Particle size analysis: 90Y and 99mTc-labelled colloids.

Colloidal particle size is an important characteristic to consider when choosing a radiopharmaceutical for diagnosis and therapeutic purposes in nuclear medicine. Photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM) were used to determine the particle-size distribution of (90)Y- and (99m)Tc-labelled antimony trisulfide (Sb(2)S(3)) and tin colloids (Sn-colloid). (90)Y-Sb(2)S(3) and (99m)Tc-Sb(2)S(3) were found to have a diameter of 28.92 +/- 0.14 and 35.61 +/- 0.11 nm, respectively, by PCS. By TEM, (90)Y-Sb(2)S(3) particles were measured to be 14.33 +/- 0.09 nm. (90)Y-labelled Sn colloid were found to exist with a d(v(max1)) of 805 nm and a d(v(max2)) of 2590 nm, by PCS, whereas (99m)Tc-Sn colloid was shown to have more than 80% of radioactive particles of approximately 910 nm by PCS. For (90)Y-labelled Sb(2)S(3) and Sn colloid, a comparison of TEM and PCS indicates that these techniques found significantly different mean diameters. TEM has an excellent resolution necessary for radiocolloid particle-sizing analysis, and it is a desirable size-measuring technique because it is more reliable than PCS.

99Tcm-p-aminohippuric acid as a new renal agent.

99Tcm-p-aminohippuric acid (99Tcm-PAH) is a new renal radiopharmaceutical prepared from a lyophilized kit by the addition of sodium pertechnetate (Na99TcmO4). Each vial contains PAH, the calcium trisodium salt of diethylenetriamine pentaacetic acid (CaNa3DTPA) and stannous chloride (SnCl2.2H2O) in an inert atmosphere. It is a stable radiopharmaceutical with high radiochemical purity (> 95%). Its protein binding is very similar to that of 131I-OIH, but it is hydrophilic in character. Animal studies using 99Tcm-PAH have indicated that it provides renal images of satisfactory quality with no external background. Despite its almost identical radiochemical purity and HPLC analysis results to 99Tcm-DTPA, 99Tcm-PAH is rapidly secreted by the kidneys in a manner consistent with tubular secretion, as confirmed by rat probenecid studies, whereas 99Tcm-DTPA is excreted by glomerular filtration. The pharmacokinetic parameters of 99Tcm-PAH (t1/2(alpha)) = 2.5 min, t1/2(beta) = 41.7 min, Cl = 5.22 ml.min-1, Kel = 5.1 x 10(-4) min-1) differ from those of 99Tcm-DTPA. Evaluation of 99Tcm-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 effect of contaminants on characteristics of 99mTC radiopharmaceuticals]. / Uticaj primesa na karakteristike 99mTc-radiofarmaceutika.

The influence of 99Tc, oxygen and cupric ions on labeling yield of eight radiopharmaceuticals was examined. The results obtained for commercial and experimental preparations were compared. The latter were formulated so that the content of 99Tc was 4 times, hydrogen peroxide 5 times and copper 50 times higher than in commercial preparations. It was found that these impurities did not affect labeling of 99mTc(Sn)tetracyclin, 99mTc(Sn)dimercaptosuccinate and 99mTc(Sn)diethylida. Long-living 99Tc did not affect any preparations. Oxygen influenced in lesser extent 99mTc(Sn) DTPA, 99mTc(Sn)pyrophosphate and 99Tc(Sn) dicarboxy-propane diphosphonate but strongly 99mTc(Sn) phytate 99mTc(Sn)methylene diphosphonate. Copper influenced only 99mTc(Sn)-methylene diphosphonate. Therefore this preparation was examined in broader range of copper concentrations. According to the results of radiochemical and biodistribution analyses it was concluded that under the experimental conditions the effect of oxygen and copper resulted in an increased content of free 99mTc-pertechnetate in the examined preparations.

Change of pharmacokinetic parameters of 131I-hippuran caused by heparin.

The radiochemical purity of 131I-hippuran determined by radiochromatographic analysis using Whatman No 3 MM paper and a mixture of n-butanol, acetic acid and water as developer, was 97.3 +/- 1.2%. O-131IB acid and less than 1% of free 131I were separated from the preparation. No radioactivity which would correspond to O-131IB acid was observed on the radiochromatogram when 131I-hippuran was incubated with HSA and heparin. Protein binding of 131I-hippuran as a function of radiochemical purity, and HSA and heparin concentrations were determined by the method of equilibrium dialysis. No effect of radiochemical purity on protein binding of 131I-hippuran was observed, the value obtained being 1.3 +/- 0.1%. Higher HSA concentrations increased protein binding but decreased retention activity on the dialysing membrane. Heparin decreased protein binding of 131I-hippuran by 47%. The biological half-times of excretion of 131I-hippuran with heparin were 4 min for the fast phase and 107 min for the slow phase. The results of biodistribution in experimental animals showed increased localization of 131I-hippuran with heparin in the kidneys and liver during the first 15 min after injection.

Comparative quality control of 99mTc-Pyrophosphate and 99mTc-diphosphonate radiopharmaceuticals.

The results of analysis of 99mTc-Pyrophosphate (99mPyP), taken as a representative of the group of compounds having an organic P-O-P bond, and of the three diphosphonate compounds: methylene diphosphonate (MDP), 2,3-dicarboxy propane diphosphonate (DPD) and ethane-1-hydroxy-1, 1-diphosphonate (EHDP), which differ in their chemical structure, are shown. Also, some physicochemical parameters such as chloroform-water apparent partition coefficient, the osmotic pressure and pH values in final preparations were studied. The radiochemical purity of these radiopharmaceuticals was determined by the two methods: Sephadex chromatography for separation of 99mTc-hydrolysate and TLC on silica gel with 85% methanol for the determination of free 99mTcO-4. The yield of labelling for both methods was over 90%. Also, pharmacokinetic parameters such as binding to the plasma proteins and to erythrocytes were determined. 99mTc-PyP binding to plasma proteins was higher than the binding of diphosphonate compounds. The quantitative distribution of preparations was determined in experimental animals.