Venous thrombosis: a controlled study on the performance of scintigraphy with 99Tcm-HMPAO-labelled platelets versus venography.

Thirty-three patients with symptoms and signs of a deep venous thrombosis (DVT) were examined by contrast venography and radionuclide imaging with 99Tcm-hexamethylpropyleneamineoxime (99Tcm-HMPAO)-labelled autologous platelets. There were 13 patients on heparin therapy and 20 without anticoagulation during the scintigraphy. Scintigraphy consisted of blood pool imaging at 5 to 20 min and accumulation imaging at 2, 4-6 and 18-24 h. In scintigraphy a positive finding was either a defect of radioactivity in the immediate blood pool phase or a hot spot indicative of accumulation of platelets in later phases. Fifteen out of 23 patients positive by venography were also positive by scintigraphy. Five of the eight false negative patients were on heparin treatment, two probably had DVT which were not quite fresh. The venography negative patients were also negative on scintigraphy. Nine out of 12 patients without anticoagulation had positive platelet accumulation compared with two out of 11 patients on heparin therapy. This difference was statistically significant (P less than 0.025). The sensitivity and specificity of platelet scintigraphy were 65 and 100%, respectively, in all patients and 83 and 100% in patients without anticoagulation. Our results suggest that scintigraphy with 99Tcm-HMPAO-labelled platelets is a useful alternative in diagnosing DVT in patients in whom a standard contrast X-ray venograph is contraindicated or otherwise unsuccessful.

Radiolabelling of human platelets with 99mTc-HMPAO.

The optimum conditions for labelling platelets with lipophilic 99mTc-hexamethyl propylene amine oxime (99mTc-HMPAO) were evaluated. An aseptic closed system was used throughout the procedure in patient studies. 48 ml blood were withdrawn into 12 ml ACD using sterile 60 ml plastic syringes. After mixing, the blood was transferred to sterile 10 ml vacuum tubes and platelets were isolated according to standard centrifugation procedures. The labelling efficiency was not dependent upon incubation temperature (22 degrees C, 37 degrees C) but was greater in saline than in the presence of plasma. The labelling efficiency increased with time up to 60 min in saline. The elution of 99mTc from platelets was about 25% in plasma milieu in vitro but did not increase with time during 160 min. 5 patients with verified fresh deep vein thrombosis in the lower leg were imaged after injection of labelled autologous platelets. All 4 of the patients without anticoagulant therapy showed positive uptake of 99mTc-HMPAO-labelled platelets, but the 5th patient--under heparin therapy--was negative in scintigraphy. Our results are encouraging and 99mTc-HMPAO-labelled platelets offer a promising tool for evaluating various clinical situations.

Radionuclide venography and uptake imaging using 99Tcm-fibrinogen in the detection of venous thrombosis and its correlation with contrast venography.

Thirty-eight patients (76 legs) with suspected deep vein thrombosis were examined with 99Tcm-fibrinogen study (Tc-F), which consists of three parts: (1) radionuclide venography (RNV) of both legs after injection of 150 MBq of 99Tcm-fibrinogen into the dorsal veins of each foot, (2) blood pool imaging (BPI) at 5 to 20 min and (3) uptake imaging (UI) at 4 to 6 and 17 to 26 h. The clinical diagnosis was deep vein thrombosis in 27 legs. Twenty-nine patients (with 18 thrombi) were also studied with contrast venography (CV). Comparison of RNV with BPI suggests that the time-consuming and laborious RNV could, without affecting the diagnosis, be substituted by BPI, which is possible to perform after a single antecubital injection. When all patients were taken into consideration the sensitivity of Tc-F to detect fresh thrombosis was 100% but the specificity was lower (73%) because of the false positive findings in RNV/BPI. However, the specificity of UI was 100%. Previous anticoagulation did not prevent the uptake of fibrinogen within thrombi. There was good agreement of RNV/BPI and CV in the popliteal, femoral and iliac veins but the calf veins were better delineated in CV. Seventeen of the 18 thrombi examined both with Tc-F and CV were positive with RNV/BPI, 14 with UI and 13 with CV. Sensitivity, specificity, accuracy, positive predictive value and negative predictive value (%) were with RNV/BPI: 83, 73, 86, 90, 83, with UI: 78, 100, 86, 100, 74 and with CV: 73, 100, 83, 100, 69. Our results suggest that Tc-F could be used not only as a screening test but also instead of CV in the detection of venous thrombosis.

