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Biomedical subjects

D M Hadley

Publications and source records attributed to D M Hadley.

At least 73 records · Page 4Linked to original sources
PubMed1987

Invasive v non-invasive assessment of the carotid arteries prior to trans-sphenoidal surgery.

Imaging studies in 47 patients who were to undergo trans-sphenoidal surgery were analysed with reference to the vascular structures in the parasellar region. The results of cavernous sinography, dynamic contrast enhanced Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) showed good correlation with each other and with the appearances found at operation. CT and MRI, both non-invasive investigations, are therefore reliable preliminary screening methods for identifying the small proportion of patients on whom other imaging techniques need to be performed.

Carotid Artery, Internal↗
PubMed1987

Human cranial CSF volumes measured by MRI: sex and age influences.

Accurate measurements of CSF volumes would assist in the diagnosis of several important neurological conditions. Using Magnetic Resonance Imaging (MRI) we have devised a method to measure both total intracranial CSF volume and ventricular volume. This initial study, in normal humans, provides an answer to two longstanding questions: first, do these volumes differ between the sexes; second, do both total and ventricular CSF volumes increase with normal aging? We found that the total cranial CSF volume and skull size of males were significantly greater than those of females, but that there was not a statistically significant difference between the ventricular volumes of the sexes. Total cranial CSF volume increased steeply with age in both sexes but although there was an increase in ventricular volume with age in males, no significant increase with age could be demonstrated in females.

Adult↗
PubMed1987

Magnetic resonance imaging in the management of resistant focal epilepsy: pathological case report and experience of 12 cases.

Clinical improvement in epilepsy following temporal lobectomy is more often obtained when an abnormality is found on subsequent histological examination. Pre-operative MRI demonstrated an abnormal signal in the temporal lobe of a patient with pathologically proven mesial temporal sclerosis with microvascular anomaly. MRI may therefore be helpful in the selection of patients for temporal lobectomy. MRI findings of 12 patients with resistant focal epilepsy are reviewed. A wide range of T1 and T2 weighting is suggested to maximise selection of patients.

Adult↗
PubMed1987

MRI measurement of syrinx size before and after operation.

When patients with syringomyelia fail to improve after operation, factors such as incomplete cyst decompression or type of operation are often implicated. MRI has been used to confirm adequate syrinx decompression post-operatively and to compare the degree of collapse with the type of operation. Foramen magnum decompression was at least as effective in reducing cyst size as syringo-subarachnoid shunting. MRI may also provide a better classification of syringomyelia.

Foramen Magnum↗
PubMed1987

Syringomyelia: cyst measurement by magnetic resonance imaging and comparison with symptoms, signs and disability.

The severity and distribution of symptoms and signs in patients with syringomyelia is considered to be dependent on the longitudinal and transverse dimensions of the syrinx and it is thought that clinical examination can identify the extent of the cyst. Magnetic resonance imaging has made the anatomical localisation of intramedullary spinal lesions more exact and probably more specific than previous methods of investigation. Syrinx length, diameters, cyst:cord and cord:canal ratios have been studied in 12 patients with syringomyelia to assess whether the dimensions of the syrinx relate to the clinical findings. The length of syrinx appeared to be related to cyst diameter, cyst:cord and cord:canal ratios. Patients with a small syrinx tended to have a small cyst diameter, and small cyst:cord and cord:canal ratios. No significant relationship was found between muscle wasting or weakness, distribution of sensory loss, degree of disability or distress and the dimensions of the syrinx. These findings should be borne in mind when surgical management is being considered.

Adult↗
PubMed1986

Accuracy of stereotaxic localisation using MRI and CT.

The accuracy of stereotaxic coordinates determined using the Leksell apparatus with CT and MRI was investigated using an Agar filled head phantom. Both imaging techniques were found to produce an accuracy of better than 2 mm with the exception of the Z coordinate as measured by CT (2.3 mm). This latter error is greater because of the 3 mm slice width used. Direct coronal views were used to determine Z more accurately using MRI. The measurement procedures are described and it is shown that the Leksell system of using orthogonal coordinates enables the scaling of images, which is particularly necessary with MRI, to be done easily.

Humans↗
PubMedDate not supplied

Digital mapping of multi-parameter contrast functions in magnetic resonance (MR) imaging using a standard MR computer system and digital display.

A technique is described which utilises the full analysis and display capabilities of a commercial MRI system to produce digital maps of multi-parameter functions produced by MR contrast theory. The technique is utilised to determine the effects of nominating specific overall scan times on the optimum solutions as produced by the theory and it is shown that different solutions are obtained when the theory is applied using typical clinical constraints. The digital mapping approach is potentially of great value in prospectively determining pulse timing parameters to produce optimum contrast images, in producing contrast maps to aid retrospective image interpretation, and as a training aid for clinicians inexperienced in the interpretation MR images.

Computer Graphics↗
PubMedDate not supplied

The use of in vitro magnetic resonance tissue studies to optimise pulse sequences in the imaging of intracranial haemorrhage.

The choice of appropriate MR pulse sequences to highlight a particular pathology to best advantage is not always straightforward. In this study of intracranial haemorrhage, tissue relaxation times measured in vitro were entered into a computer program which calculated the signal intensity of each tissue (brain, blood, CSF, and bloody CSF) for all possible echo (TE) and repeat (TR) times. Analysis of graph plots of the results enabled the selection of pulse sequences which gave optimal separation of the signal intensities of intracranial haemorrhage from those of normal intracranial contents. The sequences thus chosen were used successfully in the imaging of patients with intracranial haemorrhage.

