The harmful biological effect of excessive aluminum(Al) load in humans has been well documented in the literature. Al stored in bone, for instance due to dialysis treatment or occupational exposure, can interfere with normal bone remodeling leading to osteodystrophy, osteoarthritis, or osteomalacia. On the other hand, the relationship between chronic Al exposure and the risk of Alzheimer’s disease remains controversial. In this work, the feasibility of in vivoneutron activation analysis (IVNAA) for measuringAl levels in the human hand bone, using the thermal neutron capture reaction , is reported. This noninvasive diagnostic technique employs a high beam current Tandetron accelerator based neutron source, an irradiation/shielding cavity, a NaI(Tl) detector system, and a new set of hand bone phantoms. The photon spectra of the irradiated phantom closely resemble those collected from the hands of nonexposed healthy subjects. A protocol was developed using the newly developed hand phantoms, which resulted in a minimum detectable limit (MDL) of Al in the human hand. Using the ratio of Al to Ca as an index of Al levels per unit bone mass, the MDL was determined as , which is within the range of the measured levels of [ICRP, Report of the Task Group on Reference Man, Publication 23 (Pergamon, Oxford, 1975)] found in other in vivo and in vitro studies. Following the feasibility studies conducted with phantoms, the diagnostic technique was used to measureAl levels in the hand bones of 20 healthy human subjects. The mean hand bone Al concentration was determined as . The average standard error in the is , which corresponds to an average relative error of 50% in the measured levels of . These results were achieved with a dose equivalent of to a hand and an effective dose of . This effective dose is approximately half of that received in a chest radiograph examination. It is recommended to investigate the use of the bone Al IVNAA diagnostic technique for in vivomeasurements of patients with documented overload of Al in bone.
The authors are grateful to John Oudyk and Dr. Michael W. Pysklywec of Occupational Health Clinics for Ontario Workers (OHCOW) for their help in recruiting the volunteers for this study. Dr. Colin Webber and Dr. Karen Gulenchyn of McMaster University Medical Center are acknowledged for their help in the ethical approval process for this human study. The authors acknowledge the help of Dave Tucker and Christopher Malcolmson of McMaster University Health Physics, for providing assistance in the implementation of radiation protection and safety. They extend their gratitude to Scott McMaster, Accelerator Manager, and Jason Falladown for their assistance in the operation of the Tandetron accelerator and for helping in licensing related issues. The authors also wish to acknowledge L. M. Watters for her assistance in conducting the in vivo study. This project was funded by a research grant provided by the Workplace Safety and Insurance Board (Ontario), principal investigator A.P-M. The authors would also like to acknowledge CFI, OIT, and NSERC for funding important parts of this research. One of the authors, Aslam, pursued this research under the H. G. Thode research fellowship at McMaster University.
II. MATERIALS AND METHODS
II.A. IVNAA measurement of Al
II.B. Hand phantom measurements
II.C. Tissue equivalent proportional counter (TEPC) measurements
II.D. In vivo human measurements
III. ANALYSIS AND RESULTS
III.A. Hand phantom measurements
III.B. In vivo human measurements
III.C. Survey of reference values of the amounts of Al to Ca in human skeleton
IV. SUMMARY AND CONCLUSIONS
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