P1080Magnetic resonance imaging after electrical cardioversion of recent-onset atrial fibrillation in anticoagulant-naive patients - a study exploring clinically silent cerebral lesions

Funding Acknowledgements

Unrestricted grants from the Swedish Heart-Lung Foundation, the Swedish Research Council, Correvio International Sárl (CH) and Selanders stiftelse

Background

Patients with atrial fibrillation (AF) have a high incidence of cognitive impairment, which may be related to clinically silent microembolism causing cerebral infarctions.

Purpose

To explore the occurrence and timing of silent brain lesions following electrical cardioversion (CV) of recent onset AF in anticoagulant-naïve patients and to further study related effects on cognitive function and biomarkers of cerebral damage, S100b.

Methods

Patients with AF duration < 48 hours were prospectively included. Brain magnetic resonance imaging (MRI) and S100b, were obtained prior, after and 7-10 days following CV. Trail making tests (TMT-A and TMT-B) and their difference, ΔΤΜΤ, were assessed prior to CV, 7-10 days and 30 days after CV.

Results

Forty-three patients (84% males) with mean CHA2DS2-VASc score 0.6 ± 0.7 were included. Sequential MRI, including diffusion weighted scans, showed no new brain lesions after CV.

Chronic white matter hyperintensities (WMH) were present at baseline in 21/43 (49%) patients. By partitioning the study population into four major groups according to the extend of WMH (Fazekas score 0 or ≥ 1) and the presence or absence of TE risk factors (CHA2DS2-VASc score 0 or ≥ 1), the TE risk as defined by CHA2DS2-VASc score ≥ 1, was associated with a higher incidence of WMH, Pearson χ2(1,N = 43)=3.95, p = 0.047.

The S100b (µg/l) levels increased significantly from baseline, (mean ± SD) 0.0472 ± 0.0182 to 0.0551 ± 0.0185 after CV, p = 0.001 and then decreased 7-10 days after CV to 0.0450 ± 0.0186, p < 0.001. Subgroup analysis according to the presence of at least one TE risk factor as defined by CHA2DS2-VASc score showed that statistical significance of repeated measures ANOVA was maintained; for patients with no risk factors F (2,30)=12.59, p < 0.001 and for patients with CHA2DS2-VASc score ≥1 F(2,36)=4.43, p < 0.019.

Consecutive TMT scores improved successively after CV, being statistically and clinically significant for TMT-B (p < 0.01) and ΔΤΜΤ (p = 0.005) between 7-10 days and 30 days after CV (Reliable Change Index >1.96).

Conclusion

New brain lesions could not be detected on MRI after CV, but the high incidence of white matter hyperintensities and the transient increase in S100b may indicate transient or minor brain damage undetectable by MRI thus heightening the need to reevaluate thromboembolic risk prior to CV even in low risk patients.

Abstract Figure. S100b_TMT

Ultrafast vibrations of gold nanorings

We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We elucidate the corresponding mode shapes and find that the substrate plays an important role in determining the mode damping. This study demonstrates the need for a plasmonic nano-optics approach to understand the optical excitation and detection mechanisms for the vibrations of plasmonic nanostructures.

Magnetic resonance imaging of the knee: a tool for prediction of joint damage in early rheumatoid arthritis?

OBJECTIVE

To evaluate the usefulness of magnetic resonance imaging (MRI) in predicting destructive rheumatoid arthritis (RA) in the knee joint, and to compare this method with clinical examination and conventional radiography (CR).

METHODS

Clinical evaluations of the knee joint, followed by MRI and CR examinations were performed in 30 patients with early RA. The MRI examination included evaluation of inflammation using a synovitis score and evaluation of destruction with an erosion score. The first examinations were performed within 14 months from disease onset. Twenty-eight patients were re-examined after 1 year, and 23 patients after 3 years. 'Disease activity score' (DAS), using a 28 joints score (DAS28); health assessment questionnaire (HAQ); rheumatoid factor (RF); and C-reactive protein (CRP) were also analysed.

RESULTS

At baseline, MRI found synovitis in 29 patients, of whom 18 also had clinical synovitis. At baseline five patients had 17 MRI erosions, whereas on CR two patients had one erosion each. After 1 year 17 of 35 and after 3 years 28 of 55 MRI erosions were detected also on CR. In only one case CR showed an erosion that was not visible on MRI. The MRI synovitis score (reflecting the extent of the synovitis) at baseline correlated significantly with the number of erosions on MRI both at year 1 and 3, and with the number of erosions on CR at 3 years. In logistic multiple regression analyses the MRI-synovitis score proved to be the best independent predictor of erosiveness.