Cerebral Hemorrhage↗
PubMedDate not supplied

A quantitative index of ventricular and extraventricular intracranial CSF volumes using MR imaging.

A new technique is described that utilises a novel magnetic resonance pulse sequence to produce a quantitative index both for ventricular and, for the first time, extraventricular intracranial CSF volumes. The pulse sequence is a combination of a null-point inversion recovery sequence with an extended spin-echo read (echo time = 400 ms), which produces a contrast of CSF to white or grey matter of approximately 120:1. A series of experiments are performed on phantoms representing CSF filled ventricles and sulci over a wide range of volume values, and it is found that the standard deviation of differences between true and estimated values is 3.9% for ventricles, 4.6% for total cranial CSF, and 7.9% for CSF within the sulci. Normal volunteer reproducibility studies revealed corresponding standard deviations of less than 5.5%. Using the technique to produce absolute estimates of CSF volumes in normal subjects and patients produced results in good agreement with previously published necropsy studies. The technique has wide neurological and neurosurgical applicability particularly in terms of differential diagnosis and as an objective monitor of therapy or progression in conditions such as hydrocephalus, atrophy, and benign intracranial hypertension.

Adolescent↗
PubMedDate not supplied

Is cranial CSF volume under hormonal influence? An MR study.

We used magnetic resonance to investigate the hypothesis that premenstrual neurological symptoms are due to cerebral oedema and brain swelling. Total cranial and lateral ventricular CSF volumes were measured midcycle and premenstrually in 20 women with a normal menstrual cycle, and similar measurements were made 2 weeks apart in 10 postmenopausal women and 10 men. Total cranial CSF volume increased premenstrually in 19 women. The mean premenstrual increase was by 11.5 ml. There was not a significant difference between those women who were taking an oral contraceptive and those who were not. The CSF volume did not change significantly on repeat measurement in men and postmenopausal women. The CSF changes observed reflect a reduction in brain volume and do not support cerebral swelling as the cause of premenstrual neurological symptoms.

Adult↗
PubMedDate not supplied

Quantification of cord deformation and dynamics during flexion and extension of the cervical spine using MR imaging.

The magnetic resonance (MR) cine display of flexion and extension (F/E) manoeuvres in the cervical spine has proved useful in the evaluation of cord compression due to bone and joint instability, spondylosis, and multiple tumours. It has advantages over X-ray F/E and CT myelography in that it is noninvasive and produces images with high soft tissue contrast. The MR F/E technique does have its limitations, however, in that each structure in the images has a degree of independent movement and rotation that can make visual interpretation difficult. It also does not address the problem of assessing the relative significance of each lesion where numerous lesions may be present, for example, in compression due to spondylosis, rheumatoid arthritis, or neurofibromatosis. In this paper a novel technique is described that produces quantitative indices of cord deformation and dynamics during MR F/E. A computer program automatically calculates a series of contiguous profiles perpendicular to the cord throughout its length and for each image in the manoeuvre. Orthogonal polynomial curve fitting techniques are used to fit these profiles and extract statistical parameters that are quantitative indices of deformation and dynamics. The four main parameters calculated are kurtosis as an index of bilateral cord compression, skewness as an index of unilateral or asymmetric contact pressure, angulation as a measure of cord deformation about a lesion, and anteroposterior cord width as a direct measure of indentation and attenuation. Illustrative examples of results from normal volunteers and patients suffering from cervical myelopathy are presented. The technique may prove particularly useful to the spinal surgeon in assessing the relative significance of individual lesions and may also be a powerful research tool in the study of cord biomechanics in the living body.

Adult↗
PubMedDate not supplied

Effects of level of retrieval success on recall-related frontal and medial temporal lobe activations.

Brain dedicated single photon emission computed tomography (SPECT) was used to compare the neuroactivation produced by the cued recall of response words in a set of studied word pairs with that produced by the cued retrieval of words semantically related to unstudied stimulus words. Six of the 12 subjects scanned were extensively trained so as to have good memory of the studied pairs and the remaining six were minimally trained so as to have poor memory. When comparing episodic with semantic retrieval, the well-trained subjects showed significant left medial temporal lobe activation, which was also significantly greater than that shown by the poorly trained subjects, who failed to show significant medial temporal lobe activation. In contrast, the poorly trained subjects showed significant bilateral frontal lobe activation, which was significantly greater than that shown by the well-trained subjects who failed to show significant frontal lobe activation. The frontal activations occurred mainly in the dorsolateral region, but extended into the ventrolateral and, to a lesser extent, the frontal polar regions. It is argued that whereas the medial temporal lobe activation increased as the proportion of response words successfully recalled increased, the bilateral frontal lobe activation increased in proportion to retrieval effort, which was greater when learning had been less good.

Adult↗
PubMedDate not supplied

Intercorrelation of lesions detected by magnetic resonance imaging after closed head injury.

Forty-three patients with closed head injuries were followed up 5 to 12 months post-injury. Patients had magnetic resonance imaging (MRI) and performed a variety of neuropsychological tests. There were systematic relationships between lesions in different sites: depth of lesions in orbito-frontal regions, frontal regions, and temporal poles were particularly strongly intercorrelated. Depth of lesions in specific sites also correlated with an overall measure of brain damage: the number of areas with lesions present. After correcting for premorbid differences there were significant correlations between lesions in specific sites and scores on three out of five WAIS subtests. Scores on these three subtests also correlated significantly with overall brain damage. In general, hemispheric sites which were significantly related to neuropsychological measures also showed significant intercorrelations among themselves. The findings stress the importance of patterns of lesions in head injury, and emphasize the difficulty of showing differential localization of cerebral function in this population.

Adolescent↗