Biomedical subjects
Publications and source records attributed to J M Taveras.
The implementation of an oncologic diagnostic radiology subspecialty would provide better communication between the radiologist and the clinician and a greater opportunity to teach the general principles of therapeutic radiology. Practical aspects of the development of a section in oncologic radiology are discussed.
Fat density in the cavernous sinus on computed tomography (CT) is described in 6 out of 16 (37.5%) patients with Cushing disease. This finding may aid in making a specific diagnosis in patients with a pituitary mass. It was not seen in 30 random CT studies of the sella; however, parasellar fat was incidentally noted in one patient with acromegaly.
The present use of computers in radiology is reviewed. The major functions of a fully digital radiology department are described as (a) control and management, (b) image acquisition, (c) image distribution, (d) image interpretation, (e) image redisplay, and (f) image archiving. In addition, the benefits of a fully digital department and the problems that must be solved before it can be achieved are discussed.
A prospective study was performed for 48 patients who had histories of angina and were referred for digital subtraction angiography (DSA). Cardiac disease was graded according to the American Heart Association (AHA) functional classification system. Each patient received 2-5 injections of 40-ml diatrizoate meglumine and diatrizoate sodium (Renografin-76, Angiovist-370, or MD-76) at 15 ml per second in the superior vena cava. Of the 28 patients in functional Classes I or II (no or slight limitation of activity), 11% had angina and 32% had definite ischemic ECG changes after the DSA injections. Of the 19 patients in functional Class III (marked limitation of activity), 63% had angina, and 58% had definite ischemic ECG changes after the injections. One patient in functional Class IV (total disability) developed ventricular fibrillation after the second injection. These observed cardiac effects following bolus injections of hypertonic ionic contrast media indicate that special precautions are necessary when performing intravenous DSA examinations on this group of high risk patients.
One hundred and two patients, who were being evaluated for carotid artery disease, were prospectively studied for complications occurring as a result of intravenous digital subtraction angiography (DSA). We recorded the type, number, and outcome of complications and reviewed the amount of contrast material used, along with the patient's age and medical history for possible correlation with increased complications. There were 55 total complications or side effects involving 37 patients. Central nervous system (CNS) complications included six major-transient and one major-permanent complication. Systemic complications included 20 major-transient and two major-permanent events. The patient's age and the amount of contrast material used did not appear to be significant risk factors. Complications in our series were significantly higher than previous DSA reports and published data on conventional angiography studies. Many of our patients were in a relatively high risk group, including 74 patients who had multisystem disease and 30 who had histories of angina.
Intravenous digital subtraction angiography (DSA) was performed in 111 patients with vertebrobasilar ischemia. Ninety percent of the vertebral images were of diagnostic quality; 23% of the basilar images were good quality and 53% fair quality; and 58% of the posterior cerebral images were poor. Compared with selective film arteriography in 23 patients, DSA tended to underestimate the degree of atheromatous disease. Segments of the basilar artery were often poorly seen, which could result in false-negative errors. DSA can provide a general assessment of atheromatous disease of the brachiocephalic vessels, including the vertebral and carotid arteries, and in many cases can exclude occlusion or critical stenosis of the vertebrobasilar system. However, it does not adequately image the posterior cerebral or cerebellar artery.
Axial computed tomographic (CT) images were compared with sagittal and coronal reformations and myelograms in 60 patients to evaluate the diagnostic usefulness of multiplanar reconstructions for the recognition of lumbar disk disease. The axial CT scans were most sensitive and specific. The sagittal scans were helpful in evaluating the neural foramina, the size of the disk bulge into the spinal canal, especially at L5-S1, and patients with spondylolisthesis. The coronal images were the least informative, although they contributed to the evaluation of lumbar nerve roots. The myelograms and the sagittal images were equally useful in the detection of herniated disk, but axial scans were superior to either. It was concluded that reformatted sagittal and coronal images are not required if all axial images are normal. However, when uncertainty exists or complex anatomy is being evaluated, reformatted images may be helpful, particularly for reassurance.
The time course of the distribution of carbon-11 (11C, t1/2 = 20.4 min) in brain after the i.v. administration of 11C-labeled glucose [( 11C]glucose) was studied in an effort to understand and explore its behavior in relation to the known factors concerning the catabolic fate of glucose carbon in the brain. The biodistribution of 11C from [11C]glucose was studied in rats using organ dissection. Human radiation doses were estimated from rat biodistribution data. All the rat organs except the brain cleared with a half time of 30-60 min. The brain showed delayed uptake that plateaued from 20 to 60 min. The 11C distribution in normal, non-ischemic, brain 30 min after intravenously administered [11C]glucose is due to labeled carbon incorporation into amino acids associated with tricarboxylic acid cycle intermediates. External imaging with the Massachusetts General Hospital positron camera, PC I, was performed in dogs and humans and the time course of 11C incorporation was similar to the rat brain results. Regional uptake paralleled known metabolic differences between grey and white matter in normal human volunteers. A patient with progressive dementia had less uptake in an area of decreased perfusion as demonstrated angiographically, suggesting that the image obtained 20 min after tracer administration could be used to detect abnormalities in cerebral metabolism due to pathology.
