G. H. du Boulay

Intracranial infections: Investigation by computerized axial tomography

SummaryThe value of computerized axial tomography (CAT) in the management of intracranial infections is described and the findings compared with those of other conventional neuroradiological investigations. The most important contribution is in the diagnosis and localization of cerebral abscess. CAT provides not only information of the nature of the lesion but also the number of loculi and the presence of multiple lesions; it is the investigation of choice for follow-up of patients with cerebral abscess treated either by operation or conservatively. CAT is invalueither in the investigation of other infectious conditions affecting the intracranial structures, especially when patients present with a focal neurological deficit and it is vital to exclude an abscess.

Computed tomography in cervical spondylotic myelopathy and radiculopathy: visualisation of structures, myelographic comparison, cord measurements and clinical utility

SummarySixty-nine patients with cervical spondylotic myelopathy (CSM), radiculopathy (CSR), or both (CSMR) were studied with computed tomography (CT). Computer-assisted myelography (CAM) accurately determines the site and nature of spondylotic protrusions and provides good visualisation of the subarachnoid space and cord deformities even in areas with dilute metrizamide. However, excessive vertebral movement and bulging ligamenta flava with their effects on cord deformity, so easily visualised in myelograms, are completely or partially missed. In the assessment of CSM, metrizamide myelography (MM) followed by CAM should be performed, particularly when the myelographic images are unsatisfactory due to contrast dilution or blockage, when cord compression cannot be ascertained with MM and when cord atrophy is suspected. In CSR, the diagnostic information from MM and CAM is comparable. The diagnostic criteria in CAM are, however, less direct and since MM is adequate in uncomplicated cases, CAM is generally not necessary. The APD, APD/TD ratio, area and circularity are sensitive indices of cord deformity and the first two should be used more often to assist visual assessment of cord deformity. The relation between cord parameters and treatment response is better reflected in CSM cases managed conservatively and the results suggest that the degree of cord deformity is helpful in determining the outcome and hence the choice between surgical and conservative treatment. In plain CT, the osteophytes and calcified discs are adequately visualised and canal dimensions measured with accuracy, but the cervical cord and roots cannot be properly assessed and the diagnosis of CSM or CSR cannot be ascertained. At present, its role in cervical spondylosis is therefore limited.

The Demonstration of the Auditory Ossicles by High Resolution CT

SummaryThe high resolution CT scanning system introduced by EMI in 1978 has added a new dimension to computerised tomography in otology. The apparatus used for this study was an EMI CT 5005 body scanner adapted for head and neck scanning and incorporating a high resolution facility. The latter has proved most advantageous in areas of relatively high differential absorption, so that its application to the demonstration of abnormalities in the petrous temporal bone, and in particular middle ear disease has been very rewarding. Traumatic ossicular disruptions may now be demonstrated and the high contrast of CT often shows them better than conventional hypocycloidal tomography. The stapes is also better visualised and congenital abnormalities of its superstructure have been recorded. These studies have been achieved with a very acceptable level of radiation to the eye, lens and cornea and the technique is clearly a rival to conventional pluridirectional tomography in the assessment of the petrous temporal bone. With further design improvements high resolution CT could completely replace existing techniques.

Comparison of Angiographic and CT Findings between Patients with Multi-Infarct Dementia and Those with Dementia Due to Primary Neuronal Degeneration

The CT and angiographic appearances in multi-infarct dementia have been compared with those of primary neuronal degeneration. It was possible to make a CT or angiographic diagnosis of multi-infarct dementia in about 40% of patients diagnosed by the ischaemic scoring method of Hachinski et al. [1].

Morphology and measurements of the cervical spinal cord in computer-assisted myelography

SummaryThirty-six control subjects had computer assisted myelography (CAM) using the EMI CT 5005 scanner. The normal cervical cord is elliptical, more circular at the upper and lower ends and flatter in the mid-segments. Asymptomatic cord deformities, usually mild, were present in nine subjects (25%). Four measurements, namely, sagittal diameter (APD), transverse diameter (TD), area (a) and circumference (c) were made and two more parameters calcultted i.e. APD/TD ratio and circularity (=4 π a/c2). These control values form the basis of qualitative and quantitative assessment of cord deformity. When cord measurements are to be used, control values should be obtained for each scanner and procedures should be standardized

The calibre of cerebral arteries of the rat studied by carotid angiography: a model system for studying the aetiology of human cerebral arterial constriction after aneurysmal rupture.

