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Evaluation of Penile Ultrasonic Velocitometry Versus Penile Duplex Ultrasonography to Assess Penile Arterial Hemodynamics
ADULT UROLOGY
EVALUATION OF PENILE ULTRASONIC VELOCITOMETRY VERSUS PENILE DUPLEX ULTRASONOGRAPHY TO ASSESS PENILE ARTERIAL HEMODYNAMICS L. DEAN KNOLL
AND
JEROME H. ABRAMS
ABSTRACT Objectives. A prospective study was performed comparing duplex ultrasonography (DU) and ultrasonic velocitometry (UV), using a new fixed-angle device, in assessing penile arterial hemodynamics. Cavernous arterial peak systolic and end-diastolic flow velocities were measured. Methods. Twenty-four consecutive patients (mean age 47 years) underwent DU (Ultramark 9 HDI System) and UV (Knoll/MIDUS system) at the same setting by the same technician. After preinjection scanning, all patients received 60 mg of papaverine intracavernosally. Repeat scanning was performed at 5, 10, 15, and 20 minutes. Results. The statistical significance between the two techniques was assessed by examining the correlation. For all patients (n 5 24) and all velocity determinations in all patients (n 5 554), the equation for the linear regression line is y 5 0.952x 1 1.453, r 5 0.91 (r2 5 0.82) and P ,0.05. Conclusions. UV is as accurate as DU in measuring peak flow velocities of the cavernous artery. This new fixed-angle device is capable of identifying a vessel without real time imaging. UV is a safe, office-based procedure and scanning is less operator-dependent and easier to learn. UROLOGY 51: 89–93, 1998. © 1998, Elsevier Science Inc. All rights reserved.
E
rectile dysfunction (ED), defined as the inability to maintain an erection sufficient for satisfactory intercourse, has been estimated to affect 10 to 20 million men in the United States.1 Penile erection is a complex neurovascular phenomenon involving not only the coordination of three physiologic events (increased arterial flow, sinusoidal smooth muscle relaxation, and decreased venous drainage) but also the interaction of nerves, neurotransmitters, striated and smooth muscle, and the tunica albuginea.2 Despite a better understanding of the pathophysiology of erectile dysfunction, controversy remains regarding the optimal diagnostic evaluation and proper therapy. Goal-directed therapy, frequently used today, relies on a minimum diagnostic evaluDr. Knoll has a financial proprietary relationship with Urometrics, Inc. From the Center for Urological Treatment and Research, Nashville, Tennessee; and Department of Surgery, University of Minnesota, Minneapolis, Minnesota Reprint requests: L. Dean Knoll, M.D., The Center for Urological Treatment and Research, 2400 Patterson Street, Suite 101, Nashville, TN 37203 Submitted: May 30, 1997, accepted (with revisions): August 1, 1997 © 1998, ELSEVIER SCIENCE INC. ALL RIGHTS RESERVED
ation and stratification of all treatment options that are offered to the patient for selection. For some patients, particularly the younger aged group, a limited, specific diagnostic assessment may be appropriate, for it may identify a reversible or treatable underlying cause or an undiagnosed medical condition that may exist. Determination of etiology may affect prognosis or provide insight into risk factors. An understanding of etiology can help guide patients into appropriate acceptable therapy. For example, a patient diagnosed with severe arterial insufficiency will not be a suitable candidate for oral therapy or intraurethral pharmacotherapy. These patients can save money and avoid frustration by being directed into other more appropriate therapies such as an injection program, a vacuum device, or an implant. Initial history and physical examination alone have a low specificity in diagnosing organic ED. A comprehensive approach, including historical and physiologic factors, is required to evaluate fully and diagnose ED.3 For some patients, the differentiation between psychogenic and organic etiologies is of the greatest importance. For these patients, an etiology-directed evaluation may be necessary. This idea has 0090-4295/98/$19.00 PII S0090-4295(97)00493-7 89
been supported by the Society for the Study of Impotence’s position statement on the diagnostic evaluation of impotence. It states: Diagnostic studies used to identify the pathophysiology of impotence should be individualized for each patient. For the patient who wishes to identify the cause or causes of his erectile dysfunction as organic and/or psychogenic, nocturnal penile tumescence and rigidity (NPTR) monitoring, vascular and other testing may be indicated and useful, but the patient must be provided information permitting an informed decision to seek testing which is not essential to the selection of treatment options.
