1984 Volume 24 Issue 8 Pages 545-556
Digitally controlled ultrasonography using a 5-MHz mini-sized, sector-scanning probe was performed in 21 cases of craniotomy, in 22 cases of burr-hole opening, and in 2 cases of laminectomy. The probe could be sterilized. The tip of the probe measured 17.8×19.6 mm. Among craniotomy cases, one small pituitary adenoma case and two small berry aneurysm cases failed visualization. Another adenoma and a large aneurysm were imaged. Ultrasound was helpful in 11 cases (52%), and most of them were supratentorial intraparenchymal masses, such as gliomas and intracerebral clots. In 5 of them puncture and/or biopsy was successfully performed under ultrasonic monitoring: 2 manually and 3 using a needle-guide apparatus and a guideline superimposed on the cathode-ray tube image. Maneuverability of the biopsy needle or forceps could be controlled, and no hemorrhage was encountered. The burr-holes were mostly conically enlarged using a Hudson No. 3 drill. Sterile echo-jelly was placed in the gap between the probe tip and the dural surface. Two targets were not visualized; one was an aneurysm and the other a cavernous sinus tumor. In 2 ventricular tappings through the hole, ultrasound showed both the direction and the depth of the target. In a case of brain abscess, two burr-holes were placed so that an ultrasonically monitored puncture could be performed using the needle-guide apparatus. The needle tip position could be adjusted accordingly with the gradual shrinkage of the capsule by aspiration. In 2 cases of laminectomy, the normal subarachnoid space was clearly exhibited. In a total of five cases, ultrasound was found not only helpful but in fact indispensable. However, several imperfections were noted: First, areas close to the probe could hardly be seen due to the near-field artifact. Second, the thickness of the ultrasonic beam limited image resolution in its direction. Third, the size of the probe was still larger than the diameter of a burr-hole. Finally, there were still image artifacts due to the sidelobe, reverberation, and acoustic enhancement, especially when metallic material was introduced into the ultrasonic field. In conclusion, electronic sector-scanning ultrasonography should become an indispensable tool in the neurosurgical operating theater in the near future.
