Gerontology 25 : 291 - 298 (1979)
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging R.R. Lewis, M.G. Beasley and R.G. Gosling Guy’s Hospital Non-Invasive Angiology Research Group, Clinical Science Laboratories, London
Key Words. Carotid arterial disease • Non-invasive ■Vessel-imaging system • Doppler-shift ultrasound • Spectral analysis Abstract. A non-invasive method for visualising the carotid bifurcation using continuous-wave
It is now well recognised that disease in the extracranial cerebral vessels is an important cause of strokes (Gunning et al., 1964; Hass et al., 1968). Although atheroma is often gener alised, it has a predilection for certain arterial sites and in arteries supplying the brain the most common site for disease is near the origin of the internal carotid (IC) artery, where it occurs in approximately 40% of patients with symptoms of ischaemic cerebro-vascular disease (Hassetal., 1968). The use of X-rays for visualising the cerebral arteries was first described by Moniz (1927), who exposed the carotid arteries surgically before injecting a bolus of contrast medium. Although carotid arteriography and arch aor
tography are now the standard methods for investigating arterial disease of these vessels, a number of complications may occur as a result of these investigations. Such complications have been assessed by Hass et al. (1968) in over 4,500 patients following arteriography for symptoms of cerebrovascular insufficiency. The overall mortality was 0.7%, and 0.5% developed severe hemiplegia. Less severe complications occurred in 5.3% of direct carotid punctures and in 14.3% of patients investigated by a retrograde catheter technique. An important complication of the catheter studies was occlu sion of the peripheral artery used for passing the catheter, which occurred in 10.7%. Nonirivasive techniques for investigating cerebro
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
Doppler-shift ultrasound and spectral analysis is described. The system is directional so that arteries can be visualised without interference by signals from adjacent veins. The technique uses a transducer attached to a position-sensing arm so that the position of arterial flow-velocities can be translated onto a storage oscilloscope. A two dimensional image of the carotid bifurcation is formed by moving the transducer along the length of each vessel while repeatedly scanning across the vessel lumen. The clinical application of this technique is illustrated by some specific cases.
Lewis/Beasley/Gosling
292
Materials and Methods The equipment was designed and built by members of the Guy’s Non-lnvasive Angiology Research Group and is described in detail elsewhere (Coghlan and Taylor. 1978). Continuous-wave ultrasound is used and the system basically consists of a focused trans ducer attached to a position-sensing mechanism and a 5-MHz directional Doppler-shift velocimeter, which
are connected to a spectrum analyser and processor (fig. 1). The transducer is placed on the skin and emits a narrow beam of ultrasound across the lumen of an underlying artery. The ultrasound causes erythro cytes within the beam to vibrate and backscattered signals are altered in frequency as a result of the Doppler effect. Erythrocyte velocities vary across the lumen and therefore a wide spectrum of Dopplershifted frequencies is backscattered at each instant and detected by the transducer. As the differences be tween the frequencies of the emitted and backscattered signals are within the audible range they can be monitored with a pair of headphones. They are also displayed by spectral analysis instantaneously on an oscilloscope screen (Coghlan et al., 1974) in the form of a sonagram (fig. 2). Sonagrams from the IC, ex ternal carotid (EC) and common carotid (CC) arteries each have a characteristic shape (fig. 2) so the ex aminer knows which artery is being imaged. The same backscattered ultrasound is also used to develop an image of the carotid bifurcation by utilis ing a mechanism which determines the position of the transducer on the neck. The system responds to the amplitude of backscattered signals and when blood flow is detected a bright spot is permanently registered on a second oscilloscope screen. To obtain a lateral view of the bifurcation the transducer is placed on the side of the neck as shown in figure 1. During the scan the transducer is moved vertically across the artery until no further signals are heard or seen on the spectral analyser display, so the examiner is then certain that the transducer has crossed the total vessel lumen. Vertical movements arc repeated along the length of the CC artery to the bifurcation, following which the IC and EC arteries are imaged. The system is directional and will therefore separate arterial from venous signals, so that when an artery is being visual ised venous signals are not incorporated onto the image. However, an image of a vessel in which blood is flowing in the opposite direction can be obtained if required. Each scan takes approximately 10-15 min.
