Thorax
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Most measurements of pulmonary blood volume have been based on the Stewart-Hamilton dye dilution principle and have required direct catheterisation of the cardiac chambers. Alternatively a precordial counter may be used to detect the composite right and left heart curves after an intravenous injection of radionuclide. We investigated the use of a gamma camera/computer system to determine the radionuclide dilution curves from individual cardiac chambers. ⋯ The effect of posture on pulmonary blood volume was determined in six subjects lying supine and tilted at a 45 degree angle. A reduction in pulmonary blood volume in the tilted position was observed in each subject (p less than 0.005). This simple non-invasive measurement should allow more detailed assessment of physiological or pharmacological changes of the pulmonary vascular bed.