Clinical studies have shown that vascular problems are the most common cause of organic ED.4 Noninvasive evaluation procedures for the penile arterial system have included penile brachial index,5 Doppler pulse wave analysis,6 penile plethysmography,7 and xenon-133 (133Xe) penile washout study.8 Limitations of these tests are related to measurement of vascular function, when the penis is flaccid. These tests provide no diagnostic information about the dynamic process of erection. In 1985, Lue et al.9 introduced duplex ultrasonography (DU) with intracavernous pharmacologic stimulation as a noninvasive tool in the evaluation of penile circulation. Many investigators have reported that DU, in both impotent and potent patients, provides a functional assessment of penile blood flow and veno-occlusive function.10 –19 When indicated for select patients, DU is a useful diagnostic modality for etiology-directed therapy. It, however, has some limitations, including high cost of equipment and significant operator dependency. An ideal device for screening and diagnosis of ED would be office-based, relatively inexpensive, easy to use, and less dependent on the operator. We report the use of a new device that substantially satisfies these criteria, a new fixed-angle ultrasonic velocitometer. We used this device to measure cavernous arterial peak systolic and end-diastolic flow velocities in comparison with DU-generated peak flow velocities. MATERIAL AND METHODS PATIENT POPULATION Penile DU and penile ultrasonic velocitometry (UV), before and after intracavernous injection of papavarine, were performed on 24 consecutive patients who presented with a complaint of ED for 1 to 11 years (mean 3.0). These patients ranged in age from 32 to 60 years (average 47). All patients were evaluated with a detailed medical history, sexual questionnaire, and physical examination. Risk factors for ED in the study group are outlined in Table I. Measurements of serum blood chemistries, complete blood count, and testosterone levels were also performed. No patient had been previously diagnosed or treated for ED. 90
TABLE I. Risk factors for erectile dysfunction No. of Patients
Risk Factor Diabetes Hypertension Coronary artery disease Abdominal or pelvic surgery Hypercholesterolemia/hyperlipidemia Spinal cord disease, trauma Alcoholism (.5 ounces/day) Smoking (.15 cigarettes/day)
3 6 4 5 6 1 7 10
TECHNIQUE OF PENILE DUPLEX ULTRASONOGRAPHY DU was performed using the Ultramark 9 HDI ultrasound system (Advanced Technology Laboratories, Bothell, Wash) by the same technician. Patient position was supine, and the penis was placed with the dorsum exposed. The transducer was placed over the proximal dorsum of the penis near the base and initial scanning performed in the longitudinal and transverse planes. Baseline cavernous arterial peak systolic and end-diastolic flow velocities were measured near the base of the penis. Doppler angle was programmed to approximately 60°. Following the initial scan, 60 mg of papavarine (2-mL ampule) was injected intracavernosally with a 25-gauge needle. Digital pressure was applied to the injection site for 30 seconds to 1 minute. Gray scale and Doppler studies were repeated at the base of the penis at 5, 10, 15, and 20 minutes after injection, or sooner, if a full erection began. The same procedure for measuring velocities was used after injection, as before injection, such that each patient was his own control. If the patient did not achieve a full erection, he or his partner were asked to stimulate his penis privately to see if his erection improved. The patient was seen in the office 1 hour after the study to make sure detumescence of the penis occurred. If the patient had a full erection, aspiration of the corpus cavernosum alone or in combination with injecting small amounts of a 1:10,000 solution of epinephrine was used to achieve detumescence.
TECHNIQUE OF PENILE ULTRASONIC VELOCITOMETRY Penile UV was performed using the Knoll/MIDUS system (UroMetrics, St Paul, Minn). The scanning device contains a penile cradle which contains two movable fixed-angle (60°) ultrasonic transducers— one for each cavernous body. The carrying frequency of each transducer is 8 mHz in frequency and can measure blood velocities ranging from 1 to 200 cm/s. The transducers have a focal length of 1.2 cm. With the penis placed in the penile cradle, the transducers were moved laterally until the strongest cavernous signal was heard and visualized on the screen. Once the transducers were positioned, measurement of cavernous peak flow velocities was performed at the same times and location as for DU as described above. The Doppler signal was evaluated by graphing velocities as a function of time. A pointer was moved on the displayed graph to measure the peak flow velocity, systolic velocity, and enddiastolic velocity. This information was placed into the computer program of the analyzer by the technician and was later evaluated after the testing to determine all velocities. The ultrasound technician was blinded to this information; he was not allowed to visualize the peak systolic and end-diastolic velocities obtained by the penile ultrasonic velocitometer.
