Statistical support for uncertainty in radiological diagnosis.

Radiological interpretation and diagnosis involves the comparison and classification of complex medical images and is typical of the categorisation tasks that have been the subject of observational studies in Cognitive Science. This paper considers the affinity between statistical modelling and theories of categorisation for naturally occurring categories. Statistical based measures of similarity and typicality with a probabilistic interpretation are derived. The utilisation of these measures in the support of diagnosis under uncertainty via interactive overview plots is described. The application of the methodology to magnetic resonance imaging of the head is considered. The methods detailed have application to other fields involving archiving and retrieving of image data.

Structured computer-based training in the interpretation of neuroradiological images.

Computer-based systems may be able to address a recognised need throughout the medical profession for a more structured approach to training. We describe a combined training system for neuroradiology, the MR Tutor that differs from previous approaches to computer-assisted training in radiology in that it provides case-based tuition whereby the system and user communicate in terms of a well-founded Image Description Language. The system implements a novel method of visualisation and interaction with a library of fully described cases utilising statistical models of similarity, typicality and disease categorisation of cases. We describe the rationale, knowledge representation and design of the system, and provide a formative evaluation of its usability and effectiveness.

The story of the internal carotid artery of mammals: from Galen to sudden infant death syndrome.

Some anatomical aspects of the blood supply of the brains of mammals have been examined to illuminate their functions. A fundamental explanation of sudden infant death syndrome (cot death) is suggested following experimental observations. Speculative contributions have been made to comparative physiological ideas concerning mammals of pronograde and erect habitus, their vascular pressure adaptations and temperature management. Neuro- and interventional radiologists may make some significant future applications of these ideas. Of immediate practical interest is the possibility of influencing the well-being of human embryos' neural tube development in utero by a comprehensive study of their temperature environment.

Focal signal hyperintensities in schizophrenia.

The presence of focal signal hyperintensities on MRI images of the brain was compared in 48 schizophrenic patients, 26 patients with bipolar disorder and 34 healthy controls. Significantly larger areas of brain were affected by focal signal hyperintensities, particularly in the frontal lobes, in the schizophrenic group compared to the bipolar group and the controls. Although the bipolar group had more such foci than controls, this difference did not reach statistical significance.

The Maudsley Family Study. I: Structural brain changes on magnetic resonance imaging in familial schizophrenia.

1. The authors investigated the prevalence of qualitatively rated structural brain abnormalities in schizophrenic probands and their first-degree relatives from families multiply affected with schizophrenia. 2. Magnetic resonance imaging was used to evaluate brain morphology in 33 schizophrenic probands, 54 of their non-schizophrenic first-degree relatives (including 11 presumed obligate carriers) and 37 unrelated control subjects. Structural images were examined by a neuroradiologist who was blind to diagnostic and family status. 3. 52% of the schizophrenic subjects were rated as showing abnormalities compared with 27% of presumed obligate carriers, 16% of their non-schizophrenic relatives and 11% of unrelated controls. 4. Brain abnormalities were more frequent in schizophrenic subjects from multiplex families than in their first-degree relatives and controls. Abnormalities were also found in unaffected relatives particularly those who appear to be transmitting the disorder.

Patterns of disease activity in multiple sclerosis patients: a study with quantitative gadolinium-enhanced brain MRI and cytokine measurement in different clinical subgroups.

In this study we assessed the subclinical disease activity in 45 patients with primary progressive, secondary progressive or relapsing-remitting multiple sclerosis (MS). The patients had gadolinium-enhanced brain MRI scans, which were analysed using a semiquantitative method both for lesion load and for degree of enhancement. At the same time cerebrospinal fluid (CSF) and serum samples were collected and, from these, cytokine levels were measured in most cases by enzyme-linked immunoassay using commercially available kits. Enhancing lesions on MRI were found in 73% of the patients. The sensitivity of this test was greatly increased by our method of analysis as far as the primary progressive patients are concerned (70% vs 40% for conventional evaluation). CSF interleukin-1 beta (IL-1 beta) levels were above the normal range in 22% and IL-6 levels in 13% of patients, while tumour necrosis factor alpha (TNF-alpha) was undetectable or below the upper normal limits in all the samples tested. Serum IL-1 beta was above the normal limits in 40%, IL-6 in 42% and TNF-alpha in 7% of patients. No significant differences in cytokine profiles were found between the clinical subgroups. This study confirms the high sensitivity of gadolinium-enhanced MRI in detecting MS activity, which was further increased by our method of analysis. Longitudinal studies performed with more sensitive immunological techniques are needed to define better the relationship between cytokine, clinical and MRI data in MS patients.

