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.