STATISTICAL ANALYSIS It should be emphasized that the design of the study was based on obtaining measurements of two variables, namely UROLOGY 51 (1), 1998
FIGURE 1. Comparison of velocity determinations for all patients between duplex ultrasonography (Ultramark 9) and ultrasonic velocitometry (Knoll/MIDUS).
measurement of cavernosal arterial peak systolic and end-diastolic flow velocities using the two methods described. The statistical significance between the two techniques was assessed by examining the correlation.
RESULTS Figure 1 shows the cavernous arterial peak systolic and end-diastolic flow velocities measured before and after injection with DU and UV for all patients (n 5 24) and all velocity determinations in all patients (n 5 554). The equation for the linear regression line is y 5 0.952x 1 1.453, r 5 0.91 (r2 5 0.82) and P ,0.05. Figure 2 shows typical results for a single patient. In this patient, arterial peak systolic and end-diastolic flow velocities are displayed for DU and UV. The equation for the linear regression line is y 5 0.999x 1 0.900, r 5 0.98 (r2 5 0.97), P ,0.05. COMMENT During the last decade, significant advances in our understanding of the hemodynamics of penile erectile physiology have been made, which have resulted in the identification of specific and potentially correctable vascular disorders. Since the probability of identifying a specific etiology of ED is obtainable today, many physicians and surgeons who treat patients with this disorder agree that a screening/diagnostic device is of great importance in selected younger patients. The ideal screening/ UROLOGY 51 (1), 1998
FIGURE 2. Comparison of velocity determinations in a single patient between duplex ultrasonography (Ultramark 9) and ultrasonic velocitometry (Knoll/MIDUS).
diagnostic device would have several characteristics: 1. Inexpensive and, consequently, able to be used in the office setting, where patients are initially evaluated 2. Easy to use and operator independent 3. Accurate over a wide range of velocities 4. Able to measure the time dependence of blood velocity 5. Able to make reproducible measurements to evaluate the effect of treatment over time Recent technologic advances in the field of ultrasound allow for the determination of the velocity of moving blood. Duplex ultrasonographic assessment of penile blood flow is one of the best screening tools currently available: it is relatively noninvasive, it is commonly found in hospitals, and it provides a functional assessment of the cavernous arteries.10 –19 It aids in selecting patients for penile angiography and cavernosometry/cavernosography and allows urologists to help patients differentiate between psychogenic and organic etiologies. Despite these apparent advantages, the use of DU as a tool to assess penile blood flow is controversial and limited. The necessary equipment is expensive and, in many medical centers, access is limited to radiologists or vascular surgery departments. The procedure is operator dependent: learning the technique can be difficult and time-consuming. Lack of standardization of testing and of reference values, psychologic aspects of testing, the timing of measurements during penile erection, location on the penis, where measurements are taken, and possible variations in arterial anatomy20 are other fac91
tors that can affect results with duplex ultrasound measurement. For the interested reader, detailed discussions of advantages and disadvantages of duplex ultrasound measurement have been reported in the urologic literature.10 –19 Peak flow velocity is the most commonly used ultrasonographic variable to evaluate the cavernous inflow tract. Although continuous wave Doppler is accurate, it suffers from limitations in identifying vessels. Real time imaging can help to identify vessels, but is not necessary and adds significant cost. Measurement of cavernous artery dilatation as an indicator of blood flow has reported limitations.16 The new fixed-angle transducer has solved the difficulties of vessel identification in a novel, cost-effective manner. The device is successful for two reasons: anatomy of the cavernous arteries and the use of a fixed range of focal length for each transducer. Although the origin and number of deep cavernous arteries shows marked variation, the intracavernous artery is more constant in number and in location.20 After the cavernous artery enters the hilum of the penis, it travels distally in the center of the corpora cavernosa to nearly the most distal extent. Combining a fixed range of focal length with the ability to measure blood velocity in the lateral corpora at the 2 o’clock and 10 o’clock positions, respectively (midline of the dorsum of the penis is defined as 12 o’clock), allows measurement of the cavernous artery velocities. That imaging of the cavernous arteries is not a necessary requirement allows the possibility of substantially reducing the cost of the screening device, as much as 3 to 8 times less expensive than conventional duplex scanning equipment. Patients who have atretic arteries, tortuous intracavernous arteries, branching of the cavernous arteries, or well-developed collaterals present difficulties for measurement for both the duplex Doppler device with imaging capability