Reduction of cortical volume in schizophrenia on magnetic resonance imaging.

The MRI scans of 48 schizophrenic patients, fulfilling RDC criteria, were compared to those of 34 healthy controls matched for age, ethnicity and parental social class. The volume of the frontal and anterior parietal lobes was significantly reduced in the schizophrenic group as a result of a selective decrease in cortical volume, with a corresponding increase in the volume of sulcal fluid. Reduction in the volume of the temporal grey matter was more marked on the right, but was not in excess of the loss of volume observed in other areas of the cortex. MRI abnormalities correlated poorly with clinical parameters, although both unemployment and poor pre-morbid adjustment predicted reduced cerebral volume and increased sulcal volume. These results question whether the medial temporal lobes are the only site of structural pathology in schizophrenia.

Psychotic illness in multiple sclerosis. A clinical and magnetic resonance imaging study.

Ten patients with multiple sclerosis (MS) and psychosis were assessed using the Present State Examination, and matched retrospectively with respect to age, disability, duration of symptoms, and disease type with 10 MS patients without psychosis. Both groups underwent MRI of the brain. There was a trend for the psychotic group to have a higher total lesion score, particularly around the periventricular areas. This reached statistical significance in the areas around the temporal horn. In all cases, neurological symptoms preceded the onset of psychosis. The psychotic group also had a later age of onset of psychosis than psychotic patients without brain disease. These results point to an aetiological association between the pathological process of MS and psychosis.

Age determination of common marmosets (Callithrix jacchus) by radiographic examination of skeletal development.

Seventy-four animals were examined radiographically to determine the skeletal development of the common marmoset (Callithrix jacchus) from 6 months of age. Twenty-one epiphyses were examined and five stages of ossification were described for each. The animals were divided into nine groups, according to age, and a table of the stage of ossification and age was produced, which may be used for determining the age of animals of unknown history.

The measurement of blood flow waveforms from X-ray angiography. Part 1: Principles of the method and preliminary validation.

The principles and implementation of a method for measurement of blood flow waveforms from X-ray angiography are described. Contrast medium mass values are obtained at multitudinous positions along individual vessels and from numerous images in a time sequence. These values are represented as a matrix of grey levels in a parametric image. This image is normalized to represent contrast medium concentration, and the movement over time of isoconcentration portions of the contrast bolus is recovered to determine blood flow. Preliminary validation has been undertaken using parametric images generated in two ways: synthesis from a computer model of vascular pulsatile flow and analysis of cine-angiograms of physical models (plastic and perspex tubes) carrying known pulsatile flows. Two distinct methods for interrogation of parametric images by digital image processing were employed; both provided accurate flow measurements.

The measurement of blood flow waveforms from X-ray angiography. Part 2: Application to video recordings of digital subtraction angiography.

A method of measuring blood flow from X-ray angiograms recorded on cine film, by obtaining contrast mass values at numerous positions along individual vessels and at multiple instants of time, has been previously reported. In the present work it was hypothesized that the signal-to-noise limitations of recordings on video tape could be overcome by recording already-subtracted angiograms from a digital subtraction angiographic (DSA) system and that the spatial resolution of video was adequate to use a similar measurement method. Validation experiments were recorded, in which flows measured using a calibrated electromagnetic flowmeter passed through tubes of 4-7 mm diameter, during injections of 2-5 ml contrast medium. The video sequences were computer analysed and produced angiographic flow measurements agreeing with the electromagnetic flows to within 5 per cent. A case study of a clinical carotid artery DSA in a patient with secondary carcinoma metastases in the brain is described. It is concluded that accurate flow measurements can be made from DSA video recordings.

Volume measurement of multiple sclerosis lesions with magnetic resonance images. A preliminary study.

The ability to visualise multiple sclerosis lesions in vivo with magnetic resonance imaging suggests an important role in monitoring the course of the disease. In order to help the long-term assessment of prospective treatments, a semi-automated technique for measuring lesion volume has been developed to provide a quantitative index of disease progression. Results are presented from a preliminary study with a single patient and compared to measurements taken from lesion outlines traced by a neuroradiologist, two neurologists and a technician. The semi-automated technique achieved a precision of 6% compared to a range of 12-33% for the manual tracing method. It also reduced the human interaction time from at least 60 min to 15 min.

Frequent involvement of the optic radiation in patients with acute isolated optic neuritis.

Magnetic resonance imaging revealed asymptomatic lesions in white matter regions corresponding with the optic radiations in 20 of 28 patients (71%) with clinically isolated optic neuritis. In contrast to the findings with symptomatic lesions, there was no relationship between the latency of the visual evoked potential and the presence of these asymptomatic posterior visual pathway lesions.

