Hepatobiliary scanning using Tc-pyridoxylideneglutamate

Technetium 99m-pyridoxylideneglutamate (^99mTc-PG) administered intravenously is excreted by hepatocytes into the bile canaliculi and enters the gallbladder through the cystic duct and, consequently, can be used for scanning the hepatobiliary ductal system. A total of 166 patients representing 27 normal subjects, 84 patients referred for investigation of pain in the upper right quadrant of the abdomen, and 55 jaundiced patients were evaluated with ^99mTc-PG. In normal human volunteers, the agent reached the liver in five minutes, and the common bile duct, gallbladder, and duodenum within 15 minutes. Satisfactory images of the hepatobiliary tract were obtained using small dosages of ^99mTc-PG.     

Measurement of functioning hepatocyte mass via [99mTc]galactosyl-neoglycoalbumin

Technetium-99m-galactosyl-neoglycoalbumin (TcNGA) is a synthetic radiolabeled ligand specific for hepatic binding protein (HBP), a receptor that resides exclusively on hepatocytes.In vivo measurement of receptor concentration was obtained via kinetic analysis of liver and blood time-activity data obtained during the hepatic clearance of intravenously administered TcNGA. The purpose of this study was to assess receptor concentration as a measure of the functioning hepatocyte mass. Therefore, TcNGA and dualinjection indocyanine green maximal removal rate (ICG R_max) studies were performed on nine patients with hepatic cirrhosis associated or not with hepatocellular carcinoma. Receptor concentration was compared with ICG R_max, which is a validated method for the estimation of the functioning hepatocyte mass. The correlation coefficient was 0.76 (P=0.017). It is concluded that HBP concentration ([HPB]_o) as measured by functional imaging is a measure of functioning hepatocyte mass. This implies that measurement of an individual's receptor concentration by using nuclear medicine techniques provides an objective index of hepatic functional mass and supports attempts to rigorously evaluate [HBP]_o for its clinical efficacy.     

Biliary tract cholescintigraphy using Technetium-99m-labeled disofenin

Technetium-99m-labeled disofenin is a new iminodiacetic acid analog for imaging the biliary tract and the gallbladder. Biliary cholescintigraphy with ^99mTc-disofenin was performed on 148 patients referred for evaluation of hepatobiliary tract disease. Four millicuries was administered intravenously to nonjaundiced patients and 7 mCi to jaundiced patients. Scintigraphy was performed on patients in supine position and was accomplished via a large-field-of-view camera with a low-energy, all-purpose collimator. Technetium-99m-labeled disofenin rapidly cleared the blood which permitted excellent images of the biliary system with minimal interference from renal activity in only 11% of the patients. Of the 34 patients confirmed operatively and histologically to have acute cholecystitis, 32 had positive ^99mTc-disofenin cholescintigram, a sensitivity rate of 94%. Only 2 of the 8 patients with chronic cholecystitis had positive scan with nonvisualization of the gallbladder. This is not surprising, since scintigraphic study may be normal in patients with chronic cholecystitis if the cystic duct is patent. A normal biliary tract was detected in 63% of our jaundiced patients ($\text{25}\text{40}$), thus excluding biliary tract disease. Radioactivity was definitely identified in the gastrointestinal tract when the serum bilirubin level was as high as 27.3 mg/100 ml, thus differentiating hepatocellular disease from complete extrahepatic biliary tract obstruction. However, in 6 patients (15%), ^99mTc-disofenin cholescintigram could not differentiate between liver disease and biliary tract obstruction. It is concluded that ^99mTc-disofenin has rapid blood clearance, which permits satisfactory images of the biliary system in a variety of hepatobiliary diseases encountered in routine clinical practice. It is particularly sensitive in the diagnosis of acute cholecystitis.     

Clinical evaluation of 99mTc-pyridoxylideneglutamate for hepatobiliary scanning

Clinical evaluation of hepatobiliary scanning using ^99mTc-PG was done in twenty normal volunteers and eighty-three patients with liver and biliary tract disease. Satisfactory images of the biliary tract were obtained using small dosages of this agent. In normal humans, the agent reached the liver in 5 minutes, and the common bile duct, gallbladder, and duodenum in 10 to 20 minutes. The gallbladder was not visualized when the cystic duct was obstructed in patients with acute and chronic cholecystitis. In patients with partial common bile duct obstruction, a distended duct was visualized and there was delay in transit of radioactivity into the duodenum. With complete common bile duct obstruction, no radioactivity was seen in the biliary or gastrointestinal tracts up to 24 hours after injection. Hepatocellular disease was characterized by delayed liver clearance and delayed visualization of the biliary and gastrointestinal tracts. There were no toxic or other untoward effects in any patient.     

Definitive diagnosis of choledochal cyst by 99mTc-pyridoxylideneglutamate sequential scintiphotography

Sequential supine scintiphotography of the abdomen was performed after intravenous administration of 99mTc-pyridoxylideneglutamate (99mTc-PG) to verify the presence of choledochal cyst in an 18-month-old boy who presented with a mass in the right upper quadrant of the abdomen. The total body radioactivity effect, which is similar to the total body opacification during intravenous cholangiography or urography, was clearly demonstrated as a cold area corresponding to the cyst and assisted in the diagnosis. The specific finding was sequential filling of the gallbladder and cyst. In view of the relatively low radiation dose and good physical characteristics of 99mTc for imaging, 99mTc-PG sequential scintiphotography is useful for the definitive preoperative diagnosis of choledochal cyst in infants and children.