Near infrared spectrophotometry for the diagnosis of vasculogenic erectiledysfunction

A specialized near infrared spectrophotometry instrument for noninvasive, c ontinuous monitoring of the hemodynamic events of erection in the human pen is has been developed. Its potential application for the diagnostic evaluat ion of erectile dysfunction was investigated. Thirty-eight patients and 18 volunteer subjects underwent penile near infrared spectrophotometry using a n optical sensor probe with wavelength selectivity for hemoglobin absorptio n spectra. Penile blood volume changes and their time courses were measured following intracavernous pharmaco-stimulation in patients and visual sexua l stimulation in volunteers. Spectrophotometric results were compared with results obtained simultaneously using color duplex ultrasonography, strain gauge penile circumference monitoring, penile tonometry, and clinical asses sments. Spectrophotometric recordings of penile erection showed measurable blood volume changes consistent with the hemodynamic events of this biologi cal function. flood volume per cent (BV%) increase correlated with clinical ratings of erection quality (P<0.001), penile rigidity measurements (P < 0 .005), and penile circumference increases (P < 0.0001), and it correlated w ith mean peak systolic velocity measurements when BV% increase was restrict ed to values less than 50% (P < 0.001). The time to reach half the maximum blood volume change (EV T 1/2) correlated directly with the time to reach h alf the maximum penile circumference size increase(P < 0.001), whereas BV T 1/2 correlated inversely with mean resistive index measurements only when BV T1/2 was restricted to values greater than 120 s (P < 0.05). Spectrophot ometric criteria consisting of BV% less than 35% and BV T 1/2 greater than 120 s affirmed the diagnosis of severe erectile impairment with a similar d egree of accuracy as standard ultrasonographic criteria (P < 0.002). Penile near infrared spectrophotometry is a safe, inexpensive and simply used bio medical optics technique that provides quantitative measurements of the vas cular physiology of penile erection and appears to offer clinical utility i n the diagnosis of vasculogenic erectile dysfunction.