Juan M. Taveras

Computerized Axial Tomography with the EMI Scanner

The results of 300 computerized axial tomographic (CT scanning) examinations are reviewed. This new technique involves the use of an EMI brain scanner. The patients head is placed in a “cap” which projects into a water-containing box, and the head is scanned with a slit x-ray beam. A completed study consists of 28,000 absorption values which are analyzed by density. Certain physical properties of normal cerebral tissue and many pathological lesions, including gliomas, meningiomas, metastatic neoplasms, craniopharyngiomas, pituitary adenomas, and others, can be evaluated. The accuracy of CT scanning is exceptional. It is anticipated that this safe noninvasive method will decrease use of such techniques as cerebral angiography and pneumography.

Strategy for the Measurement of Regional Cerebral Blood Flow Using Short-Lived Tracers and Emission Tomography

This report describes a strategy for measurement of regional CBF that rigorously accounts for differing tracer partition coefficients and recirculation, and is convenient for use with positron emission tomography. Based on the Kety model, the measured tissue concentration can be expressed in terms of the arterial concentration, the rate constant K, and the blood flow f. The local partition coefficient may be computed as p = f/K. In our approach, maps of K and f are computed from two transverse section reconstructions. The reconstructions are based on weighted sums of projection data measured frequently during the observation period. Theoretical studies of noise propagation in the estimates of K and f were carried out as a function of tomographic count rate, total measurement time, and tracer half-life for varying input functions. These calculations predict that statistical errors in f of between 5 and 10% at a resolution of 1 cm full width at half maximum can be obtained with existing tomographs following i. v. injection. To compare theory and experiment, a series of flow studies were carried out in phantoms using a positron tomograph. These measurements demonstrate close agreement between computed flow and noise estimates and those measured in a controlled situation. This close agreement between theory and experiment as well as the low statistical errors observed suggest that this approach may be a useful tool in clinical investigation.

Cerebral blood flow and cerebrovascular CO2 reactivity in stroke‐age normal controls

We used the noninvasive 133-xenon inhalation technique to determine cerebral hemodynamics in 55 normal volunteers aged 18 to 88. Values for cerebral blood flow and cerebrovascular CO2 reactivity in fastclearing tissue (flow gray) and slow-clearing tissue (flow white) were examined as functions of age and in relation to hematocrit, blood pressure, and evidence of extracranial vascular disease. Flow gray declined linearly with age, but no corresponding change was found in flow white or in CO, reactivity. The data suggest that the progressive fall in flow gray is due to a physiologic aging process.

Estimation of the Local Statistical Noise in Emission Computed Tomography

A simple modification of the filtered backprojection algorithm is presented for the computation of the local statistical noise in emission computed tomography. The technique is general in that any distribution of radioactivity may be accommodated. When applied to positron emission tomography, it is shown that the effects of photon absorption, random coincidences, radioactive decay, and detector nonuniformity may be included. Calculations have shown the effects of resolution, object size, and photon absorption on the statistical noise of disk-shaped emitters. Comparison of calculation and experiment show close agreement both in magnitude and spatial variation. Measurements of the noise level in tomograms of the brain obtained during continuous inhalation of 150-CO2 demonstrate that estimates of radioactivity concentration with a precision of a few percent are readily attainable.

Diagnosis of epidermoid tumor by computed tomography. Analysis and evaluation of findings.

Primary intracranial intradural extraventricular epidermoid tumor may be suggested by the findings on computed tomography (CT), which is also useful during the follow-up period. Epidermoid tumors may exhibit minimal symptoms and have usually spread far beyond their original site by the time they are found. Early detection, delineation, and characterization are possible with CT.

The value of radiation therapy in the management of glioma of the optic nerves and chiasm.

The most common primary tumors of the optic nerves and chiasm are those which arise from the glial stroma of the visual pathways. Growth of the neoplasms is slow but the natural course is an extension of the process with the production of blindness and often death. Since optic nerve gliomas are encountered infrequently, the effect of various forms of treatment is difficult to assess. It is the purpose of this paper to report, in summary, the case histories of 34 patients with primary glioma of the optic nerves and chiasm and to evaluate the use of radiation therapy and surgery in their management. Incidence and Pathology Optic nerve gliomas are tumors of young people. They are not, however, closely related to the highly malignant retinoblastoma, which also is a disease of early life. Optic gliomas are relatively uncommon, constituting only 1 to 2 per cent of all glial new growths (Martin and Cushing, 11; Lundberg, 10). The 34 cases to be reported here occurred during a period when approximately 2,000 surg...

Computed Tomography of Herpes Simplex Encephalitis, with Clinicopathological Correlation

The computed tomographic (CT), clinical, and pathologic findings in 9 patients with biopsy-proven herpes simplex encephalitis (HSE) were reviewed. Seventeen scans (5 plain, 12 contrast enhanced) were analyzed. The major CT finding was a low-absorption abnormality, present in 11 of 17 scans (64%), affecting primarily the temporal lobes. Mass effect was evident in 9 of 17 (52%). Of the 12 contrast-enhanced scans, 6 (50%) showed an abnormal enhancement pattern affecting primarily the sylvian fissure and opercular areas. CT abnormalities are characteristic enough that, in the proper clinical setting, they lend support to the correct diagnosis.

Computed Tomography with the EMI Scanner in the Diagnosis of Primary and Metastatic Intracranial Neoplasms

The findings and diagnostic results in 600 examinations of primary and metastatic intracranial neoplasms performed at one hospital with the EMI scanner are presented and the effectiveness of this method is compared with that of radionuclide imaging, cerebral angiography, and pneumoencephalography. The computed scan proved to be highly reliable in the diagnosis of glioma, cerebral metastases, meningioma, and acoustic neuroma.

Evaluation of mucoceles of the paranasal sinuses with computed tomography.

Eighteen patients with mucoceles of the paranasal sinuses were studied by plain radiography, pluridirectional tomography, and computed tomography (CT). Sixteen of the lesions had a homogeneous appearance on CT but demonstrated variable absorption characteristics, with acutely infected mucoceles showing rim enhancement. Plain radiography and pluridirectional tomography were usually sufficient for making a diagnosis and defining the extent of the lesion, but CT more accurately demonstrated orbital and intracranial extension. Both transverse and coronal CT are essential for adequate evaluation.

Nuclear magnetic resonance (NMR) imaging of tumors in the posterior fossa.

Nuclear magnetic resonance (NMR) images were obtained in 12 patients with mass lesions in the posterior fossa and the results compared with X-ray computed tomography (CT). Inversion recovery T1-weighted images demonstrated abnormalities in six of six intrinsic lesions and three of six extrinsic lesions. Spin echo T2-weighted images demonstrated abnormalities in two of two intrinsic lesions and four of five extrinsic lesions. Saturation recovery T1-weighted images were normal in two of two intrinsic lesions and two of four extrinsic lesions. Overall, NMR detected 11 of 12 lesions. Two intrinsic tumors detected by NMR were not detected by CT evaluation. Two small extrinsic tumors required CT gas cisternography for detection.