Interlaboratory Comparison of Techniques for Measuring Lung Burdens of Low-energy Photon-emitters

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Abstract
An interlaboratory exercise was conducted to assess techniques of detection and calibration in the direct measurement of lung contamination with Pu and other nuclides emitting only low-energy X-rays. Three volunteers, of small, intermediate and large physique, inhaled an aerosol incorporating 103Pd, a 20-keV X-ray emitter and visited 13 other laboratories in the UK, Europe and North America. Participants estimated each subject''s lung content, using their procedures for assessing burdens of Pu, and their estimates were compared with values derived independently from measurements of 51Cr, also incorporated in the inhaled particles, by .gamma.-ray spectrometry. Laboratories'' calibration procedures were based on elaborate thorax phantoms, and these generally led to underestimates of the subjects'' contents, in some instances by 3 or more; only one such laboratory produced estimates in satisfactory agreement with the independently known values. The phoswich detectors, employed by most participants, apparently were more sensitive than gas counters. If a standard configuration were required, offering the highest sensitivity in most situations, the choice would be a pair of 12-cm diameter phoswich detectors viewing the left and right anterior surfaces of the upper thorax. No improvement in sensitivity would result from increasing the size, although larger units may offer other advantages.

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