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Phantoms designed to simulate cysts or avascular masses and other material encountered in computed tomographic (CT) body and head scanning were used to evaluate the effect of beam hardening in a GE CT/T 8800 scanner. The phantoms were scanned before and after the addition of iodinated contrast material to various compartments within the phantoms. The results indicate that in general the addition of contrast material in the CT body phantom resulted in a decrease in the CT numbers recorded from the cyst phantoms. Conversely, the addition of contrast material in a concentric peripheral cylinder (simulating the addition or presence of the calvarium in CT head scanning) resulted in a generalized inhomogeneous increase in CT numbers of specimen materials contained in that ring.

Intraoperative ultrasound (US) was compared to computed tomography (CT) in 41 intracranial and 6 spinal cord tumors. The studies correlated closely except for primary gliomas. Eight of the 22 primary intracranial gliomas (37%), including 1 low-grade and 7 anaplastic tumors, were larger and more extensive on US than on CT. Margins of non-enhanced primary astrocytomas were shown by US but not CT. Four anaplastic tumors (19%) exhibited echogenicity extending beyond the enhanced area. In 4 patients an enhanced lesion contained a lucent center which proved to be echogenic. Low-grade astrocytomas were relatively homogeneous on US, while anaplastic astrocytomas were more inhomogeneous. Cysts could be found in both types of astrocytomas and were often small and multiple. The echo pattern was not helpful in differentiating metastases from primary tumors, although all of them had sharp margins. Sonography of the central nervous system can provide valuable information about tumor morphology and margins.