Facility optimization to improve activation rate distributions during IVNAA

• Published in: Journal of radiation research Vol. 54; no. 3; pp. 515 - 531
• Main Authors: Ebrahimi Khankook, Atiyeh, Rafat Motavalli, Laleh, Miri Hakimabad, Hashem
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.05.2013
• Subjects: Activation; Activation analysis; Algorithms; Anthropometry - instrumentation; Anthropometry - methods; Body Composition - physiology; Collimators; Computer Simulation; Equipment Design; Equipment Failure Analysis; Humans; In vivo methods and tests; Mathematical analysis; Models, Biological; Neutron Activation Analysis - instrumentation; Neutron Activation Analysis - methods; Nondestructive testing; Optimization; Paraffins; Physics; Radiation Dosage; Reproducibility of Results; Scattering, Radiation; Sensitivity and Specificity; activation rate; neutron flux uniformity; collimator; MCNP; IVNAA; pre-moderator
• ISSN: 0449-3060; 1349-9157
• DOI: 10.1093/jrr/rrs124

Currently, determination of body composition is the most useful method for distinguishing between certain diseases. The prompt-gamma in vivo neutron activation analysis (IVNAA) facility for non-destructive elemental analysis of the human body is the gold standard method for this type of analysis. In order to obtain accurate measurements using the IVNAA system, the activation probability in the body must be uniform. This can be difficult to achieve, as body shape and body composition affect the rate of activation. The aim of this study was to determine the optimum pre-moderator, in terms of material for attaining uniform activation probability with a CV value of about 10% and changing the collimator role to increase activation rate within the body. Such uniformity was obtained with a high thickness of paraffin pre-moderator, however, because of increasing secondary photon flux received by the detectors it was not an appropriate choice. Our final calculations indicated that using two paraffin slabs with a thickness of 3 cm as a pre-moderator, in the presence of 2 cm Bi on the collimator, achieves a satisfactory distribution of activation rate in the body.