Transjugular intrahepatic portosystemic shunt (TIPS), a new therapeutic method, has been performed widely for the treatment of portal hypertension. TIPS produces a decrease in the portal blood flow to the hepatic parenchyma, which is considered to cause a reduction in hepatic functional reserve. To evaluate the changes in hepatic functional reserve after TIPS, we performed technetium-99m DTPA-galactosyl human serum algumin (99mTc-GSA) hepatic scintigraphy before and after TIPS in eight male patients, ranging in age from 54 to 72 years (mean 62.2 years). Two quantitative indices - blood clearance index (uptake ratio of the heart at 15 min to that at 3 min, HH15) and hepatic accumulation index (uptake ratio of the liver to the liver plus heart at 15 min, LHL15) - were calculated from the time-activity curves of the heart and liver. Early and late uptake constant indices (early and late KU) were also calculated from the time-activity curves of the heart and liver by means of Patlak plot. The values of HH15, LHL15 and late KU deteriorated after TIPS in all patients. Early KU (1-3 min) decreased by more than 55% in two patients who showed a poor prognosis and corresponded well with the status of the portosystemic shunt. It is concluded that 99mTc-GSA hepatic scintigraphy is a useful means of evaluating the degree to which hepatic function is compromised following TIPS. The post-TIPS alterations in HH15, LHL15 and late KU (5-10 min) reflect the changes in hepatic functional reserve, and early KU is a useful index for evaluating the degree of portosystemic shunt.
We are proposing a method to accurately measure renal activity in renography using Tc-99m labeled tracers. This method uses a conjugate-view image and transmission data for attenuation correction, the triple energy window (TEW) method for scatter correction, and background correction techniques that consider the source volume for accurate background activity correction. To examine this method in planar imaging, we performed two renal phantom studies with various uniform background activity concentrations. One study used two ideal box-shaped kidney phantoms with a thickness of 2 or 4 cm in a water tank and the other study employed two real kidney-shaped phantoms in a fillable abdominal cavity. For these studies the kidney phantom-to-background activity concentration ratio (S) was changed from 5 to infinity. The transmission data were obtained with an external Tc-99m line array source. The anterior- and posterior-view emission images were acquired with a dual-headed gamma camera simultaneously and the TEW method was used to correct scatter for the emission and transmission images. The results showed that this method with both the accurate background correction and scatter correction could give depth-independent count rates and could estimate the true count rate with errors of less than 5% for all S values. However, if either accurate background correction or scatter correction was performed alone, the absolute error increased to about 50% for the smaller S values. Our proposed method allows one to accurately and simply measure the renal radioactivity by planar imaging using the conjugate-emission image and transmission data.
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