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J M Taveras

Publications and source records attributed to J M Taveras.

At least 19 recordsLinked to original sources
PubMed1991

Past, present, and future of radiology of meningioma.

The evolution of the radiologic findings associated with meningiomas represents a microcosm of the evolution of diagnostic radiology that has occurred since the discovery by Röntgen of the x-ray beam in 1895 and the founding of the Radiological Society of North America in 1915. What will the next new, as yet unimagined, imaging modality contribute to our current ability to detect and diagnose these lesions? No one can forecast this, but it should prove to be both fascinating and challenging.

Brain Neoplasms↗
PubMed1991

Abnormal corpus callosum: a sensitive and specific indicator of multiple sclerosis.

The authors investigated whether identification of corpus callosal (CC) involvement might increase the specificity of magnetic resonance (MR) imaging in differentiating multiple sclerosis (MS) from other periventricular white matter diseases (PWDs). They prospectively evaluated 42 patients with MS and 127 control patients with other PWDs. Ninety-three percent of the MS patients demonstrated confluent and/or focal lesions involving the callosal-septal interface (CSI). These lesions characteristically involved the inferior aspect of the callosum and radiated from the ventricular surface into the overlying callosum. CSI lesions were optimally demonstrated on sagittal long repetition time (TR)/short echo time (TE) images and frequently (45% of cases) went undetected on axial images. Only 2.4% of the control patients had lesions of the CC. The authors conclude that midsagittal long TR/short TE images are highly sensitive and specific for MS and that callosal involvement in MS is more common than previously reported.

Adult↗
PubMed1989

Wallerian degeneration after cerebral infarction: evaluation with sequential MR imaging.

The dynamic signal intensity changes at magnetic resonance (MR) imaging in active and chronic wallerian degeneration in the corticospinal tract were evaluated. Forty-three patients with wallerian degeneration seen on MR images after cerebral infarction were studied. When possible, patients with acute stroke were examined with MR imaging prospectively at the onset of symptoms and then at weekly intervals for several months. Focal infarction without distal axonal degeneration is demonstrated for the 1st month following onset of clinical symptoms. At 4 weeks, a well-defined band of hypointense signal appears on T2-weighted images in the topographic distribution of the corticospinal tract. After 10-14 weeks, the signal becomes permanently hyperintense. Over several years, accompanying ipsilateral brain stem shrinkage occurs. The dark signal intensity observed on T2-weighted images between 4 and 14 weeks is believed to result primarily from transitory increased lipid-protein ratio.

Adult↗
PubMed1986

Assessment of ventricular shunt patency by sonography: a new noninvasive test.

This report describes a new test of patency of the ventricular component of a ventriculoperitoneal shunt that precludes injection into the shunt reservoir. Preliminary clinical experience confirms that digital compression of the ventricular shunt reservoir (Cordis standard and pediatric reservoir), while occluding the shunt distal to the reservoir, generates microbubbles that increase the echogenicity of the catheter, demonstrating shunt patency. In vitro, the extrusion of microbubbles from catheter side holes can be imaged during digital compression of the reservoir, but so far this has not been imaged in patients as a direct sign of shunt patency. A sonographic means of assessing shunt function offers the advantage of simultaneously imaging the ventricular catheter, determining its location, and assessing the etiology of shunt failure. Its usefulness is limited to pediatric cases in which an adequate transfontanelle cranial sonographic study can be obtained and to individuals with large craniotomy defects.

Adolescent↗
PubMed1984

Positron imaging in ischemic stroke disease.

Positron emission tomography (PET) is well suited to the study of ischemic stroke disease. It has the potential to help elucidate pathophysiological mechanisms, differentiate viable from nonviable tissue, and provide a more rational basis for developing specific therapies for ischemic lesions. The different tracer strategies that may be applied to the study of ischemic disease, however, all have relative limitations, which may be related to the physical or biological determinants of the tracer distributions, to the tracer half-lives, or to the methods required for quantitation of the data. Determination of blood flow and oxygen metabolism are useful for characterizing stroke lesions, but other parameters, such as the oxygen extraction fraction, blood volume, and glucose metabolism, can provide important interpretative information. Correlation of the physiological PET data with the clinical presentation and course is a primary requisite for the development of the full potential of PET.

Adult↗
PubMed1984

Computed tomography in experimental allergic encephalomyelitis--preliminary results.

Four dogs were immunized with a mixture of spinal cord homogenate and complete Freund's adjuvant. One of these dogs developed hyperacute allergic encephalomyelitis. Cranial computed tomography in this animal demonstrated a low absorption area in the internal capsule that corresponded to the pathologic lesion. Computed tomography scanning may be a useful tool in monitoring experimental allergic encephalomyelitis.

Animals↗
PubMed1984

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.

Cerebrovascular Circulation↗
PubMed1984

NMR imaging of intracranial hemorrhage.

Twenty-one intracranial hemorrhagic lesions were imaged at 0.15 and 0.6 T using inversion recovery (IR), spin echo (SE), and multiple SE (Carr-Purcell-Meiboom-Gill, CPMG) pulse sequences. Two subarachnoid hemorrhages (SAH), nine acute intraparenchymal hemorrhages (IPH), ten chronic IPH, and one subdural hematoma were studied. Acute SAH could not be identified on the T1-weighted, IR images but was clearly seen on a T2-weighted, CPMG image. Acute (7 days or less) intraparenchymal hematoma showed signal intensity on IR and CPMG images similar to white matter. The T1 and T2 times of acute intraparenchymal hematoma were also similar to white matter. Some small acute hematomas could not be distinguished from white matter on IR and CPMG images. Acute hemorrhagic tissue showed image intensities and relaxation times similar to gray matter. All acute hemorrhages were identified on CT. Chronic IPH lesions (14 days or more) showed high signal intensity, greater than white matter, on IR, SE, and CPMG images. The T1 of the chronic lesions was similar to the acute lesions but T2 was significantly longer (p less than 0.05). Available evidence suggests that the nonspecificity of acute IPH signal and relaxation times may not be restricted to our pulse sequences or magnetic field strengths.

Adult↗
PubMed1984

Oncologic diagnostic radiology: a model for implementation.

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.

Education, Medical↗
PubMed1984

Fat deposition in the cavernous sinus in Cushing disease.

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.

Adipose Tissue↗
PubMed1984

The digital computer in medical imaging: a critical review.

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.

Computers↗
PubMed1984

Myocardial ischemia during intravenous DSA in patients with cardiac disease.

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.

Aged↗
PubMed1984

Complications of intravenous DSA performed for carotid artery disease: a prospective study.

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.

Aged↗