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Biomedical subjects

A A Chambers

Publications and source records attributed to A A Chambers.

At least 19 recordsLinked to original sources
PubMed1990

Hyperdense middle cerebral artery sign on CT: efficacy in detecting middle cerebral artery thrombosis.

The hyperdense middle cerebral artery sign is a CT predictor of the development of a large cerebral infarct. The limits of detectability were tested in a blinded, then unblinded analysis of CT scans from 25 acute stroke patients. In the initial blinded analysis, sign detection exhibited the following mean values: sensitivity, 78.5%; specificity, 93.4%; positive predictive value, 66%; negative predictive value, 96.4%; accuracy, 91.3%. Kappa statistics analysis indicated poor interobserver agreement (k = .38). Results of unblinded analysis were as follows: sensitivity, 69%; specificity, 94.4%; positive predictive value, 82.8%; negative predictive value, 88.7%; accuracy, 87.3%. There was fair unblinded interobserver agreement (k = .53). Unblinded analysis had a lower false-positive frequency and did not increase the number of true-positive determinations. We conclude that detection of the hyperdense middle cerebral artery sign on CT scans by multiple observers is a sensitive, accurate, and predictive indicator of middle cerebral artery thromboembolism.

Acute Disease↗
PubMed1979

Large sella.

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Diagnosis, Differential↗
PubMed1979

Intracranial blood clot volume and geometric parameters determined from CT images.

A method of determining intracranial blood vlot volumes from CT images data is presented. This technique avoids dependence on regular geometric volume approximations. Studies are presented on phantoms of known volume (ranging from 3.5 to 108 cm3) but with varying size, shape, and density relative to the surrounding medium. For a wide range of differential densities across the boundary, these phantom results indicate that volumes may be calculated to an accuracy generally better than +/- 2 cm3. A series of clinical cases, principally hypertensive intracranial hemorrhages, have been studied to demonstrate the technique. Three-dimensional axes, which allow clot localization relative to cerebral anatomy, are defined using the anterior/posterior falx attachment points and the dorsum sellae. Clot volume, center of mass, vector of clot expansion, and shift of anatomical structures are determined. Correlation of these data with clinical outcome and surgery is discussed.

Cerebral Hemorrhage↗
PubMed1978

Pericollicular syndromes.

Five cases of pericollicular focal hemorrhages are presented with a description of their effect on vision and consciousness. Loss of vision, loss of consciousness, extraocular muscle dysfunction, mutism, and dyslexia may result from expansive lesions near the collicular plate.

Adolescent↗
PubMed1978

Skull fractures.

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Brain Injuries↗
PubMed1975

Thrombosed giant middle cerebral aneurysms.

Two giant thrombosed aneurysms of the middle cerebral artery are reported with a review of the pertinent literature. A tortuous channel through the thrombus results in an unusual and characteristic angiogram. Mechanisms involved in the formation of this lesion are discussed.

Adult↗
PubMedDate not supplied

Midline anterior atlas clefts: CT findings.

Anterior atlas clefts (AACs) are rare developmental variants that may mimic fractures. Due to the potential severe implications of craniocervical junction trauma, expeditious differentiation between a Jefferson burst fracture and a congenital cleft is essential in trauma patients. Three cases of AAC are presented. Two cases demonstrated incidental AACs; the third case was associated with a Jefferson burst injury. Computed tomography is most helpful in evaluating the integrity of the atlas; however, plain radiography or pluridirectional tomography are best for evaluating displacement of the lateral masses of C1 in relation to C2.

Accidents, Traffic↗
PubMedDate not supplied

An evaluation of the performance characteristics of different types of collimators used with the EMI brain scanner (MKI) and their significance in specific clinical applications.

The characteristics of various types of collimators have been studied systematically for the EMI Mark I brain scanner. The degree of collimation ranged from the 13-mm adjacent A and B slices to 3-mm separated slices. Multiple phantom studies (including variable density immiscible liquid interfaces) have been performed to evaluate the effect of collimation on (a) the line-spread function, (b) the change in effective absorption number, and (c) volume averaging. Effects associated with the technique settings involving the kVp, the mA, and the scan time were also investigated. The results of TLD dose measurements as a function of collimation are presented. The significance of collimation in specific clinical studies involving small, fairly well-circumscribed lesions is discussed.

Brain Diseases↗
PubMedDate not supplied

Why not the eighth nerve? Neurovascular compression--probable cause for pulsatile tinnitus.

Carotid arteriograms on three patients with unilateral pulsatile tinnitus demonstrated an ipsilateral atypical trigeminal artery extending from the cavernous portion of the internal carotid artery to form the posterior inferior cerebellar artery. Illustrations and a dissection of a human fetus with a similar finding show this artery crossing the cochlear nerve near its insertion in the pons. Evidence is presented suggesting that neurovascular compression of the eighth nerve is the source of pulsatile tinnitus in these patients.

Adult↗