Comparison of gallium-67 citrate and technetium-99m glucoheptonate in the evaluation of pulmonary malignancies.

Sixty-five patients with suspected or proven pulmonary malignancy were examined with [67Ga]citrate and [99mTc]glucoheptonate ([99mTc]GH) scintigraphy. In the final diagnosis 39 had primary lung carcinoma, four metastases in lung, mediastinum, and pleura from carcinomas elsewhere, and 22 benign pulmonary diseases. The sensitivity in the detection of pulmonary malignancies was 91% with 67Ga and 95% with [99mTc]GH. The intensity of uptake was somewhat greater with 67Ga than with [99mTc]GH in almost all malignant lung tumor groups. The specificity to detect malignant tumors was 82% with both radiopharmaceuticals. Irradiation and chemotherapy seemed to decrease 67Ga uptake but not [99mTc]GH uptake. Only four of 22 benign diseases showed accumulation of both 67Ga and [99mTc]GH. The intensity of uptake in benign processes was almost equal with that in malignant diseases, but most malignant processes were better delineated than the benign lesions. There were many differences between 67Ga and [99mTc]GH uptake, which suggest different mechanisms of accumulation of these agents. It is concluded that some 67Ga studies could be replaced by cheaper and more practical [99mTc]GH.

Detection of inflammation with 99mTC-HMPAO labelled leucocytes.

20 patients were studied with 99mTcHMPAO labelled leucocytes for detection of inflammation. 14 patients had positive uptake. 6 patients were examined also with 67Ga-citrate and 5 with 99mTc-nanocolloid. The 99mTc-HMPAO images were superior to other methods. Abscesses, osteitis, inflammatory bowel disease and graft infection were positive. Abscesses were positive at 30 min images and became more positive at 4 h. The 99mTc-HMPAO labelled leucocyte scan can be used also to follow up healing of inflammation.

Better visualization of a lung tumour with 99mTc-DPD than with 99mTc-glucoheptonate or 67Ga-citrate.

A case of a squamous cell lung carcinoma detected with 99mTc-DPD, 67Ga-citrate and 99mTc-glucoheptonate (GH) is reported. The highest uptake was seen with DPD and the lowest with 67Ga. Emission-computed tomography was very useful in DPD imaging but gave less new information in GH and 67Ga studies in comparison to traditional planar imaging. The patient had been given both irradiation and chemotherapy, which might be the cause of good accumulation of DPD and rather poor accumulation of GH and 67Ga.

Tc-99m glucoheptonate in detection of lung tumors.

Sixty-three patients aged 21-80 yr were examined. Tc-99m glucoheptonate (Tc-GH) scintigraphy was performed in 32 patients: 26 with primary lung carcinoma; six with metastases in lung, mediastinum, and pleura from carcinomas elsewhere; eight with benign pulmonary diseases; and 23 without known pulmonary disease. Tc-GH accumulated in 23 of 26 primary pulmonary carcinomas as active foci. The specificity of Tc-GH scans for neoplasm detection was higher than that of chest radiographs. The visualization of malignant tumors was much better in the late Tc-GH images (5-6 hr) than in the early (1 hr). Metastases from other carcinomas were positive in four of six patients, but they were considerably better detected in the radiographs, except in one patient with metastatic hepatocellular carcinoma. Neoplasms or their metastases in the hilar and mediastinal regions were better detected in the Tc-GH scans than in the chest radiographs. Only one of eight benign lung processes was visualized (as a weak diffuse accumulation of Tc-GH in hilar scar formation), and 23 patients without pulmonary disease had no pathological foci.