Rapid localization of indium-111-labeled inhibited recombinant tissue plasminogen activator in a rabbit thrombosis model.

The thrombus localizing properties of indium-111-recombinant tissue plasminogen activator (111In-rt-PA) have been investigated in an effort to achieve prompt and accurate detection of thrombi. Unlike previous studies with rt-PA, the active plasminogen catalytic site was permanently inhibited with peptides of chloromethyl ketone so that the radiotracer binds to fibrin without causing fibrinolysis. Thrombi were created in the external jugular vein of 14 male New Zealand white rabbits followed by injection of 111In-rt-PA. The agent cleared rapidly in vivo with a half-time of 4.6 min. The thrombus: blood ratio in nonheparinized rabbits (n = 7) was 6.39 +/- 0.86. The ratio in heparinized rabbits (n = 4) was 3.11 +/- 0.23. Thrombi were clearly visible in the planar images of both groups 1 hr postinjection. The combination of rapid thrombus localization and positive images, especially in the presence of anticoagulation, suggests that further work is warranted with rt-PA thrombus imaging.

Hepatic ultrasonic tissue characterization of video image data.

A study measuring in vivo three quantitative parameters of human liver was performed to assess the feasibility of measuring these parameters using standard ultrasound equipment and technique and to evaluate their potential for diagnosing diffuse liver disease. The parameters measured were: (1) d-bar, the average scatter spacing between semiperiodic scatterer; (2) r, a measure of the relative scattering strength; and (3) sigma, a measure of the variability in the relative scattering strength. Using linear discriminant and multivariate analysis, the above parameters are able to significantly separate normal livers from those with cirrhosis. This technique shows promise in the clinical identification of diffuse liver disease.