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At least 271 records · Page 15Linked to original sources
PubMed1987

A mathematical simulation of oxygen delivery in rat peripheral nerve.

We have performed a mathematical simulation on a CYBER computer of the release, diffusion, and consumption of oxygen in the capillaries and surrounding tissue of peripheral nerve under steady-state conditions. The Krogh-Erlang equation was used to calculate oxygen tension in tissue, while numerical solution of the differential equation governing oxygen release from hemoglobin and diffusion was used to calculate oxygen tension in the capillary. Using average measured values for the parameters of oxygen solubility, diffusion coefficient, capillary diameter, capillary density, nerve blood flow, oxygen consumption rate, and arterial oxygen tension in rat peripheral nerve, we calculated the endoneurial oxygen tension as a function of distance from the nearest capillary and distance along the capillary from the arterial end to the venous end. The range of calculated values agreed with experimental measurements obtained from the sciatic nerves of rats. Alterations in these parameters produced changes in the calculated oxygen tension distributions. Conditions which adversely affected oxygen delivery include reduced capillary diameter, increased intercapillary distance, reduced blood flow, and reduced arterial oxygen tension. The lower experimentally obtained oxygen tensions in sciatic nerves of diabetic rats could be accounted for reasonably by this model on the basis of a 33% reduction in nerve blood flow (consistent with previously measured flow reduction). However, the measured reduction in oxygen tensions in sciatic nerves of rats with experimental galactose neuropathy were not as marked as those predicted on the basis of a 22% increase in tissue cylinder radius in the model (consistent with experimental observations). This may be due to the fact that the oxygen consumption rate is reduced in hypoxic regions of tissue.

Animals↗
PubMed1981

[Computed tomography and densitometric pattern of pulmonary lesions (author's transl)].

Fifty-five peripheral pulmonary lesions in 46 patients were examined by computed tomography. The results were correlated with histologic diagnoses. The series comprised 26 bronchial carcinomas, 17 metastases, 4 chondromas, 5 tuberculomas and 3 echinacoccal cysts. The high resolution capacity of CT in the evaluation of macro pathologic pattern specially with the electronic image processing, with densitometry in regional interest is emphasised. Therefore cysts, fatty and other solid masses in the lung can be distinguished. Further more one can gain information of the underlying tissue on the basis of absorption profile.

Absorptiometry, Photon↗
PubMed1988

[Ultrasonography and x-ray computed tomography in the diagnosis of intra-abdominal textiloma. Apropos of 12 cases].

Feared by every surgeon, retained surgical sponges (or gossypiboma) are rare iatrogenic entities. Ultrasonography and computed tomography are very valuable, providing an immediate answer in the majority of cases. We report 12 cases of intra-abdominal retained surgical swabs. The ultrasonic pattern was made whether of a large poorly echogenic mass with a hyper-echogenic center and sharply delineated posterior acoustic shadow (7 cases) or of a large acoustic shadow posterior to a solitary highly echogenic area (4 cases). Computed tomography demonstrated whether large peripherally enhanced cystic mass associated with serpiginous or spongiform central area (5 cases) or heterogeneous abscess-like fluid mass.

Abdomen↗
PubMed1978

Measurements in microscopic images: an inexpensive device for semi-automatic analysis of microscopic images.

Measurement of histological and cytological parameters can be performed much faster and more accurate by means of a semi-automatic device that is described in detail. The system consists mainly of a medium-sized computer and one or more peripheral terminals. Each terminal incorporates a special measurement table for data acquisition, a keyboard for manual data input, and an interface. The software program for the evaluation and storage of the digital data is simple to write and offers a high degree of flexibility to the user. The system can be operated in real time.

Computers↗
PubMed1992

[Bronchiolo-alveolar carcinoma in a solitary site. The computed tomographic characteristics].

Bronchioloalveolar carcinoma is a peripheral, well-differentiated neoplasm arising beyond a recognizable bronchus, with a tendency to spread to the peripheral air spaces using the lung structure as stroma. This tumor has better prognosis than other lung neoplasms if it is diagnosed early (stage I). For this reason, the CT scans of 16 patients (all of them asymptomatic, only 2 smokers) were reviewed to assess CT capabilities. The cytologic diagnosis was made with CT-guided fine-needle aspiration biopsy in 4 patients (surgical confirmation followed); the histologic diagnosis was made in 12 patients after surgery. CT findings included the peripheral (14 cases) or subpleural (2 cases; 12.5%) location, irregular margins forming a star-like pattern (2 cases; 12.5%), pseudocavitation (13 cases; 81%), heterogeneous attenuation (11 cases; 69%), pleural tags (14 cases; 87.5%) and air bronchogram (2 cases; 12.5%). These CT findings, if compared with the same number of CT scans in patients with adenocarcinoma and squamous cell carcinoma, are present in 70% of patients (11/16) and, although not highly specific (specificity: 36%), they are typical enough to suggest the diagnosis.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1988

Extracranial and extraspinal nerve sheath tumors: computed tomographic evaluation.

