In brain tumor surgery, navigation is helpful for precise targeting of deeply seated lesions and important structures, and for performing accurate tumor resection. Intraoperative echo-guided surgery through a cranial window has been used for removal of tumors, arteriovenous malformations, and other pathological structures. The echo probe can be applied intermittently through the cranial window to visualize the operating field. Initially, very good images can be obtained, but during the operation the images deteriorate and become difficult to visualize. To obtain clear echo images without interruption of the surgical procedure, we created another small cranial window at the opposite side of the operating field, into which an echo-guiding probe was inserted. We were then able to produce clear images continuously until the end of the operation. The shifting of intradural structures caused by CSF drainage and/or reduction of the tumor mass was detectable in real time. This method also allowed clear evaluation of the relationship between the tumor and blood vessels. We used this method for 16 cases that involved large and deeply located brain tumors, including meningiomas, gliomas and pituitary adenomas, and were able to perform the required surgery safely, easily, and with a high degree of success. This method for continuous echo-guided surgery has already proved to be useful for the safe removal of brain tumors.
We studied eleven cases of intracranial tumor by contrast sonographic imaging using the pulse inversion harmonic imaging (PIHI) method and investigated its clinical usefulness. The patients comprised 5 males and 6 females, with an average age of 47.7 years. We examined the perfusion of the tumor through a temporal bone window (TBW), the tumor site or the brain surface. The instrument used for ultrasound sonography was HDI 5000 with a broad-band sector probe (P4-2). The probe was placed on the TBW (6 cases) or the brain surface (7 cases) at a slice level that gave a good image. The microbubbled contrast agent was injected into the right median cubital vein during an interval of 30 s. The frame rate was set to trigger images once every 2 cardiac cycles and to record for 3 min. In this way, we were able to obtain contrast sonographic images and transfer them to a personal computer. We analysed the images using HDILab and obtained the time intensity curves (TIC). Many TIC parameters have clinical significance. It was found that intracranial contrast sonographic imaging by PIHI provided clearer images than transcranial one Influenced by attenuation, especially through the TBW. The subtraction images showed clear discrimination of intracranial brain structures similar to that of CT and MRI.
The beneficial potential of ultrasound for neurosurgical procedures has been noted for decades. However, after intraoperative manipulations, many acknowledge that there are difficulties in obtaining high-quality images. Therefore, we analyzed the causes of these problems and possible measures to prevent them. Intraoperative ultrasonography (IOUS) was performed on patients with intracranial mass lesions using a convex-type ultrasound probe (7.5MHz). We performed mainly B-mode scan, and adjusted the imaging parameters when images were of poor quality. We obtained high-quality images with pre-procedural IOUS, but this became more difficult after surgical manipulation. We found that it was very important to position the head to allow filling of the skull with saline by rotation of the operation bed. Walls of cavities left after lesion removal by electrocoagulation and cottonoid coverings were the major causes of poor imaging of residual tumors. This problem was overcome by carrying out IOUS of residual tumors from the intact brain surface, rather than via the removal cavities. Adoption of these strategies made IOUS a very easy and useful intraoperative navigation tool.
We measured the size of the cerebral ventricles in 86 pre-term infants by ultrasonography every 2 to 3 months for one year. Their developmental quotients (DQ) were examined at the age of 1 to 2 years. Ventricular size in a control group of 50 normal full-term infants was also measured. The size of the cerebral ventricles in the full-term infants had increased by three months after birth, whereas that in the pre-term infants had increased not by chronological 3 months after birth, but by corrected 3 months of age. In the pre-term infants, the left ventricle was larger than the right at a few months after birth. However, there was no difference between left and right ventricular size in the normal full-term infants. Infants with a lower DQ had larger lateral ventricles. Although the sensitivity of ventricular enlargement as a predictor of mental development was 50%, the specificity was high.
We report the use of wavelet transformation for quantitative analysis of cerebral circulation, visualized as the Doppler flow velocity signal. One full-term and two preterm neonates without intracranial lesions were examined as normal subjects, and two neonates with asphyxia and one with viral myocarditis were examined as subjects with pathological conditions. All were treated in the NICU at Yamaguchi University Hospital. We sampled the Doppler signal at the anterior cerebral artery (ACA) and the basilar artery (BA) using a color Doppler unit (Aloka SSD 2200) with a 5-MHz sector probe. Color Flow Doppler images and Pulsed Doppler images were recorded on videotape. The Doppler sound on the videotape was uploaded into a personal computer as a digital signal and subjected to wavelet analysis with the Gabor 8 function φ(x) = exp(−x2/σ2)exp(ix) as the mother wavelet. In the normal neonates, wavelet analysis revealed strong components at levels 7 and 8 on the ACA; these components could not be disclosed on the BA. Two of the neonates with pathological conditions did not show any components at levels 7 and 8 on either the ACA or the BA; the remaining one showed very strong components on both the ACA and BA. The components at levels 7 and 8 in wavelet analysis with the Gabor 8 function may be useful markers of effective cerebral perfusion.