Results
Disease of the carotid arteries is shown on the ultrasound image by interruptions in the continuity of the image outline and distortion
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
vascular disease have been developed to avoid the complications which occur using X-rays. However, most of these techniques are unable to demonstrate whether the disease is in the IC artery near the carotid bifurcation where it is accessible to surgery (Kartchner et al., 1973; Shapiro et al., 1970). The use of Doppler-shift ultrasound as a non-invasive method for investigating arterial disease has made considerable advances in recent years (Wells, 1969; Brockenbrough, 1970; Gosling, 1978). Brockenbrough (1970) described the classical Temporal Artery Occlu sion Test for detection of severe IC disease, but the main limitations of this test are that it is unable to: (1) detect lesions which do not cause a pressure drop, i.e. a stenosis of less than 60% of the vessel diameter (De Weese et al., 1970); (2) distinguish between complete occlusion and severe stenosis; (3) demonstrate whether the lesion is intra- or extra-cranial. We can now detect the presence of some smaller lesions by the use of a spectrally ana lysed Doppler-shifted ultrasound (Baskett et al., 1977). However, to effect 2 and 3 above, we believe that it is necessary to resort to vessel imaging. In 1972, Reid and Spencer connected an ultrasound transducer to a position-sensing device to enable an image of a vessel to be obtained. This paper is a report on a method of vessel imaging we have recently developed, which utilises continuous-wave ultrasound with spectral analysis.
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging
Case I The ultrasound image and carotid arterio gram from a 64-year-old woman who presented with transient ischaemic attacks are compared in figure 4. The ultrasound image clearly shows a small operable lesion near the origin of the IC artery, as seen in the arteriogram.
Fig. 1. The continuous-wave ultrasound imaging system. The insert shows the transducer/patient configuration for a lateral image of the carotid bifurcation.
Case II The ultrasound image and carotid arterio gram from a 20-year-old man are compared in figure 5. The patient had a severe traumatic injury to the neck, following which he devel oped a large haematoma in the neck and a dense hemiplegia affecting the opposite side of the body. Arteriography demonstrated a com pletely occluded 1C artery and at operation pulsations were felt in this artery after removal of the haematoma. There was initial improve ment in his symptoms but as severe weakness
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
of the spectral analysis display is often associ ated with these interruptions (fig. 3). The cases presented below illustrate some clinical uses of this non-invasive technique.
293
Fig. 2. Typical normal sonagrams from internal (a ), external (b) and common (c) carotid arteries for one heart beat. Sonagram format shows time on the x axis and Doppler-shift frequency on the y axis. The blackness of the trace at any point is related to the number of erythrocytes generating the same Dopplershift (i.e. moving at the same velocity). During systole there are two peaks. The internal carotid artery
Lewis/Bcasley/Gosling
can usually be distinguished from the external carotid artery by both the relatively higher second systolic peak and the higher diastolic flow-velocity level. Fig. 3. Sonagram illustrating turbulence: the nor mally smooth outline is fragmented due to sudden random increases in erythrocyte velocities (as shown by Basket! et al., 1977).
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
294
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging
was still present some weeks later an ultrasound image was requested. This showed that the IC artery remained totally occluded and thus avoided the need for further arteriography. The demonstration of this condition by ultrasound will usually avoid the need for an arteriogram as an endarterectomy is rarely performed. This case also illustrates the usefulness of re-assessing the carotid bifurcation by ultrasound without risk. Case III A 65-year-old man, who 5 years previously had a myocardial infarct, presented with tran sient ischaemic attacks. Sonagrams from the IC,
EC and CC arteries on both sides were dis torted. The ultrasound image and carotid arte riogram (lateral views) from the left side are compared in figure 6 and show the presence of multifocal disease in the carotid arteries. A similar picture was obtained on the right side. The demonstration of multifocal disease by ultrasound could obviate the necessity for an arteriogram as surgery is unlikely to be per formed in such cases.
Case IV A 49-year-old man, admitted with a myo cardial infarct, was found to have an asymp tomatic bruit in the neck. Distorted sonagrams were obtained near the origin of the EC artery and the ultrasound image demonstrated a severe lesion at this level (fig. 7). An arteriogram was
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
Fig. 4. Ultrasound image and carotid arteriogram showing disease of the internal carotid artery (lateral views).
