Xenon ventilation-perfusion lung scintigraphy immediately following technetium microsphere scanning: a computer-assisted background subtraction technique

The conventional /sup 99m/Tc-albumin capillary blockade type of radionuclide lung scan suffers from a lack of sensitivity in identifying small perfusion defects and from an inability to distinguish between the various causes of perfusion defect. This paper presents a simple computer-assisted technique which allows a 133Xe ventilation-perfusion (V:Q) study to be performed immediately after the /sup 99m/Tc-albumin microsphere scans with the gamma camera optimally positioned over any defect that is seen. Crossover from the /sup 99m/Tc into the 133Xe window is subtracted from the xenon study by the computer. This procedure allows advantage to be taken of a unique character of the acute pulmonary embolus, namely an elevation of the V:Q ratio in the affected area of lung. In this way, the specificity of the lung scan can be increased for pulmonary embolism