Imaging of Clot by ^99mTc-HMPAO Labeled Platelet in Animal Model Induced Thrombosis

^99mTc-HMPAO labeled platelet (LP) imaging may integrate thrombosis imaging into routine clinical procedures. In the current study, we assessed the feasibility of the use of ^99mTc-HMPAO LP for imaging of small clots in an animal model. Thrombosis was induced by application of FeCl₃ solution in the distal part of the inferior vena cava (IVC) of a 6100 g anesthetized rabbit and in a male Wistar rat weighing 420 g. Twenty minutes later, 178 MBq ^99mTc-HMPAO LP was injected. ^99mTc-HMPAO LP preparation was done as defined and standardized in a previous report. Whole body and SPECT imaging were done 60, 90, and 120 min after tracer injection. Then, the clotted part of the vein was extracted and then its activity and pathologic evaluations were compared with the proximal part of the IVC at a similar volume. A 17 × 6 mm clot was clearly detected with both planar and SPECT imaging. The count to pixel ratio (CPR) of the clotted part of the vein was 35, 40, and 40 compared to the non-clotted vein (i.e. 19, 18, and 21) at 60, 90, and 120 min, respectively. After clot extraction, the CPR decreased to 14. The clot activity was 0.44 MBq compared to 0.01 MBq of the normal control vein. Also, clot induction was pathologically proven. ^99mTc-HMPAO LP preparation is logistically possible in clinical nuclear medicine and the ability of imaging small size clots encourages future trials for real clinical thrombotic scenarios.