SUMMARY We evaluated emission computed tomography (ECT) for thallium-201 (201TI) myocardial imaging in estimating infarct size (IS). In 18 patients in whom IS was estimated enzymatically at the time of the acute episode, planar 2"1T1 perfusion scintigraphy and ECT with a rotating gamma camera were performed 4 weeks after the first myocardial infarction. From the size of 201T1 perfusion defects, the infarct area in planar images and the infarct volume in reconstructed ECT images, were measured by computerized planimetry. When scintigraphic IS was compared with the accumulated creatine kinase-MB isoenzyme release (CK-MBr), infarct volume determined from ECT correlated closely with CK-MBr -(r 0.89), whereas infarct area measured from planar images correlated less satisfactorily with the enzymatic IS (for an average infarct area from three views, r = 0.69; for the largest infarct area, r = 0.73). Although conventional scintigraphic evaluation is useful for detecting and localizing infarction, quantification of ischemic injury with this two-dimensional technique has a significant inherent limitation. The ECT approach can provide a more accurate three-dimensional quantitative estimate of infarction, and can corroborate the enzymatic estimate of IS.

Sensitive radioimmunoassays were developed to measure the two groups of major allergens (Der I and Der II) of Dermatophagoides pteronyssinus and Dermatophagoides farinae, in which radiolabeled protein A served as a general tracer. Glass rods covalently coupled with F(ab′)₂ fragments of rabbit antiserum IgG were incubated first with mite or house dust extracts, and then with affinity-purified rabbit antibodies. The bound allergen-antibody complex was detected with a ¹²⁵I-labeled protein A. The two Der I allergens, Der p I and Der f I, were measured separately with the use of immunoabsorbed rabbit antibodies directed against species-specific determinants, while the two Der II allergens, Der p II and Der f II, were measured as ‘Der II’ with the use of antibodies directed against common determinants on both allergens. Each assay demonstrated consistently parallel dilution curves with mite and house dust extracts. The mean intraassay and interassay coefficient of variation for each assay ranged from 4.3 to 7.7% and from 3.6 to 9.0%, respectively. The Der p I and Der f I assays were shown to be highly species-specific so that the ratio of Der p l:Der f I would provide a good index of the distribution of the two mite species in a dust sample. The concentrations of the Der I and Der II allergens in different types of mite extract and dust samples from houses were compared using these assays. The results demonstrated that the ratio of Der I: Der II in the mite body extracts varied markedly from those in the whole culture extracts, while the ratio in individual dust samples was nearly constant and was close to that in the mite body extracts. These assays will be useful in standardizing mite and house dust extracts and for assessments of mite allergen exposure. Furthermore, the high assay sensitivity will make it possible to use these assays to measure mite allergens associated with airborne particles.

No abstract