and the ultrasonic velocitometer. None of the patients in our study group presented with these anatomic variants. The ultrasonic velocitometer is easy to use and meets the second requirement of an ideal device for screening/diagnosis. The combination of the software and the cradle that positions the ultrasound transducers over the intracavernous arteries provides a fixed-angle and rapid adjustment. Throughout the entire study, except when a patient needs to stimulate himself, the transducers are stationary and require no manipulation by the operator. As a result, the measurements are operator independent, unlike DU, which requires an operator to hold by hand the scanning probe and program in the angle for each measurement taken. This procedure may result in variability of the angle of the ultrasound beam with respect to the blood velocity vector. 92
The ultrasonic velocitometer demonstrates excellent dynamic range, the third requirement of the ideal screening/diagnostic device. Figure 1 shows correlation over a range of blood velocities from 0 to 54 cm/s. The device is capable of measuring velocities up to 200 cm/s. In determining correlation, some points in Figure 1 require comment. In those patients in whom the response to intracavernous injection of papaverine is sustained, correlation is excellent as seen in Figure 2. In those patients in whom the response is transient, a limitation of the present study may be apparent. The differences in blood velocity measured by the two systems may be real. The arterial blood velocity may have changed in the length of time required to change from duplex ultrasonography to ultrasonic velocitometry, typically 75 to 90 seconds. The new fixed-angle ultrasonic velocitometer can provide the time dependence of blood velocity, the fourth requirement of the ideal screening diagnostic device. Additional diagnostic information may be obtainable regarding pathophysiology by studying the curve of velocity versus time for patients with different pathophysiologic mechanisms. An analogous situation is the flow versus time curves for pulmonary function tests. With improved understanding, the need for angiography, or other invasive tests, may be reduced. The study of time dependency of blood velocity using both procedures will be a subject for further investigation. The cradle that positions the ultrasound transducers with respect to the cavernous arteries provides reproducible positioning of the transducers. Blood velocities at different times in the course of treatment can then be compared and the efficacy of different treatments can be evaluated over longer intervals of time, the fifth requirement. CONCLUSIONS UV is of comparable accuracy to DU in measuring peak flow velocities of the cavernous artery. The ultrasonic velocitometer is capable of measuring, safely and accurately, blood velocities over a wide range. The fixed-angle device can identify the relevant arteries without real time imaging. It is simple to use and minimizes operator dependency. The cradle that positions the ultrasound transducers with respect to the blood velocity vector is stable and will allow for analysis of time dependence of the blood velocity after injection of intracavernous vasoactive agents. The fixed position will allow repeat measurements in the same patient and comparison of the effects of treatment. ACKNOWLEDGMENT. To David Howard, ultrasonographic technician, Department of Radiology, Centennial Medical Center, for his technical assistance. UROLOGY 51 (1), 1998
REFERENCES 1. NIH Consensus Statement. Impotence 10: 1–33, 1992. 2. Brock G, and Lue TF: Impotence—a patient’s goal-directed approach. Monogr Urol 13: 99 –110, 1992. 3. Davis-Joseph B, Tiefer L, and Melman A: Accuracy of the initial history and physical examination to establish the etiology of erectile dysfunction. Urology 45: 498 –502, 1995. 4. Lue TF: Physiology of erection and pathophysiology of impotence, in Walsh PC, Retik AB, Stamey TA, and Vaughan ED Jr (Eds): Campbell’s Urology, 6th ed. Philadelphia, WB Saunders, 1992, p 709 –728. 5. Abelson D: Diagnostic value of the penile pulse and blood pressure: a Doppler study of impotence in diabetics. J Urol 113: 636 – 639, 1975. 6. Malvar T, Baron T, and Clark SS: Assessment of potency with the Doppler flowmeter. Urology 2: 396 – 400, 1973. 7. Karacan I, and Moore C: Nocturnal penile tumescence. An objective diagnostic aid for erectile dysfunction, in Bennett AH (Ed): Management of Male Impotence. Baltimore, Williams & Wilkins, 1982, pp 62–74. 8. Nseyo UO, Wilbur HJ, Kang SA, Flesh L, and Bennett AH: Penile xenon (133Xe) washout: a rapid method of screening for vasculogenic impotence. Urology 23: 31–35, 1984. 9. Lue TF, Hricak H, Marich KW, and Tanagho EA: Vasculogenic impotence evaluated by high-resolution ultrasonography and pulsed Doppler spectrum analysis. Radiology 155: 777–781, 1985. 10. Gall H, Bahren W, Scherb W, Stief C, and Thon W: Diagnostic accuracy of Doppler ultrasound technique of the penile arteries in correlation to selective arteriography. Cardiovasc Intervent Radiol 11: 225–229, 1988. 11. Shabsigh R, Fishman IJ, Quesada ET, Seale-Hawkins CK, and Dunn JK: Evaluation of vasculogenic erectile impotence using penile duplex ultrasonography. J Urol 142: 1469 – 1474, 1989.
