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PubMed1987

Comparison of two 99mTc(V)-dimercaptosuccinic acid preparations.

99mTc(V)-DMSA labelled either by increasing the pH together with a low concentration of Sn, or by increasing the pH only are compared in vitro and in vivo. The gel chromatographic separation shows that after incubation with blood, all the 99mTc(V)-DMSA preparations are stable and do not bind to the plasma proteins. The behavior in rats as well as in clinical studies does not demonstrate any distinctive characteristics between the different radiomolecules. It seems that the pH of the solution is an important factor which controls the formation of 99mTc(V)-DMSA.

Animals↗
PubMed1989

Physico-chemical study of the radiopharmaceuticals 99mTc-DMSA, 99mTc-EDTA and 99mTc-DTPA interaction with plasmatic proteins.

This report studies the binding rate of the radiopharmaceuticals 99mTc-DTPA, 99mTc-EDTA and 99mTc-DMSA to plasmatic proteins. The proteins bind to the tested radiopharmaceuticals in the following sequence: 99mTc-DTPA less than 99mTc-DMSA(C1) less than 99mTc-EDTA less than 99mTc-DMSA(C2) where C1 and C2 represent two different Tc-DMSA complexes. The thermodynamic study suggests a quantitative relationship of radiopharmaceutical:protein = 1:1 and an almost nonexistent influence of the temperature, which means that the interacting forces in this process are relatively weak.

Blood Proteins↗
PubMed1989

Improvement of the reproducibility of ion-pair HPLC of 99mTc(Sn)EHDP complexes and the influence of the Sn(II) concentration on the composition of the reaction mixture.

The use of a non-volatile modifier and the simultaneous exclusion of oxygen by flushing with helium in ion-pair HPLC of 99mTc(Sn)EHDP-complexes prevents spurious oxidation during the separation process. It thus enables the omission of the reducing agent from the eluent solution and the determination of the labelling percentage from the TcO4(1)-peak. In addition, retention times become more reproducible.

Chromatography, High Pressure Liquid↗
PubMed1990

Quantitative study of the structure-stability relationship of Tc complexes.

By studying structural parameters (van der Waals radius and bond length from x-ray crystallography) of more than 100 known Tc compounds and using the cone packing model, a stability indicator of the Tc compounds was derived. The indicator is based on the solid angle factor sum (SAS), which is calculated from van der Waals radii and bond lengths between all coordinating atoms and Tc. The average SAS value is 0.97 +/- 0.13. The SAS value reflects the limits of the packing of ligand around Tc. The quantitative calculation of the SAS is useful for predicting stability and designing new Tc radiopharmaceuticals.

Drug Stability↗
PubMed1990

The adsorption of 99mTc(Sn)-diphosphonate complexes on tri-calciumphosphate: the influence of preparation conditions, ligand-type, incubation media and adsorption conditions. The reversibility of the adsorption.

The influence of several variables on the adsorption of 99mTc(Sn)-diphosphonate complexes on tri-calciumphosphate was determined. The composition of the incubation medium influenced the percentage adsorption: with Hank's balanced salt solution (a medium frequently used for bone cell cultures) and Tris buffer lower percentage adsorption was obtained than with physiological saline as the incubation medium. The influence of addition to the incubation medium of some ions and neutral species, some of which occur in bone fluid, is very specific. Addition of Sn(II) or Mg(II) (a component of HBSS) reduces the amount of adsorption. Addition of Ca(II) and Al(III) had no effect. Addition of sodium-citrate and MDP to the medium and an increase of the pH of the medium decreased the percentage adsorption. The ligand that was used in the preparation of the complex mixture influences the percentage adsorption considerably. The Sn(II) concentration used during the preparation of the 99mTc(Sn)-MDP and 99mTc(Sn)-MHDP complexes showed no definite influence on the percentage adsorption. The pH and ligand concentration, used in the preparation, however, did effect the percentage adsorption. It was concluded that the 99mTc(Sn)-disphosphonate mixtures are part reversibly and part irreversibly bound to tri-calcium-phosphate.

Adsorption↗
PubMed1989

Clinical and radiographic correlates of femoral artery visualization on bone scan.

In order to determine if the linear pattern of thigh uptake medial to the femur often seen on a 99mTc diphosphonate bone scan (DiP) is caused by calcification of the femoral artery, 42 patients with and without this pattern were studied by a combination of conventional radiographs, radioisotope angiography and/or computed tomography. Risk factors for arteriosclerotic disease were recorded for all patients. These techniques identified the postulated femoral artery pattern on bone scan as always corresponding to calcified femoral arteries. The prevalence of diabetes, cigarette use, hypertension and a family or clinical history of arteriosclerotic vascular disease was the same in the groups with or without DiP uptake.

