Measurement of regional changes in myocardial perfusion using dynamic computed tomography and contrast medium.

Changes in regional myocardial perfusion were measured using rapid sequence dynamic transmission tomography to detect differences in the initial distribution of contrast medium injected as an intravenous bolus. The experiments were carried out on 8 mongrel dogs instrumented with flow probes and vascular occluders around the coronary arteries. Flow reductions of 50 per cent or more were detected as regions of myocardium with less contrast enhancement than those with normal perfusion. Reactive hyperemia induced by transient ischemia was detected as areas of relatively increased contrast enhancement. These changes could be demonstrated on the images and quantitated using data depicting changes in HU (Hounsfield units) with time to develop an index of perfusion. The images obtained were of satisfactory quality and differences between the underperfused and normal myocardium were made more prominent by using dipyridamole infusions.

Giant intracranial aneurysms: rapid sequential computed tomography.

Giant intracranial aneurysms often present as mass lesions rather than with subarachnoid hemorrhage. Routine computed tomographic (CT) scans with contrast material will generally detect them, but erroneous diagnosis of basal meningioma is possible. Rapid sequential scanning (dynamic CT) after bolus injection of 40 ml of Renografin-76 can conclusively demonstrate an intracranial aneurysm, differentiating it from other lesions by transit-time analysis of the passage of contrast medium. In five patients, the dynamics of contrast bolus transit in aneurysms were consistently different from the dynamics in pituitary tumors, craniopharyngiomas, and meningiomas, thereby allowing a specific diagnosis. Dynamic CT was also useful after treatment of the aneurysms by carotid artery ligation and may be used as an alternative to angiographic evaluation in determining luminal patency or thrombosis.

Quantitative evaluation of the canine brain using computed tomography.

Methods have been developed for the quantitative evaluation of the canine brain using computed tomography (CT). Sixteen studies in 10 adult Beagle dogs were used to define the precision for densitometry and dynamic studies in the normal canine brain. For various regions of the brain, intraanimal and interanimal variability was determined for normal tissue CT number, contrast enhancement, and parameters relating to blood flow and blood volume. High precision was obtained for densitometry both within and among animals when evaluated over a 9 month period. Both intra- and interanimal variability in dynamic measurements was relatively large between studies, but hemispheric comparisons within a given study and between studies showed high precision. These methods can be used to evaluate morphologic and physiologic changes in the canine brain following radiation or other cytotoxic treatments.

Reformatted coronal display of upper abdominal computed tomography: comparison with ultrasonography.

The coronal plane is the most common format used for descriptions of the radiographic and surgical anatomy of the upper abdomen. Coronal reformatted computed tomographic (CT) studies of the upper abdomen were compared to coronal ultrasonic images of equivalent cephalocaudad dimension obtained with a water path echoscope. In most cases, the reformatted CT images were equivalent or superior in the display of selected mass lesions and their anatomic relationships. Direct coronal CT studies should be useful in the evaluation of upper abdominal pathology.

Dynamic computed tomography of the brain: techniques, data analysis, and applications.

Rapid sequence computed tomography (CT) scanning has many potential applications in studying intracranial physiologic events. However, visual inspection of these rapid sequence scans fails to extract the large amount of information inherent in the digital data. The concept of corrected mean transit time applied to rapid sequence scans after intravenous bolus injection of contrast material provides quantitative data on relative hemispheric flow. Use of histogram-based areas of interest permits accurate and reproducible identification of anatomic structures including arteries and gray and white matter. Gamma variate curve fit techniques reduce statistical noise. The concept of transit time can be expanded to the creation of functional CT images.

Detection and quantitation of myocardial infarction in vivo using transmission computed tomography.

In vivo studies were performed on 28 dogs to evaluate the usefulness of transmission computed tomography (CT) in the detection and quantitation of experimentally induced myocardial infarction. Intravenously administered contrast material was required to define the internal structure of the heart and to differentiate normal from infarcted tissue. Transmural infarcts with homogeneous central regions were visualized as areas of diminished contrast enhancement compared with the normal myocardium. All transmural infarcts of at least 24 hours' duration showed a surrounding border zone of patchy necrosis that was variable in size and had high CT numbers due to slow washout of the contrast material from this region. Infarct area determined from the images for individual slices correlated well (r = 0.976) with that calculated using pathology. The technique is very sensitive and can detect infarction within a papillary muscle. Nontransmural or patchy infarcts show up as areas of diffuse contrast enhancement without a central core of diminished enhancement. The distribution of the contrast material is similar to that of technetium-99m pyrophosphate in the border zone of the infarct in infusion studies, but in bolus studies it behaves more like thallium-201.