UROLOGY 51 (1), 1998
12. Quam JP, King BF, James EM, Lewis RW, Brakke DM, Ilstrup DM, Parulkar BG, and Hattery RR: Duplex and color Doppler sonographic evaluation of vasculogenic impotence. AJR Am J Roentgenol 153: 1141–1147, 1989. 13. Benson CB, and Vickers MA: Sexual impotence caused by vascular disease: diagnosis with duplex sonography. AJR Am J Roentgenol 153: 1149 –1153, 1989. 14. Hwang TI-S, Liu PZ, and Yang CR: Evaluation of penile dorsal arteries and deep arteries in arteriogenic impotence. J Urol 146: 46 – 49, 1991. 15. Lopez JA, Espeland MA, and Jarow JP: Interpretation and quantification of penile blood flow studies using duplex ultrasonography. J Urol 146: 1271–1275, 1991. 16. Meuleman EJH, Bemelmans BLH, VanAsten WNJC, Doesburg WH, Skotnicki SH, and Debruyne FMJ: Assessment of penile blood flow by duplex ultrasonography in 44 men with normal erectile potency in different phases of erection. J Urol 147: 51–56, 1992. 17. Kropman RF, Van Oostayen JA, Zwinderman KH, Lycklama GA, Nijehold A, Schipper J, and Meinhardt W: Relation of intracorporal pressure and end-diastolic velocity during duplex Doppler sonography in the evaluation of venoocclusive dysfunction. Int J Impotence Res 6: 125–130, 1994. 18. Oates CP, Pickard RS, Powell PH, Murthy LNS, and Whittingham TAW: The use of duplex ultrasound in the assessment of arterial supply to the penis in vasculogenic impotence. J Urol 153: 354 –357, 1995. 19. Rhee E, Osborn A, and Witt M: The correlation of cavernous systolic occlusion pressure with peak velocity flow using color duplex Doppler ultrasound. J Urol 153: 358 –360, 1995. 20. Breza J, Aboseif SF, Davis BR, Lue TF, and Tanagho EA: Detailed anatomy of penile neurovascular structures: surgical significance. J Urol 141: 437– 443, 1989.
93
EVALUATION OF PENILE ULTRASONIC VELOCITOMETRY VERSUS PENILE DUPLEX ULTRASONOGRAPHY TO ASSESS PENILE ARTERIAL HEMODYNAMICS L. DEAN KNOLL
AND
JEROME H. ABRAMS
ABSTRACT Objectives. A prospective study was performed comparing duplex ultrasonography (DU) and ultrasonic velocitometry (UV), using a new fixed-angle device, in assessing penile arterial hemodynamics. Cavernous arterial peak systolic and end-diastolic flow velocities were measured. Methods. Twenty-four consecutive patients (mean age 47 years) underwent DU (Ultramark 9 HDI System) and UV (Knoll/MIDUS system) at the same setting by the same technician. After preinjection scanning, all patients received 60 mg of papaverine intracavernosally. Repeat scanning was performed at 5, 10, 15, and 20 minutes. Results. The statistical significance between the two techniques was assessed by examining the correlation. For all patients (n 5 24) and all velocity determinations in all patients (n 5 554), the equation for the linear regression line is y 5 0.952x 1 1.453, r 5 0.91 (r2 5 0.82) and P ,0.05. Conclusions. UV is as accurate as DU in measuring peak flow velocities of the cavernous artery. This new fixed-angle device is capable of identifying a vessel without real time imaging. UV is a safe, office-based procedure and scanning is less operator-dependent and easier to learn. UROLOGY 51: 89–93, 1998. © 1998, Elsevier Science Inc. All rights reserved.