295
296
Fig. 5. Ultrasound image and carotid arteriogram showing total occlusion of the internal carotid artery (lateral views).
not performed as disease was confined to the EC artery, and in the circumstances of this case surgery was not contemplated. Discussion
Much valuable information about the carotid bifurcation can be obtained by the use of this non-invasive technique and we have found this information can be used to affect patient management. The addition of an instantaneous sonagram display allows the examiner to know which carotid artery is being imaged. This is particularly important in either elderly patients or when disease is present, as in both these
situations the geometry of the carotid bifurca tion may be distorted. Furthermore, identifica tion of the artery being imaged is important when either the IC or EC is blocked. Spectral analysis also often demonstrates distorted flowvelocity patterns around an interruption in the image outline, thus helping to confirm the presence of disease. If the image is normal in a lateral view but distorted sonagramsare shown, then antero-posterior and oblique views can also be taken to visualise disease in a different plane by either turning the patients on their side or by altering the angle of the transducer. This technique of vessel imaging is capable of demonstrating all severe disease as well as some of the minor lesions, although the wave length of ultrasound is such that it is unlikely to diagnose lesions intruding into the lumen by less than 1 mm. However, the demonstration of
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
Lewis/Beaslcy/Gosling
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging
297
Fig. 6. Ultrasound image and carotid arteriogram showing generalised disease of the carotid arteries (as shown by Lewis et al., Stroke 9: 465-471, 1978).
severe lesions has an important application in the elderly, for such lesions are likely to reduce volume flow. It could therefore be argued that this non-invasivc investigation should be used in
Fig. 7. Ultrasound image showing disease near the origin of the external carotid artery (lateral view).
cerebro-vascular disease could be assessed by ultrasound without risk. If the ultrasound image suggests disease is present the patient may then proceed to arteriography and endar terectomy if clinically indicated. However, it is possible to envisage surgery being performed
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
elderly patients who are being considered for either a general anaesthetic or treatment with drugs which lower the blood pressure, for both may result in a stroke or mental impairment. Disease around the carotid bifurcation is an important cause of transient ischaemic attacks (Gunning et al., 1964; Fischer, 1959) and ap proximately 30% of patients with these attacks develop a stroke within 5 years (Toole et al., 1975). Patients suffering from transient isch aemic attacks or any other form of ischaemic
Lewis/Beasley/Gosling
without an arteriogram, for example a patient presenting with classical transient ischaemic attacks may undergo surgery following the demonstration of an operable lesion in the neck by ultrasound, provided that no intracranial pathology is shown by other investigations such as a brain scan or computerised axial tomog raphy. This non-invasive technique also has an application in the initial screening of any pa tient likely to have atheroma in the carotid vessels but with no symptoms of cerebro vascular disease, which includes those suffering from peripheral vascular disease, ischaemic heart disease, hypertension and hyperlipidaemia. It could therefore play an important role in the prevention of strokes.
Acknowledgements We are most grateful to the Medical Research Council for their financial support. We would like to thank the clinicians at Guy’s Hospital who allowed access to their patients and to personnel in the X-ray Department for their assistance. We gratefully ac knowledge the help given by fellow members of the Guy's Non-lnvasive Angiology Research Group and members of the Photographic Department.
