Comparison of In-111-labeled platelets and iodinated fibrinogen for the detection of deep vein thrombosis.

Indium-111-labeled platelets and I-125 fibrinogen were administered to dogs with experimentally induced deep-vein thrombosis. The thrombus uptake of both labeled compounds was studied as a function of thrombus age. In thrombi less than 24 hr old, thrombus-to-blood ratios for In-111 platelets were about twice as great as those obtained for I-125 fibrinogen. Excellent scintiphotos were obtained with In-111 platelets. In thrombi older than 24 hr, uptake of both agents was low, but good images were still obtained with In-111 platelets. The images in this case are not of thrombi, but rather of damaged vessel wall. Indium-111-labeled platelets are superior to iodinated fibrinogen for imaging fresh thrombi, but offer no advantage for thrombi over 24 hr old.

Scintigraphic diagnosis of experimental pulmonary embolism with In-111-labeled platelets.

Stasis thrombi, radiolabeled with Tc-99m sulfur colloid, were produced in six dogs by the injection of human thrombin into isolated jugular vein segments. After release of the thrombi, scintigraphic images demonstrated 16 pulmonary emboli containing Tc-99m. Autologous platelets labeled by the In-111 oxine method were injected. Sequential images demonstrated platelet accumulation in 14 of the 16 emboli within 1 hr. The emboli were recovered at autopsy and their activity assayed. The mean uptake of In-111-labeled platelets was 1.1% dose/g of embolus, and the mean embolus-to-blood ratio was 16. Our results demonstrate that fresh pulmonary emboli in dogs can be detected by imaging with In-111-labeled platelets, and suggest that radiolabeled platelets may provide a simple, noninvasive method for the direct visualization of pulmonary emboli in patients.

Carbon-11-labeled methylated polyamine analogs: uptake in prostate and tumor in animal models.

The polyamines putrescine, spermine, and spermidine were methylated by the addition of carbon-11-labeled formaledehyde followed by sodium borohydride. High labeling yields wrbon-11-labeled formaldehyde followed by sodium borohydride. High labeling yields were obtained and the final products were purified by simply boiling the solution. This decomposed the excess sodium borohydride and removed the volatile impurities. The final radiochemical purity of all the methylated compounds was above 85%. All three methyltated compounds accumulated in the prostates of male rats and the distribution of N-methyl-1,4-diaminobutane (the putrescine analog) was very similar to that previously obtained with tritiated putrescine. The uptake of the putrescine analog in both the prostate and in mouse tumor was slightly higher than that obtained with the other two analogs studied. Utilizing a positron transaxial tomographic scanner and the putrescine analog, we have been able to image the prostate gland of a dog.