Patterns of chronic adhesive arachnoiditis following Myodil myelography: the significance of spinal canal stenosis and previous surgery

109 patients who had undergone Myodil myelography on at least one occasion were identified. The patterns of lumbar nerve root distribution in this group were examined using magnetic resonance imaging. The relationship between these patterns and the presence of spinal stenosis or previous surgery was investigated. Chronic adhesive arachnoiditic nerve root patterns were seen in 68 patients and were classified into three groups according to Delemarter et al. Central clumping of nerve roots (type 1) and complete opacification of the thecal sac (type 3), extending over at least one vertebral level, were significantly related to spinal stenosis at an adjacent level (p < 0.0001). Peripheral adhesion of nerve roots to the theca (type 2) was significantly related to previous surgery at the level of abnormality (p < 0.00005). Only a single case of arachnoiditic nerve root patterns was seen in the absence of stenosis or previous surgery. We conclude that chronic adhesive arachnoiditis is significantly related to previous Myodil myelography in the presence of spinal stenosis or previous surgery but that Myodil alone rarely produces these changes.

Magnetic resonance image synthesis using a flexible model

Image synthesis methods are based on the hypothesis that a magnetic resonance (MR) image with optimized contrast can be reproduced by synthesis from three calculated basic images of T1, T2 and spin density. This method, however, is limited by noise due to uncertainties in the initial measurements. The principal component analysis (PCA) method is based on an information theory approach that decomposes MR images into a small set of characteristic feature images. PCA images, or eigenimages, show morphology by condensing the structural information from the source images. Eigenimages have also been shown to improve contrast-to-noise ratio (CNR) compared with source images. In this study we have developed a method of synthesizing MR images using a flexible model, comprising a set of eigenimages derived from PCA. A matching process has been carried out to find the best fit between the model and a synthetic image calculated from the Bloch equations. The method has been applied to MR images obtained from a group of patients with intracranial lesions. The images derived from the flexible model show increased lesion conspicuity, reduced artefact and comparable CNR to the directly acquired images while maintaining the MR characteristic information for diagnosis.

Does degenerative disease of the lumbar spine cause arachnoiditis? A magnetic resonance study and review of the literature

The magnetic resonance appearances in 165 patients with symptoms suggestive of degenerative lumbar spine disease were reviewed. The aim of the study was to evaluate the relationship between abnormalities of nerve root distribution and degenerative disease of the lumbar spine in the absence of other known risk factors for arachnoiditis. Central clumping of nerve roots was present in 16 patients (9.7%) and was associated with spinal stenosis at one of the affected levels in all (p < 0.001). Spinal stenosis was present in 44 patients giving an incidence of abnormal nerve root distribution of 36% in this group. Nerve root clumping occurred in association with pure spinal stenosis (10 cases), stenosis secondary to disc prolapse (four cases) and degenerative spondylolisthesis (two cases). Nerve root clumping was confined to one vertebral level in nine cases and extended over two to four levels in seven. In five of the latter spinal stenosis was present at multiple levels. The appearance of nerve root clumping described here may result entirely from mechanical apposition of nerve roots but is indistinguishable from the central pattern of nerve root adhesions which occurs in adhesive lumbar arachnoiditis. No abnormalities of nerve root distribution were seen in association with any indicator of degenerative disk disease in the absence of stenosis. We have been unable to demonstrate the previously reported relationship between lumbar disk degeneration and arachnoiditis and discuss this with a critical review of the literature. Abnormal central clumping of nerve roots as described in arachnoiditis may occur in association with spinal stenosis in the absence of other risk factors although the cause for this appearance remains unexplained. Arachnoiditis-like changes extending over more than one vertebral level are rare (7%) except in the presence of spinal stenosis at multiple levels (29%). Awareness of this appearance may avoid a possibly incorrect diagnosis of arachnoiditis in the presence of a treatable stenosis.