Thirty-five patients with 37 peripheral nerve sheath tumors (NST) (16 schwannomas, 11 neurofibromas, 5 plexiform and 1 diffuse neurofibroma, and 4 malignant NST) were studied respectively. The benign NST usually appeared on CT as well-defined oval, spherical or fusiform masses, centered at the expected anatomic location of a cranial, spinal, autonomic or peripheral nerve with characteristic displacement of adjacent muscles and blood vessels. None of the schwannomas appeared homogeneously hypodense on IV enhanced CT, whereas close to half of neurofibromas and plexiform neurofibromas were so. This fact, which had not been reported in the past, may be related to differences in inherent vascularity and blood-nerve barrier (fenestrated blood vessels) between schwannomas and neurofibromas and may be a useful distinguishing CT feature. The most reliable, though not infallible criterion of malignant NST was poor definition of their margins. Ninety-two per cent of NST (34 out of 37) were diagnosed or included in a limited differential pre-operatively.

Female↗
PubMed1985

Use of the calibrated carotid pulse tracing for calculation of left ventricular pressure and wall stress throughout ejection.

Calibrated carotid pulse tracings have been found previously to provide accurate estimates of end-systolic pressure. This study extends this technique to the estimation of arterial pressure throughout ejection. In twenty patients without aortic stenosis (age range 8 to 67 years), simultaneous recordings were made of the pressure tracing in the ascending aorta, externally recorded carotid pulse tracing, phonocardiogram, left ventricular echocardiogram, and peripheral blood pressure. Data were computer digitized and plots of arterial pressure were derived from the aortic pressure tracing (PA) and from the carotid pulse tracing (Pc). Left ventricular (LV) wall stress was then calculated throughout ejection using PA or Pc. The noninvasive estimation of pressure was excellent, with a maximum difference of 3.4 mm Hg between population means. This occurred within the first third of ejection. The wall stress calculations were similar, with a maximum mean population error of 3.5 gm/cm2 at 20% of ejection. The peak wall stress values had a mean difference of 1.4 gm/cm2; mean wall stress over the LV ejection period was 0.5 gm/cm2 higher when calculated from Pc than from PA. Thus, the carotid pulse tracing provides an accurate reproduction of the morphology of the pressure tracing recorded from the ascending aorta, and when calibrated by peripheral blood pressure measurement, it can be used to calculate LV pressure throughout ejection. These pressure estimates can be used to calculate wall stress throughout ejection with a high degree of accuracy.

Adolescent↗
PubMed1980

[Computer tomographic and angiographic studies of histologically confirmed intrahepatic masses (author's transl)].

The computer tomographic and angiographic findings in 53 patients with intrahepatic masses were compared. The histological findings show that 17 were due to echinococcus, 12 were due to hepatic carcinoma, ten were metastases, five patients had focal nodular hyperplasia, three an alveolar echinococcus and there were three cases with an haemangioma of the liver and a further three liver abscesses. Computer tomography proved superior in peripherally situated lesions, and in those in the left lobe of the liver. Arteriography was better at demonstrating lesions below 2 cm in size, particularly vascular tumours. As a pre-operative measure, angiography is to be preferred since it is able to demonstrate anatomic anomalies and variations in the blood supply, as well as invasion of the portal vein or of the inferior vena cava.

Angiography↗
PubMed1979

Evidence of CSF enhancement in the spinal subarachnoid space after intravenous contrast medium administration: is intravenous computer assisted myelography possible?

Following intravenous injection of iodinated contrast medium, peripheral enhancement of the area inside the spinal canal, is frequently observed by computed tomography. This may be due, at least in part, to enhancement of the cerebrospinal fluid in the spinal subarachnoid space. Our preliminary observations in human patients and in animal experiments are reported. The goal of intravenous computer assisted myelography is worth pursuing.

Cerebrospinal Fluid↗
PubMed1985

Computed tomography of the heart: evaluation of anatomy and function.

Diseases of the heart and blood vessels represent one of the most challenging problems for advanced diagnostic imaging systems. Computed tomographic scanning is potentially an ideal cardiac imaging modality since it is a cross-sectional imaging method with very high resolution. Currently available computed tomographic scanners have exposure speeds of 1 to 5 seconds, which are inadequate for the majority of cardiovascular imaging applications. Nevertheless, a variety of limited computed tomographic scanning techniques have been successfully performed in selected patient subgroups. These methods require the administration of contrast medium injected or infused into a peripheral vein, combined with either dynamic computed tomographic scanning or some form of electrocardiographic gated computed tomography. The newer conventional computed tomographic scanners can display anatomic structures in the heart and great vessels with considerable fidelity and provide not only cross-sectional displays but also, by means of computer manipulation, any selected reconstructed images in oblique, coronal or sagittal projections. Feasibility studies indicate improved accuracy of computed tomographic measurements of cardiac chamber volumes. Physiologic measurements include estimation of shunt flows and cardiac output and analysis of myocardial wall thickening. The full potential of computed tomography should be reached once fast, multiple slice, computed tomographic scanners using scanning electron beam techniques become available. The prototype CVCT (cine computed tomographic C-100 scanner) designed at the University of California, San Francisco, is now undergoing evaluation. This instrument images up to eight contiguous slices at the rate of 16 to 24 images/s. The computed tomographic scanner specifically designed for cardiac imaging should extend the utility of computed tomography in the evaluation of cardiac diseases and the study of cardiovascular physiology.

