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Estrada Julio J. S.; Laurer, Gerard R.
Health Physics: September 1993
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Background for an in-vivo whole-body counter measurement is commonly obtained by averaging the counts of one or more matched (size, weight, gender) control subjects who have not been exposed to the radionuclide of interest. This limits the statistical significance to the time of the count, generally 30 min to 1 h when counting people. To obtain a human background with a small associated counting error in this manner would require counting the matching control subjects for a period much longer than they could tolerate. Also, it may not be possible to find a matching control subject who has not been exposed to the radionuclide of interest, as in the case of 210Pb, a nuclide that is normally present in air, food, and water, and to which everyone has been exposed all of their lives. This paper presents a method developed at New York University Medical Center, Nelson Institute of Environmental Medicine to obtain a matching background for any subject, for use in the measurement of 210Pb in the skull, invivo. It is obtained using a head phantom containing known amounts of potassium and calcium. The phantom, surrounded by three phoswich detectors in the same position as the subject's head, is counted repeatedly for long periods. Although it has been used to obtain “head” backgrounds only in the 210Pb spectral region, the method should be applicable to other regions of the low-energy phoswich spectrum.

©1993Health Physics Society