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Electrocardiogram gated single photon emission computed tomography of the intracardiac blood pools is a recent development that involves the acquisition of images in multiple projections after in vivo erythrocyte labelling with technetium-99m and reconstruction of these images into tomographic sections in any desired plane. The technique was used in 25 subjects to measure left ventricular volume, by summing the areas of the ventricle in each of the tomographic sections, and the results compared with those using a counts based (non-geometric) technique from planar radionuclide ventriculography. Endocardium was defined with the aid of a contour at 43% of maximum left ventricular counts, and this contour was validated for a left ventricular phantom. Correlation between tomographic and counts based left ventricular volume was close. Similarly, ejection fraction correlated well. The technique is therefore an accurate method for determining left ventricular volume and ejection fraction, avoiding the assumptions about shape made by other geometric methods.

Summary A 44-year-old woman presented with hyperthyroidism and a nodule in her thyroid. 131I-scintigraphy of the gland showed concentration of the tracer within the nodule and suppressed activity in the rest of the gland. Histology of the resected thyroid proved the nodule to be a papillary carcinoma. The presence of carcinoma within an autonomous hyperactive thyroid in a patient with hyperthyroidism has been reported only rarely, and to the authors’ knowledge such a case has never been reported in Great Britain. Furthermore, unlike previously reported cases, the carcinoma was confined solely to the nodule.

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In a study of the cerebral consequences of cardiopulmonary bypass (CPB), we have assessed cerebral blood flow (CBF) by intra-arterial Xenon 133 clearance, utilising a Novocerebrograph 10a, before, during and immediately following CPB. All patients (n = 51), under the care of a single surgical team underwent elective coronary revascularisation using a standardised anaesthetic and surgical protocol. CBF, measured as the initial slope index (ISI), fell significantly from before (median 22.5) to on bypass (median 20) (Wilcoxon P less than 0.005) and was significantly increased in the immediate post-bypass period (median 28) compared with pre-bypass (Wilcoxon P less than 0.001). Scattergrams reveal CBF to be independent of arterial pressure (BP) but show an important relationship between arterial PaCO2 and CBF. The correlations between PaCO2 and CBF prior to bypass (r = 0.46 P less than 0.005) and post-bypass (r = 0.46 P less than 0.001) are very similar, whilst on bypass, the correlation, although remaining significant, is reduced (r = 0.31 P less than 0.02). The median values for arterial PaCO2 are low throughout the study (pre-bypass median 33 mmHg, on bypass median 28 mm Hg and post-bypass median 36 mm Hg). The maintenance of PaCO2 within the normal range of 35-45 mm Hg may minimise the risk of low CBF due to hypocarbia which could theoretically be harmful in patients known to be at risk of both short term and long term cerebral dysfunction.