Kinetics of 99mTc-labeled pyrophosphate and polyphosphate in man.

Thekinetic of 99mTc-labeled pyrophosphate were compared with those of polyphosphate in ten patients in a combined study. Both agents cleared from the blood in a biexpoential fashion. The clearance half-time of Exponent I was the same for both and was shorter than the clearance half-time of Exponent ii. Urinary excretion of both agents was the same during the first hour but during the next 3 hr Tc-pyrophosphate cleared at a slightly more rapid rate, resulting in lower blood background radioactivity. Both agents were bound loosely to plasma proteins, mainly to globulin fractions. The sensitivity of lesion detection was similar for both. Excellent bone images were obtained with both agents. The images with Tc-pyrophosphatewere consistently superior owing to the low blood background and they took less time to accumulate an identical number of counts from identical regions. With the amount of 99mTc-complex used, no hyocalcemia or tetany was noted, nor was there any significant effect on 1-hr serum levels of inorganic phosphours and alkaline phosphatase. Four hours after injection, 9.5% of the dose of Tc-pyrophosphate was circulating in blood, 31.7% was excreted in urine, and the remaining 58.8% was taken up by bone and other tissues. The corresponding values with Tc-polyphosphate were 12.5% in blood, 29.0% in urine, and 58.5% in bone and other tissues. Among the soft tissues, the genitourinary system is most consistently visualized. It is concluded that both Tc-pyroposphate and Tc-polyphosphate are excellent skeletal-imaging agents and that Tc-pyrophosphate appears slightly superior to Tc-polyphosphate.

Synthesis of indium-labeled antibody-chelate conjugates for radioassays.

A method has been developed to achieve rapid and reproducible complexation of indium to transferrin at pH 7.4. The system consists of nitrilotriacetic acid (NTA) as the intermediate carrier ligand, whose function is to allow the 113m In ion, in a solution in Tris buffer, pH 7.4, to be transferred rapidly to the specific binding sites on transferrin. Just as in the case of iron, this complexation requires the presence of a synergistic ion such as bicarbonate. The present system can be used to allow the binding of 113mIn to transferrin when coupled to an antibody. This method has been tested by studying the conjugation of an antibody, the IgG fraction of goat anti-rabbit-IgG, with either transferrin or desferoxamine, using glutaraldehyde as the coupling agent. Optimization in terms of total protein concentration and glutaraldehyde levels lead to products where the specific metal binding capacity of the transferrin moiety remains unchanged, and where the antibody retains 70% of its antigenic activity. The present system can be considered an extension of the ELISA techniques and can be used to determine, by a terminal 113mIn labeling technique, the level of specific binding of an antibody to its antigen.

Review of nuclear pharmacy practice in hospitals.

An operational profile for nuclear pharmacy practice is presented, and the technical and professional role of nuclear pharmacists is reviewed. Key aspects of nuclear pharmacy practice in hospitals discussed are the basic facilities and equipment for the preparation, quality control, and distribution of radioactive drug products. Standards for receiving, storing, and processing radioactive material are described. The elements of a radiopharmaceutical quality assurance program, including the working procedures, documentation systems, data analysis, and specific control tests, are presented. Details of dose preparation and administration and systems of inventory control for radioactive products are outlined.

Distribution pattern of metastatic bone disease. A need for total body skeletal image.

Distribution patterns of metastatic bone disease in 62 patients with soft-tissue cancers showed that 60% of bone lesions were located in the axial and 40% in the appendicular skeleton. Thirteen percent of the lesions were in appendicular regions not usually included in routine imaging studies. The majority of the metastatic skeletal lesions were clinically asymptomatic. The serum alkaline phosphatase level is a poor indicator of early bone metastases.

Indium-111-labeled antibody heavy metal chelate conjugates: a potential alternative to radioiodination.

An alternative method to radioiodination is outlined for labeling antibodies with a radioactive marker. The method requires the conjugation of the antibody molecule to chelating agents that contain a free amino group and are capable of binding heavy metal ions. Glutaraldehyde is the coupling agent used to bridge the free amino groups on both the chelate and the antibody molecules. 111In is then added to the antibody-chelate conjugate and is bound instantaneously by the chelating portion. Electrophoretic, autoradiographic, immunodiffusion, and hemagglutination techniques were used to confirm the integrity of the 111In-labeled antibodies.