CONCLUSION

MRI was superior to clinical examination and CR in detecting erosions. MRI synovitis score was the best independent predictor of erosiveness in the knee joint in patients with early RA.

Cognitive dysfunction 24–31 years after isolated optic neuritis

Objective

Cognitive dysfunction is common in multiple sclerosis (MS), but long-term data on cognition in patients with clinically isolated syndromes are sparse.

Methods

We determined cognitive functions in 22 patients 44–75 years old diagnosed with optic neuritis 24–31 years earlier but had no further clinical bouts and had not progressed clinically to MS. We used a neuropsychological test battery covering nine cognitive domains. Magnetic resonance imaging (MRI) of the brain had been performed earlier and was normal in six patients and showed two or more white matter abnormalities compatible with demyelinating lesions in 16 patients.

Results

On neuropsychological testing, one patient was within normal range on all tests, six subjects showed borderline results, and 15 patients (68%) showed significantly impaired performance in at least one cognitive domain. Seven patients showed significant impairment in two or more domains. Executive function, visuo-spatial ability, and information processing speed were the most frequently affected domains. There was no apparent correlation between MRI findings and cognitive function.

Conclusions

We conclude that cognitive dysfunction is common in patients many years after clinically isolated optic neuritis. Cognitive dysfunction was found even in patients who had no apparent demyelinating lesions on follow-up MRI.

Impact of extended written information on patient anxiety and image motion artifacts during magnetic resonance imaging

PURPOSE

To evaluate whether increased written information to patients prior to magnetic resonance imaging (MRI) decreases patient anxiety and image motion artifacts.

MATERIAL AND METHODS

A two-group controlled experimental design was used. Of 242 patients, 118 received routinely given basic written information (control group) while 124 were given increased written information (intervention group). To measure patient anxiety before and during scanning, the self-report psychometric test State-Trait Anxiety Inventory (STAI) was used. After MR examination, the patients answered a questionnaire on satisfaction with the written information. The images were assessed with regard to motion artifacts.

RESULTS

Motion artifacts were present in fewer patient images in the intervention group than in the control group (4.0% versus 15.4%,; P=0.003). There was no significant difference between the control and the intervention group regarding patient anxiety and satisfaction with the information. Women in both groups showed a higher level of anxiety than the men did.

CONCLUSION

Increased information about the MRI scanning procedure and expected experiences during the scan may help patients to lie still during the sequences, with a decrease in motion artifacts. However, further research is needed to evaluate the effect of other interventions on patient anxiety during MRI scanning.

Large area protein nanopatterning for biological applications

Large area nanopatterns of functional proteins are demonstrated. A new approach to analyze atomic force microscopy height histograms is used to quantify protein and antibody binding to nanoscale patches. Arrays of nanopatches, each containing less than 40 laminin molecules, are shown to be highly functional binding close to 1 monoclonal anti-laminin IgG (site by IKVAV sequence) or 3-4 polyclonal anti-laminin IgG's per surface bound laminin. Complementary quartz crystal microbalance measurements indicate higher functionality at nanopatches than on homogeneous surfaces.

Tumor extension in high-grade gliomas assessed with diffusion magnetic resonance imaging: values and lesion-to-brain ratios of apparent diffusion coefficient and fractional anisotropy

PURPOSE

To determine whether the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) can distinguish tumor-infiltrated edema in gliomas from pure edema in meningiomas and metastases.

MATERIAL AND METHODS

Thirty patients were studied: 18 WHO grade III or IV gliomas, 7 meningiomas, and 5 metastatic lesions. ADC and FA were determined from ROIs placed in peritumoral areas with T2-signal changes, adjacent normal appearing white matter (NAWM), and corresponding areas in the contralateral healthy brain. Values and lesion-to-brain ratios from gliomas were compared to those from meningiomas and metastases.

RESULTS

Values and lesion-to-brain ratios of ADC and FA in peritumoral areas with T2-signal changes did not differ between gliomas, meningiomas, and metastases (P = 0.40, P = 0.40, P = 0.61, P = 0.34). Values of ADC and FA and the lesion-to-brain ratio of FA in the adjacent NAWM did not differ between tumor types (P = 0.74, P = 0.25, and P = 0.31). The lesion-to-brain ratio of ADC in the adjacent NAWM was higher in gliomas than in meningiomas and metastases (P = 0.004), but overlapped between tumor types.