References Baskett, J.J.; Beasley, M.G.; Murphy, G.J.; Hyams, D.E.. and Gosling. R.G.: Screening for carotid junction disease by spectral analysis of Doppler signals. Cardiovas. Res. 11: 147 155 (1977). Brockenbrough, E.C.: Pamphlet from the Information and Education Resource Support Unit of the Washington/Alaska Regional Medical Program (1970). Coghlan, B.A. and Taylor, M.G.: A carotid imaging system utilising continuous-wave Doppler-shift ultrasound and real time spectral analysis. Med. Biol. Engng Comp. 56/ 739 774 (1978). Coghlan, B.A.; Taylor, M.G., and King, D.H.: On-line display of Doppler-shift spectra by a new time compression analyser. Cardiovascular applications
of ultrasound; chapt. 5, pp. 56-65 (North Hol land, Amsterdam 1974). De Weese, J.A.; May, A.G.; Lipchik, E.O., and Rob, C.G.: Anatomic and haemodynamic correlations in carotid artery stenosis. Stroke 1: 149-157 (1970). Fischer, C: Observations of the fundus oculi in tran sient monocular blindness. Neurology, Minneap. 9: 333-347 (1959). Gosling, R.G.: Doppler ultrasound assessment of oc clusive arterial disease. Practitioner 220: 599-609 (1978). Gunning, A.J.; Pickering, G.W.; Robb-Smith, A.H.T., and Ross Russell, R. : Mural thrombosis of the internal carotid artery and subsequent embolism. Q. JIMed. 33: 155 193 (1964). Hass, W.K.; Fields, W.S.; North, R.R.; Krichcff, I.I.; Chase, N.E., and Bauer, R.B.: Joint study of extracranial arterial occlusion. 11. Arteriography, techniques, sites and complications. J. Am. mcd. Ass. 203: 961-968 (1968). Kartchner, M.M.; McRae, L.P., and Morrison, F.D.: Non-invasive detection and evaluation of carotid occlusive disease. Archs Surg., Chicago 106: 528535 (1973). Moniz, E.: L’encéphalographie artérielle: son impor tance dans la localisation des tumeurs cérébrales. Revue ncurol. 34: 72-90(1927). Reid, J.M. and Spencer, M.P.: Ultrasonic Doppler technique for imaging blood vessels. Science 176: 1235-1236 (1972). Shapiro, H.M.; Lawrence, N.G.; Mishkin, M., and Reivich, M.; Direct thermometry, ophthalmo dynamometry, auscultation and palpation in extra cranial cerebrovascular disease; an evaluation of rapid diagnostic methods. Stroke 1: 205 -218 (1970). Toole, J.F.; Janeway, R.; Choi, K.; Cordell, R ; Davis, G ; Johnston, F., and Miller, H.S.: Transient ischaemic attacks due to atherosclerosis. Archs Neurol., Chicago 32: 5 -1 2 (1975). Wells, P.N.T.: Physical principles of ultrasound diag nosis (Academic Press, London 1969). Received: December 4, 1978 Accepted: January 3, 1979 R. R. Lewis, Guy’s Hospital Non-lnvasive Angiology Research Group, Clinical Science Laboratories, 17th Floor, Guy's Tower, London SE1 9RT (England)
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298
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging R.R. Lewis, M.G. Beasley and R.G. Gosling Guy’s Hospital Non-Invasive Angiology Research Group, Clinical Science Laboratories, London
Key Words. Carotid arterial disease • Non-invasive ■Vessel-imaging system • Doppler-shift ultrasound • Spectral analysis Abstract. A non-invasive method for visualising the carotid bifurcation using continuous-wave
It is now well recognised that disease in the extracranial cerebral vessels is an important cause of strokes (Gunning et al., 1964; Hass et al., 1968). Although atheroma is often gener alised, it has a predilection for certain arterial sites and in arteries supplying the brain the most common site for disease is near the origin of the internal carotid (IC) artery, where it occurs in approximately 40% of patients with symptoms of ischaemic cerebro-vascular disease (Hassetal., 1968). The use of X-rays for visualising the cerebral arteries was first described by Moniz (1927), who exposed the carotid arteries surgically before injecting a bolus of contrast medium. Although carotid arteriography and arch aor
tography are now the standard methods for investigating arterial disease of these vessels, a number of complications may occur as a result of these investigations. Such complications have been assessed by Hass et al. (1968) in over 4,500 patients following arteriography for symptoms of cerebrovascular insufficiency. The overall mortality was 0.7%, and 0.5% developed severe hemiplegia. Less severe complications occurred in 5.3% of direct carotid punctures and in 14.3% of patients investigated by a retrograde catheter technique. An important complication of the catheter studies was occlu sion of the peripheral artery used for passing the catheter, which occurred in 10.7%. Nonirivasive techniques for investigating cerebro
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
Doppler-shift ultrasound and spectral analysis is described. The system is directional so that arteries can be visualised without interference by signals from adjacent veins. The technique uses a transducer attached to a position-sensing arm so that the position of arterial flow-velocities can be translated onto a storage oscilloscope. A two dimensional image of the carotid bifurcation is formed by moving the transducer along the length of each vessel while repeatedly scanning across the vessel lumen. The clinical application of this technique is illustrated by some specific cases.
