A cross-over study comparing the kinetics of Tc-99m-labeled diisopropyl and p-butyl IDA analogs in patients

Synthesis of multidentate ligands with amido or amino donor groups for the preparation of rhenium and technetium radiopharmaceuticals

A new method to prepare novel semi-rigid multidentate ligands containing nitrogen atom, to coordinate with rhenium and technetium, was established. The method was based on formylation of substituted anilines, followed by Mannich reaction with glycine and paraformaldehyde. The method was very promising to design ligands of various molecular structures (L₁–L₅) to coordinate with rhenium metal ions. The complexes were prepared through ligand exchange with the complex ReOCl₃(PPh₃)₂, giving new complex of the structure ReOCl₃L_(1–5). The prepared ligands and complexes were identified by the use of UV–vis, and infrared absorption spectrometric techniques, elemental analysis, molecular weight determination by depression of freezing point. These ligands were labeled with ^99mTc pertechnetate, and the labeling efficiency of the complexes was measured using a well type scintillation gamma counter equipment and obtained a good yield.

Evaluation of 99mTc-mercaptoacetyltriglycine-biocytin as a new hepatobiliary imaging agent in mice coinjected with bilirubin

We evaluated 99mTc-labeled mercaptoacetyltriglycine (99mTc-MAG3)-biocytin as a hepatobiliary imaging agent in the absence and presence of bilirubin in mice. We then compared its pharmacokinetic parameters; peak liver/heart activity ratio (rmax) and half clearance time (HCT) with those of 99mTc-labeled diisopropyl-iminodiacetic acid (99mTc-disofenin). Balb/c mice were injected intravenously with hepatobiliary agent (99mTc-MAG3-biocytin or 99mTc-disofenin) alone or in combination with bilirubin at two doses (7 and 14 mg/kg) dissolved in 5% human serum albumin. Images were acquired every 15 s for 30 min with a gamma-camera equipped with a pinhole collimator. Dynamic images showed rapid hepatic uptake of 99mTc-MAG3-biocytin, with rapid clearance from the blood and rapid excretion via the biliary system. Its hepatic uptake was not affected by bilirubin coinjection, whereas 99mTc-disofenin coinjected with bilirubin showed a higher blood background than 99mTc-disofenin alone. These qualitative findings were reflected in pharmacokinetic parameters, rmax and HCT. The rmax was obtained from plots of time versus liver/heart activity ratios obtained in equal-area regions of interest over the heart and liver. The HCT was calculated from the hepatic clearance curve from plots of time versus liver activity. 99mTc-MAG3-biocytin without bilirubin coinjection showed an rmax of 8.9+/-1.3 and an HCT of 399+/-36 s. These values did not change even when 14 mg/kg of bilirubin were coinjected. By contrast, the parameters for 99mTc-disofenin with bilirubin were significantly (p < 0.01) affected by 14 mg/kg of bilirubin coinjection: rmax was decreased from 7.9+/-2.5 to 1.4+/-0.2 and HCT was increased from 292+/-32 s to 782+/-133 s. 99mTc-MAG3-biocytin hepatobiliary scintigraphy in mice is not affected by bilirubin coinjection, and this hepatobiliary agent appears to offer promise for estimating hepatic function in patients with high bilirubin levels.

Use of 99mTc-mercaptoacetyltriglycine (MAG3)-biocytin hepatobiliary scintigraphy to study the protective effect of a synthetic enzyme inhibitor on acute hepatotoxicity in mice

Recent data suggest that inhibitors of ethanol-inducible cytochrome P450 (CYP2E1) can protect the liver from injury caused by various substrates of CYP2E1. In this study, we measured the protective effect of isopropyl-2-(1,3-dithioetane-2-ylidene)-2[N-(4-methylthiazol -2-yl)-carbamoyl]acetate (YH439), a transcriptional inhibitor of CYP2E1, against carbon tetrachloride (CCl4)-induced hepatotoxicity by using various conventional methods and dynamic scintigraphy with 99mTc-mercaptoacetyltriglycine (MAG3)-biocytin, a recently developed scintigraphic agent. Balb/c mice were pretreated with two doses of YH439 (50 or 150 mg/kg per day) at 48 h and 24 h and one dose of CCl4 (0.25 mL/kg) at 18 h before scintigraphy. The results were compared with those of two other groups, one that received CCl4 but not YH439, and the other that received neither (control). Scintigraphic images were acquired continuously at 15-sec intervals for 30 min. Pharmacokinetic parameters, such as peak liver/heart ratio (r(max)), peak liver uptake time (t(max)), and hepatic half-clearance time (HCT), were obtained from time-activity curves derived from regions-of-interest (ROI) over the liver and the heart. Acute administration of CCl4 alone caused centrilobular necrosis and serum transaminase levels to rise more than 5 times higher than those of the control group. Pharmacokinetic parameters also changed significantly from those of the control group. Administration of YH439 prevented centrilobular necrosis and significantly improved pharmacokinetic parameters. This study demonstrates for the first time that hepatobiliary scintigraphy can be used to study in vivo biochemistry of the CYP2E1 inhibitor (YH439) against liver toxicity.