Adult↗
PubMed1991

Synthesis and preliminary evaluation of a new chelate N2S4 for use in labeling proteins with metallic radionuclides.

The successful attachment of various metallic radionuclides such as 99mTc to monoclonal antibodies for targeting tumor tissue in vivo depends upon the development and use of suitable bifunctional chelating agents. We have successfully synthesized a new N2S4 (compound 4) chelate. This chelate forms a stable complex with 99mTc and is capable of coupling to different proteins. The N2S4 compound is quite stable if kept as a hydrochloride salt and is coupled to antibody under neutral conditions with better than 95% efficiency without the loss of immunoreactivity.

Antibodies, Monoclonal↗
PubMed1992

Labeling and stability of radiolabeled antibody fragments by a direct 99mTc-labeling method.

The in vitro labeling and stability of 99mTc-labeled antibody Fab' fragments prepared by a direct labeling technique were evaluated. Eight antibody fragments derived from murine IgG1 (N = 5), IgG2a (N = 2) and IgG3 (N = 1) isotypes were labeled with a preformed 99mTc-D-glucarate complex. No loss of radioactivity incorporation was observed for all the 99mTc-labeled antibody fragments after 24 h incubation at 37 degrees C. The 99mTc-labeled antibody fragments (IgG1, N = 2; IgG2a, N = 2; IgG3, N = 1) were stable upon challenge with DTPA, EDTA or acidic pH. Furthermore, using the affinity chromatography technique, two of the 99mTc-labeled antibody fragments displayed no loss of immunoreactivity after prolonged incubation in phosphate buffer up to 24 h at 37 degrees C. The bonding between 99mTc and antibody fragments was elucidated by challenging with a diamide ditholate (N2S2) compound. The Fab' with IgG2a isotype displayed tighter binding to 99mTc in comparison to the Fab' from IgG1 and IgG3 isotype in N2S2 challenge and incubation with human plasma. The in vivo biodistribution of five 99mTc-labeled fragments were evaluated in normal mice. In conclusion, the direct labeling method allows stable 99mTc labeling of antibody fragments from three of the major murine isotypes.

Chelating Agents↗
PubMed1996

Cerebral perfusion in early and late opiate withdrawal: a technetium-99m-HMPAO SPECT study.

The purpose of this study was to determine if cerebral blood flow (CBF) alterations are associated with discontinuation of heroin in chronic heroin users, and whether these alterations are reversible during abstinence. Ten physically healthy opioid-dependent males, hospitalized on an inpatient drug rehabilitation unit, were studied. Each patient had an initial single photon emission computed tomographic (SPECT) scan with the radiotracer technetium-99m-d,l-hexamethylpropyleneamine oxime (99mTc-HMPAO) 1 week after opiate discontinuation and a repeat scan 2 weeks later. The initial scans in 9 of the 10 subjects demonstrated significant, often discrete, perfusion defects, especially in the frontal, parietal, and temporal cortices. Two weeks later, repeat brain perfusion SPECT scans showed improvement in all nine subjects who had abnormal scans. Comparisons of the first scan with the second scan showed an increase in cortical uptake on the repeat SPECT study. All subjects had normal computed tomographic or magnetic resonance imaging scans. The results of this preliminary study suggest that the chronic use of opiates, like chronic use of cocaine, results in perfusion abnormalities without corresponding abnormalities on imaging studies of cerebral anatomy and morphology. This study also documents that these perfusion defects are partially reversible with short-term abstinence.

Adult↗
PubMed1996

Focal cerebral perfusion defects demonstrated by 99mTc-hexamethylpropyleneamine oxime SPECT in elderly depressed patients.

High resolution single photon emission computed tomography (SPECT) was used to evaluate regional cerebral blood flow (rCBF) in 14 acutely depressed elderly patients and 29 normal subjects. SPECT images of the two groups were randomized and blindly read. Foci of decreased radionuclide uptake were assessed by number and location. The total number of rCBF defects per whole brain study was significantly greater in the depressed patients than in the normal subjects. A significantly greater number of rCBF defects was found most strikingly in the lateral frontal and less prominently in the lateral and medial temporal brain regions of the depressed patients.

Aged↗
PubMed1994

Characterization of insoluble macromolecular Sn(II) complex and its application to the 99mTc labeling of human serum albumin-bearing mercapto groups.

