Recently highlighted topics in maternal and fetal neurosonology are as follows:
1. Material ophthalmic artery Doppler blood flow vclocimetry in pre-eclampsia, pregnancy with intrauterine growth restriction, and pregnancy with type I diabetes mellitus.
2. Normal embryonic brain anatomy wing intrauterine sonography with a 20-MHz flexible catheter-based, high-resolution, real-time miniature transducer and three-dimensional sono; graphic visualization of the normal cmbryo.
3. Fetal cerebral artery Doppler blood flow celocimetry in normal and multiple pregnancies, and fetuses is-ith CNS anomaly.
4.3D sonography in normal and abnormal fetuses.

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Transcranial sonography is anticipated to be a convenient method for clinical diagnosis, and evaluation of therapeutic progress. Another modality, three-dimensional power Doppler (also known as 3-dimensional color power angio: 3D CPA), is now being used to visualize intracranial vascular structures in a similar way to cerebral angiography.
Recently, there have been some reports on the detection of cerebral aneurysms by transcranial sonography with the use of contrast medium, although this approach is not good enough for clinical diagnosis. However, we have used this method mainly for detecting intraoperative vascular structures, especially cerebral aneurysms, and found that the results have been as good as intraoperative angiography.
Another modality is transcranial harmonic imaging using gastrointestinal area that has been suggested to be useful for diagnosis of cerebral ischemic diseases and brain tumors. Postert and Seidel have already reported the application of this method for studying normal volunteers and patients with cerebral infarction at the early stage. Thus it is anticipated that transcranial sonography may be as useful as CT, MRI and cerebral angiography for intracranial imaging diagnosis. In the future, transcranial sonography may be used for intracranial diagnosis of conditions such as cerebral aneurysm, cerebral ischemic disease, and brain tumors. However, this method has several imaging characteristics and technical problems. One is variability of the slice level. Our method of transcranial sonography is restricted to a temporal bone window and sometimes a frontal bone window. Furthermore, the size of the bone window varies among different patients, so the images obtained change according to the patient and the degree of ultrasound attenuation through the bone. Furthermore the examiners using this technique need to be experienced and skillful. Because of these problems, transcranial B-mode imaging has been mainly employed.
Standard images obtained with transcranial sonographic B-mode have not been reported up to now. The further development of transcranial sonographic instruments should make it possible to obtain intracranial images showing anatomical structures, such as the third ventricle, midbrain, lateral ventricle (anterior, posterior and inferior horns, body), cistern, and intracranial bone structures, allowing correct understanding of intracranial position by transcranial sonography. This will undoubtedly be useful for further clinical application to intracranial diseases. It is anticipated that this report will be helpful for interpreting transcranial sonographic images.

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The significance of Intraoperative ultrasound (US) monitoring during foramen magnum decompression (FMD) was studied in five patients. Two of the patients had Chiari type I malformation with syringomyelia, one had Chiari type I malformation with hydrocephalus, and two had stenosis of the foramen magnum (Chiari type I malformation with basilar compression and achondroplasia) . Intraoperative ultrasound examinations were performed with a linear array real-time unit (ALOKA Corporation, Japan) equipped with a 7.0-MHz transducer. In four of the patients, re-establishment of cerebrospinal fluid flow was clearly demonstrated. One patient with hydrocephalus revealed adhesion at the foramen of Magendie. Neurological symptoms and signs improved in four of the five patients and were unchanged in one patient with obstructive hydrocephalus. The most important ultrasound findings during Intraoperative us monitoring were clear demonstration of the subarachnoid space at the cisterna magna, pulsation of the cerebellar tonsil, and cerebrospinal fluid flow in the foramen of Magendie. We conclude from this study that Intraoperative us monitoring during FMD is necessary for following the clinical progress.

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To establish an objective method for assessment of carotid artery lesions depicted on B-mode ultrasonography, semiquantitative findings, analysed and evaluated by computer, were compared with the histological findings of endarterectomy specimens. Seven carotid artery lesions in 5 patients with carotid stenosis were examined preoperatively by B-mode ultrasonography, and these images were incorporated into a computer by a scanner using Adobe Photoshop software. The echogenicity of all pixels included in the lesion and optional areas of both muscle tissue and the vascular lumen was measured, and the mean values and histograms of echogenicity from zero to 255 density levels were determined. Based on the shape of the histogram, the lesions were classified into 3 types: hyperechoic (H) and echolucent (L) types, which showed a monopeak or skewed distribution curve but in which the curve did not reach the abscissa on at least one side, and the mixed (M) type, in which the curve extended near the abscissae on both sides. The H and M types, which have an adjusted mean echogenic value greater than the mean plus 1 standard deviation of muscle tissue, showed calcification or organized hyaline fibrosis. In contrast, the L type showed atheroma consisting of lipid deposition, necrotic tissue, cellular infiltration, and hemorrhage. These findings indicated that the histogram and echogenicity of carotid artery lesions analyzed by a computer could provide objective evaluation comparable to visual subjective assessment of the lesion.

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We report a case of reversed vertebral artery blood flow in a patient with hemodialysis arteriovenous fistula. The patient was a 65-year-old woman who had been diagnosed as having chronic glomerulonephritis and hypertension at the age of 42. The arteriovenous fistula for hemodialysis had been made in her left arm when she was 62 years old. We carried out initial Doppler sonography vascular evaluation of the neck in June 1999. This showed that blood flow in the vertebral arteries was antegrade bilaterally with a maximum flow velocity of 73.0 cm/s in the right and 42.6 cm/s in the left. We re-evaluated the patient in January 2001 and found that the blood flow was retrograde in the left vertebral artery, with a maximum flow velocity of 60.7 cm/s. During compression of the left brachial artery, the left vertebral artery flow became antegrade. The patient had no signs or symptoms suggesting vertebrobasilar insufficiency.
We consider that the reversed left vertebral flow in this case was a subclavian steal phenomenon caused by the arteriovenous fistula in the patient's arm. We suggest that Doppler evaluation of vertebral artery blood flow is useful in patients with arteriovenous fistulas for hemodialysis.

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The correlation between continuity of cerebral blood flow velocity (CBFV) pattern (internal carotid artery) and cerebral vascular resistance, indicating cerebral arteriosclerosis (CA), was investigated by the ultrasonic Doppler technique. A significant correlation between continuity of the CBFV pattern and the severity of CA was recognized: the greater the decrease in continuity of the CBFV pattern, the greater the severity of CA. In a previous study, the continuous index (CI) of the CBFV pattern was devised as an objective parameter of the continuity of the CBFV pattern for evaluating cerebral hemodynamics in CA. Pulsatility index (PI) and resistance index (RI) are similar in nature to the CI. These parameters are useful as objective indexes of cerebral vascular resistance, indicating CA, particularly of the arteriole. Among these parameters, PI seems to be more useful clinically than CI and RI. Criteria for the quantitative detection of CA, particularly of the arteriole, are proposed by calculation of the PI.

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