Correlation of SEP abnormalities with brain and cervical cord MRI in multiple sclerosis.

In 31 patients with definite or suspected multiple sclerosis (MS) presenting with a cervical cord syndrome, somatosensory evoked potentials (SEPs) were recorded to median and posterior tibial nerve stimulation, using cephalic and noncephalic reference electrodes. Magnetic resonance imaging (MRI) of the brain and cervical spinal cord was performed, the latter in sagittal and axial views. SEPs were abnormal in 67.7% of patients, whereas MRI showed cervical cord lesions in 74.2% and intracranial lesions possibly involving the somatosensory pathways in 64.5% of cases. A significant correlation was found between abnormalities of cervical (N13) and cortical (N20) potentials following median nerve stimulation with Fz reference and MRI abnormalities involving the ipsilateral or posterior half of the cervical cord, but not the contralateral or anterior half. The N13 potential, recorded from the low cervical region to a supraglottal reference, was most frequently abnormal in patients with MRI lesions at C6 or C7, whereas P14, recorded from the scalp to a clavicle reference, was most often affected by lesions at Cl or the cervicomedullary junction. Abnormalities of the cortical P40 to tibial nerve stimulation were less significantly correlated with cervical MRI lesions. The latency of N20 measured from N9 at the clavicle and the absolute latency of P40 were significantly correlated with the length of MRI abnormalities in the ipsilateral cervical cord. No significant correlation was observed between SEP abnormalities and brain MRI lesions, which it was considered might possibly involve the intracranial somatosensory pathways. It was concluded that (1) the morphological lesions seen in MRI of the cervical cord usually give rise to appropriate electrophysiological deficits, but the occasional finding of a widespread MRI lesion with normal SEP suggests that myelin damage is not the only or the major factor responsible for abnormal MRI signal; and (2) 'clinically silent' lesions apparently involving the radiations and other sensory structures of the brain appear not to give rise to detectable SEP abnormalities, using the methods of the present study.

Abnormalities of horizontal gaze. Clinical, oculographic and magnetic resonance imaging findings. I. Abducens palsy.

Fifty one patients with abnormalities of horizontal gaze were studied with magnetic imaging of the brain (MRI) and eye movement recordings to identify the loci of lesions responsible for isolated abducens palsy, conjugate gaze palsy and different types of internuclear ophthalmoplegias. The lesions responsible for a particular disorder were identified by overlapping enlarged drawings of the individual scans at comparable brain-stem levels and identifying the areas where the abnormal MRI signals intersected. A statistical procedure was devised to exclude the possibility that the areas of overlap occurred by chance. In this paper, the findings in the group of patients with VI nerve palsy are reported since the location of their lesions could be predicted from known anatomy, so validating the procedure. The results were independently obtained with the overlapping technique and the statistical procedure and showed that the lesions were located in a region corresponding to the posterior part of the abducens fasciculus. This confirms that central lesions producing isolated lateral rectus weakness spare the abducens nuclei. The agreement between the procedures used and earlier clinical and experimental results suggest that the method we describe can be applied to locate the site of lesions on MRI scans in other groups of patients with more complex gaze disorders.

Abnormalities of horizontal gaze. Clinical, oculographic and magnetic resonance imaging findings. II. Gaze palsy and internuclear ophthalmoplegia.

The site of lesions responsible for horizontal gaze palsy and various types of internuclear ophthalmoplegia (INO) was established by identifying the common areas where the abnormal MRI signals from patients with a given ocular-motor disorder overlapped. Patients with unilateral gaze palsy had lesions in the paramedian area of the pons, including the abducens nucleus, the lateral part of the nucleus reticularis pontis caudalis and the nucleus reticularis pontis oralis. Patients with abducens nucleus lesions showed additional clinical signs of lateral rectus weakness. Lesions responsible for bilateral gaze palsy involved the pontine tegmental raphe. Since this region contains the saccadic omnipause neurons, this finding suggests that damage to omnipause cells produces slowing of saccades rather than opsoclonus, as previously proposed. All INOs, regardless of the presence of impaired abduction or convergence, had similar MRI appearances. Frequently the lesions in patients with INO, were not confined to the medial longitudinal fasciculus (MLF) but also involved neighbouring structures at the pontine and mid-brain levels. There was a statistically significant association between the clinical severity of the INO and the presence of abnormal abduction or convergence. The findings suggest that the lesions outside the MLF, which may affect abducens, gaze or convergence pathways, are responsible for the presence of features additional to INO, depending on the magnitude of functional disruption they produce.

Comparing the cost of spinal MR with conventional myelography and radiculography.

All 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.