CONCLUSION

Values and lesion-to-brain ratios of ADC and FA in areas with T2-signal changes surrounding intracranial tumors and adjacent NAWM were not helpful for distinguishing pure edema from tumor-infiltrated edema when data from gliomas, meningiomas, and metastases were compared.

Functional magnetic resonance imaging at 3T as a clinical tool in patients with intracranial tumors

PURPOSE

To investigate the potential of functional magnetic resonance imaging (fMRI) at 3T as a clinical tool in the preoperative evaluation of patients with intracranial tumors. High magnetic field strength such as 3T is of benefit for fMRI because signal-to-noise ratio and sensitivity to susceptibility changes are field-strength-dependent.

MATERIAL AND METHODS

Twenty patients with tumors close to eloquent sensorimotor or language areas were studied. Motor, sensory, and two language paradigms (word generation, rhyming) were used; their effectiveness was determined as the percentage of patients in whom the functional area of interest was activated. Activation maps were calculated and their quality rated as high, adequate, or insufficient. The influence of fMRI on the neurosurgical decision regarding operability, surgical approach, and extent of the resection, was assessed.

RESULTS

Paradigm effectiveness was 90% for motor and 95% for sensory stimulation, and varied from 79% to 95% for word generation and rhyming in combination. Ninety percent of the activation maps held high or adequate quality. fMRI proved useful: in the decision to operate (9 patients), in the surgical approach (13 patients), and in extent of the resection (12 patients).

CONCLUSION

fMRI at 3T is a clinically applicable tool in the work-up of patients with intracranial tumors.

Volume rendering compared with maximum intensity projection for magnetic resonance angiography measurements of the abdominal aorta

PURPOSE

To compare the volume rendering technique (VRT) with maximum intensity projection (MIP) for aortic diameter measurements in MR angiography (MRA) data sets.

MATERIAL AND METHODS

Existing contrast-enhanced 3-dimensional MRA and digital subtraction angiography (DSA) data sets from 20 patients were analyzed. In each MRA data set, two aortic diameters were measured using MIP and VRT. Agreement with DSA measurements, dependence on rendering parameters, and interobserver agreement were assessed.

RESULTS

Diameters measured on MIP with fixed parameters showed no significant difference compared with DSA and with freely selected parameters a slight overestimation relative to DSA. Diameters measured on VRT were larger than on DSA. For both MIP and VRT, the measurements depended on the chosen parameters. The error relative to DSA was larger for VRT than for MIP with fixed parameters but not with freely chosen parameters. Interobserver agreement did not differ significantly.

CONCLUSIONS

VRT is not suitable for diameter measurements of the abdominal aorta with fixed parameter settings but may be useful with user-selected settings.

Long-term results after endovascular repair of abdominal aortic aneurysms with the Stentor and Vanguard stent-graft

PURPOSE

To present a single institution experience of long-term results after endovascular repair of abdominal aortic aneurysms (AAA) with the Stentor and Vanguard stent-grafts.

MATERIAL AND METHODS

Twenty-three patients (20 men, 3 women; mean age 68 years, range 53-81 years) were included in this prospective study. A first generation nitinol stent-graft (Stentor) was used in 12 patients and a second generation (Vanguard) in 11 patients. Follow-up was performed with magnetic resonance imaging (MRI) with contrast-enhanced MR angiography (CE MRA) at 1, 6, and 12 months, and thereafter annually (median follow-up 3 years; range 8 months to 8 years). A conventional radiograph of the abdomen was also performed. Before secondary intervention the findings on MRI with CE MRA were confirmed with spiral computed tomography (CT) and/or angiography (DSA).

RESULTS

Only one patient (4%) had no complication. Endoleak was found in 15 patients (65%), graft migration in 8 (35%), and graft deformation in 18 (78%). Secondary endovascular repair was required in 7 patients (30%) and 7 (30%) were converted to open repair.

CONCLUSION

Complications with the Stentor and Vanguard stent-grafts were common. Long-term follow-up of endovascularly repaired AAA is mandatory.

Magnetic resonance imaging of the fifth metatarsophalangeal joint compared with conventional radiography in patients with early rheumatoid arthritis

OBJECTIVE

To evaluate if magnetic resonance imaging (MRI) is superior to conventional radiography for detection of erosions in the fifth metatarsophalangeal (MTP5) joint.

