Regional ventilation studies with Kr-81m and Xe-133: a comparative analysis.

Krypton-81m and Xe-133 ventilation scintigrams, and particulate per fusion scintigrams with Tc-99m, were obtained on the same day in 41 pa tients. Of 14 studies demonstrating pulmonary embolism, Kr-81m corn plernented the perfusion study better than Xe-133 in seven and was judged essential for that diagnosis in two. Xenon-133 was better in none. On the other hand, in 29 studies with obstructive or parenchymal lung disease, Kr-81 rn was essential for the diagnosis in only one of seven cases in which it was judged superior to Xe-133, whereas Xe-133 was essential in six of nine studies in which it was judged superior. Ventilation scintigraphy with Kr-81 m offers important advantages over Xe-133 in the diagnosisof embolic lung diseasedue to its improved spatial resolution and capacity to provide superirnposable ventilation and perfu sion images in multiple projections, so that defects can be accurately matched. Obstructive pulmonary disease may be more easily diagnosed with Xe.133 ventilation images, because areas of gaseous retention, not visible with Kr-81 m, can be seen on Xe-133 washout images.