Biomedical subjects
Publications and source records attributed to M M Gupta.
Hypocalcaemia may manifest with tetany, convulsions and even status eqilepticus. Recognition of underlying hypocalcaemia in convulsions is mandatory because the fits may not be adequately controlled by anti-convulsant drugs which may also aggravate hypocalcaemia. Vitamin D, by relieving hypocalcaemia, reduces the frequency of convulsions and may even eliminate them.
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In internal gamma-ray dosimetry, the conventional geometric factor approach, where the "effective absorption coefficient" is taken as 0 or 0-028 cm-1, irrespective of source energy, leads to significant errors especially in the low energy region. An ettempt has been made in this paper to modify the approach to increase the accuracy of calculation and to extend its usefulness to low energies while retaining its inherent simplicity. The modification consists in replacing the effective absorption coefficient by the attenuation coefficients appropriate to the source energies and taking into account the effects due to multiple scattering by using point source build-up factor. The method has been applied for the particular case of dosimetry of a sphere. Comparison of the results obtained by this method with those got from Monte Carlo computations indicates excellent agreement at higher energies and a departure of around 15 per cent only at lower energies (as against a variation of 400 per cent when conventional geometric factor approach is used).
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In the Marinelli chair, a geometry widely used in whole body counting, the lower part of the leg is seen quite inefficiently by the detector. The present paper describes an attempt to modify the standard chair geometry to minimise this limitation. The subject sits crossed-legged in the "Buddha Posture" in the standard chair. Studies with humanoid phantoms and a volunteer sitting in the Buddha posture show that this modification brings marked improvement over the Marinelli chair both from the point of view of sensitivity and uniformity of spatial response.
The conventional radioisotope scanner has been used as a whole body counter. The background index of the system is 10.9 counts per minute per ml of sodium iodide crystal. The sensitivity and derived sensitivity parameters have been evaluated and found to be suitable for clinical studies. The optimum parameters for a single detector at two positions above the lying subject have been obtained. It has been found that for the case of 131I measurement it is possible to assay a source located at any point in the body with coefficient of variation less than 5%. To add to the versatility, a fixed geometry for in-vitro counting of large samples has been obtained. The retention values obtained by the whole body counter have been found to correlate with those obtained by in-vitro assay of urine and stool after intravenous administration of 51Cr-albumin.
Plasma 25-hydroxyvitamin-D(25-O.H.D.), Ca, P, and alkaline-phosphatase levels were determined in three separate periods during pregnancy in 14 Caucasian mothers, 23 vegetarian Asians, and 16 non-vegetarian Asians. Non-pregnant women from the same group were used as controls. The expected steady rise in alkaline phosphate during pregnancy due to increase in the placental isoenzyme, and the fall in total Ca due to haemodilution, were noted. No appreciable changes in 25-O.H.D. levels occurred, but throughout pregnancy the levels in the vegetarian Asians were lower than in the other two groups. The same analyses were made in maternal and cordplasmas in some of these patients. The babies' 25-O.H.D. levels averaged 87% of their mothers'. There was no clear evidence that pregnancy as such led to increased vitamin-D requirement in any case of these groups.
A preliminary study of iron absorption by whole body counting was carried on a group of 16 women. The cases included 8 patients suffering from iron deficiency anaemia and various infections as well as 8 healthy controls. High iron absorption is associated with iron deficiency, these changes being more marked in iron deficient controls than in those with infection or malignancy. In iron deficient controls results of whole body counting correlate very well with other haematological investigations.
A new technique using a single NaI(Tl) detector (9 cm x 6.3 cm) in two positions and based on the response curves of the detector has been described. Also a different approach to select the energy band was adopted which is helpful in reducing the dependence of counting efficiency on source depth. Various portions of the compton continuum were taken rather than confining to valley and photo-peak. For transverse uniformity it was found that the energy band which gave 50% normalized count rate at half depth would give a resultant flat response with least variation. For longitudinal uniformity the separation between the two positions of the detector need to be nearly equal to the full width at half maximum of the response curve. The response curve coupling technique described here is different from the commonly used technique of iso-response curves.
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The relationship of plasma calcium levels to changes in plasma specific gravity, total protein, and albumin induced by venous stasis was investigated. Factors were derived for adjusting calcium results to offset the effects of variation in protein concentration and thus to make them of increased discriminatory value to the clinician. The validity of an existing specific gravity correction has been substantiated, but a more exact adjustment of 0.23 mg/100 ml of calcium for every 0.001 change in specific gravity is proposed. We recommend for automated laboratories that the factor based on albumin be used: 0.09 mg/100 ml of calcium should be subtracted from the total calcium value for every increase of 0.1 g in albumin above 4.6 g/100 ml, and a corresponding addition should be made for values of albumin below 4.6 g/100 ml.Using a calcium specific electrode, it has been shown that the ionized calcium concentration does not alter with prolonged venous stasis.
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