METHODS

Within one year from the onset of rheumatoid arthritis (RA) (baseline), one and three years thereafter MRI and conventional radiographs of the MTP5 joint were performed in 23 patients.

RESULTS

MRI revealed erosions in 10 patients at baseline, in 15 after one year and in 15 patients after 3 years. On conventional radiography, there were erosions in 10 patients at baseline, 16 after one year as well as after 3 years. The agreement between the two imaging methods was fair to good at baseline and after one and three years (kappa 0,65, 0,51 and 0,51 respectively). The number of patients with clinical evidence of synovitis decreased considerably over time although the number of patients with MRI-synovitis was unchanged and the number of patients with erosions increased.

CONCLUSIONS

MRI was not superior to conventional radiography in detecting erosions in MTP5 joints in patients with early RA. Most erosions developed during the first year of observation. Synovitis on MRI may be a marker of future development of erosions in the MTP5 joint.

Hand-arm-vibration syndrome (HAVS): is there a central nervous component? An fMRI study

Hand-held vibrating tools may result in neuromuscular dysfunction and vasospastic problems of the hand. Sensory and motor dysfunction can be explained by injury to peripheral structures, but could also be due to changes in cortical somatotopic mapping of the hand in the brain. The purpose of the present study was to use functional magnetic resonance imaging (fMRI) to assess the somatotopic cortical representation of the hands of workers subjected to occupational vibration. The study included six men with severe vibration exposures who were suffering from hand-arm-vibration syndrome (HAVS) and six controls. The analysis focused on the pattern and degree of activation of contra- and ipsilateral hemispheres of the brain with tactile stimulation and motor activation of the hand. These stimulations resulted in well-defined activation of the contralateral, and to a lesser extent the ipsilateral hemisphere. Statistical analysis of this limited patient material did not indicate any significant somatotopic cortical changes following long-term exposure to vibrating hand-held tools, although there was a tendency to a shift of activation towards the more cranial parts of the cortex in the patient group.

MR evaluation ex vivo and in vivo of a covered stent-graft for abdominal aortic aneurysms: ferromagnetism, heating, artifacts, and velocity mapping

Magnetic resonance imaging (MRI) safety was evaluated at 1.5 T in a covered nickel titanium stent-graft (Vanguard) used for endovascular treatment of abdominal aortic aneurysms (AAAs). Imaging artifacts were assessed on MRI with contrast-enhanced (CE) three-dimensional (3D) MR angiography (MRA) and spiral computed tomography (CT) in 10 patients as well as ex vivo. Velocity mapping was performed in the suprarenal aorta and femoral arteries in 14 patients before and after stent-graft placement. For comparison it was also performed in six healthy volunteers. No ferromagnetism or heating was detected. Metal artifacts caused minimal image distortion on MRI/MRA. The artifacts disturbed image evaluation on CT at the graft bifurcation and graft limb junction. No significant differences in mean flow were found in patients before and after stent-graft placement. Our study indicates that MRI at 1.5 T may be performed safely in patients with the (Vanguard) stent-graft. MRI/MRA provides diagnostic image information. Velocity mapping is not included in our routine protocol.

Image artifacts due to a time-varying contrast medium concentration in 3D contrast-enhanced MRA

The purpose of this work was to study image effects due to time-varying contrast medium concentration in contrast-enhanced three dimensional (3D) magnetic resonance angiography (MRA) images. Two different simulation models (1D and 3D) and two different contrast medium variation schemes were used. Phantom measurements were also performed. Experiments were performed for several different bolus timings. Similar sequence and image object parameters were used in both simulations and measurements (TE/TR 2. 1/7.8 mses, flip angle 30 degrees, T1/T2 1200-80/150-40 msec, flow velocity 100 cm/sec). A small variation in bolus timing yielded large variations in the appearance of the image effects, especially if the center of k-space was sampled in the vicinity of rapid contrast medium concentration variation. For a typical bolus injection in a patient, a severe signal loss but only minor ringing and edge artifacts appeared if the bolus injection was poorly timed. Effects of pulsatile flow were minor. The 3D model proved to be a useful tool in these studies. J. Magn. Reson. Imaging 1999;10:919-928.

