H. I. Glass

Elution Correction in 51Cr Red Cell Survival Studies

Summary. Red cell survival has been studied in 13 normal adults using simultaneous labelling with DF32P and 51Cr; elution correction factors have been determined for the51 Cr labelling in which ACD NIH formula A has been used as an anticoagulant with ICSH recommended method. The mean rate of 51Cr elution was 1.0% per day and there was no demonstrable early loss of either51 Cr or DF32P. The mean value for mean cell lifespan was found to be 111.2 days with an SD of 20.3 days.

Quantitative Analysis of Exponential Curve Fitting for Biological Applications

A preliminary quantitative assessment of the ability of two computer programs for fitting the sum of two exponential functions is presented with reference to the errors and number of data points normally encountered in biological investigations. Results suggest that, even in a typical biological investigation with good control of experimental errors, the errors in quantities formed by compounding all the parameters of the function may well exceed ±50% in certain circumstances. These results cast doubt on the usefulness of many compartmental analyses of biological systems where good accuracy is not obtainable and a simple model unacceptable. Error values are given for specific models. For example, the estimates of the errors in calculating grey and white matter blood flow in the brain are 5% and 13% respectively in a typical experiment; the error in estimating bone formation rate by curve analysis could be ±25%.

MEASUREMENT OF SPLENIC RED-BLOOD-CELL MASS WITH RADIOACTIVE CARBON MONOXIDE

Abstract A method has been developed for direct in-vivo measurement of the red-blood-cell (R.B.C.) mass in the spleen by radioisotope scanning after administration of R.B.C.S labelled with [ 11 C]-carbonmonoxide. Measurements have been carried out in four healthy volunteers and in two patients. The normal R.B.C. was between 20 and 45 ml. In one of the patients the spleen was just palpable and its R.B.C. mass was 183 ml.; in the other patient the spleen was grossly enlarged and its R.B.C. mass was 1010 ml. If considered necessary to delineate the spleen with greater precision, a second scan was carried out after injection of 1-mercuri-2-hydroxypropane damaged R.B.Cs labelled with 81 Rb. The quantity of isotope used would give a whole-body radiation dose of 8.8 mrad, an acceptably low level.

Quantitative estimation of red-cell uptake in the spleen using 81Rb – and 51Cr-labelled red cells

Abstract A method is described for converting the data obtained by external counting after administration of 51Cr-labelled red cells into a quantitative measurement of splenic sequestration. This involves the administration at a later stage of a second sample of red cells, which are double labelled with 81Rb and 51Cr and are damaged in vitro with l-mercuri-2-hydroxypropane to ensure their preferential uptake by the spleen. By means of a scan of the 81Rb activity the fractional uptake of the in vitro-damaged cells by the spleen can be measured, and then related to the external count. This permits the sequestration by the spleen of 51Cr-labelled natural cells to be estimated quantitatively. This provides a more reliable measurement than external counting alone in evaluating the role of the spleen in haemolytic anaemias and the indications for splenectomy. The reasons for selecting 81Rb and the theoretical considerations are presented. The method has been applied in a study on a patient suffering from heredi...

Measurement of the uptake of 99mTc by the thyroid.

Abstract The uptake of 99mTc by the thyroid has been measured in a group of normal subjects and in patients with various thyroid disorders. 99mTc gives a very low radiation dose to the thyroid but apart from this it does not seem to have any great advantage compared with radioactive iodine for the routine assessment of thyroid function. Its potential advantage in the assessment of thyroid function in patients being treated with an antithyroid drug is discussed.

Labelling of red blood cells with 81Rb for spleen scans

Abstract For spleen scanning there may be advantages in damaging red cells with non-radioactive 1-mercuri-2-hydroxypropane (MHP) and labelling them with a short-lived isotope which emits medium energy γ rays. This is especially so if quantitative measurement of red-cell destruction in the spleen is to be attempted. 81Rb has been proposed as an isotope of choice for this purpose. Factors which influence the uptake of rubidium by red cells have been studied; it has been found that it is mainly dependent on the concentration of ionic Rb+ and only to a minor extent on the volume of red cells in the incubation mixture. 81Rb, together with non-radioactive Rb+ in a concentration of about 5 mM 1−1 gives maximum labelling efficiency. A technique has been developed which ensures that blood can be labelled with 81Rb with an efficiency of 15 per cent per ml. of red cells. This is sufficient to produce a satisfactory spleen scan, and results in a radiation dose to the spleen of 16·5 mrads per μCi injected. This is con...

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 reticulo‐endothelial system may be deduced. Results are given for measurements on a series of 11 patients.

An off-line digital system for use with a gamma camera

A system for the off-line collection of data from a gamma camera is described. The data are digitized, buffered and recorded on computer-compatible magnetic tape, together with timing information. A program for processing the magnetic tape records on a powerful, batch-processing computer (CDC 6600) is described briefly. The performance and characteristics of the system are described, and the merits of such a system are discussed relative to small dedicated computer systems attached to gamma cameras.