A chelating ion exchange resin containing aminophosphonic acid groups was used as a polymer matrix for the preparation of an insoluble macromolecular Sn(II)(R-Sn) complex. Sn(II), which strongly bound to the surface of the polymer matrix by chelation, retained the ability to reduce 99mTc in the R-Sn complex. Human serum albumin-bearing-mercapto groups (HMA) was labeled with 99mTc at pH 2-3 using the R-Sn complex or SnCl2 as reducing agent. The 99mTc-HMA labeled with the R-Sn complex resulted in a higher sustained level of radioactivity in the blood of mice than the 99mTc-HMA labeled with SnCl2. These results suggest that the use of the R-Sn complex minimized Sn(II) contamination of the 99mTc labeling solution and can be used effectively as a reducing agent for 99mTc labeling of proteins containing sulfhydryl groups.

Animals↗
PubMed1993

Studies of quality control of 99mTc-labelled macroaggregated albumin--Part 1. Aggregation of non-mercaptalbumin and its conformation.

The aggregative condition of albumin was investigated using bovine serum albumin (BSA) as a model for quality control of 99mTc-macroaggregated albumin (99mTc-MAA). Uniformalized aggregates were obtained from the oxidized non-mercapt-type of BSA by heating. The size of the aggregates was affected by the pH and the types of buffer solutions used as well as the concentrations of albumin and buffers. The beta form structure of the albumin was more stable on heating and this may contribute to its aggregation. Aggregation of oxidized non-mercaptalbumin afforded a portion of smaller sized particles in MAA, this being an inappropriate factor for scintiscanning of lungs. Our results suggest that it is necessary to remove oxidized type albumin from human serum albumin as the starting material, in order to prepare MAA with a uniform and larger particle size.

Albumins↗
PubMed1993

Scintigraphic potentials of J001X acylated poly-galactoside for imaging inflammatory lesions in pigs.

Although several approaches already exist for the imaging of inflammatory foci, new specific strategies providing functional data on the lesions are required to determine the extent of the disease and also to assess anti-inflammatory treatment. In our study, we investigated the scintigraphic potential of 99mTc-J001X, an agent developed for the targeting of macrophages. Due to its well documented and progressive evolution of lesions, a model of radiation-induced inflammation in pigs was chosen. Our results demonstrated the ability of J001X to provide images of inflammatory foci with a high contrast. The contribution of some specific and non-specific parameters possibly involved in the scintigraphic behavior of J001X is discussed.

Acetylation↗
PubMed1994

The safety and pharmacokinetics in adult subjects of an intravenously administered 99mTc-labeled 17 amino acid peptide (CYT-379).

A phase I study was designed to evaluate the safety and pharmacokinetics of a novel platelet reactive peptide, peptide acetyl-SYGRGDVRGDFKCTCCA-amide (CYT-379), which binds to the fibrinogen receptor of activated platelets and also binds to 99mTc. Eleven subjects with suspected deep venous thrombosis had 0.1, 0.5 or 1.0 mg of the peptide infused intravenously. Pharmacokinetics were determined by assaying blood samples in 6 of the 11 subjects and by urine sampling in 5 of these 6 subjects. Plasma and whole blood time-activity curves demonstrated an initial fast component with half-time clearance of 0.2 +/- 0.01 and 0.2 +/- 0.02 h and a slow component with half-time clearance of 2.8 +/- 0.3 and 2.7 +/- 0.2 h (mean +/- SEM for plasma and whole blood, respectively). Urine clearance was 22.6 +/- 3.3 and 10.8 +/- 1.6 mL/min when normalized to body surface area. The cumulative excretion of 99mTc-CYT-379 in the urine was 16.6 +/- 3.6, 45.6 +/- 16.9 and 45.6 +/- 1.8% of the administered dose over 0-2, 0-12 and 0-24 h after radiopharmaceutical injection, respectively. Images obtained in 11 subjects immediately, at 1-2, and 4-6 h after injection were evaluated for abnormalities and were compared with duplex Doppler ultrasonography. 99mTc-CYT-379 images were positive in only 3 of 7 subjects who had a positive duplex Doppler examination in at least one lower extremity. One subject with negative duplex Doppler had also negative 99mTc-CYT-379 scintigraphy. One subject with negative scintigraphy and two other subjects with positive scintigraphy had no other imaging studies of the deep venous system performed. No adverse reactions were observed during or after the infusion of 99mTc-CYT-379. 99mTc-CYT-379 appears to be a safe radiopharmaceutical and demonstrates rapid clearance from plasma in human subjects.

Adult↗
PubMed1994

Accumulation of some small molecular weight complexes of 99mTc in experimental abscesses.