Cholescintigraphy with 99mTc-penicillamine.

D-pencillamine labeled with 99mTc (Tc-Pen) was used for cholescintigraphy in dogs and man. Satisfactory images of the gallbladder were obtained using a scintillation camera fitted with a pinhole collimator. The results of cholescintigraphy and contrast cholecystography compared favorably. The authors suggest that Tc-Pen is taken up by the hepatocytes and excreted into the bile canaliculi which enter the gallbladder. Tc-Pen may prove to be an ideal agent for evaluation of hepatocellular function.

Pharmaco-kinetics of current skeletal-seeking radiopharmaceuticals.

The blood clearance of all current bone-seeking radiopharmaceuticals is biexponential during the first four hours after injection. Exponent I represents bone uptake and its clearance half-time is less than 30 min. Exponent II represents mainly urinary excretion and its clearance half-time varies from 168 to 512 min. The blood background is highest with 99mTc-labeled polyphosphate (Tc-Poly) and lowest with sodium fluoride (F-18); 99mTc-labeled diphosphonate (Tc-Dip) and 99mTc-labeled pyrophosphate (Tc-Pyro) show intermediate blood levels. The slower blood clearance of 99mTc-phosphate complexes in comparison with F-18 is due primarily to their increased protein binding. Tc-Poly blood clearance, which is slower than that of Tc-Dip and Tc-Pyro, is due primarily to its increased red cell binding and the larger size of its molecule. Bone uptake and urinary excretion of all 99mTc-labeled phosphate complexes are approximately the same: in the range of six to ten per cent in the blood, 30-33% in the urine, and 55-58 percent in the bone and other tissues. F-18 concentration in the bone is almost 1.5 times that of the 99mTc-labeled phosphate complexes. The sensitivity and resolution of lesions are identical for all 99mTc-labeled phosphate complexes and are far better than those for F-18. No toxicity is noted with the amount of phosphate present in the marketed kits, and it appears reasonable to use the minimal amount so long as efficiency is not compromised.

Double antibody immunoradiometric assay of hGH employing a terminal labeling technique.

A method is described, and validated for hGH, using a double antibody immunoradiometric assay and a universal antibody coupled to a chelating moiety that can be labeled as the terminal step in the assay procedure. This technique, usable for any antigen, precludes the need for radiolabeled specific antibodies, and because of the short-lived radionuclide used in the terminal labeling step, generates no radioactive waste. The assay itself uses a specific first antibody coupled to a solid support (paper disc) to which the antigen binds. A specific second antibody from a second species is then attached to the solid phase retained antigen. Now a third antibody is attached, which has been generated from a third species against the second antibody acting as an antigen, and which carries transferrin as a chelating moiety. This final complex is labeled with 113mIn and the plot of the percentage of the total activity bound against the hGH concentration provides the derived values for the antigen levels present in the assay solution.

Scintigraphic demonstration of amebic liver abscesses with 131iodine labeled bromometronidazole.

This case report demonstrates an hepatic amebic abscess by scintigraphy, utilizing a new radiopharmaceutical designed specifically for that purpose. The abscess is delineated as a positive lesion after twenty four hours. The agent 131I-labeled bromometronidazole, may prove to be specific for the diagnosis of these abscesses.

Labeled metronidazoles as potential new agents for amebic hepatic abscess imaging.

Two new radiopharmaceuticals were developed as possible agents for demonstrating the presence of hepatic amebic abscesses by selective accumulation of these agents in the abscess contents. These agents are: 131I-labeled Bromometronidazole, that has been shown to possess some of the antibiotic activity of metronidazole or Flagyl; and a Technetium 99m-penicillamine-Flagyl complex. A method of radioiodination has been devised which can be performed in radiopharmaceutical laboratories. Both radiopharmaceuticals are of very low toxicity. Distribution studies in animals show accumulation in the liver and elimination by way of the gallbladder. Scintillation camera studies depict a rapid uptake by the liver with subsequent biliary excretion. Animal models for the study of hepatic amebic abscesses are not available. A human patient with suspected amebic abscesses has been studied with negative findings that were confirmed at surgery. Collaborative studies are now in progress in several areas of the world where amebiases is endemic.