A method for quantitative estimation of split renal function using a computerized gamma camera system is described. 42 children and adolescents with existing or preexisting vesicoureteric reflux and recurrent urinary tract infection were investigated. Total renal clearance of DTPA was calculated with a disappearance curve derived from the largest extrarenal area in the field of view of a gamma camera with diverging collimator. Split renal function was estimated with the slopes of second phase renograms. The plasma disappearance clearance of DTPA, calculated using one compartment model with two late blood samples, gave similar results with the clearance estimated from the body disappearance curves. The proportional planimetric renal parenchymal areas had good correlation with the split clearance estimated from renogram slopes. The method offers data on renal function and urinary tract dynamics which is very valuable in the follow-up of children with recurrent urinary tract infection and vesicoureteric reflux.

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Studies were made using ordinary selective coronary angiography and angiography during ischaemia produced by right atrial pacing, on a series of 41 patients with ischaemic heart disease, to examine the response of the collaterals to the ischaemia stimulus. Regional myocardial perfusion was determined under the same circumstances by measuring regional 133Xenon washout curves. No collaterals were found in 8 patients, none of whom demonstrated collaterals when angiography was repeated during ischaemia. Eleven of the 33 patients with prepacing collaterals (33%) responded to ischaemia with an increase in the collaterals, 16 patients (49%) showed no change, 5 patients (15%) showed a decrease in the collaterals, and one patient exhibited a bidirectional change. Regional myocardial perfusion responses closely paralleled the angiographic changes, yielding suggestive evidence that the collaterals were intimately involved in the enhancement of the flow. Despite different collateral and flow responses to ischaemia, the data on exercise tolerance, left ventricular end-diastolic pressure, ejection fraction, prevalence of left ventricular asynergy, and the topographic relation between synergy and collaterals, were largely similar. The data show that in some patients the collateral circulation reacts to ischaemia by enhancement, but the functional significance of this response is obscure.

The body disappearances and the liver mean transit times of a hepatobiliary tracer, 99mTc-diethyl IDA, were measured from 100 cholescintigraphies of 98 patients. Fifteen patients had no hepatobiliary disease; their mean body disappearance was 6.6, SD 1.1%/min, and mean liver mean transit time 32, SD 19 min. The values within 2 SDs, disappearance greater than or equal to 4.4%/min and mean transit time less than or equal to 70 min, were used as reference values. Disappearance constants below 4.4%/min were observed 29% and mean transit times exceeding 70 min in 49% of the examinations performed on patients with some hepatobiliary abnormality. The calculated parameters were compared with the levels of serum bilirubin and ASAT. Disappearance constants below 4.4%/min were seen in 33% and mean transit times exceeding 70 min in 55% of the patients who had either abnormal serum bilirubin or ASAT due to a hepatobiliary disease. The correlation between the serum bilirubin and the disappearance was -0.13, and between ASAT and body disappearance it was -0.28. The corresponding correlation coefficients of serum bilirubin and ASAT with the liver mean transit times were 0.33 and 0.44. Long mean transit times in relation to bilirubin and ASAT were seen in some acute cases. Short mean transit times in relation to bilirubin and ASAT were seen with falling serum levels of the latter.

Simultaneous assessment of coronary flow and flow-volume relation makes it possible to evaluate the dilatatory responses of coronary vasculature. A new set up of methods for investigation of the coronary circulation was employed to study the nature of the coronary flow and volume responses to dipyridamole in dogs. The turnover rate of coronary blood, the reciprocal value of the mean transit time, can be accurately determined by computer simulation analysis of coronary dye dilution curves. After intravenous dipyridamole (0.5 mg/kg) both coronary turnover rate and electromagnetically assessed blood flow were observed to increase in parallel and to the same degree (+55%). This indicates that no increase in the coronary vascular volume and, accordingly, no significant overall coronary dilatation takes place. The effective coronary blood flow in relation to the myocardial oxygen consumption, i.e. the nutritional flow, and the myocardial oxygen consumption decreased by 25% concomitant to a corresponding fall in myocardial oxygen requirements. Thus, the increase in total coronary flow after dipyridamole is useless for myocardial metabolism, and may properly be denoted as luxury perfusion or throughput flow.