An abnormal uptake pattern of 201Tl thallous chloride observed during myocardial scintigraphy of a patient with known thoracic tumour localization suggested the possibility that thallous chloride may also accumulate in tumours. This was confirmed by observing 201thallous chloride accumulation in rhabdomyosarcoma implants in rats. Thallium 201 accumulation in tumour cells should be borne in mind as a possible complicating factor when using this reagent for the evaluation of cardiac conditions in oncological patients.

In 61 patients, 66 scans were performed with 111In-labelled autologous leucocytes to evaluate this method in the diagnosis of inflammatory disease. All scintigraphic results were compared with clinical, operative or postmortem findings. In the first 20 examinations in 19 patients, 2 scintigrams were true positive, 9 true negative one of false positive, whereas 9 scintigrams had to be considered as false negative. These false negative results were probably due to loss of viability of the labelled cells. A modified labelling technique, in which a much lower concentration of oxine was used, was employed for a further 46 examinations in 42 patients. Twenty-four scintigrams were true positive and 22 true negative, while no false positive or false negative results were observed. These results suggest that this modified technique is useful in the diagnosis of inflammatory disease.

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Bacterial abscesses were evoked in goats. Imaging of these abscesses was obtained by means of labelling autologous granulocytes with 111In oxinate, reinjection of the cells into the animal, and scintigraphy by gamma camera one day later. Comparable imaging results, however, were obtained after intravenous injection of 111In oxinate or of 111In chloride. The gamma camera images were supported by tissue distribution studies. In the case of administration of 111In oxinate to the goats, the radioactivity accumulated in the cell fraction of the blood to a significant extent. This did not occur in the case of plain 111In chloride. It remained unexplained why such different accumulation in cells did not result in differences in the scintigraphic studies. Blood clearance studies supplied conclusive evidence that the granulocytes stayed in the circulation for several days following labelling with 111In oxinate and reinjection of the cells into the animals.

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