Segmental assessment on ordinary scintigrams and SPECT images of the liver

Measurement of parenchymal function and bile duct flow in primary sclerosing cholangitis using dynamic 99mTc-HIDA SPECT

BACKGROUND AND AIM

Primary sclerosing cholangitis is a chronic cholestatic disease characterized by obliterative fibrosis of intrahepatic and/or extrahepatic bile ducts. The unpredictable clinical course of the disease can be relentless, leading to premature death in a large percentage of patients. Prognostic index formulas, the revised Mayo model being the most frequently used, have been developed to predict clinical course and prognosis. The aim of this study was to investigate the potential value of dynamic (99m)Tc-HIDA SPECT in patients with primary sclerosing cholangitis by correlating scintigraphic results with cholangiographic and biochemical findings and prognostic scoring systems used in clinical practice.

METHODS

In 18 patients with primary sclerosing cholangitis, segmental parenchymal and bile duct functions were measured using dynamic (99m)Tc-HIDA SPECT. Quantitative scintigraphic results were compared to cholangiographic findings, as graded by a biliary classification system, the Child-Pugh score and revised Mayo prognostic score, as well as the individual biochemical parameters included in the scoring systems.

RESULTS

In individual segments, scintigraphic quantitative parameters indicative of bile flow showed a statistically significant correlation with the state of the bile-flow path for the respective segments as assessed by the biliary classification system. The revised Mayo score correlated with the scintigraphic quantitative parameters indicative of parenchymal function and bile flow as calculated for the whole liver.

CONCLUSIONS

Dynamic (99m)Tc-HIDA SPECT, capable of assessing different aspects of liver function for the total liver, as well as for individual segments, has potential value in the management of patients with primary sclerosing cholangitis.

Dynamic 99Tcm-HIDA SPET: non-invasive measuring of intrahepatic bile flow. Description of the method and a study in primary sclerosing cholangitis

In this study dynamic 99Tcm-HIDA single photon emission tomography (SPET) was performed in patients with primary sclerosing cholangitis and normal test subjects. The method offers the possibility of functional analysis of individual liver segments. After injection of 120 MBq of 99Tcm-HIDA, 12 consecutive SPET examinations were performed at 6-min intervals. The segmental borders of liver segments as seen on computed tomography or magnetic resonance examinations were superimposed on the scintigraphic images allowing placement of regions of interest (ROIs) in specific liver segments. Sampling from the same ROIs in consecutive SPET images enabled creation of time-activity curves for individual liver segments. A range of normal values was created by quantitative analysis of normal volunteer studies. Results of the studies in patients correlated well with cholangiographic extent of disease, liver function tests and histological stage. The technique may have particular value in diseases that affect the liver in a nonhomogenous or segmental fashion. Giving an indication of bile clearance from individual liver segments, it can quantify the functional importance of radiologically detected strictures. Percutaneous liver biopsy can be directed to the worst affected parts of the liver, making biopsy more representative. Sequential studies may allow monitoring of disease progression, aiding in selection and timing of therapeutic procedures.

Specific diagnosis of hepatocellular carcinoma by delayed hepatobiliary imaging

For assessment of the value of delayed hepatobiliary imaging with technetium 99m (99mTc)-(Sn)-N-pyridoxyl-5-methyltryptophan (99mTc-PMT) for specific diagnosis of hepatocellular carcinoma, 88 patients with various malignant and benign liver diseases (49 with hepatocellular carcinoma, 4 with cholangiocellular carcinoma, 10 with metastatic liver carcinoma, 2 with liver cysts, 2 with liver hemangioma, 1 with liver abscess, 2 with intrahepatic lithiasis, 12 with liver cirrhosis, and 6 with chronic hepatitis) were studied. In 20 (41%) of the 49 patients with hepatocellular carcinoma, greater uptake of 99mTc-PMT by the tumor than by the surrounding liver tissue was seen in delayed hepatobiliary images, whereas in eight patients (16%), equilibrated uptake was seen. No increased uptake of the radioisotope by hepatic lesions was seen in 21 patients with localized liver diseases other than hepatoma. Moreover, in 18 patients with diffuse liver diseases, no focal accumulation of the radioisotope was seen in delayed 99mTc-PMT images. In addition, of 28 patients with hepatocellular carcinoma in whom the serum alpha-fetoprotein level showed little or no increase, 12 showed increased uptake of 99mTc-PMT by the tumor. In assessing delayed 99mTc-PMT images, however, it was necessary to consider following complications: accumulation of tracer in obstructed and dilated biliary trees; retention of radioactivity in nonneoplastic liver tissues; difficulties in evaluating 99mTc-PMT uptake by small hepatic tumors; overlapping of radioactivity in the gut and gallbladder in delayed 99mTc-PMT images of tumors. This study indicates that delayed 99mTc-PMT images can be useful in the diagnosis of hepatocellular carcinoma.

Specific considerations in the interpretation of single-photon-emission computed tomography of the normal liver

In our hospital, single-photon-emission computed tomography (SPECT) has been routinely used instead of conventional scintigraphy in the examination of the liver and spleen in more than 3,000 patients. This technique is preferred because it provides more detailed information and better contrast resolution than planar views. However, using the SPECT technique, normal variations in liver anatomy are more apparent, and certain cases--in particular those with a wide main lobar fissure combined with a prominent gall bladder fossa as well as cases with a large hilus--may erroneously be interpreted as having a focal lesion. In order to facilitate the interpretation of SPECT examinations of the liver, the most common difficulties and pitfalls arising from normal variations in hepatic anatomy, indentations caused by surrounding organs and partial-volume effects are described and compared with the findings of corresponding transmission computed tomograms.