D. Vartsky

The use of body hydrogen as an internal standard in the measurement of nitrogen in vivo by prompt neutron capture gamma-ray analysis

The previously established technique of analysis of neutron capture γ-rays for the determination of nitrogen in-vivo has been modified to make estimates of absolute quantities of nitrogen mass. Hydrogen is used as an internal standard and the nitrogen mass is determined from the observed ratio of nitrogen to hydrogen counts, together with the hydrogen mass, estimated from body parameters. Phantom and cadaver studies indicate that nitrogen mass can be estimated to ±4% or better by this means.

Prompt gamma neutron activation analysis to measure whole body nitrogen absolutely: Its application to studies of in-vivo changes in body composition in health and disease

Whole body nitrogen has been measured absolutely in male volunteers and patients by in-vivo neutron activation analysis using whole body hydrogen as an internal standard. The 10.8 MeV and 2.2 MeV prompt gamma rays from nitrogen and hydrogen respectively give a result reproducible to 4% for a dose of 100 mRem. Whole body potassium measured by whole body counting natural40K and whole body nitrogen have been correlated in normal adult males and patients. In the normals the correlation coefficient was 0.96 with coefficient of variation 4%. In the patients these parameters were 0.92 and 8% in 140 measurements. The ratio of N/K increased significantly as the degree of clinical wasting progressed.

Fractional charge collection technique for pile-up reduction - counting low intensity radiation in presence of intense gamma-ray and neutron background

Abstract Properties of a fractional charge collection technique for pile-up reduction in large volume NaI(Tl) crystals have been investigated for the particular use of measurement of whole body nitrogen by in vivo neutron activation analysis. The resolution of the system and the photomultiplier anode pulse length has been measured as a function of pulse clipping times. A comparison between conventional voltage mode and the fractional charge collection mode has been made from the point of view of pile-up effect. The performance of the system has been tested in our application to a total count rate of 2×10 5 pulses/s.

A preliminary investigation of nuclear resonant scattering as a new technique for the in vivo measurement of hepatic copper.

A method using nuclear resonant scattering of gamma-rays from a vapour phase 65ZnI2 source is described. A NaI:Tl crystal detector coupled to a photomultiplier is used and the output is amplified and the signals analysed in a 512 channel multichannel analyser.

In vivo neutron activation analysis: preliminary investigations of a technique for improving the uniformity of thermal neutron flux in the body.

In a limited investigation using a 24 cm thick phantom irradiated with neutrons produced by a cyclotron and by an isotopic source, it was found that the uniformity of the thermal flux distribution can be considerably improved by the introduction of a thin thermal neutron absorber into the premoderating material.

An investigation of nuclear resonance scattering for in vivo analysis of liver copper

Nuclear resonance scattering has been applied to the measurement of copper. It has been shown that this method is sufficiently sensitive to measure, in-vivo, liver copper accumulations associated with certain diseases. The method and some preliminary results are described.