Interferences in in vivo neutron activation analysis

Area of Science:

• Medical Physics
• Nuclear Chemistry
• Human Physiology

Background:

• In vivo neutron activation analysis (NAA) is crucial for measuring total body elemental composition (N, P, Cl, Na, Ca, K).
• Interfering gamma-ray activities in the energy spectrum can lead to significant measurement errors.
• These interferences stem from administered radioisotopes and activation of non-native elements.

Purpose of the Study:

• To investigate sources of interfering activity in human in vivo NAA.
• To quantify the impact of specific radioisotopes (67Ga, 47Ca) and activated elements (Fe, Cr, I, Ba) on elemental measurements.
• To describe a method for correcting these interferences and improve measurement accuracy.

Main Methods:

• Analysis of gamma-ray energy spectra from in vivo NAA.
• Examination of interferences from administered radioisotopes (67Ga, 47Ca).
• Assessment of interferences from activated elements in prostheses (Fe, Cr) and contrast media (I, Ba).
• Development and application of a spectral correction method using least squares analysis.

Main Results:

• Identified significant errors in N, P, Cl, Na, Ca, and K measurements due to specific interfering activities.
• Quantified the size and duration of errors caused by 67Ga, 47Ca, activated Fe, Cr, I, and Ba.
• Demonstrated a method to correct for these interferences, enhancing measurement reliability.
• Evaluated the influence of standard spectra shape on least squares analysis results.

Conclusions:

• Interfering activities pose a significant challenge to accurate in vivo NAA for body composition.
• The described correction method effectively mitigates errors from administered radioisotopes and activated elements.
• Accurate elemental body composition analysis using in vivo NAA requires careful consideration and correction of spectral interferences.