A comparison of three-dimensional time-of-flight magnetic resonance angiography (MRA) with B-mode and colorcoded Doppler ultrasonography (US) was made in 56 carotid arteries in 28 individuals (male 24 and female 4, age 64.5±7.2 years) . The degree of stenosis of the carotid arteries was classified as normal: 0-19%, mild: 20-39%, moderate: 40-59%, severe: 60-79%, critical: 80-99%, and occlusion: 100%. MRA showed two false-positive cases, one false-negative case and one undergraded case. US showed no false-positive and no false-negative case. MRA was relatively insensitive for detection of mild stenosis, but showed good correlation with US in detection of severe, critical stenosis or occlusion. Comparison of US with conventional angiography demonstrated 100% accuracy for carotid stenosis (sensitivity 100%, specificity 100% for stenosis) . Comparison of MRA with US demonstrated 95% accuracy for carotid stenosis (sensitivity 98%, specificity 96% for stenosis) . It was concluded, that the diagnostic pitfalls of MRA are artifacts caused by turbulent nonlaminar flow, flow separation, reversal of flow and motion. US is useful for interpreting intraplaque morphology and for detecting turbulence or vortex flow using color Doppler flow imaging. However, the major limitation of US is the difficulty in detecting plaques in the high cervical carotid area. This study suggests that combined use of MRA and US is accurate for detection and evaluation of carotid stenosis in patients with cerebrovascular symptoms.
To visualize the vascular anatomy of the brain, we have developed a system for producing three-dimensional (3D) color Doppler images from a series of two-dimensional color Doppler images. Two-dimensional images of cerebral vessels were digitized, and specially designed software reconstructed the 3D volumes and displayed volume-rendered images of the cerebral vessels during surgery for cases of aneurysm or arteriovenous malformation. Intraoperative 3D color Doppler images represented as cerebral vessels were successfully obtained from both of two patients. Especially in the patient with an aneurysm, 3D color flow images were equal in their displayed features to images obtained by CT angiography. We discuss the possibility of the applying ultrasound 3D imaging in patients with neurosurgical disorders.
A study was conducted to evaluate the relationship between ophthalmic artery (OA) color Doppler flow imaging (CDFI) and single photon emission computed tomography (SPECT) in ischemic cerebrovascular diseases. We examined 32 patients (mean age; 64 years) having ischemic cerebrovascular diseases, who underwent OA CDFI and SPECT within ten days. The OA CDFI findings showed a normal pattern in 3 patients, a sclerotic pattern in 9, a stenotic pattern in 11, and a reversed pattern in 9. SPECT showed severe hypoperfusion in 8 patients, moderate hypoperfusion in 8, mild hypoperfusion in 6, and normal perfusion in 10. Most of the cases with a normal and sclerotic pattern by OA CDFI showed normal or mild hypoperfusion on SPECT. Among the eleven patients showing the stenotic pattern, six (55%) showed normal or mild hypoperfusion on SPECT. The SPECT findings in the nine patients with the reversed pattern were severe or moderate hypoperfusion. Among the ischemic cerebrovascular diseases, the cases showing a normal, sclerotic, and reversed pattern by OA CDFI correlated well with the SPECT findings. OA CDFI should be performed with SPECT for a more precise understanding of intracranial hemodynamics.
Carotid duplex ultrasound and transcranial Doppler (TCD) monitoring during carotid endarterectomy (CEA) is described. The safety of this procedure is crucial in determining the value of CEA. Eight CEAs have been performed at our center since the introduction of power Doppler imaging (PDI) in duplex ultrasound. PDI visualizes intravascular morphology from the integrated power of the reflected echo, mainly from red blood cells, which delineates the hypoechoic plaque. We examined the extent of stenotic lesions and plaque morphology in this series of 8 cases. PDI is useful for depicting the stenotic vessel lumen and the extent of the lesion, especially in hypoechoic atheromatous plaque, whereas conventional color Doppler flow imaging is superior for demonstrating the flow pattern in the carotid artery. Although PDI enhances surface morphology and depicts rough structures, its image quality is not adequate for delineating the ulcerative plaque surface clearly. In two cases, the distal ends of the stenotic lesion were not demonstrated due to difficulty in applying the echo probe. TCD provides hemodynamic information on the cerebral hemisphere during and after CEA, and allows prompt correction of impaired cerebral perfusion. With the aid of noninvasive monitoring using duplex scanning and TCD, CEA can be performed with real-time information on vessel shape and blood velocity, thereby reducing perioperative cerebrovascular complications.
Cardiogenic embolism is one of the main causes of stroke. We analyzed the prevalence of microembolic signals (MES) in patients with recent cardiogenic embolism using a multigate technique. We examined 9 patients with cardiogenic embolism and 10 healthy controls, performing transcranial Doppler (TCD) monitoring from one middle cerebral artery using a 2-MHz probe of a multigated tanscranial pulsed Doppler system. The prevalence of MES was 22%. Most of the patients receiving antithrombotic therapy showed no MES. Two patients with acute stroke before initiation of therapy had no MES. In one of them, TCD detected no MES at 4 days after the onset of stroke, but another embolic stroke recurred only one day after TCD monitoring. All the healthy controls were free of MES. TCD was useful for confirming the stroke mechanism and for predicting individual prognosis in some patients. The prevalence of MES was not so high, and TCD did not always detect MES in patients with acute cardiogenic embolism. Recording for longer than 30 min, or on multiple occasions per patient will be necessary.
The history of ultrasound diagnostic equipment began with the A-mode machine. Nowadays, not only pulsed Doppler, but also color flow mapping can be done on a real time B-mode machine. The circuit of the ultrasound transmitter/receiver, the so-called beam former, will soon be digitized, and this will markedly improve its performance. The diagnostic ability of ultrasound equipment will be expanded to a wide range of applications, such as 3D display, clinical visualization of ultrasound contrast media, etc..