Detection of postoperative deep-venous thrombosis using technetium-99m-labeled tissue plasminogen activator.

UNLABELLED: The current noninvasive methods of deep-venous thrombosis (DVT) detection in the asymptomatic patient are sufficiently inaccurate so as to preclude their routine use. This present study reports the accuracy of scintigraphic scanning with 99mTc-rt-PA in asymptomatic postoperative patients using contrast venography as the gold standard. METHODS: Fifty-three consecutive postarthroplasty patients (30 THR, 23 TKR) (16 women, 37 men; mean age 71 yr; range 52-85 yr) underwent scintigraphic scanning with 99mTc-rt-PA and contrast venography, on the operated leg, in order to assess the accuracy of this new technique in these asymptomatic patients. RESULTS: Eighty-four segments were of diagnostic quality on contrast venography. Of the 15 thrombosed segments, 14 had positive scans. In the 69 nonthrombosed segments, 63 had negative scans. Thus, scintigraphic scanning with 99mTc-rt-PA had a sensitivity of 93% and a specificity of 91%. CONCLUSION: This study demonstrated that scintigraphic scanning with modified 99mTc-rt-PA is accurate in the detection of DVT in patients undergoing total hip or total knee arthroplasty.

Technetium-99m-modified recombinant tissue plasminogen activator to detect deep venous thrombosis.

UNLABELLED: We report a method for deep venous thrombosis (DVT) detection which uses 99mTc-labeled modified recombinant tissue plasminogen activator (rt-PA) scintigraphy. A Phase III clinical trial was performed on 79 patients with suspected DVT. METHODS: The plasminogen binding site of rt-PA was permanently inhibited without inactivating the fibrin binding site. The modified molecule was radiolabeled with 99mTc. Scintigraphy was performed and the results were compared to those of contrast venography. RESULTS: Of 14 thrombosed proximal segments, 13 had positive scans; in the 53 nonthrombosed proximal segments, 49 had negative scans. In proximal vein thrombosis, rt-PA scintigraphy had a sensitivity of 93% and a specificity of 92%. Of the 36 thrombosed calf vein segments, 31 had positive scans; in the 30 nonthrombosed calf segments, 28 had negative scans. In calf vein thrombosis, scanning has a sensitivity of 86% and a specificity of 93%. CONCLUSIONS: Scintigraphic scanning with this 99mTc modified rt-PA permits accurate detection of thrombus in both proximal and calf veins in patients with clinically suspected DVT. The technique detects both fresh and aged thrombi and is unaffected by heparin administration. Further study in other patient groups is needed to define the overall clinical utility.

The influence of generator eluate on the radiochemical purity of 99Tcm-sestamibi prepared using fractionated Cardiolite kits.

The reconstitution of fractionated Cardiolite kits with sodium 99Tcm-pertechnetate eluted from a wet-column 99Mo/99Tcm generator results in a preparation that contains elevated amounts of a polar radiochemical impurity, which is normally present in only trace amounts when such kits are reconstituted with eluate from a dry-column generator. A consequence of this impurity, which appears to be an organotechnetium compound, is that it causes a positive bias in several quality control methods for 99Tcm-sestamibi, including that recommended by the manufacturer. This impurity was isolated, and its biodistribution determined in Wistar rats. Two alternative methods for the preparation of 99Tcm-sestamibi from fractionated Cardiolite kits using eluate from a wet-column generator were investigated. A rapid procedure, based on a C18 solid phase extraction (SPE) cartridge, for measuring the radiochemical purity of 99Tcm-sestamibi samples, which had been prepared using fractionated Cardiolite kits, was developed and compared with two other methods including high-performance liquid chromatography (HPLC). Over a radiochemical purity range of 49-98%, the values obtained using our quality control method deviated from those obtained using HPLC by 1.1 +/- 1.3% (n = 26). In contrast to some of the rapid quality control methods assessed in our investigation, the SPE technique was not biased by the presence of the organotechnetium impurity.