Ultrasound has been in use for the last three decades as a modality for medical diagnostic imaging. Recently, there have been numerous reports about the application of nonthermal ultrasound energy for targeting or controlling drug release. This new concept of therapeutic ultrasound combined with drugs has led to great excitement in various medical fields. Ultrasound energy can enhance the effects of thrombolytic agents, such as urokinase, and clinical trials of therapeutic ultrasound catheters for treatment of strokes are underway. Devices with ultrasound transducers implanted in transdermal drug patches for possible delivery of insulin through the skin are also being evaluated. Chemical activation of drugs by ultrasound energy for treatment of various cancers, such as brain tumors, is being studied. This new field was recently termed “Sonodynamic Therapy”. Various examples of ultrasound applications that could lead to revolutionary ultrasound therapies in the future are under investigation.
When undertaking diagnostic and treatment procedures for stroke patients, it is essential to evaluate vascular lesions at the extracranial and intracranial cerebral arteries and aortic arch and to look for underlying heart diseases. Ultrasonographic examination is particularly important in elderly or major stroke patients, because it is non-invasive and can be performed repeatedly at the bedside. Transesophageal echocardiography has been widely used for exploring embolic sources in the heart and aortic arch in young and cryptic stroke patients. It frequently demonstrates complicated atherosclerotic lesions in the aortic arch and right-to-left shunts in the heart or lung, such as patent foramen ovale, pulmonary arteriovenous fistula with concomitant pulmonary embolism and deep vein thrombosis shown by venous ultrasonography. Transoral carotid ultrasonography gives us additional information to conventional carotid ultrasonography about the vascular pathology of the distal portion of the extracranial internal carotid artery and a transpulmonary contrast medium, which has made it easy to assess intracranial vascular structures, is now available. Contrast harmonic imaging is a novel technique for observing the state of brain perfusion, but it needs further study. In conclusion, we recommend all stroke neurologists (strokologists) to become familiar with neurosonology for exploring the heart, aortic arch, extracranial and intracranial arteries and peripheral leg veins.
We examined the usefulness of ultrasonography, single photon emission computed tomography (SPECT) and neuropsychological function assessment pre- and postoperatively in 14 patients with occlusive cerebrovascular disease who underwent surgical revascularization. Two groups were analyzed: patients who underwent carotid endarterectomy (CEA; n=7) and extracranial-intracranial (EC-IC) bypass (n=7) . The mean flow velocity (MFV) and pulsatility index (PI) of the common carotid artery (CCA), internal carotid artery (ICA) and external carotid artery (ECA) were determined by spectral pulsed Doppler ultrasonography. The cerebral blood flow (CBF) in the affected frontal lobe under resting conditions and after acetazolamide loading was evaluated using SPECT. Neuropsychological function was assessed by carrying out the kana pick-up test, revised Hasegawa dementia scale (HDS-R) and mini-mental state examination (MMS) . In the CEA group, the proximal PI of the CCA was lower and the distal PI of the ICA was higher postoperatively than preoperatively. In the EC-IC bypass group, the PI values of the CCA and ECA were lower postoperatively than preoperatively. These findings showed hemodynamic improvement of the surgically revascularized carotid arteries. Twelve of the 14 patients showed postoperative improvements in their kana pick-up test scores and the CBF evaluated by SPECT. In conclusion, surgical revascularization improves hemodynamic insufficiency and neuropsychological function in patients with occlusive cerebrovascular disease. Follow-up study using ultrasonography is useful for evaluating hemodynamic changes in patients with cerebrovascular disease.
The authors describe the use of Intraoperative ultrasonography during anterior keyhole surgery without fusion in 165 patients with cervical spondylotic myelopathy. They comprised of 97 men and 68 women, aged 21 to 86. Intraoperative ultrasound demonstrated movements of the spinal cord at the cardiac rate, and delineated the configuration of the cord. The reference endpoint ndpoint for decompression to be satisfactory was (1) clear sagittal imaging of sufficient pulsation of the cord and (2) good axial configuration of the cord. Levels of decompression included 60 cases of one level decompression, 63 cases of two levels, 40 of three levels, and 2 of four levels decompression. The overall recovery rate indicated that 74 cases in “excellent” (45%), 64 in “effective”, 17 in “improved” (10%), 9 in “unchanged” (5.4%), 1 in “worse” (0.6%) . The excellent, effective, and improved results was obtained in the cases in which good pulsation was observed in Intraoperative ultrasonography. In the cases with unchanged and worse results, good pulsation was observed in 7 cases. In our study, the intraoperative ultrasonography was not used as a predictor of the postoperative improvement but as an indicator for Intraoperative good decompression. The satisfactory surgical results was obtained with acceptable morbidity. The real-time ultrasonography is more simple, no time-consuming, and low-cost examination, and is proved to be quite versatile and useful for Intraoperative monitoring of good cervical decompression.
In August 1999, an 81-year old woman suffered back pain, which gradually improved within 2 weeks. On the morning of January 7 2000, she was admitted to our hospital with speech disturbance. Magnetic resonance imaging (MRI) demonstrated a cortical infarct in her left frontal lobe. Transesophageal echocardiography (TEE) revealed an elevated lesion (2cm × 5cm) in the descending aorta, which had three oscillating flaps and two pseudolumens. Computed tomography (CT) showed severe calcification in the aortic wall, but no aortic dilatation near this lesion. This elevated lesion showed severe atherosclerotic changes and an intimal defect, but neither dilatation nor dissection of the aortic wall had occurred, suggesting the lesion was a penetrating atherosclerotic ulcer (PAU) . Hematological examination in August 1999 disclosed a hypercoagulable state (TAT 558 ng/ml, F1+2 8.6 nmol/l) . Three months after the onset of the cerebral infarction, the pseudolumen had expanded markedly. We consider that the presence of a PAU may be another risk factor for cerebral infarction.
The wave intensity (WI) is a new hemodynamic index, which is defined as (dP/dt) (dU/dt) at any site of the circulation, where dP/dt and dU/dt are the time derivatives of blood pressure and velocity, respectively. The WI provides information about the dynamic behavior of the heart and vascular system and the interactions between them. We have developed a new real-time system, based on a conventional color Doppler system, for measuring the WI. The blood pressure waveforms were obtained non-invasively from the arterial diameter-change waveforms by an echo-tracking method. Using a 7.5-MHz linear array probe, we obtained the carotid arterial WI and analyzed the characteristics of the cardiac and vascular interactions. The results suggest that this system has great potential and will be very useful in clinical practice.
Color flow imaging (CDI) is widely used for ultrasound diagnosis today. However the spatial and temporal resolution of CDI are expected to improve further. A new technique called B-Flow, which uses a pulse compression technique, extends the broadband resolution and high frame rate of B-mode ultrasonography for blood flow imaging. Since the intra-venous ultrasound contrast agent LevovistTM became available, several new contrast imaging methods have been proposed. Coded harmonic angio (CHA), developed by GE, provides an effective means of suppressing non-moving tissue signals and enhancing broadband contrast signals.