging agent in Staphylococcus aureas infected mice by comparison with 99mGa-citrate, and also examined for influence of septic status on tracer biodistribution by comparison with normal mice.
MATERIAL AND METHODS: Intramuscular doses of S. aureus were administered into the right thigh muscle of mice and the infection was allowed to develop for 20 hours. In separate experiments, 99mTc-alafosfalin and 67Ga-citrate were subsequently administered and allowed to localise. Quantitative organ distribution studies were performed in conjunction with scintigraphic images at 1 and 4 hours post injection. An additional biodistribution with 99mTc-alafosfalin in normal mice was also performed.
RESULTS: 99mTc-alafosfalin was predominantly renal excreted, with low liver, intestine and bone uptake. There was no difference in the uptake of these organs when infected mice were compared with normal mice. 99mTc-alafosfalin activity in the intestine at 1 and 4 hours was substantially less than 67Ga-citrate. For 99mTc-alafosfalin, infected/non-infected thigh ratios of 2.8/1.0 and 3.6/1.0 were determined at 1 and 4 hours post injection respectively. 67Ga-citrate gave ratios of 1.6/1.0 and 3.7/1.0 at the corresponding time points.
CONCLUSIONS: 99mTc-alafosfalin uptake was more rapid than 67Ga-citrate, yet diffuse at the infectious sites in mice. The small and juvenile mouse model resulted in uptake of the phosphonic acid tracer by active bone growth areas which may be a disadvantage. This 99mTc-antibiotic peptide has potential as an infection imaging agent, and will be investigated further in another rodent infection model in the future.
MATERIAL AND METHODS: Intramuscular doses of S. aureus were administered into the right thigh muscle of mice and the infection was allowed to develop for 20 hours. In separate experiments, 99mTc-alafosfalin and 67Ga-citrate were subsequently administered and allowed to localise. Quantitative organ distribution studies were performed in conjunction with scintigraphic images at 1 and 4 hours post injection. An additional biodistribution with 99mTc-alafosfalin in normal mice was also performed.
RESULTS: 99mTc-alafosfalin was predominantly renal excreted, with low liver, intestine and bone uptake. There was no difference in the uptake of these organs when infected mice were compared with normal mice. 99mTc-alafosfalin activity in the intestine at 1 and 4 hours was substantially less than 67Ga-citrate. For 99mTc-alafosfalin, infected/non-infected thigh ratios of 2.8/1.0 and 3.6/1.0 were determined at 1 and 4 hours post injection respectively. 67Ga-citrate gave ratios of 1.6/1.0 and 3.7/1.0 at the corresponding time points.
CONCLUSIONS: 99mTc-alafosfalin uptake was more rapid than 67Ga-citrate, yet diffuse at the infectious sites in mice. The small and juvenile mouse model resulted in uptake of the phosphonic acid tracer by active bone growth areas which may be a disadvantage. This 99mTc-antibiotic peptide has potential as an infection imaging agent, and will be investigated further in another rodent infection model in the future.
Keywords: technetium-99m-alafosfalinantibiotic-peptideinfection imaging
