Abstract:
:Measurement of total body nitrogen is assuming increasing importance in the nutritional evaluation of seriously ill patients. Nitrogen has been previously measured either by counting (i) the annihilation radiation from 13N immediately after neutron irradiation with 14 MeV neutrons or (ii) the 'prompt' gamma rays from thermal neutron capture by 14N during irradiation with 14 MeV neutrons or with those produced by isotopic sources or a cyclotron. The present work describes studies into the feasibility of measuring 13N produced by irradiation with a neutron beam from the MRC Cyclotron. A complication of this method is that 13N is also produced in a reaction with 16O. Direct measurement of oxygen by use of the reactions 16O(n, p)16N or 16O(n, 2n)15O enables this interference to be estimated. The former reaction is possible with both 14 meV and cyclotron-produced neutrons but the 7.1 s half-life of 16N requires detectors to be placed in or very close to the irradiation site. In our particular circumstances this is not possible but the more energetic cyclotron neutron spectrum allows the production of 15O which has a half-life of 2.05 min and can be measured in a remote whole-body counter. A disadvantage with the cyclotron beam, in comparison with 14 MeV neutrons, is that a higher dose is required for similar accuracy. A reproducibility of about 4% is obtained with a dose equivalent of 0.01 Sv.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Spinks TJ,Goode AW,Ranicar AS,Steere Edoi
10.1088/0031-9155/29/4/008subject
Has Abstractpub_date
1984-04-01 00:00:00pages
385-94issue
4eissn
0031-9155issn
1361-6560journal_volume
29pub_type
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