Biomedical subjects

W F Good

Publications and source records attributed to W F Good.

43 records · Page 3Linked to original sources

PubMedDate not supplied

Errors in cerebral blood flow determinations by xenon-enhanced computed tomography due to estimation of arterial xenon concentrations.

Errors in the determination of xenon concentrations in arterial blood during inhalation of xenon-oxygen mixtures are used to assess errors in the derivation of regional cerebral blood flow by the xenon-enhanced computed tomography (CT) method. The results of this study indicate that approximating the arterial buildup by a single exponential introduces relatively small errors in estimated flow values. The most significant systematic error is introduced by errors in estimation of the xenon arrival time to the brain in relationship to sequential (CT) scanning times.

Cerebrovascular Circulation↗

PubMedDate not supplied

The effect of computed tomography noise and tissue heterogeneity on cerebral blood flow determination by xenon-enhanced computed tomography.

The errors associated with derivation of cerebral blood flow values by the xenon-enhanced computed tomography (CT) method have been evaluated as a function of tissue heterogeneity and CT noise. The results of this study indicate that CT noise introduces large errors in the derived flow value when data for a single, unprocessed voxel are used for this purpose. CT noise increases the derived flow values in a systematic way. Tissue heterogeneity results in a systematic error which lowers the derived flow values. Errors due to both parameters are computed for typical and extreme conditions.

Brain↗

PubMedDate not supplied

Progress in cerebrovascular disease: local cerebral blood flow by xenon enhanced CT.

A noninvasive technique for measuring local cerebral blood flow (LCBF) by xenon enhanced x-ray transmission computed tomography (CT) has been developed an reported quite extensively in recent years. In this method, nonradioactive xenon gas in inhaled and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential computed tomography. Time dependent xenon concentrations within various tissue segments in the brain are used to derive both local partition coefficient (lambda) and LCBF. An assessment of this method reveals that although it provides functional mapping of blood flow with excellent anatomic specificity, there are distinct limitations. The assumptions underlying this methodology are examined and problems associated with various potential applications of this technique are discussed.

Animals↗

PubMedDate not supplied

Clinical experience with the use of xenon-enhanced CT blood flow mapping in cerebral vascular disease.

Cerebral blood flow mapping with the xenon-enhanced/CT method has become a useful clinical tool in the management of patients with occlusive cerebral vascular disease. Studies involving 4-5 minutes of inhaling a xenon/oxygen mixture (less than or equal to 35%) can now be performed routinely with acceptable patient tolerance and compliance. Four cases with acute and chronic ischemic injuries are reported here to illustrate the manner in which this method has been used to characterize flow pattern in such patients and the relevance of this flow information to clinical patient management.

Adult↗

PubMedDate not supplied

Measurement of cerebral blood flow during xenon inhalation as measured by the microspheres method.

Measurements of cerebral blood flow (CBF) were performed using the microsphere technique in non-human primates (baboons) to assess the effect of non-radioactive xenon gas inhalation on CBF. Blood flows in small tissue volumes (approximately 1 cm3) were directly measured before and during the inhalation of xenon/oxygen gas mixtures. The results of these studies demonstrated that when inhaled in relatively high concentrations, xenon gas does increase CBF, but the changes are more global than tissue-specific. The problems and limitations of such evaluations are discussed.

Animals↗

PubMedDate not supplied

Xenon-enhanced CT of the brain: effect of flow activation on derived cerebral blood flow measurements.

The errors associated with derivation of cerebral blood flow values by the xenon-enhanced CT method have been evaluated through computer simulations as a function of flow-activation patterns and different scanning protocols. The results of this study indicate that actual flow activation during inhalation increases the derived flow values in a systematic way. Compared with the errors introduced by CT noise and/or variations in scanning protocols, flow activation introduces relatively small errors in the derived flow value when the washin technique is used.

Administration, Inhalation↗

PubMedDate not supplied

Stable xenon CT cerebral blood flow imaging: rationale for and role in clinical decision making.

The stable xenon CT method of measuring cerebral blood flow has been investigated in research studies for over 10 years. Recently, it has been gaining clinical acceptance, primarily owing to a combination of several unique advantages it holds over other cerebral blood flow measurement techniques. The accuracy of this technique in quantifying low cerebral blood flow gives it a unique application in cases of brain death and acute stroke and it can be repeated after an interval of 20 min. making it possible to evaluate autoregulation and cerebrovascular reserve. Furthermore, cerebral blood flow information is directly coupled to CT anatomy. Although it is more difficult to administer than a standard CT scan, careful monitoring can ensure patient safety during the examination. In this article we review the physiologic and technical bases for the clinical application of xenon CT-derived quantitative cerebral blood flow information and discuss the advantages and disadvantages of the technique. We also describe its current clinical applications, including its usefulness in the evaluation of acute stroke, occlusive vascular disease, carotid occlusion testing, vasospasm, arteriovenous malformations, and head trauma management.

Cerebrovascular Circulation↗