THE USE OF IRIDIUM-191M FOR PULMONARY BLOOD-FLOW IMAGING

A preliminary evaluation of the potential utilisation of osmium-191/ir idium-191m for pulmonary blood flow imaging was performed. This evalua tion was part of a more general study concerning the use of Ir-191m fo r first-pass radionuclide angiocardiography (FPRNA). In eight selected patients with suspected pulmonary disease, we generated, from the dat a collected during FPRNA, an image representing blood flow distributio n to the lungs. A software program was developed in order to different iate the lungs from the heart, to define the wash-in lung phase and fi nally to construct an image representing pulmonary blood flow distribu tion. We compared that image with a standard lung perfusion image usin g technetium-99m macroaggregated albumin (MAA) and plain chest X-ray a nd computerized tomography (CT). The obtained Ir-191m perfusion images showed a spatial activity distribution similar to that seen on Tc-99m -MAA lung perfusion scans, and in most cases the same perfusion defect s. Disease revealed by plain chest X-ray and CT was nicely correlated with perfusion defects seen on the Ir-191m images. The combined inform ation of lung perfusion and dynamic cardiac parameters obtained by FPR NA (right and left ventricular ejection fractions) added another relev ant dimension to the clinical picture of patients with pulmonary embol ism, chronic obstructive lung disease, lung tumour or suspected conges tive heart failure. We conclude that Ir-191m may become a practical to ol for achieving the conceptually promising approach of combined lung- heart real-time imaging.