The design and construction of a realistic thorax phantom for in vivo measurements of low-energy photon emitters.

Calibration of detector systems for the in vivo measurement of transuranic radionuclides is notoriously difficult due to the low energies and intensities of the photon emissions and their severe attenuation within the tissues of the body. A realistic chest phantom has been designed and constructed to provide calibration data to relate detector responses to lung contents of radionuclides; the phantom incorporates a human thoracic cage and tissue substitutes that have been carefully selected to reproduce the scattering and absorption coefficients of muscle and lung tissue. The measured attenuation coefficients of the substitutes are compared with values calculated for the tissues of interest. Preliminary calibration data obtained from this phantom are presented and the uses and limitations of this calibration procedure are discussed.