Radioisotope bone scanning in horses.

The detection of radionuclide activity in the living equine skeleton, using bone seeking radiopharmaceuticals and a hand-held radiation detector, is reported. Pathological changes in bone can be detected and subsequent development monitored. The availability and use of this diagnostic technique in equine practice is discussed.

Quantitative studies of splenic erythropoiesis in polycythaemia vera and myelofibrosis.

A quantitative scanning method employing cyclotron-produced 52Fe has been developed to assess splenic erythropoiesis in patients with myeloproliferative disorders. In 12 patients with myelofibrosis splenic uptake of 52Fe was from 5.0% to 48% of the injected dose. Although a single patient with classical polycythaemia vera had a minor uptake of 2.8% of six other patients with this diagnosis showed no concentration of isotope in the splenic area. The fraction of 52Fe in the spleen of four patients with 'transitional' myeloproliferative disorders characterized by a high red cell mass, hypercellular bone marrow and a leucoerythroblastic blood film varied from 5% to 41%. No clear relationship was noted between the degree of splenic erythropoiesis as defined by this technique and the level of haemoglobin, the degree of splenomegaly, the effectiveness of erythropoiesis of traditional 59Fe surface counting. If splenectomy is considered in patients with myelofibrosis splenic 52Fe quantitation will provide more precise data on the contribution of splenic erythropoiesis than 59Fe surface counting alone.

Rate of clearance by the spleen of heat-damaged erythrocytes.

The rate of uptake in the spleen of heat-damaged red blood cells labelled with 99mTc has been measured by radioisotope scanning in 38 patients. The values obtained for the half-clearance time into the spleen using this method have been compared with the values obtained simultaneously by blood sampling for the rate of loss of radioactivity from the circulation. It was found that the uptake into the spleen was approximately three times faster than the measured rate of loss of radioactivity from the blood. The reasons for this are discussed and it is suggested that the scanning technique is more reliable as a measure of this aspect of splenic function.

Quantitative measurement of splenic and hepatic red-cell destruction.

A method has been developed by means of which independent measurement can be made of the amount of red-cell destruction occurring in the spleen and the liver. The technique involves a standard red-cell survival study and surface-counting measurements together with quantitative scanning of the spleen and liver with 113mIn colloid in order to calibrate the surface counter. The rate of destruction in each organ is obtained by fitting the measured uptake curve for the organ to a theoretical uptake curve by computer. In addition, if whole body counting is also performed, the amount of red-cell destruction occurring in the rest of the reticuloendothelial system may be deduced. Results are given for measurements on a series of 11 patients.

Collimation and surface counting in haematology.

The effect on the results obtained in surface counting investigations of using a dual detector counting system and multihole collimators has been investigated. The use of the additional detector results in smoother curves for the uptake of the radionuclide and the use of multihole collimators increases the discrimination of the counting system against the effects of radioactivity outside the region of interest. In a clinical trial to compare multihole collimation with conventional single hole collimation it was found that increased excess counts were obtained over the spleen with the multihole collimators in eight of ten cases.