Magnetic resonance imaging and MR angiography of endoluminally treated abdominal aortic aneurysms

OBJECTIVES

To evaluate magnetic resonance imaging (MRI) with gadolinium-based contrast medium-enhanced MR angiography (MRA) for the follow-up of endoluminally treated abdominal aortic aneurysms.

DESIGN

MRI/MRA, angiography and computed tomography (CT) were performed 1 month after endoluminal stent-graft placement. MRI/MRA was repeated at 6 and 12 months and angiography and CT were added to confirm unexpected findings.

MATERIALS

Fifteen male patients with endoluminally treated abdominal aortic aneurysms.

METHODS

MRI with MRA, spiral CT with transverse images and angiography were performed.

RESULTS

MRI/MRA demonstrated changes of stent-graft morphology, aortic neck- and aneurysmal diameter, stent-graft blood flow, stent-graft leakage, blood flow in lumbar arteries, intra-aneurysmal thrombus, periaortic inflammation and vertebral body infarction. For most of these features MRI/MRA provided more information than angiography and/or CT. MRI was the only method demonstrating thrombus reorganisation and vertebral body infarction.

CONCLUSIONS

MRI with MRA provides the relevant information needed for follow-up of endoluminally treated abdominal aortic aneurysms (AAA). This may be the method of choice because of its use of contrast media with very low nephrotoxicity, lack of ionising radiation and non-invasiveness.

[Endovascular technique in aortic aneurysm. A promising alternative to open surgery]

The article consists in a presentation of endovascular surgery for abdominal aortic aneurysm repair in 23 cases. Two cases required conversion to open surgery, but the procedure could be completed in the remaining 21 cases, with a current duration of follow-up of up to 30 months. There was early leakage in one case, and late leakage in five cases. Late conversion has been necessary in three instances, and supplementary endovascular measures have been required in a further two instances. All complications have occurred in those cases operated during the first half of the study period. Modification of the endoprosthesis used and increasing skill have reduced both operation time and the complication rate. Intensive care is no longer required, and the median duration of hospitalisation is three days. Follow-up with magnetic resonance imaging has yielded new and important information.

Detection of joint pathology by magnetic resonance imaging in patients with early rheumatoid arthritis

Magnetic resonance imaging (MRI) permits the visualization of anatomical structures not appreciated by conventional radiographic imaging, and may assess inflammatory disease and its progression with greater sensitivity than conventional radiography. In this study of 30 patients with early rheumatoid arthritis (RA), which could be considered as a pilot study because of the relatively small number of patients, we compare MRI of the knee and the fifth metatarsophalangeal joint with clinical and radiographic findings. A parallel study of 10 healthy individuals served as a reference group. In all but one of the 30 patients, MRI revealed some kind of joint abnormality, whereas conventional radiography was normal in 14 patients. The present study thus suggests that MRI may detect inflammatory and/or destructive joint changes in patients with early RA, and that these changes may occur in the absence of clinical symptoms or signs and/or radiographic signs in the examined joint. If these data prove to be confirmed in further controlled studies, MRI may be of importance both for the assessment of prognosis and for the decision to treat in the early critical stages of RA.

Evaluation of time-of-flight and phase-contrast MRA sequences at 1.0 T for diagnosis of carotid artery disease. I. A phantom and volunteer study

PURPOSE AND MATERIAL: The aim of this work was, firstly, to compare different manufacturer-provided MRA sequences in a 1.0 T MR unit, with respect to the visibility of an artificial stenosis in a flow phantom and, secondly, to evaluate the same sequences in healthy volunteers with respect to S/N ratio levels and practical in vivo implementation routines.

METHODS

The studied sequences were 2D and 3D TOF and sequences with an acquisition time of approximately 10 min. Quantitative signal evaluation was made using single transverse partitions in all phantom experiments. MIP angiograms and MPR reconstructions were made for visual inspection of image quality. In vivo, the images were individually evaluated by visual inspection by experienced neuroradiologists.

RESULTS

In the evaluation of the grade and length of a stenosis, a combination of MIP and MPR was seen to be the optimal and necessary procedure. A shortening of TE played an important and significant role in the visualization of the poststenotic flow in the phantom using TOF MRA. However, the shortest TE values gave poor S/N ratio in vivo. The good results achieved in the phantom studies for 3D phase-contrast were somewhat reversed in the volunteer studies, whereas 3D TOF sequences showed good results in both the phantom and the volunteer studies.

