Experiences at the new magnetic resonance imaging centre at Bristol

Further experience at the Bristol Centre, following the installation of a second MRI unit

A second magnetic resonance imaging (MRI) machine has been installed at the Bristol Centre, which therefore now has two systems (both 0.5T), working alongside, one being 5 years older than the other. This has allowed a virtual doubling of patient throughput. The financial cost of adding the necessary building extension and the comparative capital costs of the two machines, together with the differences in the cryogen requirements are itemized; as are the extra number of staff engaged. It is estimated that the new machine cost approximately half that of the original, bought in 1987, after allowing for inflation; and that the revenue costs have increased by only 25% in the first year, with a likely increase of about 45% in year two. One result has been that in Bristol, where there are now three MRI machines, myelography and knee arthrography as diagnostic procedures have almost disappeared.

MRI of the cervical spine: rheumatoid arthritis compared with cervical spondylosis

This study is a comparison of the cervical spine MR images from 26 patients with rheumatoid arthritis of the cervical spine with those from an age and sex matched group suffering from cervical spondylosis. Erosion of bone and major atlanto-axial subluxation were confined to rheumatoid arthritis. Soft tissue changes revealed by MRI included distortion of normal ligaments and bursae around the dens, particularly in rheumatoid arthritis. Abnormal masses of soft tissue were found in both groups, but those suggesting acute inflammation were much more frequent in rheumatoid arthritis than in cervical spondylosis. Neural compression was well demonstrated, and in rheumatoid arthritis was usually caused by bony structures whereas in cervical spondylosis it was usually due to disc material. It is concluded that MRI should be used as the first investigation to follow plain films in rheumatoid arthritis of the cervical spine. Bone and soft tissue changes are clearly shown, but interpretation of the images requires the recognition that some observed abnormalities may be due to coincidental cervical spondylosis.

Steps towards cost-benefit analysis of regional neurosurgical care

OBJECTIVE

To determine the cost of averting death or severe disability by neurosurgical intervention.

DESIGN

Retrospective analysis of one year's admissions for neurosurgery; comparison of outcome with expected outcome in the absence of neurosurgical intervention and with the cost of neurosurgery.

SETTING

Wessex Neurological Centre.

PATIENTS

1026 Patients were admitted to the neurosurgical service in 1984. Of 1185 admissions, 978 case records were available and outcome was known in 919.

MAIN OUTCOME MEASURES

Outcome was assessed with the Glasgow outcome scale, modified as necessary, from the case notes, or by letter follow up to the general practitioner. Expected outcomes for each of the 54 diagnoses were derived from both published reports where available and an expert panel of 18 consultant neurosurgeons. The cost of the neurosurgical service for 1983-4 was known from a separate study and the cost per patient was calculated using the length of stay.

RESULTS

The cost of neurosurgery in 1983-4 was 1.8 million pounds. In all, 243 deaths or severe disabilities were estimated to have been averted at an average cost of 7325 pounds (range 5000 pounds to 70,000 pounds). The overall cost per quality adjusted life year (QALY) was 350 pounds (range 34 pounds to greater than 400,000 pounds). The cost of long term care for severely disabled survivors is at least 18-fold greater than the cost of neurosurgical intervention to avert such disability.

CONCLUSIONS

In Britain neurosurgery is not expensive in comparison with the costs and benefits of other areas of medicine, and the cost per QALY is unexpectedly low except for severe diffuse head injury, malignant brain tumors, and cerebral metastases. The neurosurgical budget should be assessed in the context of managing a patient in hospital and subsequently in the community.

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.

A prospective audit of the use and costs of myelography in a regional neuroscience unit

A consecutive series of 397 myelograms performed in 385 patients over a six month period at the Mersey Regional Neurosciences Unit is reported. The reasons for performing the myelogram were to identify the cause of a radicular lesion in 54% of patients, a chronic spinal cord lesion in 30%, an acute cord lesion in 9%, suspected disease at the level of the foramen magnum 6%, and for a variety of other conditions in 8%. For the 385 patients undergoing a myelogram in the study period, the median interval from admission to request, request to myelography and from myelography to discharge was nought, one and three days respectively. The proportion of patients submitted to myelography by individual consultants ranged from 7% to 28%. There was a two-fold variation in the delays in the time to requesting and performing myelograms. There was room for improvement in the clinical information supplied on the myelography request form. The role of ancillary investigations and their effect on myelography was unclear. Only 16 of the patients with suspected cord disease had visual evoked responses performed before myelography. Five of them had myelography after an abnormal result. The estimated annual direct cost of myelography in the unit was at least 486,000 pounds. Reorganisation might have yielded hypothetical "savings" of between 30,000 pounds (6%) and 155,000 pounds (32%), though in practical terms these "savings" represented resources which might have been freed for use in other higher priority clinical problems within the unit, rather than true reductions in monetary cost.

Comparison of magnetic resonance imaging and computed tomography in suspected lesions in the posterior cranial fossa

OBJECTIVE

To compare computed tomography and magnetic resonance imaging in investigating patients suspected of having a lesion in the posterior cranial fossa.

DESIGN

Randomised allocation of newly referred patients to undergo either computed tomography or magnetic resonance imaging; the alternative investigation was performed subsequently only in response to a request from the referring doctor.

SETTING

A regional neuroscience centre serving 2.7 million.

PATIENTS

1020 Patients recruited between April 1986 and December 1987, all suspected by neurologists, neurosurgeons, or other specialists of having a lesion in the posterior fossa and referred for neuroradiology. The groups allocated to undergo computed tomography or magnetic resonance imaging were well matched in distributions of age, sex, specialty of referring doctor, investigation as an inpatient or an outpatient, suspected site of lesion, and presumed disease process; the referring doctor's confidence in the initial clinical diagnosis was also similar.

INTERVENTIONS

After the patients had been imaged by either computed tomography or magnetic resonance (using a resistive magnet of 0.15 T) doctors were given the radiologist's report and a form asking if they considered that imaging with the alternative technique was necessary and, if so, why; it also asked for their current diagnoses and their confidence in them.

MAIN OUTCOME MEASURES

Number of requests for the alternative method of investigation. Assessment of characteristics of patients for whom further imaging was requested and lesions that were suspected initially and how the results of the second imaging affected clinicians' and radiologists' opinions.

RESULTS

Ninety three of the 501 patients who initially underwent computed tomography were referred subsequently for magnetic resonance imaging whereas only 28 of the 493 patients who initially underwent magnetic resonance imaging were referred subsequently for computed tomography. Over the study the number of patients referred for magnetic resonance imaging after computed tomography increased but requests for computed tomography after magnetic resonance imaging decreased. The reason that clinicians gave most commonly for requesting further imaging by magnetic resonance was that the results of the initial computed tomography failed to exclude their suspected diagnosis (64 patients). This was less common in patients investigated initially by magnetic resonance imaging (eight patients). Management of 28 patients (6%) imaged initially with computed tomography and 12 patients (2%) imaged initially with magnetic resonance was changed on the basis of the results of the alternative imaging.

CONCLUSIONS

Magnetic resonance imaging provided doctors with the information required to manage patients suspected of having a lesion in the posterior fossa more commonly than computed tomography, but computed tomography alone was satisfactory in 80% of cases...