The purpose of the present investigation was to evaluate the feasibility of imaging inflammatory lesions with some small molecular weight complexes of 99mTc with renal excretion in comparison to 99mTc-dextran (D), 99mTc-HIG and 67Ga-citrate. The biodistributions of pertechnetate (P), 99mTc-citrate (Cit), -gluconate (G), -glucoheptonate (GH), -DTPA, -glucose phosphate (GP), -D, -HIG and 67Ga-Cit were determined in mice with turpentine-induced abscesses at 1, 3, 6 and 24 h after i.v. injection of 15 MBq. % uptake/g tissues and abscess/muscle (A/M), blood (A/B), liver (A/L), intestine (A/J) and kidney (A/K) concentration ratios were calculated. The scintigraphic images of all mice were obtained by a 7-camera. The abscesses were well visualized with all the radiopharmaceuticals (RPs). The excretion was mainly via the kidneys except for 99mTc-D, 99mTc-HIG and 67Ga-Cit. They showed variable amounts of liver and kidney uptake. Similar A/M ratios were obtained with all the RPs, reaching max. at 3 h with pertechnetate, 99mTc-Cit and 99mTc-GP, at 6 h with 99mTc-DTPA and at 24 h with 99mTc-G, 99mTc-GH, 99mTc-D and 99mTc-HIG. The max. A/M ratios were 3.61 +/- 1.63, 4.61 +/- 3.92, 5.21 +/- 1.24, 3.60 +/- 0.52, 3.43 +/- 0.92, 5.37 +/- 0.67, 5.98 +/- 1.17 and 4.76 +/- 2.03 for 99mTc-P, -Cit, -G, -GH, -DTPA, -D, -HIG and 67Ga-Cit, respectively. Our results indicated that small molecular weight complexes of 99mTc can be used in imaging inflammation as well as high molecular weight complexes such as 99mTc-D, 99mTc-HIG and 67Ga-Cit. However, the first group is preferred, because of rapid blood clearance and excretion predominantly via the kidneys, which is an advantage for the identification of abdominal abscesses. The main mechanism of accumulation of all the RPs might be a simple diffusion process through the injured capillaries. An additional mechanism of binding to proteins was considered in view of the increasing concentration ratios with 99mTc-G, -GH, -D and -HIG as time progressed.

Abscess↗
PubMed1994

Evaluation of a direct method for technetium labeling intact and F(ab')2 1A3, an anticolorectal monoclonal antibody.

A direct method for 99mTc-labeling monoclonal antibodies (MAb) has been evaluated for labeling intact and F(ab')2 1A3, an anticolorectal carcinoma MAb. The method employs ascorbic acid to reduce the MAbs. By altering the reaction conditions for 99mTc-1A3, a maximum radiolabeling yield of 48% was obtained with an immunoreactivity (IR) value of 87%; and for 99mTc-1A3-F(ab')2, a yield of 49% and an IR value of 70% was obtained. Biodistribution of 99mTc-labeled 1A3 MAbs was performed in a Golden Syrian hamster model and compared to 125I-labeled 1A3 MAbs. Tumor uptake (%ID/g) was significantly better for the intact 125I-1A3 at 24 h post-injection compared to the intact 99mTc-1A3. For 99mTc-1A3-F(ab')2, %ID/g tumor was low, and did not increase over 24 h. High %ID/g kidney persisted at 24 h for both 99mTc-labeled intact and F(ab')2 1A3. Serum stability was performed in Sprague-Dawley rats for the 99mTc-labeled 1A3 MAbs, and compared to 125I-labeled 1A3 MAbs, which showed intact 99mTc-1A3 cleared similarly to 125I-1A3, and 99mTc-1A3-F(ab')2 cleared more rapidly than 125I-1A3-F(ab')2 indicating instability of the 99mTc-labeled 1A3-F(ab')2.

Animals↗
PubMed1994

Preparation of a pure 99mTc-F(ab')2 radioimmunoconjugate by direct labeling methods.

Intact IgG and Fab' can be labeled directly with 99mTc to give quantitative incorporation of radioactivity into the protein. With F(ab')2 the reductive conditions yield a mixture of 99mTc-F(ab')2 and 99mTc-Fab'. We now report a direct labeling method to produce only 99mTc-F(ab')2 in quantitative yield and contaminated with 99mTc-Fab'. The properties, stability and biodistribution of the 99mTc-F(ab')2 have been compared to 99mTc-Fab'. This new technology will allow us to compare technetium direct-labeled IgG, F(ab')2 and Fab' derivatives of the same antibody for radioimmunodetection.

Animals↗