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Biomedical subjects

D Gur

Publications and source records attributed to D Gur.

At least 127 records · Page 7Linked to original sources
PubMed1982

Mapping of human local pulmonary ventilation by xenon enhanced computed tomography.

Functional maps of local pulmonary ventilation are derived from serial computed tomographic images acquired prior to and during a short period of inhalation of subanesthetic xenon/oxygen gas mixtures. Preliminary results from human studies yield quantitative maps of local ventilation rates with excellent anatomic specificity demonstrating nonuniformities in the distribution of ventilation in normal and abnormal human lungs.

Adult↗
PubMed1981

Xenon enhanced dynamic computed tomography: multilevel cerebral blood flow studies.

Xenon enhanced computed tomography with a fast scanning mode and interscan table incrementation was used to derive local cerebral blood flow in a nonhuman primate 19 days following infarction. The in vivo autoradiographic methodology was used to derive blood flow in normal and diseased tissue at four different brain levels (slices) during a single inhalation study.

Animals↗
PubMed1981

Side effects of xenon inhalation.

Short- and long-term side effects during and after inhalation of premixed xenon oxygen (28-47%) from 12 studies are reported. While all but one subject tolerated xenon inhalation without ill effects, that individual did experience unpleasantly severe dysesthesias and a brief period of unresponsiveness. We believe that further human studies with xenon inhalation should be conducted to explore possible early indicators for reduced tolerance of xenon by certain individuals.

Anxiety↗
PubMed1981

Regional pulmonary ventilation measurements by xenon enhanced dynamic computed tomography: an update.

New developments in computed tomographic technology permit rapid, serial images that may yield information concerning tracer kinetics through a large tissue volume. One possible application of these developments is the derivation of local lung ventilation by observing the temporal changes of stable xenon concentrations. Preliminary results from six multilevel ventilation studies in dogs demonstrate that the lung may be repeatedly imaged during reproducible phases of respiration even when interscan table incrementation is employed to survey a number of tissue segments and breathing is permitted between scans. In addition, subanesthetic xenon concentrations provide adequate enhancement for possible quantification.

Animals↗
PubMed1980

Abnormality of the xenon brain:blood partition coefficient and blood flow in cerebral infarction: an in vivo assessment using transmission computed tomography.

Xenon-enhanced computed tomography (CT) was used to analyze, in vivo, the patterns of blood flow of cerebral infarction in a nonhuman primate model. Consistent and reproducible results were attained utilizing the numerical data from CT scans obtained during the inhalation of nonradioactive xenon. The spatial resolution of CT defined a morphophysiologic map of the variability in brain:blood partition coefficient and flow rate constant that exist within and around an infarct. Both the flow and the partition coefficient were significantly diminished in the ischemic focus in all animals studied. Although the partition coefficients were normal, the flow was decreased in the other locales sampled in the ipsilateral hemispheres. In the contralateral hemispheres, both flows and partition coefficients were within the range of normal for adolescent baboons.

Animals↗
PubMed1980

Experimental xenon enhancement with CT imaging: cerebral applications.

Xenon-enhanceed cranial computed tomography (CT) was used to derive the partition coefficient (lambda) and flow rate constant (kappa) and thus provide a functional neuroanatomic map of local cerebral blood flow in eight nonhuman primates. Sequential CT imaging defined the temporal changes of xenon concentration in arterial blood and brain tissue both during and after xenon inhalation. Several methodologies including clearance, buildup, and in vivo "autoradiography" were used to estimate flow in various brain locales. A typical derived fast flow rate using xenon CT methodology was 85 ml/100 g/min, with a range of 58--108. The in vivo autoradiographic method of defining flow seems more clinically applicable in man. The limitations and potential solutions using CT blood flow techniques are discussed.

Animals↗
PubMed1980

Xenon- and iodine-enhanced CT of diffuse cerebral circulatory arrest.