Functional imaging of the brain using computed tomography.

Data from rapid-sequence CT scans of the same cross section, obtained following bolus injection of contrast material, were analyzed by functional imaging. The information contained in a large number of images can be compressed into one or two gray-scale images which can be evaluated both qualitatively and quantitatively. The computational techniques are described and applied to the generation of images depicting bolus transit time, arrival time, peak time, and effective width.

CT of the lumbosacral spine: importance of tomographic planes parallel to vertebral end plate.

An experimental computer program capable of reformatting stored display data from a CT scanner into true cross-sectional images of the spine has been clinically tested over a 1 year period. With this program, tomographic planes exactly parallel to the vertebral end plate can be imaged at the lumbosacral level even in patients who are markedly rotated or have scoliotic deformities. The reformatted image planes are tilted in the dorsoventral and mediolateral directions to compensate for lordosis or scoliosis. The reformatting can also produce images in coronal and sagittal planes on axes other than true horizontal or vertical. The program has been used in the examination of 269 spines and has been found to be valuable in demonstrating the spinal canal and the intervertebral foramina.

Myocardial infarction in dogs, demonstrated by non-enhanced computed tomography.

The capability of non-enhanced and enhanced CT scanning of the heart without ECG gating to detect myocardial infarction in living dogs was explored. CT findings were correlated with those at post mortem. In large transmural infarctions, areas of lower attenuation were detected without contrast medium enhancement and appeared as defects when intravenous contrast medium was administered. The infarct size as estimated on each CT scan correlated closely with post mortem values.

Detection of patent coronary bypass grafts by computed tomography. A preliminary report.

Twenty-three coronary bypass graft patients were evaluated by a contrast-enhanced computed tomography (CT) technique to determine graft patency. Four to six 4.8-second sequenced scans with a 1-second interscan interval were obtained in each patient during the hand injection of 25-30 ml of contrast medium in a peripheral vein. Patency of grafts was determined by a characteristic contrast enhancement. The CT technique correlated with angiographic assessment of graft patency in 59 of 62 grafts (95%). We conclude that this relatively noninvasive technique shows promise as a method for determining coronary bypass graft patency.

[Experience with computed transmission tomography of the heart in vivo]. / Erfahrungen mit der Computer-Tomographie bei der in vivo-Herzdiagnostik.

Cardiac computed tomography in its present form provides useful information about the heart for clinical use in patients with heart disease and for investigative work in such patients and living animals. Its great reconstructive power and unmatched density resolution are particularly advantageous in the study of ischemic heart disease. Because of its non-invasive character cardiac computed tomography has the potential of becoming an effective screening tool for large numbers of patients with suspected or known coronary heart disease. Other cardiac conditions such as valve disease and congenital lesions can also be examined with high diagnostic yield. However presently available scanners suffer from low repetion rate, long scan times and the fact that only one transverse cardiac level at a time can be obtained. The development which must be accomplished in order to eliminate these weaknesses is technically feasible. The availability of a dynamic cardiac scanner would greatly benefit the treatment of patients with heart disease and facilitate the inquiry into the pathophysiology of such diseases.

Evaluation of brain circulation by rapid rotational computed tomography.

Continuous rapid rotational CT brain scanning now permits the study of brain circulation. The parameters studied are related to the transit time of circulation and to blood flow differences within small portions of the brain. For ease of description, this study is called regional brain circulation (rBC). This preliminary report is based on our experience with 75 consecutive cases studied since August 1, 1978. Displays of normal brain, cerebral ischemia, and arteriovenous malformations are analyzed in this paper. The normal graphic display of rBC includes peak concentration, transit time, washin and washout phases. Clinical application to medical-surgical treatment is illustrated.

Gated cardiac scanning: canine studies.

Retrospective electrocardiograph gating of data from a rotating detector fan beam computed tomography system was employed to produce end systolic and end diastolic images of the beating heart in a series of normal and experimentally infarcted canines. The gating window was typically less than 20% of the cardiac cycle, and the gated images showed superior spatial resolution compared with ungated images of the same cross section. Comparison of the scans of the normal and of the infarcted animals shows abnormal contrast enhancement of the myocardium in the region of the infarct, and the gating studies demonstrate dyskinetic behavior of the infarct zone.