The design, construction and commissioning of a unique, versatile clinical instrument for multi-element in vivo analysis by neutron activation is described. In this instrument a 4 GBq Cf-252 neutron source is stored below ground level and can be pneumatically propelled to one of two irradiation ports. From these ports collimated beams of fast neutrons, of different intensities and dose-rates, are delivered either to a localised volume such as the liver or kidneys, or across the width of a patient for head-to-toe scanning. The instrument is intended primarily for measurement of total-body calcium and nitrogen, and partial-body cadmium via the prompt-gamma-ray technique in which the characteristic gamma-ray emission is measured during neutron activation. Repeated bilateral irradiations of a tissue equivalent phantom have shown that using high-resolution germanium spectroscopy the elements calcium, chlorine, nitrogen, carbon and hydrogen can be simultaneously measured with precisions (the coefficient of variation) of 2.6% , 1.5% , 3.1% , 4.3% and 0.4% respectively for a radiation dose equivalent to the skin of 6.4 mSv (QF= 10). When nitrogen is the element of prime interest it is advantageous to use NaI(Tl) rather than germanium detectors and the elements nitrogen, chlorine and carbon can then be simultaneously measured with precisions of 1.6% , 5.1% and 7.9% respectively for a radiation dose equivalent to the skin of 0.45 mSv. The detection limits (2 standard deviations of the net peak counts) obtained for cadmium are 2.8 mg and 3.5 ppm for the kidney and liver respectively, for an incident dose equivalent to the skin of 4.4 mSv. The instrument has so far been calibrated for quantitative in vivo measurement of nitrogen and cadmium, and for measurements of calcium counts in sequential studies of the same individual.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:638733 |
| Date | January 1988 |
| Creators | Ryde, S. J. S. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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