Staging, volume estimation and assessment of nodal status in carcinoma of the cervix: comparison of magnetic resonance imaging with surgical findings

Pre-operative magnetic resonance imaging (MRI) was carried out in 50 women scheduled for operative treatment of invasive carcinoma of the cervix. The extent of the primary tumour (stage), its dimensions and the presence of lymph node enlargement were assessed and compared with findings at surgery and/or histopathological examination of the resected uterus. In 45 patients undergoing radical hysterectomy, accuracy of MRI staging of the primary tumour was 84.4%. In the group as a whole, including four patients with inoperable disease, staging accuracy was 84%. Most errors were due to difficulty in identifying early vaginal or parametrial invasion by tumour. There was close correlation between the volume of tumour measured from pre-operative MRI scans and measurements made on the hysterectomy specimen (r = 0.95). MRI had a sensitivity of 75% and a specificity of 88% in predicting metastatic lymphadenopathy, based solely on the criterion of enlargement of any pelvic or para-aortic nodes to 1.5 cm or greater. However, retrospective analysis of the presence or absence of metastases by site in 49 patients undergoing lymphadenectomy or lymph node sampling at laparotomy showed that true sensitivity to be 57.1% and the specificity 96.8%. Differentiation between malignant and reactive lymphadenopathy was not reliably achieved on MRI, and in several patients, metastases were present in normal-sized lymph nodes.

Clinical evaluation of fast spin echo sequences for cranial magnetic resonance imaging at 0.5 tesla

Fast spin echo (FSE) sequences enable T2-weighted MR scans to be obtained in a fraction of the time necessary for conventional SE sequences with long TR and long TE. Comparison has been made of a FSE sequence (TR = 4000 ms, effective TE = 100 ms, 2 NEX) with the T2-weighted SE sequence (TR = 2000 ms, TE = 90 ms, 1-2 NEX) normally used in 35 patients referred for cranial MRI. Contrast-to-noise ratios (CNR) for grey:white matter and brain:CSF on the FSE sequence compared favourably with variable echo (VE) sequences which take up to three times as long to acquire. Although the conspicuity of some pathological lesions such as multiple sclerosis plaques was inferior to that of conventional T2-weighted SE scans, no lesions were missed on FSE scans. The FSE sequence was more prone to movement artefacts. The benefit of the markedly increased patient throughput made possible by using the FSE sequence outweighs the slight reduction in sensitivity for small lesions.

Magnetic resonance imaging with Gadolinium-DTPA for assessment of bladder carcinoma and its response to treatment

Magnetic Resonance Imaging (MRI) with intravenous Gadolinium-DTPA (Gd-DTPA, Magnevist, Schering-AG) was performed in 44 patients, 32 with primary bladder carcinoma and 12 with suspected recurrence after treatment. Gd-DTPA often increased diagnostic confidence in the identification and staging of tumours confined to the bladder wall and was necessary to assess depth of bladder wall invasion when T2-weighted images were suboptimal. Enhancement after Gd-DTPA enabled distinction between necrotic and viable tumour and blood clot. There was little advantage in its use for tumours infiltrating perivesical fat or with metastases to lymph nodes or bone, in the absence of a fat suppression sequence. Gd-DTPA may therefore be useful in selected patients with tumours of Stage T3a or less in whom information about depth of bladder wall invasion is inadequately shown on pre-contrast sequences. Artefacts due to variable and inhomogeneous urine signal intensity, however, often degraded post-Gd-DTPA images of the bladder. Changes in the bladder due to radiotherapy were observed on MRI 3-4 months after treatment in patients referred for routine follow-up and in some patients with suspected recurrence. Mucosal hyperintensity, thickening and abnormal signal intensity of the muscular layers of the bladder wall, with enhancement after Gd-DTPA were demonstrated. Such changes obscured small volume or superficial recurrence of tumour after radiotherapy. Abnormal enhancement was also observed in pelvic organs and soft tissues irradiated several years earlier. Enhancement after Gd-DTPA does not therefore reliably distinguish between recurrent tumour and radiotherapy change.

How frequent is chronic lumbar arachnoiditis following intrathecal Myodil?

Chronic lumbar arachnoiditis has numerous causes, including the introduction of contrast media into the lumbar subarachnoid space. The oily contrast medium Myodil (iophendylate) is often cited but the true incidence of symptomatic lumbar arachnoiditis due solely to the presence of Myodil is unknown. A retrospective review of 98 patients in whom Myodil was introduced by ventriculography or cisternography, i.e. remote from the lumbar spine, revealed no cases of chronic lumbar arachnoiditis. All patients were monitored closely for periods ranging from 1 to 28 years. We conclude that, in these circumstances, it is rare for Myodil to produce symptomatic arachnoiditis.

