Determination of intrapenial blood volume using 99mTc-labeled autologous red blood cells.

In 17 impotent patients, radioisotope penography was performed using 99mTc-red blood cells (the patient's own red blood cells labeled with 99mTc) for the quantitative analysis of intrapenial blood volume. A visual sexual stimulation (VSS) was given to the patient after injecting the 99mTc-red blood cells. Patients showing a complete erection had their intrapenial blood volumes 4.2-11.2 times greater than before VSS (mean increase, 8.0 times). In cases of incomplete erection after VSS the intrapenial blood volumes were 3.3-7.0 times greater than before VSS (mean increase, 4.9 times). In cases showing a gentle rise in their penogram curves without evidence of an erection, intrapenial blood volumes after VSS were 2.0-3.3 times those before VSS (mean increaae, 2.9 times). By contrast, in cases showing no response to the VSS or no rise in penogram curve, post-VSS increases in intrapenial pool of blood were very slight, slight, only 1.4-1.7 times the original volume of blood.