Lewis/Beasley/Gosling
292
Materials and Methods The equipment was designed and built by members of the Guy’s Non-lnvasive Angiology Research Group and is described in detail elsewhere (Coghlan and Taylor. 1978). Continuous-wave ultrasound is used and the system basically consists of a focused trans ducer attached to a position-sensing mechanism and a 5-MHz directional Doppler-shift velocimeter, which
are connected to a spectrum analyser and processor (fig. 1). The transducer is placed on the skin and emits a narrow beam of ultrasound across the lumen of an underlying artery. The ultrasound causes erythro cytes within the beam to vibrate and backscattered signals are altered in frequency as a result of the Doppler effect. Erythrocyte velocities vary across the lumen and therefore a wide spectrum of Dopplershifted frequencies is backscattered at each instant and detected by the transducer. As the differences be tween the frequencies of the emitted and backscattered signals are within the audible range they can be monitored with a pair of headphones. They are also displayed by spectral analysis instantaneously on an oscilloscope screen (Coghlan et al., 1974) in the form of a sonagram (fig. 2). Sonagrams from the IC, ex ternal carotid (EC) and common carotid (CC) arteries each have a characteristic shape (fig. 2) so the ex aminer knows which artery is being imaged. The same backscattered ultrasound is also used to develop an image of the carotid bifurcation by utilis ing a mechanism which determines the position of the transducer on the neck. The system responds to the amplitude of backscattered signals and when blood flow is detected a bright spot is permanently registered on a second oscilloscope screen. To obtain a lateral view of the bifurcation the transducer is placed on the side of the neck as shown in figure 1. During the scan the transducer is moved vertically across the artery until no further signals are heard or seen on the spectral analyser display, so the examiner is then certain that the transducer has crossed the total vessel lumen. Vertical movements arc repeated along the length of the CC artery to the bifurcation, following which the IC and EC arteries are imaged. The system is directional and will therefore separate arterial from venous signals, so that when an artery is being visual ised venous signals are not incorporated onto the image. However, an image of a vessel in which blood is flowing in the opposite direction can be obtained if required. Each scan takes approximately 10-15 min.
Results
Disease of the carotid arteries is shown on the ultrasound image by interruptions in the continuity of the image outline and distortion
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
vascular disease have been developed to avoid the complications which occur using X-rays. However, most of these techniques are unable to demonstrate whether the disease is in the IC artery near the carotid bifurcation where it is accessible to surgery (Kartchner et al., 1973; Shapiro et al., 1970). The use of Doppler-shift ultrasound as a non-invasive method for investigating arterial disease has made considerable advances in recent years (Wells, 1969; Brockenbrough, 1970; Gosling, 1978). Brockenbrough (1970) described the classical Temporal Artery Occlu sion Test for detection of severe IC disease, but the main limitations of this test are that it is unable to: (1) detect lesions which do not cause a pressure drop, i.e. a stenosis of less than 60% of the vessel diameter (De Weese et al., 1970); (2) distinguish between complete occlusion and severe stenosis; (3) demonstrate whether the lesion is intra- or extra-cranial. We can now detect the presence of some smaller lesions by the use of a spectrally ana lysed Doppler-shifted ultrasound (Baskett et al., 1977). However, to effect 2 and 3 above, we believe that it is necessary to resort to vessel imaging. In 1972, Reid and Spencer connected an ultrasound transducer to a position-sensing device to enable an image of a vessel to be obtained. This paper is a report on a method of vessel imaging we have recently developed, which utilises continuous-wave ultrasound with spectral analysis.
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging
Case I The ultrasound image and carotid arterio gram from a 64-year-old woman who presented with transient ischaemic attacks are compared in figure 4. The ultrasound image clearly shows a small operable lesion near the origin of the IC artery, as seen in the arteriogram.
Fig. 1. The continuous-wave ultrasound imaging system. The insert shows the transducer/patient configuration for a lateral image of the carotid bifurcation.
Case II The ultrasound image and carotid arterio gram from a 20-year-old man are compared in figure 5. The patient had a severe traumatic injury to the neck, following which he devel oped a large haematoma in the neck and a dense hemiplegia affecting the opposite side of the body. Arteriography demonstrated a com pletely occluded 1C artery and at operation pulsations were felt in this artery after removal of the haematoma. There was initial improve ment in his symptoms but as severe weakness
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
of the spectral analysis display is often associ ated with these interruptions (fig. 3). The cases presented below illustrate some clinical uses of this non-invasive technique.