SummaryRupture of human cerebral arterial aneurysms is followed by prolonged cerebral arterial constriction; there is evidence that cerebrospinal fluid (CSF) from such patients contains vasoconstrictor substances which may cause the arterial constriction. The aim of this study was to develop a small animal model for investigating the effects of such CSF on the calibre of cerebral vessels in situ. Carotid angiography of the cerebral arteries of the rat visualises the internal carotid, middle cerebral, anterior cerebral and stapedial arteries plus the vertebrobasilar system. Prostacyclin was injected during carotid catheterisation to prevent spontaneous and random occlusion of these cerebral arteries; in the presence of prostacyclin there was no arterial occlusion for up to 5 h. The resolution achieved by the angiographic technique, which magnified the cerebral circulations 2.9 times, was sufficient to measure the diameter of the internal carotid and stapedial arteries of the rat. Intracarotid infusion of 1.0 ml CSF collected from patients with ruptured cerebral arterial aneurysms caused a rapidly developing contraction of cerebral arteries lasting up to 5 h. Thus, we consider that the rat may also be used as a model for investigating the aetiology of human cerebral arterial constriction after aneurysmal rupture.

Comparison of the measurements of the cerebral ventricles obtained by CT scanning and pneumoencephalography

SummaryThis study was undertaken to compare the accuracy of measurements of the ventricular system obtained by the CT scanner and pneumoencephalography (PEG). In it the ventricular system was evaluated in each case by measuring the span of the frontal horns, cellae mediae and third ventricle in relation to the diameter of the inner and outer tables of the skull from the PEG films. The indices of Evans, Schiersmann, and Schaltenbrand and Nürnberger were applied to these measurements. The same indices were obtained using the appropriate CT printouts. A very good measure of agreement was obtained with the indices arrived at from both the CT scan printouts and the pneumoencephalograms.

Comparing the cost of spinal MR with conventional myelography and radiculography

SummaryAll spinal magnetic resonance imaging examinations carried out during a three month period were analysed retrospectively in order to determine the clinical reasons for the scan requests. Technical details of the examinations they received and the clinical profiles formed a data set which revealed 10 separate “Clinical groups” for management purposes. Hardware, salary and expendables were costed as though the imaging unit had been sited within a National Health Service radiology department. A spread sheet was designed capable of calculating costs per patient for a variety of types of working week and of different staffing structures, sensitive to the mixture of clinical groups referred for examination. The spreadsheet also accomodated straight line depreciation for hardware value and interest rates for borrowed capital. A second, prospectively observed, sample of spinal MR examinations was used to improve the accuracy of the timing of the length of patient examinations. Costs were compared with those for patients submitted for myelography and radiculography at the adjacent hospital during the same period. The comparison indicated that spinal MR was less costly than myelography and radiculography. The most important element of the extra cost of myelography related to the need to admit patients to hospital for at least one night for this examination because of the likelihood of headache and other common (though usually minor) complications following lumbar puncture and/or the injection of contrast medium. From the limited information that it was possible to obtain in the period of follow up, it appeared that MR had either been superior or equivalent to myelography or radiculography in all the clinical groups of patients where both could be tested. There were a number of groups in which no myelograms had been requested, presumably because clinical suspicions had pointed toward conditions like tumours, developmental abnormalities and demyelinating diseases in which neurologists and neurosurgeons have already made up their minds about the superiority of MR.

Evaluation of computer advisor in the interpretation of CT images of the head

SummaryThis paper describes the evaluation of a computer advisor system (BRAINS), which was constructed to aid in the interpretation of CT images of the head. It was developed at the National Hospital for Nervous Diseases, Queen Square, London. The system was transferred, without difficulty, to an ‘external’, that is previously unassociated, site (the Department of Diagnostic Radiology, University of Manchester) for an external evaluation. Response of external users to the system was mixed. Many were unfamiliar with the concept of formal description of images and the evaluation demonstrated the need for a person to person training programme. Users who accessed the HELP facilities most frequently were the most successful in obtaining accurate descriptions and hence satisfactory diagnostic advice. An objective appraisal of users success in describing images to obtain the correct diagnosis as first choice indicated that, in general, the system performed well.

Brains — a computer advisor system to aid in CT scan interpretation and cerebral disease diagnosis

SummaryThis paper describes a prototype system to aid in the radiological interpretation of CT scan images of patients with cerebral disease. The system is able to provide guidance, both on diagnosis and the need for enhancement.