Saul Aronow

Localized Cooling in the Brain

A slender refrigeration probe for the production of reversible discrete lesions within the central nervous system of man and experimental animals is described. Cooling, in the region of the third nerve nucleus in cats, produced pupillary dilatation which was quickly reversed when the temperature around the third nerve nucleus returned to normal.

Human and Ecologic Effects in Massachusetts of an Assumed Thermonuclear Attack on the United States

IN recent months public anxiety and confusion over the possibility and consequences of thermonuclear war have been increased and deepened by extensive (and often conflicting) publicity in newspaper...

[The use of computerized tomography in the detection of intra-orbital foreign bodies].

Use of the CT scanner as an instrument for foreign body detection and localization was explored under experimental conditions. The results show that a sufficiently dense radiopaque foreign body as small as 0.7mm3 can be detected and localized by presently available scanners.

Scanning with positron-emitting isotopes in cerebrovascular disease.

Most reports on brain scanning have been limited to the use ofthis procedure in the diagnosis of intracranial tumors. Relatively little attention has been directed towards its value in the assessment of patients with cerebrovascular disease. During the past 8 years more than 4,000 brain scans have been performed at the Massachusetts General Hospital using the positron-emitting isotopes 74As and 64CU. In this group there were 54 scans on 48 patients with confirmed diagnoses of aneurysm, arteriovenous malformation, subarachnoid hemorrhage or intracerebral hemorrhage (Table 1) and 146 scans of patients with a history and clinical findings which pointed to the likelihood of occlusive cerebral vascular disease, e.g. either the sudden onset of a neurologic deficit followed by stabilization or some degree of recovery, or transient attacks of neurologic deficit presumably on an ischemic basis (Table 2). The important findings are summarized in this report. Detailed analyses of our results are reported elsewhere (28, 29).

Performance Analysis of Imaging Systems

The ultimate performance test of an imaging system is its medical utility. This requires clinical use and evaluation of how well the system improves the delivery of health care. The radioactive source and the medium through which it travels, the collimator, detector electronics, and display system, comprise the major components that must be calculated in judging any imaging system. The subjective role of the observer and clinical physician interpreting and utilizing the information also must be considered in the overall scheme. A variety of qualitative and quantitative methods exist for analyzing the performance of imaging systems. Detectors deal with three interrelated properties which are resolution, sensitivity and observation time. Sensitivity measurements deal with counts per unit time obtained from a point or planar source placed a specific distance from the face of the detector system. Resolution measurements deal with the ability to discriminate between adjacent point or line sources. Full width at half maximum and modulation transfer function measurements of resolution are discussed in detail. Various types of geometric absorption, and anatomical phantoms are available to assist in making these determinations. In this review, attention is mostly drawn to the instrumental aspects of the system, since these are reasonably understood and somewhat controllable. However, the elements at opposite ends of the system, the biological mechanisms in the patients body, and the human observer using the information are really the most important, if least understood and controllable elements.