E
rectile dysfunction (ED), defined as the inability to maintain an erection sufficient for satisfactory intercourse, has been estimated to affect 10 to 20 million men in the United States.1 Penile erection is a complex neurovascular phenomenon involving not only the coordination of three physiologic events (increased arterial flow, sinusoidal smooth muscle relaxation, and decreased venous drainage) but also the interaction of nerves, neurotransmitters, striated and smooth muscle, and the tunica albuginea.2 Despite a better understanding of the pathophysiology of erectile dysfunction, controversy remains regarding the optimal diagnostic evaluation and proper therapy. Goal-directed therapy, frequently used today, relies on a minimum diagnostic evaluDr. Knoll has a financial proprietary relationship with Urometrics, Inc. From the Center for Urological Treatment and Research, Nashville, Tennessee; and Department of Surgery, University of Minnesota, Minneapolis, Minnesota Reprint requests: L. Dean Knoll, M.D., The Center for Urological Treatment and Research, 2400 Patterson Street, Suite 101, Nashville, TN 37203 Submitted: May 30, 1997, accepted (with revisions): August 1, 1997 © 1998, ELSEVIER SCIENCE INC. ALL RIGHTS RESERVED
ation and stratification of all treatment options that are offered to the patient for selection. For some patients, particularly the younger aged group, a limited, specific diagnostic assessment may be appropriate, for it may identify a reversible or treatable underlying cause or an undiagnosed medical condition that may exist. Determination of etiology may affect prognosis or provide insight into risk factors. An understanding of etiology can help guide patients into appropriate acceptable therapy. For example, a patient diagnosed with severe arterial insufficiency will not be a suitable candidate for oral therapy or intraurethral pharmacotherapy. These patients can save money and avoid frustration by being directed into other more appropriate therapies such as an injection program, a vacuum device, or an implant. Initial history and physical examination alone have a low specificity in diagnosing organic ED. A comprehensive approach, including historical and physiologic factors, is required to evaluate fully and diagnose ED.3 For some patients, the differentiation between psychogenic and organic etiologies is of the greatest importance. For these patients, an etiology-directed evaluation may be necessary. This idea has 0090-4295/98/$19.00 PII S0090-4295(97)00493-7 89
been supported by the Society for the Study of Impotence’s position statement on the diagnostic evaluation of impotence. It states: Diagnostic studies used to identify the pathophysiology of impotence should be individualized for each patient. For the patient who wishes to identify the cause or causes of his erectile dysfunction as organic and/or psychogenic, nocturnal penile tumescence and rigidity (NPTR) monitoring, vascular and other testing may be indicated and useful, but the patient must be provided information permitting an informed decision to seek testing which is not essential to the selection of treatment options.
Clinical studies have shown that vascular problems are the most common cause of organic ED.4 Noninvasive evaluation procedures for the penile arterial system have included penile brachial index,5 Doppler pulse wave analysis,6 penile plethysmography,7 and xenon-133 (133Xe) penile washout study.8 Limitations of these tests are related to measurement of vascular function, when the penis is flaccid. These tests provide no diagnostic information about the dynamic process of erection. In 1985, Lue et al.9 introduced duplex ultrasonography (DU) with intracavernous pharmacologic stimulation as a noninvasive tool in the evaluation of penile circulation. Many investigators have reported that DU, in both impotent and potent patients, provides a functional assessment of penile blood flow and veno-occlusive function.10 –19 When indicated for select patients, DU is a useful diagnostic modality for etiology-directed therapy. It, however, has some limitations, including high cost of equipment and significant operator dependency. An ideal device for screening and diagnosis of ED would be office-based, relatively inexpensive, easy to use, and less dependent on the operator. We report the use of a new device that substantially satisfies these criteria, a new fixed-angle ultrasonic velocitometer. We used this device to measure cavernous arterial peak systolic and end-diastolic flow velocities in comparison with DU-generated peak flow velocities. MATERIAL AND METHODS PATIENT POPULATION Penile DU and penile ultrasonic velocitometry (UV), before and after intracavernous injection of papavarine, were performed on 24 consecutive patients who presented with a complaint of ED for 1 to 11 years (mean 3.0). These patients ranged in age from 32 to 60 years (average 47). All patients were evaluated with a detailed medical history, sexual questionnaire, and physical examination. Risk factors for ED in the study group are outlined in Table I. Measurements of serum blood chemistries, complete blood count, and testosterone levels were also performed. No patient had been previously diagnosed or treated for ED. 90
TABLE I. Risk factors for erectile dysfunction No. of Patients
Risk Factor Diabetes Hypertension Coronary artery disease Abdominal or pelvic surgery Hypercholesterolemia/hyperlipidemia Spinal cord disease, trauma Alcoholism (.5 ounces/day) Smoking (.15 cigarettes/day)
3 6 4 5 6 1 7 10
TECHNIQUE OF PENILE DUPLEX ULTRASONOGRAPHY DU was performed using the Ultramark 9 HDI ultrasound system (Advanced Technology Laboratories, Bothell, Wash) by the same technician. Patient position was supine, and the penis was placed with the dorsum exposed. The transducer was placed over the proximal dorsum of the penis near the base and initial scanning performed in the longitudinal and transverse planes. Baseline cavernous arterial peak systolic and end-diastolic flow velocities were measured near the base of the penis. Doppler angle was programmed to approximately 60°. Following the initial scan, 60 mg of papavarine (2-mL ampule) was injected intracavernosally with a 25-gauge needle. Digital pressure was applied to the injection site for 30 seconds to 1 minute. Gray scale and Doppler studies were repeated at the base of the penis at 5, 10, 15, and 20 minutes after injection, or sooner, if a full erection began. The same procedure for measuring velocities was used after injection, as before injection, such that each patient was his own control. If the patient did not achieve a full erection, he or his partner were asked to stimulate his penis privately to see if his erection improved. The patient was seen in the office 1 hour after the study to make sure detumescence of the penis occurred. If the patient had a full erection, aspiration of the corpus cavernosum alone or in combination with injecting small amounts of a 1:10,000 solution of epinephrine was used to achieve detumescence.
