The measurement of radioactive microspheres in biological samples (for blood flow studies)

The radioactive microsphere technique has been used in several previous investigations of regional coronary blood flow. Plastic microspheres are injected into the blood stream and blood flow to the organ is calculated from the number of microspheres in it and in a blood sample. The different sizes and shapes of organs and samples present problems in counting. In the method described. The samples have been retained in their original forms and correction factors derived to interrelate the various counting geometries thus encountered. This allows the use of an ordinary cylindrical sodium iodide detector and places less restriction on the size of sample that can be counted.