81mKr gas and 99mTc-MAA V/Q ratio images for detection of V/Q mismatches.

Methods for creating ventilation/perfusion ratio images have been reported previously using radioxenon. With the availability of 81mKr gas, corresponding ventilation and perfusion views in multiple projections to evaluate for V/Q mismatch may be performed more readily. A technique for the creation of a functional V/Q ratio image to highlight V/Q mismatches to aid in the evaluation of pulmonary embolism is described. By removing nonpertinent and distracting information and by converting a 'cold spot' imaging modality to a 'hot spot' modality, these functional images aid in the synthesis of the information provided by the ventilation and perfusion images. The limitations due to technical artifacts and the advantages of using these functional images are described.