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Objective Tc-99m-p-aminohippuric acid (PAH) is a new radiopharmaceutical rapidly secreted by the kidneys in a manner consistent with tubular secretion. A comparative study of renal scintigraphy and clearance with Tc-99m-PAH, diethylene triamine pentaacetic acid (DTPA) and mercaptoacetyltriglycine (MAG(3)) was performed. Methods (TC)-T-99m-PAH was prepared from a lyophilized kit by addition of sodium pertechnetate in the presence of DTPA. Ten healthy individuals were injected with 110 MBq of Tc-99m-PAH. A dynamic study was repeated with Tc-99m-DTPA and Tc-99m-MAG(3) several days later, after a 1-day interval. Clearance measurements were performed in five individuals. Results The mean values of time-to-peak activity (T-max) and the time from peak to 50% of peak activity (T-1/2) for Tc-99m-PAH (3.6 +/- 0.9 and 6.9 +/- 2.7 min, respectively) and Tc-99m-MAG, (3.5 +/- 0.8 and 6.8 +/- 2.1 respectively) were significantly lower in comparison with those of Tc-99m-DTPA (4.9 +/- 1.7 and 11.7 +/- 1.9 min, respectively). The mean value of Tc-99m-PAH clearance (186.9 +/- 12.2 ml/min) was significantly lower in comparison with MAG(3) clearance (303.9 +/- 19.5 ml/min) and significantly higher than DTPA clearance (85.0 +/- 24.1 ml/min). Conclusion Our preliminary results indicate the potential usefulness of Tc-99m-PAH for routine renal scintigraphy. Owing to its fast kinetics, excretion and high-quality images, it could be a suitable for Tc-99m-DTPA. Tc-99m-PAH clearance values, however, were significantly lower than those of MAG(3), and could not be used for the estimation of renal plasma flow. Nucl Med Commun 30:76-81 (C) 2009 Wolters Kluwer Health vertical bar Lippincott Williams and Wilkins.

99Tc m -p-aminohippuric acid ( 99 Tc m -PAH) is a new renal radiopharmaceutical prepared from a lyophilized kit by the addition of sodium pertechnetate (Na 99 Tc m O 4 ). Each vial contains PAH, the calcium trisodium salt of diethylenetriamine pentaacetic acid (CaNa 3 DTPA) and stannous chloride (SnCl 2 .2H 2 O) in an inert atmosphere. It is a stable radiopharmaceutical with high radiochemical purity (> 95%). Its protein binding is very similar to that of 131 I-OIH, but it is hydrophilic in character. Animal studies using 99 Tc m -PAH have indicated that it provides renal images of satisfactory qualit y with no external background. Despite its almost identical radiochemical purity and HPLC analysis results to 99 Tc m -DTPA, 99 Tc m -PAH is rapidly secreted by the kidneys in a manner consistent with tubular secretion, as confirmed by rat probenecid studies, whereas 99 Tc m -DTPA is excreted by glomerular filtration. The pharmacokinetic parameters of 99 Tc m -PAH (t 1/2(α) ) = 2.5 min, t 1/2(β) = 41.7 min, Cl = 5.22 ml.min -1 , K et = 5.1 × 10 -4 min -1 ) differ from those of 99 Tc m -DTPA. Evaluation of 99 Tc m -PAH in two human volunteers confirmed its good renal characteristics: rapid disappearance from the vascular system, high uptake in kidneys followed by its very fast elimination, and low residual activity 20 min after its intravenous administration.

The aim of this paper was to compare the value of bone scintigraphy and radiography in the early diagnosis of post-fracture reflex sympathetic dystrophy (RSD). Thirty-seven adult patients with post-fracture RSD (28 in the first and nine in the second clinical stage of RSD), as well as seven patients with fracture but without RSD (control group), were investigated by radiography and bone scintigraphy. All of them were immobilized (duration of immobilization: 4–22 weeks). In 21 persons three phase bone scintigraphy was performed. The best distinction between the control group and the RSD patients was achieved by delayed bone scintigrams. The sensitivity (97%), positive predictive value (97%) and accuracy (95%) of delayed bone scintigraphy were very high compared to the values for radiography, which were 73%, 90% and 70% respectively. Bone scintigraphy also displayed higher specificity (86%) and negative predictive value (86%) than radiography (57% and 29% respectively). In the first clinical stage the difference between the accuracy of bone scintigraphy (97%) and radiography (63%) was greater than for the whole group. In the second stage of RSD the accuracy of bone scintigraphy (86%) and radiography (81%) was similar. Three-phase bone scintigraphy is not necessary for the diagnosis of post-fracture RSD: it is sufficient to perform delayed bone scintigraphy. It is concluded that bone scintigraphy is to be preferred to radiography for the early diagnosis of post-fracture RSD in the first clinical stage. In the second stage the diagnostic capabilities of bone scintigraphy and radiography are more comparable.