Brain metastases--comparison of gadodiamide injection-enhanced MR imaging at standard and high dose, contrast-enhanced CT and non-contrast-enhanced MR imaging

The aim was to compare the abilities of contrast-enhanced CT, non-contrast-enhanced MR imaging and contrast-enhanced MR imaging using standard (0.1 mmol/kg b.w.) and high (0.3 mmol/kg b.w.) doses of Gadodiamide injection to detect brain metastases (i.e. blood-brain barrier damage). Sixteen patients with at least 2 metastases found by CT were evaluated by MR imaging using non-contrast-enhanced spin-echo, T1-weighted, T2-weighted sequences, and contrast-enhanced spin-echo T1-weighted sequences at 2 dose levels. Gadodiamide injection was first given at the dose of 0.1 mmol/kg b.w. After imaging, another 0.2 mmol/kg b.w. was given, yielding a cumulative dose of 0.3 mmol/kg b.w. No contrast media-related adverse events were recorded. The images were evaluated openly by one and blindly by 2 investigators and the number of metastases, size, delineation (open study) and diagnostic certainty (blind study) of each individual metastasis noted. High-dose MR imaging showed significantly more and smaller metastases than any other examination, and gave a higher diagnostic certainty. All high-dose images were superior to those with the standard dose MR imaging when compared blindly in pairs. We conclude that spin-echo MR imaging with a high dose of Gadodiamide injection is an efficient way to improve the detection of brain metastases, in particular of small ones.

Cerebral lesions on magnetic resonance imaging, heart disease, and vascular risk factors in subjects without stroke. A population-based study

BACKGROUND AND PURPOSE

To assess the prevalence of asymptomatic abnormalities on magnetic resonance imaging of the brain and their possible relation to hypertension, heart disease, and carotid artery disease, we studied 77 randomly selected subjects (mean age, 65.1 years; range, 36 to 95 years) with no history of focal brain lesions.

METHODS

The study protocol included magnetic resonance imaging of the brain, transthoracic and transesophageal echocardiography, ultrasonography of the carotid arteries, and electrocardiographic recording. Deep and periventricular white matter hyperintensities on magnetic resonance imaging were assessed both separately and together.

RESULTS

On magnetic resonance imaging of the brain 62.3% (95% confidence interval [CI], 51.5% to 73.2%) of the subjects had white matter hyperintensities. These abnormalities increased significantly with age (chi 2 test; P = .0001), from 13.6% (95% CI, 0% to 28.0%) of subjects aged younger than 55 years to 85.2% (95% CI, 71.8% to 98.6%) of subjects aged 75 years or older. Six subjects had deep gray matter hyperintensities localized in the basal ganglia, and one had a cerebellar infarction. Stepwise logistic regression analysis identified age and a history of heart disease (but not echocardiographic findings) to be independently associated with deep and periventricular white matter hyperintensities. Hypertension was only independently associated with periventricular white matter hyperintensities. Of the 68 subjects examined with both transthoracic and transesophageal echocardiography, potential cardioembolic sources were detected in 38.2% (95% CI, 26.7% to 49.8%) of the subjects with transthoracic echocardiography and in 47.1% (95% CI, 35.2% to 58.9%) of those with transthoracic and transesophageal echocardiography combined. In subjects aged 75 years or older, a possible cardiac embolic source was detected in 64.0% on transthoracic echocardiography and in 72.0% on transthoracic and transesophageal echocardiography combined, compared with 5.3% and 15.8%, respectively, in subjects aged younger than 55 years.

CONCLUSIONS

White matter hyperintensities and potential cardioembolic sources are frequently present in asymptomatic individuals, stressing the need for age-matched control subjects in studies of patients with stroke or dementia.

PACS for radiology conferences--improvement of application software

The introduction of PACS in a radiology department means that most functions that are available in the film-based system must be included. One important function is the radiology conference. The handling and application programs of digital workstations are normally not developed for demonstrations of many images in a limited time. This paper describes a workstation with specially designed software for radiology conferences. The application is separated in preparation and presentation of the cases to be demonstrated. Very fast image handling is achieved during the conference because the function is based on the principle of prefetching of the selected images. The images are presented on a large screen with high resolution. The experiences of digital radiology conferences are good. However, reference films from previous examinations create extra work because they have to be shown on the conventional lightbox.

