title: 99mTc-citrate versus 67Ga-citrate for the scintigraphic visualization of inflammatory lesions.
abstract: Citric acid was labeled with 99mTc with an efficiency of > 99%. The biodistribution of 99mTc-citrate was studied in mice with turpentine-induced abscesses in comparison to 67Ga-citrate. The max. abscess/muscle concentration ratios were 4.61 +/- 1.92 (3 h) for 99mTc-citrate and 4.76 +/- 2.04 (4 h) for 67Ga-citrate. Arthritis was induced in 10 rabbits by intra-articular injection of ovalbumin Scintigrams obtained 4 days later and at 3 h post-injection of 99mTc-citrate showed increased activity involving the synovium. The max. arthritic/contralateral knee ratio was 3.19 +/- 1.29 (3 h) and 6.47 +/- 3.71 (24 h) for 99mTc- and 67Ga-citrate, respectively. The blood clearance curve of 99mTc-citrate in rabbits was biexponential with a fast (T1/2 = 36 min) and a slow (T1/2 = 18 h) component, compared to mono-exponential clearance of 67Ga-citrate (T1/2 = 23 h). In 10 patients with rheumatoid arthritis whole-body scintigrams and spot images of involved joints indicated localization of the tracer in inflamed tissues. The mean target-to-soft tissue ratios were 3.04 +/- 0.81 and 4.95 +/- 2.56 for 99mTc-citrate and 99mTc-MDP, respectively. Renal clearance of radioactivity was evident from the scintigrams. Our results demonstrated that 99mTc-citrate is effective as a radiopharmaceutical for the visualization of inflammatory lesions and may be preferred to 67Ga-citrate due to the ideal physical characteristics of the radionuclide, easy preparation, low cost, early accumulation and the preference for the renal route of excretion.
authors.affiliation: Department of Nuclear Medicine, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
authors.forename: M T
authors.initials: MT
authors.lastname: Ercan
authors.forename: T
authors.initials: T
authors.lastname: Aras
authors.forename: E
authors.initials: E
authors.lastname: Unlenen
authors.forename: M
authors.initials: M
authors.lastname: Unlü
authors.forename: I S
authors.initials: IS
authors.lastname: Unsal
authors.forename: Z
authors.initials: Z
authors.lastname: Hasçelik
mesh_terms: D000038:Abscess / Q000000981:diagnostic imaging; D000818:Animals; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging; D002951:Citrates / Q000493:pharmacokinetics; D019343:Citric Acid; D005710:Gallium Radioisotopes; D006801:Humans; D007249:Inflammation / Q000000981:diagnostic imaging*; D051379:Mice; D011877:Radionuclide Imaging; D013667:Technetium; D014018:Tissue Distribution
chemical_list: D002951:Citrates; D005710:Gallium Radioisotopes; D019343:Citric Acid; D013667:Technetium