Indirect spectrophotometric determination of BIDA, DISIDA, DTPA and MDP in labelled compounds

N-(4-(n-butyl)-acetanilide)iminodiacetic acid (BIDA), N-(2,6-diisopropylacetanilide)iminodiacetic acid (DISIDA), diethylenetriaminepentaacetic acid (DTPA) and methylene diphosphonic acid (MDP) are used in labelling kits. The contents of BIDA, DISIDA or MDP of the 99mTc-labelled compounds can be determined (indirectly) spectrophotometrically with copper, eriochrome cyaanine R (ECC) and dodecylethyldimethylammonium bromide (DEDA) in a sodium barbital buffered system at pH 8.5. The calibration curves obey Beer's Law from 0 to 40 micrograms/25 mL for BIDA and DISIDA, 0 to 60 micrograms/25 mL for DTPA and 0 to 100 micrograms/10 mL for MDP.

Pharmacokinetic studies of DISIDA disposition. I. Animal studies

The whole blood pharmacokinetics of intravenously administered 99mTc-disofenin (DISIDA) have been studied in dogs. Serial blood sampling permitted calculation of whole blood disposition rates, which principally represent liver clearance. There were striking differences in these rates between 6 normals and 7 animals in whom liver damage was induced by chronic bile duct ligation (256 vs 58 ml/min, P less than 0.001). Blood levels of radioactivity fell in a biexponential fashion characterized by rapid and slow disposition phases, whose half times were 2.4 and 58 min in normal animals. On 3 occasions, plasma was obtained from 1 animal by exsanguination 35 min after the administration of DISIDA and rapidly transfused into a 2nd animal. The whole blood pharmacokinetics of the second (recipient) animal showed a predominance of the slow disposition phase and a small rapid phase. The hepatic extraction ratio of blood radioactivity was measured in 3 dogs and was high (75%-90%) early after injection of DISIDA, but fell rapidly to remain around 10%. These experiments suggest the presence of two different species in the radiopharmaceutical studied, each being removed from the blood stream by the liver, but at different rates. The contribution of renal clearance to overall whole blood pharmacokinetics was negligible, since three nephrectomized dogs displayed similar pharmacokinetics to normals. Whole blood DISIDA pharmacokinetics are more complex than previously thought but appear to be capable of providing an accurate measure of liver function.

Radionuclide evaluation of liver transplants

Orthotopic liver transplantation is now an established technique for treating patients with various forms of end stage liver disease. The number of centers performing the procedure is increasing and, as the number of transplant recipients in the population increases, many institutions performing nuclear medicine studies will be confronted with requests to evaluate these patients. While a variety of radionuclides are proving useful in this evaluation, the 99mTc iminodiacetic acid (IDA) compounds, particularly 99mTc diisopropyl IDA (DISIDA), will probably account for the majority of radionuclide evaluations of these patients because they are well suited to monitor both structural and functional changes of the graft. The primary application of radionuclide studies is focused in the postoperative period, when problems with the vascular and biliary anastomoses, rejection, infections, and bile leaks all produce alterations in radionuclide hepatobiliary studies. Abnormalities such as rejection and infection produce primarily functional, rather than structural changes and are not easily differentiated based upon the kinetics of 99mTc-DISIDA extraction and excretion by the liver, serial imaging and correlation with clinical data is necessary in such situations. Quantitative analyses of kinetic 99mTc IDA (DISIDA) studies and quantitative approaches with other compounds such as 99mTc galactosyl-neoglycoalbumin (NGA) may permit better assessments of relatively subtle changes in liver function in the posttransplant period.

Imaging of a pediatric abdominal mass

The approach to the child with an abdominal mass will be aided by careful consideration of the radiographic imaging modalities available at an institution. The relative advantages, disadvantages, costs, and radiation of each modality are presented. The recommended workup of a pediatric abdominal mass, as well as the most common masses and their differential diagnosis, are outlined.

Radionuclide imaging of the biliary tree

The new 99mTc biliary scintigraphy agents are highly sensitive and specific in detecting biliary tract disease and use of them is the initial procedure of choice in evaluating patients with suspected acute cholecystitis. Other clinically useful indications are evaluation of biliary kinetics; evaluation of patients with suspected traumatic bile leakage, gallbladder perforation, or postsurgical biliary tract complications; and evaluation of patients with suspected biliary obstruction. In 99mTc we have a simple radiopharmaceutical of low radiation for evaluating congenital abnormalities and neonatal jaundice. In the Orient 99mTc cholescintigraphy is extremely important in evaluating patients with suspected intrahepatic stones. The overall advantages of this technique include availability, safety, simplicity, and accuracy. In addition, it may be performed in those patients who are allergic to iodinated contrast agents.