In vivo measurement of total body chlorine using the 8.57 MeV prompt de-excitation following thermal neutron capture

Abstract

Prompt gamma neutron activation analysis with 238Pu/Be sources is used to measure total body chlorine (TBCl) in vivo following the reaction 35Cl(n, gamma)36Cl. The chlorine de-excitation at 8.57 MeV is used for calibration of the system for TBCl. Body hydrogen is used as an internal standard and TBCl is derived from the gamma-ray counts ratio of chlorine to hydrogen. The precision of the method, determined from replicate scans of a Bush-type phantom, is 4.9% (CV). To assess accuracy an anthropomorphic phantom consisting of minced meat was constructed. Replicate scans of this phantom yielded a mean total chlorine which was not significantly different from the chemical analysis value. The subject dose equivalent for the activation measurement is less than 0.3 mSv. Mean TBCl values for 63 male and 107 female healthy volunteers were in broad agreement with predicted amounts based on multiple regression equations developed at other centres from measurements using the delayed gamma approach. Good agreement was observed in 76 volunteers between total body water (TBW) measured by tritium dilution, after correction for non-aqueous hydrogen exchange, and TBW derived from the sum of extracellular water and intracellular water as measured by TBCl and total body potassium (TBK), respectively.

Calibration of a prompt gamma in vivo neutron activation facility for direct measurement of total body protein in intensive care patients

“…Hence, the result for total body protein is not obtained immediately following a scan. This applies equally to the result for total body chlorine which can be measured simultaneously (Mitra et al 1993).…”

“…MN and Mcl for a subject are obtained from where the expressions in the denominators give the net count rates per g for nitrogen (r = 0.994, S,, = 0.033) and chlorine (r = 0.978, S, = 0.73), respectively. The whole-body scanning approach was compared to partial-body scanning with hydrogen as an internal standard using a 64.4 kg anthropomorphic phantom constructed of polythene bags of minced meat (Mitra et al 1993). The maximum radiation dose for a single partial-body scan is conservatively estimated at 0.4 mSv of which the radiation dose due to an injection of 3.7 MBq of tritiated water is 0.1 mSv and the estimated dose equivalent due to neutrons is 0.2 mSv (QF = 10) at a depth of 10 cm in a subject.…”

Body Composition Analyzer Based on PGNAA Method

“…This requires correction since the proportion of body weight due to hydrogen has been estimated to vary from 9.5 to 10.8% in a large population of patients. Chlorine may be determined from its emission at 8.57 MeV after deduction of the underlying background noise due to random summing and scattered gamma rays from nitrogen (Mitra et al 1993). It may also be determined from its prominent emission at 6.11 MeV, but a high-resolution semiconductor detector (Ge(Li) or hyper pure Ge) must be employed to distinguish this emission from the emission from oxygen at 6.134 MeV.…”

A review ofin vivoexperimental methods to determine the composition of the human body

“…Chlorine may be determined from its emission at 8.57 MeV after deduction of the underlying background noise due to random summing and scattered gamma rays from nitrogen (Mitra et al 1993b). It may also be determined from its prominent emission at 6.11 MeV, but a high-resolution semiconductor detector (Ge(Li) or hyperpure Ge) must be employed to distinguish this emission from the emission from oxygen at 6.134 MeV.…”