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Thirty-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 calculated i.e. APD/TD ratio and circularity (= 4 pi 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.

This paper describes the initial findings of computer-assisted diagnosis of cerebral tumours using Bayes' Theorem and CT scans. For various sets of signs, tables of accuracy and reliability have been constructed, and a computer versus radiologist analysis for three types of tumour has been made. Based only on the results of CT scans, the computer has produced diagnoses relatively quickly, and overall these are of reasonable accuracy when compared with the radiologists' reports. The worst results occurred in the prediction of meningiomas, the reasons for which will be examined in subsequent work.

High-resolution computerized tomography (CT) has been used to investigate abnormalities of the ear and petrous bone. Congenital, traumatic, infective and neoplastic lesions have been evaluated in 30 patients with proven pathology. Some bone changes including abnormalities of the auditory ossicles have been better demonstrated than by conventional tomographic technigues, and high-resolution CT has some advantages in demonstrating both soft tissue abnormality and bone changes in the middle ear in primary neoplastic disease and secondary cholesteatoma. The absence of any practical means of taking sagittal sections with the present scanner design limits the usefulness of high resolution CT of the petrous bone, but this study has shown that the technique may now take its place as an important complementary procedure to pluridirectional tomography.

Two different types of retrospective study of the value of CT have been contrasted. In one, the patients were chosen because of the way they presented (with posterior fossa signs of symptoms) or because they were found to have posterior fossa disease; in the other, all were reported as having, or found to have, gliomas or metastases. The first type of study provides a better basis for evaluation of neuroradiological procedures.

This 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 user's success in describing images to obtain the correct diagnosis as first choice indicated that, in general, the system performed well.

In order to determine further the correlation between severe migraine and cerebral atrophy, a group of patients attending either the Charing Cross Hospital migraine clinic or outpatient clinics at the National Hospital, Queen Square, was investigated by computed tomography. The results confirm an association between atrophy and migraine of more than 5 years duration, probably more severe in men than women. The most striking changes were seen in those men who suffered from attacks lasting less than 6 hr.

The 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 invaluable 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.

This paper describes the development and use of a system to aid in the radiological interpretation of C.T. scan images of patients with cerebral disease. The system is able to provide guidance, both on diagnosis and the need for further scan investigations. Explanation and help facilities, similar to those found in certain rule-based expert systems, are available on demand. Diagnostic and other advice is, however, based on hard statistical data. The scan interpretation and diagnostic system offers important benefits in the training of less experienced radiologists.

Patients suffering from severe migraine, usually for many years, have been examined by the EMI scanner between attacks. Judged by criteria validated originally by comparison with pneumoencephalography, about half of the patients showed evidence of cerebral atrophy. Perhaps of more significance than generalised atrophy was the frequency of areas of focal atrophy and of evidence of infarction.

The spinal cord is not consistently shown by plain computed tomography or with iodide enhancement. Xenon enhancement increases the attenuation of the spinal cord and visualization is improved considerably; fluid-filled cavities, including syringohydromyelia, do not enhance and are clearly defined.

Computerized tomography has been used as the initial radiologic investigation among 212 intracranial tumor suspects. Ninety-five of these patients were ultimately shown to have tumors as a result of all their investigations. Eighty tumors were clearly defined by EMI scanning, four further scans were suspicious but not unequivocally abnormal and six scans showed complications of the tumor rather than the lesion itself. Thus, only five scans were falsely negative in the presence of a tumor. The false positive and false negative rates for EMI scanning have been compared with conventional techniques and computerized tomography shown to compare favourably with angiography or encephalography.

The contribution of plain X-rays to the management of 170 patients suspected or actually found to have posterior fossa disease has been retrospectively assessed. A useful contribution was made in 4%.

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.

The safety of post-myelogram computed tomography (PMCT) as an additional diagnostic procedure to metrizamide myelography was evaluated. One hundred and four consecutive patients with suspected cervical cord lesions were studied prospectively; 50 had both myelography and PMCT, and the 54 acting as controls had only myelography. PMCT did not increase the incidence, severity or duration of common side effects and the majority of patients accepted this additional procedure. It is concluded that as long as care is taken to avoid the occurrence of excessive contrast in the intracranial subarachnoid space, PMCT is a safe procedure.

The results of computer assisted tomography (80 x 80 matrix) of 600 patients are presented.

Referring to literature and our own cases (140.048 CT investigations--37% of them after intravenous application of contrast media) the possibility of decrease in consequence of contrast application is discussed.

Twenty-four cases have been operated upon using a prototype Brown-Roberts-Wells, CT-guided stereotactic neurosurgical system. This device has proved to be practical and flexible in clinical use. No CT scanner modifications were required, a fact which simplified its use in more than one hospital. Multiple targets can be biopsied with ease and relative safety. Drainage and other therapeutic procedures can be carried out with minimal hazard. Future applications of this system may include its use with NMR and PET images.

The 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.

This 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.

Statistical analysis was performed of the carefully coded results of computed tomographic scans, with and without contrast medium, of a substantial group of patients with proved diagnoses. Bayesian methods were used to provide computer-aided diagnoses with considerable success. Further analysis of these results suggested that expert advice can be provided by the computer concerning which patients would benefit diagnostically from enhancement after their plain scan description has been fed into the computer.