Search

Thallium-201 is known to accumulate in malignant tumours. In this work we are evaluating the role of thallium in differentiating benign from malignant solitary bone lesions in 28 patients with solitary bone lesions on 99Tcm-MDP bone scans. Lesions' uptake of 201T1 was evaluated using visual assessment and lesion to background ratio. We found significant uptake with a mean lesion to background ratio of 4.27 in malignant lesions and no or faint uptake with a mean lesion to background ratio of 1.37 in benign lesions.

Accurate assessment of the severity of soft tissue damage particularly skeletal muscle associated with fractures in trauma patients is important in determining the plan of management and prognosis. We used Indium-Ill labelled anti-myosin to determine the extent of skeletal muscle injury in five patients involved in traumatic accidents. We found abnormal uptake in all 20 sites of muscle injury in four patients, 13 at the sites of fractures and seven away from fracture sites. There was good correlation between the degree of uptake and the extent of muscle injury. No uptake was seen in a case with no fracture and no muscle injury. At surgery this case proved to be haemarthrosis of the left knee. Indium-Ill anti-myosin scanning is a potentially sensitive and useful technique in assessing extent of acute muscle injury in trauma patients.

The relationship between the concentration of tissue glutathione (GSH) content and uptake of 99TcmHMPAO in Sprague Dawley rats was investigated. The GSH content of rat tissue was depleted with diethyl-maleate (DEM) and the ratio of GSH in control to GSH depleted rat was approximately twice that in the brain, liver, kidney, spleen and lung. The GSH content in all the organs studied except the liver had no statistically significant relationship with the uptake of 99TcmHMPAO. The apparent increase of radioactivity in the liver was due to longer retention of 99TcmHMPAO. This longer retention was due to stasis of bile flow as confirmed by subsequent experiments in which cholecystokinin (CCK).was administered to GSH depleted rats and compared to the uptake of GSH depleted rats without injection of CCK.

The aim of this study was to compare 201Tl-chloride and 99Tcm-sestamibi (MIBI) SPET brain imaging for differentiating brain lymphoma from other intracranial lesions in AIDS patients. Both studies were performed on the same day in 17 AIDS patients with intracranial enhancing lesions on either CT or MRI. Eleven patients underwent brain biopsy and six patients were followed clinically. We calculated the radiopharmaceutical uptake ratio of the lesion to that on the contralateral side with the guidance of CT or MRI findings. Ratios of 1.5 or more were considered to represent malignant lesions and ratios < 1.5 were considered to represent benign lesions. Biopsy revealed four cases of lymphoma, four cases of toxoplasmosis and two cases of progressive multi-focal leukoencephalopathy; one biopsy yielded necrosis. Both the MIBI and 201Tl studies yielded no false-negative cases of lymphoma (sensitivity 1007c). Of the 13 non-lymphoma cases, the 201T1 studies showed seven true-negative cases (specificity 54) and the MIBI studies showed nine true-negative cases (specificity 69). The biopsies of the false-positive cases (toxoplasmosis) showed a pattern of healing after medical treatment. We conclude that MIBI is more helpful than 201Tl because of higher specificity and equal sensitivity. The medical treatment of toxoplasmosis is a cause of false-positive 201Tl and MIBI studies.

Chrome fatigue syndrome is a clinically defined condition of uncertain aetiology. We compared 99Tcm-HMPAO single photon emission tomography (SPET) brain perfusion with dual-head 18F-FDG brain metabolism in patients with chronic fatigue syndrome. Eighteen patients (14 females, 4 males), who fulfilled the diagnostic criteria of the Centers for Disease Control for chronic fatigue syndrome, were investigated. Thirteen patients had abnormal SPET brain perfusion scans and five had normal scans. Fifteen patients had normal glucose brain metabolism scans and three had abnormal scans. We conclude that, in chronic fatigue syndrome patients, there is discordance between SPET brain perfusion and 18F-FDG brain uptake. It is possible to have brain perfusion abnormalities without corresponding changes in glucose uptake. (© 1998 Lippincott Williams & Wilkins)

Stress thallium-201 myocardial studies in 29 patients with chest pain were performed. The findings of digital display (DD) and quantitative segmental washout curves (QSWC) were compared independently and jointly with coronary angiography. It was found that QSWC is more sensitive (71) than DD (55) but is less specific (58) than DD (98). Taking both approaches together the sensitivity rises to 94 and the specificity falls to 61. Using both DD and QSWC for interpretation of thallium studies improves the agreement ratio with coronary angiography by 25 more than when using DD only.

We have studied the mechanism of tumour uptake of 201Tl by in vivo and in vitro studies. In a series of patients with breast cancer (n=26), lung cancer (n=56) and lymphoma (n=15), the time course of tumour uptake of 201Tl paralleled that in the myocardium with almost identical times of peak uptake being obtained in tumours and myocardium. In a patient with hepatic metastases from colonic cancer undergoing laparotomy, 99mTc labelled microspheres and 201Tl were injected into the hepatic artery and biopsies of metastatic and normal liver tissue obtained. The tumour to normal liver activity ratios for 201Tl were one tenth of those for 99mTc microspheres. In the final part of the study, cells from a lung cancer tissue culture line were incubated for 30 min with 201Tl with and without the addition of cardiac glycoside, which acts a sodium potassium pump blocker. The cells exposed to the cardiac glycoside showed markedly decreased uptake of 201Tl compared to the cells not so exposed (0.6%±0.1% vs 11.8±0.7.2% of the administered dose). The mechanism of 201Tl uptake of tumours is similar to that in the myocardium. Sodium potassium pump activity appears to be more important than tumour blood flow. 201Tl uptake may provide a useful means of studying tumour viability.

To study the potential usefulness of99mTc-methoxy isobutyl isonitrile (99mTc-MIBI) as a substitute for201Tl in assessing patients with ischaemic heart disease, 24 patients underwent 1 day rest and exercise99mTc-MIBI single photon emission computerised topography (SPECT) 1 week after SPECT exercise201Tl. All patients were catheterized within 1 month after myocardial imaging. In 17 patients, resting first pass radionuclide angiography (FPRNA) was performed with99mTc-MIBI. The heart to lung ratio for99mTc-MIBI and201Tl was calculated both at rest and exercise. The segmental analysis for myocardial perfusion reveals that 87/96 segments (91 %) were correctly classified by SPECT201Tl and 84/96 segments (88%) were correctly classified by99mTc-MIBI. A significant correlation was present between LVEF measured by99mTc-MIBI FPRNA and contrast ventriculography (r = 0.85,P < 0.0001). The heart to lung ratio both at rest and exercise for99mTc-MIBI is significantly higher than201Tl (P < 0.01 and <0.001 respectively). We conclude that99mTc-MIBI is a promising agent for simultaneous evaluation of myocardial perfusion and cardiac function.