Heart↗
PubMed1989

A multichannel FES system for the restoration of motor functions in high spinal cord injury patients: a respiration-controlled system for multijoint upper extremity.

A multichannel functional electrical stimulation (FES) system for the restoration of quadriplegic upper extremity function is described. The system is composed of a personal computer NEC PC-8801mkII, peripheral electronic circuits, CRT display and respiratory sensors for volitional control by the patient, and percutaneous electrodes. A C4 quadriplegic patient could drink canned tea by herself by using this FES system. Distinct features of the system are as follows: 1) Versatile volitional control was realized by controlling the memory allocation of the stored stimulation data by voluntary respiratory signals. 2) Sophisticated fine control of the fingers, wrists, and elbow was realized by creating the multichannel stimulation data from recorded myoelectric activities of normal subjects during movements of the upper limb.

Arm↗
PubMed1991

A quick and accurate line-sampling technique to quantify myelinated axons in peripheral nerve cross-sections.

A quick and accurate computer-assisted method of quantifying the number of myelinated axons in normal and experimental or regenerated peripheral nerve cross-sections is described. Using an IBM-PC, quantitation software and a light microscope with a camera lucida attachment, the number of axons in a sciatic nerve can be calculated in fifteen minutes. Nine nerve samples with various nerve diameters and axon densities were used to test the technique. Total counts (actual count) were compared to the number of axons estimated by the line-sampling technique (projected count) and the two groups varied up to 15%. The principle advantage of this method is that it saves time by eliminating photography and performing total counts. The technique can be applied to normal and regenerated peripheral nerve.

Animals↗
PubMed1987

Functional electrical stimulation for the control of the upper extremities.

A multi-channel functional electrical stimulation (FES) system for the restoration of hand function of the quadriplegic is described. The system is composed of a personal computer NEC PC-880lmkII, peripheral electronic circuits and two kinds of sensors, i.e. an analog displacement sensor for volitional control (channel 1) and a logical sensor (high pitch sound or head switch, channel 2). Combination of the two channel signals allow three major function: 1) designation of the desired prehension pattern among cylindrical grasp, key grip and parallel extension grip; 2) selection of the operation status--'start', 'proportional control', 'hold', 'stop'--and, 3) volitional control which can be controlled by the shoulder movement. In the clinical application, Caldwell-Reswick type multistrand stainless steel percutaneous electrodes were used. In this FES system, standard multi-channel stimulation patterns were obtained from electromyographical analysis of joint movement of the upper extremities in normal subjects which gave us precise information about a role of each muscle during various kinds of motion. Such stimulation patterns have enabled us to restore motor function of the paralyzed upper extremities for activities of daily living (ADL).

Electric Stimulation↗
PubMed1990

A planning method for 125I implants in cancer therapy.

A method for planning implants of 125I seeds has been developed. The treatment dose prescribed by the physician is delivered to the tumour, as uniformly as possible, by a minimal number of seeds. The number of seeds and their locations are derived by requesting that, at any point in the tumour, the dose will be equal to or higher than the prescribed dose. As a result, the total implanted activity is lower for small volumes and higher for large volumes, relative to other implantation protocols which derive their planning from requests on the minimum peripheral dose. Results obtained from computer simulations performed on different tumour shapes and volumes, show a linear dependence between the total implanted activity and the tumour volume. The total activity does not depend on the shape of the tumour. A description of the algorithm of our procedure and a detailed example of its application are presented.

Algorithms↗
PubMed1990

Cystic rheumatoid arthritis: description of a nonerosive form.

In a study of patients with rheumatoid arthritis (RA), 9% (n = 70) were found to have a cystic form. At radiologic examination of these patients with cystic RA, the first abnormality seen consisted of periarticular intraosseous cysts without erosions. The cysts were distributed symmetrically, most often located at the proximal side of the joints and predominantly around the proximal interphalangeal, metacarpophalangeal, and wrist joints of the hands and the first interphalangeal and metatarsophalangeal joints of the feet. Computed tomographic scans showed the peripheral intraosseous location of the cysts. Magnetic resonance images showed that the cysts may contain fluid, inflamed synovia, or both. Cysts can be an important feature in the diagnosis of RA and a supplement to the criteria of the American Rheumatism Association. Osteoporosis, joint-space narrowing, and joint destruction occurred less frequently in patients with cystic RA than in patients with classic RA. Of the patients with cystic RA, 54% were male, and 50% were seronegative. This study is a supplement to and an enlargement on earlier descriptions of cyst predominance in RA.

Adolescent↗