The role of contrast-enhanced computed tomography (CT) was evaluated in three nonhuman primates with a severe cerebrovascular insult and resulting elevated intracranial pressure and diffuse circulatory arrest. In all three animals the brain vasculature did not opacify after the bolus intravenous injection of iodinated contrast media. In addition, the brain substance did not enhance although the arterial blood enhanced normally after inhalation of a high concentration of xenon. Xenon-enhanced CT scanning, like 133Xe radionuclide scanning, may be used to define the absence of generalized cerebral perfusion.

Animals↗
PubMed1979

The significance of concordance in mammographic interpretations.

Twenty-eight women participating in a screening program had a breast cancer diagnosed subsequent to the report of a negative mammogram which was read by only one of a group of radiologists. Fourteen occurred prior to a scheduled routine screening visit (interval cancers) and 14 were detected during such an examination. The negative mammograms from the 28 cancer patients, together with those from 120 women without cancer (controls) were independently reviewed by each member of a panel of three radiologists. Forty-six percent of the cancer cases and 5.8% of the controls were interpreted as positive by two or more of the radiologists. These findings suggest that agreement among several independent reviewers enchances the value and accuracy of mamography by reducing the number of false negative interpretations.

Breast Neoplasms↗
PubMed1979

Patterns of brain perfusion: dynamic computed tomography using intravenous contrast enhancement.

A representation of cerebral perfusion is obtained using cranial computed tomography following the rapid bolus injection of iodinated intravenous contrast medium. This technique permits the definition of four gross patterns of perfusion (normal, circulatory arrest, hypoperfusion, and hyperperfusion). This classification is affirmed in an experimental model of cerebral infarction in the baboon. The limitations of dynamic imaging using computed tomography are reviewed.

Animals↗
PubMed1979

Dynamic computed tomography of the lung: regional ventilation measurements.

The spatial resolution provided by computed tomography (CT) yields excellent anatomic specificity, and fast scanners are capable of the serial imaging necessary to monitor rapid changes in tracer concentration over time. In this study, sequential CT imaging defined the temporal changes of xenon concentration in peripheral lung tissue of a nonhuman primate and three sheep, both during and after xenon inhalation. Ventilation rate constants (K) in lung tissue with normal and impaired function in the evaluation of regional ventilation using xenon enhanced CT are discussed.

Animals↗
PubMed1977

Evaluation of benefits and risks of breast cancer screening.

Benefit/risk ratios derived by another study group for a population screened at a breast cancer detection center during the first year of operation are analyzed. The authors of the present paper look at the problem in a somewhat different manner. Benefit/risk ratios derived using this approach are significantly lower than those reported in the previous study. The results of the present study indicate that annual mass screening of women under the age of 50 is of questionable value.

Breast Neoplasms↗
PubMedDate not supplied

Blood flow mapping in the human liver by the xenon/CT method.

In the noninvasive, nonradioactive xenon/CT method of blood flow measurement, xenon gas is inhaled, and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential CT; time-dependent xenon concentration within various tissue segments is then used to derive local blood flow maps. The usefulness of the method in the assessment of local cerebral blood flow has been documented. In this paper we explore its application to blood flow measurement in the human liver. In our preliminary clinical studies, hepatic blood flow ranged from 50 to 120 ml/100 cc/min in normal and adequately supplied tissue, and lower flow values were observed in tissue with abnormal function. The advantages and limitations of the method in such applications are discussed.

Adult↗
PubMedDate not supplied

Fast and slow neutrons in an 18-MV photon beam from a Philips SL/75-20 linear accelerator.

Fast- and slow-neutron contamination in an 18-MV photon beam from a Philips SL/75-20 linear accelerator has been measured. Aluminum and indium foils were activated to determine fast- and slow-neutron fluence, which were largely independent of field sizes. Measured fast-neutron fluences were typically 13.9 X 10(4) and 4.4 X 10(4) neutrons/cm2/rad of x ray inside and 5 cm outside the field, respectively. Slow-neutron fluences, 1.3 X 10(4) neutrons/cm2/rad of x ray, remained relatively constant inside and outside the field. The reported results are about three times higher than neutron fluences recently reported with a betatron operated at the same energy.

Elementary Particles↗