TECHNIQUE OF PENILE ULTRASONIC VELOCITOMETRY Penile UV was performed using the Knoll/MIDUS system (UroMetrics, St Paul, Minn). The scanning device contains a penile cradle which contains two movable fixed-angle (60°) ultrasonic transducers— one for each cavernous body. The carrying frequency of each transducer is 8 mHz in frequency and can measure blood velocities ranging from 1 to 200 cm/s. The transducers have a focal length of 1.2 cm. With the penis placed in the penile cradle, the transducers were moved laterally until the strongest cavernous signal was heard and visualized on the screen. Once the transducers were positioned, measurement of cavernous peak flow velocities was performed at the same times and location as for DU as described above. The Doppler signal was evaluated by graphing velocities as a function of time. A pointer was moved on the displayed graph to measure the peak flow velocity, systolic velocity, and enddiastolic velocity. This information was placed into the computer program of the analyzer by the technician and was later evaluated after the testing to determine all velocities. The ultrasound technician was blinded to this information; he was not allowed to visualize the peak systolic and end-diastolic velocities obtained by the penile ultrasonic velocitometer.
STATISTICAL ANALYSIS It should be emphasized that the design of the study was based on obtaining measurements of two variables, namely UROLOGY 51 (1), 1998
FIGURE 1. Comparison of velocity determinations for all patients between duplex ultrasonography (Ultramark 9) and ultrasonic velocitometry (Knoll/MIDUS).
measurement of cavernosal arterial peak systolic and end-diastolic flow velocities using the two methods described. The statistical significance between the two techniques was assessed by examining the correlation.
RESULTS Figure 1 shows the cavernous arterial peak systolic and end-diastolic flow velocities measured before and after injection with DU and UV for all patients (n 5 24) and all velocity determinations in all patients (n 5 554). The equation for the linear regression line is y 5 0.952x 1 1.453, r 5 0.91 (r2 5 0.82) and P ,0.05. Figure 2 shows typical results for a single patient. In this patient, arterial peak systolic and end-diastolic flow velocities are displayed for DU and UV. The equation for the linear regression line is y 5 0.999x 1 0.900, r 5 0.98 (r2 5 0.97), P ,0.05. COMMENT During the last decade, significant advances in our understanding of the hemodynamics of penile erectile physiology have been made, which have resulted in the identification of specific and potentially correctable vascular disorders. Since the probability of identifying a specific etiology of ED is obtainable today, many physicians and surgeons who treat patients with this disorder agree that a screening/diagnostic device is of great importance in selected younger patients. The ideal screening/ UROLOGY 51 (1), 1998
FIGURE 2. Comparison of velocity determinations in a single patient between duplex ultrasonography (Ultramark 9) and ultrasonic velocitometry (Knoll/MIDUS).
