Humphries I R, Allen B J, Blagojevic N, Gaskin K J
James Fairfax Institute of Paediatric Clinical Nutrition, Children's Hospital, Camperdown, NSW, Australia.
Phys Med Biol. 1995 Jan;40(1):201-7. doi: 10.1088/0031-9155/40/1/016.
Total body nitrogen (TBN) is measured by in vivo prompt gamma neutron capture analysis. Usually the background under the nitrogen peak is subtracted before calculating TBN from the ratio of nitrogen counts (at 10.8 MeV) to hydrogen counts (at 2.2 MeV). The hydrogen acts as an internal standard. The background under the hydrogen peak is usually ignored. The current study was undertaken to measure the variation of the hydrogen background (HB) in patients of different sizes and to determine whether the accuracy of TBN measurements is improved when an HB correction is incorporated. Heavy-water (D2O) phantoms were used to quantify patient HB. D2O simulates patient neutron scattering without contributing to the hydrogen peak. Equations were developed to predict HB in patient measurements. HB was found to vary from 9% of total counts for a 99 kg subject to 19% for a 7 kg infant. It was demonstrated that the accuracy of TBN measurements is improved for child-sized anthropometric phantoms of known composition when an HB correction is incorporated.
全身氮（TBN）通过体内瞬发伽马中子俘获分析进行测量。通常在根据氮计数（10.8兆电子伏特）与氢计数（2.2兆电子伏特）的比值计算TBN之前，会减去氮峰下的本底。氢作为内标。氢峰下的本底通常被忽略。本研究旨在测量不同体型患者的氢本底（HB）变化，并确定纳入HB校正后TBN测量的准确性是否会提高。使用重水（D2O）模型来量化患者的HB。D2O模拟患者的中子散射，而不会对氢峰产生贡献。开发了方程来预测患者测量中的HB。发现HB从99千克受试者的总计数的9%变化到7千克婴儿的19%。结果表明，对于已知组成的儿童体型人体模型，纳入HB校正后TBN测量的准确性会提高。