Saturation recovery nuclear magnetic resonance (NMR) images and metrizamide computed tomography (CT) scans were obtained in an adult patient with a clinical history suggestive of syringomyelia. Both NMR and CT studies showed low lying cerebellar tonsils. The CT study demonstrated central cavitation of the spinal cord from the midthoracic to midcervical levels but could not exclude an intramedullary soft tissue mass at the cervico-medullary junction. The NMR images in transverse, coronal, and sagittal planes demonstrated extension of an enlarged central spinal cord cerebrospinal fluid space to the cervico-medullary junction. This was felt to be strong evidence for exclusion of an intramedullary soft tissue mass and in favor of a diagnosis of Arnold-Chiari Type I malformation with hydromyelia. The noninvasive nature of spinal cord and cervico-medullary junction evaluation with NMR is emphasized.
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.
The risks to patients with metal surgical implants who are undergoing nuclear magnetic resonance (NMR) imaging and the artifacts caused by such implants were studied. Twenty-one aneurysm and other hemostatic clips and a variety of other materials (e.g., dental amalgam, 14 karat gold) were used. Longitudinal forces and torques were found to be exerted upon 16 of the 21 clips. With five aneurysm clips, forces and torques sufficient to produce risk of hemorrhage from dislocation of the clip from the vessel or aneurysm, or cerebral injury by clip displacement without dislodgement were identified. The induced ferromagnetism was shown to be related to the composition of the alloys from which the clips were manufactured. Clips with 10-14% nickel are evidently without sufficient induced ferromagnetism to cause hazard. The extent of NMR imaging artifacts was greater for materials with measurable ferromagnetic properties, but metals without measurable ferromagnetism in our tests also resulted in significant artifacts. Dental amalgam and 14 karat gold produced no imaging artifacts, but stainless steels in dentures and orthodontic braces produced extensive artifacts in the facial region.
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 fast-clearing 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 CO2 reactivity. The data suggest that the progressive fall in flow gray is due to a physiologic aging process.
Explore the source record for details and available documents.
Regional brain physiology was investigated in 11 normal resting right-handed subjects using positron emission tomography. Cerebral blood flow was studied in all subjects. Cerebral oxygen metabolism was studied in six subjects, and cerebral glucose metabolism was also studied in one subject. In five subjects, physiological activity was higher in left frontotemporal regions than right. These findings may be related to structural cerebral asymmetries or to activation of brain language centers.
Explore the source record for details and available documents.
Initial results in over 50 patients with stroke suggest that positron images made during continuous inhalation of carbon dioxide labeled with oxygen 15 and molecular oxygen labeled with oxygen 15 provide data on tissue function that may be relevant to acute stroke management. Five cases illustrate the following findings: 15O-activity patterns observed in areas of ischemic injury or infarction are what one would expect if the 15O distributions represented physiologic functions, such as cerebral blood flow and metabolism. Areas of abnormal 15O activity correlate with the clinical or computed tomographic (CT) localization of the deficit. In studies performed acutely, changes in 15O distributions anticipate alterations in CT scans and may be predictive of outcome. Data related to oxygen metabolism correlate better with tissue viability than do those reflecting cerebral blood flow.
Cranial computed tomography (CT) scans were analyzed in five patients with autopsy documented intracranial aspergillosis. All infections occurred in immunocompromised hosts. Our findings included subtle low attenuation abnormalities, minimal mass effect, and poor contrast enhancement without ring configuration, in the clinical setting of lethargy, fever, and pulmonary infection. The benign CT picture did not clearly depict the aggressive intracranial parenchymal destruction.
A method for the production of thin axial transverse sections, coronal views, and sagittal views from overlapped thick computed tomography (CT) scans has been developed. Thin slices are produced by spatially filtering the overlapped CT data using a filter that is a combination of square waves in the spatial domain. Resolution recovery and noise properties have been examined in phantomas and patients for a selection of filter parameters. Sample results of these studies are presented. The method has been applied to data from several hundred patient studies. Several of these cases are shown to illustrate the method.