diagnostic device would have several characteristics: 1. Inexpensive and, consequently, able to be used in the office setting, where patients are initially evaluated 2. Easy to use and operator independent 3. Accurate over a wide range of velocities 4. Able to measure the time dependence of blood velocity 5. Able to make reproducible measurements to evaluate the effect of treatment over time Recent technologic advances in the field of ultrasound allow for the determination of the velocity of moving blood. Duplex ultrasonographic assessment of penile blood flow is one of the best screening tools currently available: it is relatively noninvasive, it is commonly found in hospitals, and it provides a functional assessment of the cavernous arteries.10 –19 It aids in selecting patients for penile angiography and cavernosometry/cavernosography and allows urologists to help patients differentiate between psychogenic and organic etiologies. Despite these apparent advantages, the use of DU as a tool to assess penile blood flow is controversial and limited. The necessary equipment is expensive and, in many medical centers, access is limited to radiologists or vascular surgery departments. The procedure is operator dependent: learning the technique can be difficult and time-consuming. Lack of standardization of testing and of reference values, psychologic aspects of testing, the timing of measurements during penile erection, location on the penis, where measurements are taken, and possible variations in arterial anatomy20 are other fac91
tors that can affect results with duplex ultrasound measurement. For the interested reader, detailed discussions of advantages and disadvantages of duplex ultrasound measurement have been reported in the urologic literature.10 –19 Peak flow velocity is the most commonly used ultrasonographic variable to evaluate the cavernous inflow tract. Although continuous wave Doppler is accurate, it suffers from limitations in identifying vessels. Real time imaging can help to identify vessels, but is not necessary and adds significant cost. Measurement of cavernous artery dilatation as an indicator of blood flow has reported limitations.16 The new fixed-angle transducer has solved the difficulties of vessel identification in a novel, cost-effective manner. The device is successful for two reasons: anatomy of the cavernous arteries and the use of a fixed range of focal length for each transducer. Although the origin and number of deep cavernous arteries shows marked variation, the intracavernous artery is more constant in number and in location.20 After the cavernous artery enters the hilum of the penis, it travels distally in the center of the corpora cavernosa to nearly the most distal extent. Combining a fixed range of focal length with the ability to measure blood velocity in the lateral corpora at the 2 o’clock and 10 o’clock positions, respectively (midline of the dorsum of the penis is defined as 12 o’clock), allows measurement of the cavernous artery velocities. That imaging of the cavernous arteries is not a necessary requirement allows the possibility of substantially reducing the cost of the screening device, as much as 3 to 8 times less expensive than conventional duplex scanning equipment. Patients who have atretic arteries, tortuous intracavernous arteries, branching of the cavernous arteries, or well-developed collaterals present difficulties for measurement for both the duplex Doppler device with imaging capability and the ultrasonic velocitometer. None of the patients in our study group presented with these anatomic variants. The ultrasonic velocitometer is easy to use and meets the second requirement of an ideal device for screening/diagnosis. The combination of the software and the cradle that positions the ultrasound transducers over the intracavernous arteries provides a fixed-angle and rapid adjustment. Throughout the entire study, except when a patient needs to stimulate himself, the transducers are stationary and require no manipulation by the operator. As a result, the measurements are operator independent, unlike DU, which requires an operator to hold by hand the scanning probe and program in the angle for each measurement taken. This procedure may result in variability of the angle of the ultrasound beam with respect to the blood velocity vector. 92
The ultrasonic velocitometer demonstrates excellent dynamic range, the third requirement of the ideal screening/diagnostic device. Figure 1 shows correlation over a range of blood velocities from 0 to 54 cm/s. The device is capable of measuring velocities up to 200 cm/s. In determining correlation, some points in Figure 1 require comment. In those patients in whom the response to intracavernous injection of papaverine is sustained, correlation is excellent as seen in Figure 2. In those patients in whom the response is transient, a limitation of the present study may be apparent. The differences in blood velocity measured by the two systems may be real. The arterial blood velocity may have changed in the length of time required to change from duplex ultrasonography to ultrasonic velocitometry, typically 75 to 90 seconds. The new fixed-angle ultrasonic velocitometer can provide the time dependence of blood velocity, the fourth requirement of the ideal screening diagnostic device. Additional diagnostic information may be obtainable regarding pathophysiology by studying the curve of velocity versus time for patients with different pathophysiologic mechanisms. An analogous situation is the flow versus time curves for pulmonary function tests. With improved understanding, the need for angiography, or other invasive tests, may be reduced. The study of time dependency of blood velocity using both procedures will be a subject for further investigation. The cradle that positions the ultrasound transducers with respect to the cavernous arteries provides reproducible positioning of the transducers. Blood velocities at different times in the course of treatment can then be compared and the efficacy of different treatments can be evaluated over longer intervals of time, the fifth requirement. CONCLUSIONS UV is of comparable accuracy to DU in measuring peak flow velocities of the cavernous artery. The ultrasonic velocitometer is capable of measuring, safely and accurately, blood velocities over a wide range. The fixed-angle device can identify the relevant arteries without real time imaging. It is simple to use and minimizes operator dependency. The cradle that positions the ultrasound transducers with respect to the blood velocity vector is stable and will allow for analysis of time dependence of the blood velocity after injection of intracavernous vasoactive agents. The fixed position will allow repeat measurements in the same patient and comparison of the effects of treatment. ACKNOWLEDGMENT. To David Howard, ultrasonographic technician, Department of Radiology, Centennial Medical Center, for his technical assistance. UROLOGY 51 (1), 1998
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