Technetium-99m-labeled chemotactic peptides: comparison with indium-111-labeled white blood cells for localizing acute bacterial infection in the rabbit.
The biodistribution and infection imaging properties of 99mTc-labeled formyl-methionyl-leucyl-phenylalanyl-lysyl-hydrazinonicotinamide (99mTc-HP) were compared with 111In-labeled leukocytes (111In-WBCs) in rabbits with E. coli infections. Groups of six animals were co-injected with 1 mCi of 99mTc-HP plus 0.05 mCi of 111In-WBCs and serial scintigrams were acquired from 3 to 6 hr and 18 hr postinjection. After acquiring the final images, the animals were killed and biodistribution was determined. At all imaging times, the distributions of 99mTc-HP and 111In-WBCs were similar and the sites of infection were well visualized with both radiopharmaceuticals. The target (infected muscle) to background (contralateral normal muscle) ratios (T/B) were: 3.38 +/- 0.46, 3.80 +/- 0.37 and 10.87 +/- 1.44 for 99mTc-HP and 1.71 +/- 0.04, 1.81 +/- 0.26 and 3.79 +/- 0.83, for 111In-WBCs at 3, 6 and 18 hr postinjection, respectively. The average ratio of T/B ratios (99mTc-HP-to-111In-WBCs) was 2.99 +/- 1.88, with no value less than unity. T/B ratios calculated from direct tissue sampling were significantly higher for 99mTc-HP than for 111In-WBCs (33.6:1 versus 8.1:1, p < 0.01). These differences were primarily due to increased absolute accumulation of 99mTc-HP (0.102%ID/g versus 0.024%ID/g, p < 0.01) in infected muscle rather than a difference in accumulation in normal skeletal muscle. These results indicate that 99mTc-HP yields target-to-background ratios greater than or equal to those achievable with 111In-WBCs probably as a result of an increase in absolute accumulation at the site of infection.
Babich
J W
JW
Department of Radiology, Massachusetts General Hospital, Boston 02114.
Graham
W
W
Barrow
S A
SA
Dragotakes
S C
SC
Tompkins
R G
RG
Rubin
R H
RH
Fischman
A J
AJ
D000208:Acute Disease; D000818:Animals; D002630:Chemotactic Factors; D004927:Escherichia coli Infections / Q000000981:diagnostic imaging*; D007205:Indium Radioisotopes; D007962:Leukocytes; D008297:Male; D008961:Models, Structural; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives*; D015609:Organotechnetium Compounds; D011817:Rabbits; D011877:Radionuclide Imaging
D002630:Chemotactic Factors; D007205:Indium Radioisotopes; D015609:Organotechnetium Compounds; C084664:technetium Tc 99m formyl-methionyl-leucyl-phenylalanyl-lysyl-hydrazinonicotinamide; D009240:N-Formylmethionine Leucyl-Phenylalanine