Magnetization transfer contrast (MTC) imaging of skeletal muscle at 0.26 Tesla--changes in signal intensity following exercise

Magnetization transfer contrast (MTC) imaging of skeletal muscle before and after exercise has been studied in normal volunteers at 0.26 Tesla. A saturation pulse was applied over a range of offset frequencies immediately before a gradient recall echo sequence. Substantial signal loss was observed in all muscles. After exercise, selective saturation resulted in a significant increase of contrast between active and less active muscle, a phenomenon attributable to an increase in extracellular water content. MTC imaging provides a more sensitive method to detect changes in water distribution in human skeletal muscle.

Investigation of children with suspected spinal dysraphism by magnetic resonance imaging

Findings on Magnetic Resonance Imaging (MRI) of 52 children with suspected spinal dysraphism have been reviewed. In 24, no significant spinal abnormality was demonstrated. Seven patients had scoliosis or vertebral segmentation anomalies without demonstrable abnormality of the underlying soft tissues and one had an isolated subcutaneous haemangioma. In 20 children with spinal dysraphism, a low tethered cord was the most frequent finding, occurring in 80%. Other manifestations included myelo- or meningocoele (60%), syringomyelia (30%), lipoma (25%), congenital tumour (20%), diastematomyelia (15%) and thickened filum terminale (5%). The relationship between the clinical reason for requesting MRI and the scan results are discussed.

The effects of sodium nitroprusside on Doppler signals from a soft tissue tumour

In a previous study, we described the effects of systemic vasoconstriction on the Doppler signals from a soft tissue tumour (Taylor et al, 1989). Our conclusions were that vasoconstriction produced significant changes in the signals from normal vessels and enhanced the differences between normal and neoplastic vessel signals. The aim of this study was to determine whether converse changes were produced by vasodilatation.

Magnetic resonance imaging of musculoaponeurotic fibromatosis

Musculoaponeurotic fibromatosis can be mistaken for soft-tissue sarcoma both clinically and on X-ray computed tomography. Magnetic resonance imaging (MRI) in three patients with this condition enabled the correct diagnosis to be made prospectively in two. The appearance on MRI of a heterogeneous mass with well-defined, predominantly peripheral areas of very low signal intensity due to dense fibrous tissue and areas of medium to high signal intensity corresponding to a more cellular stroma should raise the the suspicion of musculoaponeurotic fibromatosis. Cellular areas within the tumour showed moderate enhancement after gadolinium diethylene triamine pentaacetic acid administration.

Musculoskeletal haemangiomas: comparison of MRI with CT

MRI and CT findings were reviewed from 11 patients with musculoskeletal haemangiomas. With MRI, morphological characteristics and extent of haemangiomas were optimally demonstrated on T2-weighted spin echo scans. High-resolution contrast-enhanced CT provided equivalent information regarding lesional characteristics and extent for small, localized haemangiomas. In CT evaluation of the extent of large haemangiomas, the radiation dose, transaxial scan plane, amount of intravenous contrast medium required and the necessity for correct timing of post-contrast scans became limiting factors. For such lesions, particularly those extending into the trunk, MRI supplemented by a plain radiograph is the optimum method of evaluation.

Accuracy in staging carcinoma of the bladder by magnetic resonance imaging

Thirty-four patients with a presumptive diagnosis of carcinoma of the bladder diagnosed at EUA and cystoscopy have been staged by MRI and the findings correlated with pathology in 15 patients and clinical follow-up, including repeat cystoscopy, in the remainder. MRI is accurate in identifying tumours confined to the bladder wall or extending beyond the wall to involve perivesical fat or adjacent organs. Whilst it is not possible to distinguish between T1, T2 or early T3a tumours they can be distinguished from advanced T3a lesions and this may affect management. MRI is superior to clinical staging, particularly in detecting lymphadenopathy and provides information for optimal radiotherapy planning. The problem of distinguishing between the effects of radiotherapy and suspected recurrent tumour is discussed.

