A method for the labeling of leucocytes with 99mTc-colloid is described. The labelling can be done in samples of whole blood, because the colloid is only taken up by the phagocytosing cells, the monocytes and the granulocytes. The part of the colloid that is not phagocytosed is brought to a soluble state with Na-citrate, so that only the phagocytosed colloid is reinjected. The labelling efficiency with this method is between 80% and 90%. Measurements of the activity in the leucocytes 3 h after reinjection, have shown that at least 50% of the labelled cells are at this time still available in the blood pool. The clinical results on 32 patients with the tentative diagnosis of an abdominal abscess and on 42 patients with the tentative diagnosis of septic loosening of an endoprosthesis have shown that the labelled leucocytes are very well suited to show up local foci of inflammation.

The detection of preserved glucose uptake in hypoperfused dysfunctional myocardium by fluorine-18 deoxyglucose (FDG) positron emission tomography (PET) represents the method of choice in myocardial viability diagnostics. As the technique is not available for the majority of patients due to cost and the limited capacity of the PET centres, it was the aim of the present work to develop and test FDG single-photon emission tomography (SPET) with the means of conventional nuclear medicine. The perfusion marker sestamibi (MIBI) was used together with the metabolic tracer FDG in dual-isotope acquisition. A conventional SPET camera was equipped with a 511-keV collimator and designed to operate with simultaneous four-channel acquisition. In this way, the scatter of 18F into the technetium-99m energy window could be taken into account by a novel method of scatter correction. Thirty patients with regional wall motion abnormalities at rest were investigated. The results of visual wall motion analysis by contrast cine-ventriculography in nine segments/heart were compared with the results of quantitative scintigraphy. The scintigraphic patterns of MIBI and FDG tracer accumulation were defined as normal, matched defects and perfusion-metabolism mismatches. Spatial resolution of the system was satisfactory, with a full width at half maximum (FWHM) of 15.2 mm for 18F and 14.0 mm for 99mTc, as measured by planar imaging in air at 5 cm distance from the collimator. Image quality allowed interpretation in all 30 patients. 88% of segments without relevant wall motion abnormalities presented normal scintigraphic results. Seventy-five akinetic segments showed mismatches in 27%, matched defects in 44% and normal perfusion in 29%. We conclude that FDG-MIBI dual-isotope SPET is technically feasible with the means of conventional nuclear medicine. Thus, the method is potentially available for widespread application in patient care and may represent an alternative to the 201Tl reinjection technique.

Two 99mTc-labelled radio-diagnostics for bone scintigraphy, dicarboxypropan-diphosphonic acid (DPD) and methylene-diphosphonate (MDP) were compared. The test parameters were the time-activity curves of serum and of deproteinised serum, time-activity curves in regions of interest above the femur, the sacrum and the soft tissue medial of the femur, and the urinary excretion. The ratio of bone lesion to normal bone was compared for 6 h after the injection of each compound. The time-activity curves in the serum and the deproteinised serum were not very different, therefore the percentage of the radio-diagnostics bound to protein in blood were nearly the same. At 14 h post-injection nearly 80% of the activity remaining in the blood pool was bound to protein. The urinary excretion of MDP was 25% higher than that of DPD, because the renal clearance of DPD was 41% lower than that of MDP. The non-excreted activity was bound to bone; therefore in the regions of interest set above the sacrum, the femur and the soft tissue the activity ratio was 27% higher for DPD for the ratio os sacrum to soft tissue and 21% higher for the ratio femur to soft tissue, but there were similar results for both substances for the ratio bone lesion to normal bone; therefore MDP was not better than DPD in detecting bone lesions.

Nuclear cardiology continues to be of particular importance in nuclear medicine. In this domain, myocardial scintigraphy has become the eminent diagnostic tool in the diagnosis of cardiac disorders like coronary artery disease, myocarditis, heart transplant rejection, chemotherapy-induced cardiotoxicity, and others. In a comparison of the latest worldwide trends, European investigators seem to be more interested in recently developed myocardial tracers than those in the US. Besides research into antimyosin monoclonal antibodies for the detection of myocardial damage, the technetium 99m-labeled perfusion markers are being studied as potential substitutes for thallous chloride TI 201. In recent years, the dual use of 201TICI/99mTc-sestamibi taught us the comparable clinical value of these two radiopharmaceutics in the detection of coronary artery disease. In the future, additional 99mTc-labeled perfusion markers may contribute to the ongoing decrease in thallium's widespread use. In the area of viability (ie, the preinterventional detection of potentially reversible myocardial wall-motion abnormalities), 201TICI is still not fully accepted. The most reliable diagnostic tool for this procedure is 13N-NH3 (ammonia)/fluorine F18 fluorodeoxyglucose (FDG) positron emission tomography because of its options for quantification and high-resolution imaging. In the near future, the limited number of these sophisticated but expensive positron emission tomography centers will not satisfy the growing clinical demand for viability studies. Thus, European nuclear cardiologists are developing alternative techniques for positron imaging. They have shown that by means of a conventional gamma camera with special high-energy collimators, a reliable perfusion/viability assessment is feasible.(ABSTRACT TRUNCATED AT 250 WORDS)

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