293
Fig. 2. Typical normal sonagrams from internal (a ), external (b) and common (c) carotid arteries for one heart beat. Sonagram format shows time on the x axis and Doppler-shift frequency on the y axis. The blackness of the trace at any point is related to the number of erythrocytes generating the same Dopplershift (i.e. moving at the same velocity). During systole there are two peaks. The internal carotid artery
Lewis/Bcasley/Gosling
can usually be distinguished from the external carotid artery by both the relatively higher second systolic peak and the higher diastolic flow-velocity level. Fig. 3. Sonagram illustrating turbulence: the nor mally smooth outline is fragmented due to sudden random increases in erythrocyte velocities (as shown by Basket! et al., 1977).
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
294
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging
was still present some weeks later an ultrasound image was requested. This showed that the IC artery remained totally occluded and thus avoided the need for further arteriography. The demonstration of this condition by ultrasound will usually avoid the need for an arteriogram as an endarterectomy is rarely performed. This case also illustrates the usefulness of re-assessing the carotid bifurcation by ultrasound without risk. Case III A 65-year-old man, who 5 years previously had a myocardial infarct, presented with tran sient ischaemic attacks. Sonagrams from the IC,
EC and CC arteries on both sides were dis torted. The ultrasound image and carotid arte riogram (lateral views) from the left side are compared in figure 6 and show the presence of multifocal disease in the carotid arteries. A similar picture was obtained on the right side. The demonstration of multifocal disease by ultrasound could obviate the necessity for an arteriogram as surgery is unlikely to be per formed in such cases.
Case IV A 49-year-old man, admitted with a myo cardial infarct, was found to have an asymp tomatic bruit in the neck. Distorted sonagrams were obtained near the origin of the EC artery and the ultrasound image demonstrated a severe lesion at this level (fig. 7). An arteriogram was
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
Fig. 4. Ultrasound image and carotid arteriogram showing disease of the internal carotid artery (lateral views).
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296
Fig. 5. Ultrasound image and carotid arteriogram showing total occlusion of the internal carotid artery (lateral views).
not performed as disease was confined to the EC artery, and in the circumstances of this case surgery was not contemplated. Discussion
Much valuable information about the carotid bifurcation can be obtained by the use of this non-invasive technique and we have found this information can be used to affect patient management. The addition of an instantaneous sonagram display allows the examiner to know which carotid artery is being imaged. This is particularly important in either elderly patients or when disease is present, as in both these
situations the geometry of the carotid bifurca tion may be distorted. Furthermore, identifica tion of the artery being imaged is important when either the IC or EC is blocked. Spectral analysis also often demonstrates distorted flowvelocity patterns around an interruption in the image outline, thus helping to confirm the presence of disease. If the image is normal in a lateral view but distorted sonagramsare shown, then antero-posterior and oblique views can also be taken to visualise disease in a different plane by either turning the patients on their side or by altering the angle of the transducer. This technique of vessel imaging is capable of demonstrating all severe disease as well as some of the minor lesions, although the wave length of ultrasound is such that it is unlikely to diagnose lesions intruding into the lumen by less than 1 mm. However, the demonstration of
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
Lewis/Beaslcy/Gosling
Disease at the Carotid Bifurcation: Diagnosis by Doppler Ultrasound Imaging
297
Fig. 6. Ultrasound image and carotid arteriogram showing generalised disease of the carotid arteries (as shown by Lewis et al., Stroke 9: 465-471, 1978).
severe lesions has an important application in the elderly, for such lesions are likely to reduce volume flow. It could therefore be argued that this non-invasivc investigation should be used in
Fig. 7. Ultrasound image showing disease near the origin of the external carotid artery (lateral view).
cerebro-vascular disease could be assessed by ultrasound without risk. If the ultrasound image suggests disease is present the patient may then proceed to arteriography and endar terectomy if clinically indicated. However, it is possible to envisage surgery being performed
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
elderly patients who are being considered for either a general anaesthetic or treatment with drugs which lower the blood pressure, for both may result in a stroke or mental impairment. Disease around the carotid bifurcation is an important cause of transient ischaemic attacks (Gunning et al., 1964; Fischer, 1959) and ap proximately 30% of patients with these attacks develop a stroke within 5 years (Toole et al., 1975). Patients suffering from transient isch aemic attacks or any other form of ischaemic
Lewis/Beasley/Gosling
without an arteriogram, for example a patient presenting with classical transient ischaemic attacks may undergo surgery following the demonstration of an operable lesion in the neck by ultrasound, provided that no intracranial pathology is shown by other investigations such as a brain scan or computerised axial tomog raphy. This non-invasive technique also has an application in the initial screening of any pa tient likely to have atheroma in the carotid vessels but with no symptoms of cerebro vascular disease, which includes those suffering from peripheral vascular disease, ischaemic heart disease, hypertension and hyperlipidaemia. It could therefore play an important role in the prevention of strokes.