Diagnosis and assessment of mitral and aortic valve disease by cine-flow magnetic resonance imaging

Seventy-six aortic and mitral valves, in 44 patients and 5 normal volunteers, were studied by Cine-Flow MRI (on a 0.26-T superconducting magnet system), utilizing compound oblique imaging planes and a Field Echo Even Rephasing sequence. All patients had had cardiac catheterization and echocardiography. All patients with valvular stenosis and aortic sclerosis (n = 45) showed complete signal loss distal to the respective valve. Length of signal loss distal to the aortic valve in those in whom it was measured (n = 15) allowed differentiation of aortic stenosis (n = 9) from sclerosis (n = 6). This also permitted grading of stenosis with highly significant correlation (T = 0.86; P less than 0.002) with pressure gradient measurement. In mitral stenosis (n = 12) calculation of the area of signal loss distal to the mitral valve as a percentage of left ventricular cross-sectional area showed a highly significant correlation (T = 0.77; P = 0.001) with pressure gradient measurement. Clinically significant valvular regurgitation was graded by size and duration of signal loss proximal to the value with concordance with angiocardiography. It is concluded that Cine-Flow MRI has a clinical role in the diagnosis and assessment of valvular heart disease.

The effects of angiotensin II on Doppler signals from a soft-tissue tumour

A 10 mHz continuous-wave Doppler system has been used to detect blood flow within a sarcoma implanted in a rabbit's ear. The effects of vasoconstriction produced by intravenous angiotensin II were studied. Criteria are described that enabled differentiation of the Doppler signals from the tumour from those of the adjacent central artery. The effect of vasoconstriction upon these criteria is also described.

Quantitative magnetic resonance imaging of vertebral bodies: a T1 and T2 study

Multiple point T1 and T2 values of 424 vertebral bodies were measured and analysed. The influence of several factors including age, sex, location in the spine and status of neighbouring discs on the measured relaxation times were evaluated. The results indicate limitations in the region of interest approach. Vertebral bodies of different age, sex and location in the spine could not be distinguished. For heterogeneous tissues a more advanced form of image analysis appears to be essential. Diurnal factors resulting from the stress of normal ambulatory activity caused increased variation in vertebral body relaxation time values.

Dynamic low-dose three-dimensional computed tomography: a preliminary study

Three-dimensional (3D) computed tomographic reformations have been used successfully as an adjunct to standard axial computed tomography (CT) in the evaluation of disorders affecting areas of complex anatomy. The basic requirements for high-quality 3D reformations are an absence of patient movement and narrow-width transaxial sections. Speed of examination is an important factor in optimizing image quality. One hundred examinations were performed on an IGE CT 9800 scanner. For bone studies, 80 mAs and, for certain soft tissues, 140 or 200 mAs were employed with 120 kVp. The advantages of such a "low-dose" technique are significant reduction in patient skin dose and a faster examination. The main disadvantage is a reduction in signal-to-noise ratio. The image quality obtained in 3D presentations has nevertheless been sufficient to enable all bony abnormalities to be identified. Three-dimensional examinations are now being performed routinely using a dynamic mode and this "low-dose" technique.

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

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.

Magnetic resonance imaging of acoustic neuromas: the role of gadolinium-DTPA

Magnetic resonance imaging (MRI) was performed in 20 patients with evidence on computed tomography (CT) of 21 acoustic neuromas before and after intravenous administration (0.1-0.2 mmol/kg body weight) of gadolinium-diethylene-triamine-pentaacetic acid (Gd-DTPA). Multi-section spin-echo (SE) sequences of varying repetition (TR) and echo (TE) times were performed in the transverse and coronal planes with a section thickness of 10 mm. All acoustic neuromas displayed marked enhancement on the T1-weighted (short TR/TE) SE sequence post-Gd-DTPA. The intrameatal component was particularly well demonstrated compared with non-enhanced magnetic resonance (MR) images and contrast-enhanced CT. Identification of intrameatal tumour was difficult on T2-weighted SE images and one tumour was not identified on the T1-weighted SE sequence prior to Gd-DTPA. Four of five intrameatal tumours measuring less than 8 mm could only be demonstrated on CT by using CT air meatography. Extrameatal tumour extension was demonstrated on contrast-enhanced CT, although the assessment of brain-stem involvement and displacement was not as clearly seen as on coronal MR images. In two patients with large acoustic neuromas and a cyst, the true relationship of the cyst to the tumour could only be identified on the post-Gd-DTPA scan. Magnetic resonance imaging with gadolinium-DTPA is a relatively quick, safe, well tolerated and effective method for the diagnosis of acoustic neuroma.

