Quantitation of pharmacologically-induced penile erections: the value of radionuclide phallography in the objective evaluation of erectile haemodynamics.

: This study combines the pharmacologically-induced penile erection (PIPE) technique with radionuclide phallography (RNP) for the non-invasive study of penile haemodynamic changes during erection. Penile erections produced by the intracavernosal injections of two different vasoactive drugs, prostaglandin E1 (PGE1) and papaverine HCl (PPV) were assessed by quantitation of the dynamic RNP and parameters of erection were defined and compared. PGE1 intracavernosal injections were seen to elicit a better erectile response than PPV. Dynamic radionuclide phallography was performed using 99Tcm-labelled autologous RBCs in five normally potent volunteers, sixteen patients with psychogenic impotence, seven patients with vasculogenic impotence (three arteriogenic, four venous leakage) and one patient with neurogenic impotence. Physical parameters of erection including the penile length and circumference changes during erection and the erectile angle were compared with the indices of penile blood flow and volume derived through quantitation of the RNP. There was a close correlation between the penogram index (an index of penile blood volume) and penile circumference increase during erection (r = 0.77, p less than 10(-6). The erectile angle, a measure of penile rigidity, correlated strongly (r = 0.82, p less than 10(-6) with the flow index, a measure of penile blood volume. Patterns specific to various categories of impotence were observed and these aided in the diagnosis, especially in equivocal cases with a suboptimal clinical response to the intracavernosal injection. Quantitative RNP offers a non-invasive method which allows direct objective assessment of the erectile response providing several quantitative parameters for analysis.