Acknowledgements We are most grateful to the Medical Research Council for their financial support. We would like to thank the clinicians at Guy’s Hospital who allowed access to their patients and to personnel in the X-ray Department for their assistance. We gratefully ac knowledge the help given by fellow members of the Guy's Non-lnvasive Angiology Research Group and members of the Photographic Department.
References Baskett, J.J.; Beasley, M.G.; Murphy, G.J.; Hyams, D.E.. and Gosling. R.G.: Screening for carotid junction disease by spectral analysis of Doppler signals. Cardiovas. Res. 11: 147 155 (1977). Brockenbrough, E.C.: Pamphlet from the Information and Education Resource Support Unit of the Washington/Alaska Regional Medical Program (1970). Coghlan, B.A. and Taylor, M.G.: A carotid imaging system utilising continuous-wave Doppler-shift ultrasound and real time spectral analysis. Med. Biol. Engng Comp. 56/ 739 774 (1978). Coghlan, B.A.; Taylor, M.G., and King, D.H.: On-line display of Doppler-shift spectra by a new time compression analyser. Cardiovascular applications
of ultrasound; chapt. 5, pp. 56-65 (North Hol land, Amsterdam 1974). De Weese, J.A.; May, A.G.; Lipchik, E.O., and Rob, C.G.: Anatomic and haemodynamic correlations in carotid artery stenosis. Stroke 1: 149-157 (1970). Fischer, C: Observations of the fundus oculi in tran sient monocular blindness. Neurology, Minneap. 9: 333-347 (1959). Gosling, R.G.: Doppler ultrasound assessment of oc clusive arterial disease. Practitioner 220: 599-609 (1978). Gunning, A.J.; Pickering, G.W.; Robb-Smith, A.H.T., and Ross Russell, R. : Mural thrombosis of the internal carotid artery and subsequent embolism. Q. JIMed. 33: 155 193 (1964). Hass, W.K.; Fields, W.S.; North, R.R.; Krichcff, I.I.; Chase, N.E., and Bauer, R.B.: Joint study of extracranial arterial occlusion. 11. Arteriography, techniques, sites and complications. J. Am. mcd. Ass. 203: 961-968 (1968). Kartchner, M.M.; McRae, L.P., and Morrison, F.D.: Non-invasive detection and evaluation of carotid occlusive disease. Archs Surg., Chicago 106: 528535 (1973). Moniz, E.: L’encéphalographie artérielle: son impor tance dans la localisation des tumeurs cérébrales. Revue ncurol. 34: 72-90(1927). Reid, J.M. and Spencer, M.P.: Ultrasonic Doppler technique for imaging blood vessels. Science 176: 1235-1236 (1972). Shapiro, H.M.; Lawrence, N.G.; Mishkin, M., and Reivich, M.; Direct thermometry, ophthalmo dynamometry, auscultation and palpation in extra cranial cerebrovascular disease; an evaluation of rapid diagnostic methods. Stroke 1: 205 -218 (1970). Toole, J.F.; Janeway, R.; Choi, K.; Cordell, R ; Davis, G ; Johnston, F., and Miller, H.S.: Transient ischaemic attacks due to atherosclerosis. Archs Neurol., Chicago 32: 5 -1 2 (1975). Wells, P.N.T.: Physical principles of ultrasound diag nosis (Academic Press, London 1969). Received: December 4, 1978 Accepted: January 3, 1979 R. R. Lewis, Guy’s Hospital Non-lnvasive Angiology Research Group, Clinical Science Laboratories, 17th Floor, Guy's Tower, London SE1 9RT (England)
Downloaded by: East Carolina University - Laupus Library 150.216.68.200 - 1/13/2019 2:29:19 PM
298