Magnetic resonance imaging of the mini-pig heart: the effect of gadolinium-DTPA on normal myocardium

The effect of gadolinium-diethylene-triamine-penta-acetic acid (Gd-DTPA) on normal, mini-pig myocardium was investigated with magnetic resonance imaging. Results indicate that intravenous administration of Gd-DTPA produces a significant enhancement of mini-pig myocardial signal intensity, which in all cases was maintained in excess of 50 min. No significant enhancement was demonstrated in skeletal muscle.

Aortic dissection: morphology and differential flow velocity patterns demonstrated by magnetic resonance imaging

A case of chronic aortic dissection is presented, in which computed tomography and magnetic resonance imaging both demonstrated the abnormality non-invasively. Velocity flow patterns within the true and false lumens obtained by magnetic resonance imaging, using a flow-mapping technique, gave a more thorough analysis.

Plexiform trigeminal neurofibroma

Neurofibromas of the trigeminal nerve are uncommon tumours which usually present in patients in the third or fourth decade of life as a localised mass in the posterior or middle cranial fossa. A case is described of a plexiform neurofibroma of this nerve with unusual clinical and radiological features.

Gadolinium-DTPA as a contrast agent in magnetic resonance imaging of the brain

One hundred patients with CT-proven intracranial disease have been studied by magnetic resonance imaging (MRI) before and after intravenous injection with Gadolinium-DTPA (Gd-DTPA), in order to assess the role and clinical efficacy of Gd-DTPA. T2-weighted spin echo sequences, although sensitive to the detection of intracranial disease, in general fail to differentiate macroscopic tumor from oedema. Following Gd-DTPA, T1-weighted spin echo sequences in primary tumours demonstrated a variable degree of contrast enhancement unrelated to histological type. Small tumours, especially acoustic neuromas and meningiomas in the posterior fossa, were rendered more conspicuous. Optimum time for scanning was between five and 25 min following injection for all lesions except those adjacent to normal enhancing structures such as nasal/sinus mucosa and pituitary gland when delayed scans up to 45 min were necessary. No differences were observed between the 0.1 and 0.2 mmol/kg Gd-DTPA concentrations used and no complications attributable to Gd-DTPA were detected. Clinical advantages of Gd-DTPA include shorter scan times, macroscopic tumour/oedema separation and improved detection of certain tumours, particularly acoustic neuromas.

Detection of coronary artery bypass graft patency as assessed by magnetic resonance imaging

In a study of 22 patients with 60 coronary artery bypass grafts, magnetic resonance imaging (MRI) correctly assessed graft patency or occlusion in 90% of cases when compared with selective coronary graft angiography and computed tomography. It is concluded that MRI can detect a normally functioning coronary artery bypass graft and could be used as a non-invasive technique to assess graft patency in patients presenting with post-operative angina.

Three-dimensional computed tomographic scans in the planning of procedures for reconstructive craniofacial surgery

Three-dimensional computed tomographic (3D CT) scans were used in the assessment of three cases being considered for craniofacial reconstructive surgery; the first patient had a frontal encephalocele, the second an orbital encephalocele and the third an apparent asymmetry of the face due to cervical scoliosis caused by developmental defects of the upper two cervical vertebrae. The 3D CT scans provided information which was of great help in deciding how best to manage each case.

A comparison of angiographic and electrocardiographically gated computed tomographic measurements of left-ventricular function

Fifty patients with ischaemic heart disease have been studied by electrocardiographically gated computed tomography (CT) and left-ventricular angiography to assess the accuracy of the former in the measurement of left-ventricular volumes and ejection fraction. There was no significant difference in the measurements of end-diastolic volume (p = 0.9, r = 0.81). Computed tomography significantly overestimated end-systolic volume (p less than 0.001, r = 0.89) and significantly underestimated ejection fraction (p less than 0.001, r = 0.74). Although there is some variation between the two sets of measurements, the correlation between the two techniques is good, indicating that electrocardiographically gated CT could be a useful noninvasive technique for assessing left-ventricular function.