Vertical field MR imaging of upper thorax and spine in small children. Evaluation of a new surface coil

To improve image quality in a vertical field MR imaging unit, operating at low field strength (0.3 T), we have designed a half-elliptical coil for use in the upper thoracic region of small children. Our intention was also to shorten the examination time, which until now has been long, because several scans with different coils have been necessary to cover the thoracic region. The experimental coil is designed so that a child's shoulders fit into the central region. The coil consists of 2 serially connected cable-loops, mounted on a foam rubber vest. The coil performance was tested in a phantom and improvements relative to standard coils were demonstrated in in vivo studies. The results indicate that by using the half-elliptical coil, the signal-to-noise (S/N) ratio can be improved by a factor of 2 to 3 in the thoracic region of a child.

Aortic pathology revealed by MRI in patients with clinical suspicion of spinal disease

In five patients with clinical suspicion of spinal disease, MRI of the spine revealed unexpected aortic pathology explaining the symptoms. No significant intraspinal pathology was found on MRI. However, in one patient with clinical suspicion of spinal stenosis, an aortic occlusion was detected on MR images of the spine. The lower extremity ischaemia, caused by the occlusion, was responsible for the symptoms. In another patient a paravertebral haematoma from a ruptured aortic aneurysm resulted in spinal nerve compression, thought before MRI to be caused by a spinal tumour. In three patients aortic aneurysm or dissection resulted in spinal cord ischaemia with symptoms mimicking those of compressive spinal disease. Thus, if MRI of the spine does not provide an explanation for the patient's symptoms, examination of the aorta is recommended.

Subluxation of the upper thoracic spine in rheumatoid arthritis

Only single cases with rheumatoid arthritis of the thoracic spine with vertebral subluxation have been reported to date. In a review of 100 patients with severe rheumatoid arthritis who had undergone occipitocervical fusion, arthritis of the upper thoracic spine with subluxation was discovered on conventional radiographs in four patients. Two additional patients were found elsewhere. Magnetic resonance imaging (MRI) was performed in three of the patients, confirming the diagnosis of subluxation of the upper thoracic vertebrae. In addition, MRI revealed encroachment on the anterior subarachnoid space and compression of the spinal cord.

MRI of extradural spinal tumours at 0.3 T

Ninety-one patients with extradural spinal tumours were examined by magnetic resonance imaging. There were 76 metastases (6 from unknown primary tumours). Seven patients had primary spinal tumours and 8 had multiple myeloma. Sixteen had bulging, diseased vertebral bodies compressing the subarachnoid space and 67 had extradural tumour compressing the spinal cord. Sixty patients had paravertebral involvement. Intraspinal involvement did not correlate with the extent of spinal lesions. All patients had vertebral destruction, with hypointense or combined hypo- and isointense signal relative to bone marrow on T1-weighted images. In most of the 22 patients with T2-weighted images the tumours were isointense or slightly hyperintense. It was usually impossible to differentiate the various tumours on the basis of signal intensity and morphology. However, metastases from carcinoma of the prostate were often more hypointense than other tumours on T1- and T2-weighted images. An inhomogeneous pattern in which diffusely low signal is combined with focal lower signal on T1-weighted images may suggest myeloma. In the 22 patients examined with both T1- and T2-weighted images, T1-weighted images gave the best information in 18; in 3 they were equivalent and in 1 inferior to T2-weighted images; they are therefore recommended for routine imaging of epidural spinal tumours.

Hyperdense middle cerebral arteries identified on CT as a false sign of vascular occlusion

PURPOSE

To evaluate the middle cerebral artery (MCA) on CT, including its relationship to cerebral infarction.

METHODS

Thirteen patients with either a unilateral or bilateral hyperdense M1 segment of the MCA were evaluated. History of hypertension, diabetes, and hematocrit were obtained and compared with a control group of patients without a hyperdense MCA.

RESULTS

None of the patients had a unilateral hyperdense MCA ipsilateral to a clinically identifiable stroke. Patients with a hyperdense MCA had a statistically higher hematocrit and also a higher prevalence of hypertension and diabetes mellitus than patients without a hyperdense MCA. The higher hematocrit may have increased the density of the blood, while both diabetes and hypertension are associated with calcification within blood vessel walls.

CONCLUSION

A hyperdense MCA is not a reliable indicator of occlusion of this vessel or subsequent infarction.

MRI of intradural spinal arteriovenous fistula associated with ischemia and infarction of the cord

This report presents a patient with an intradural spinal arteriovenous fistula complicated by infarction of the cord. The diagnosis of an arteriovenous malformation was made on the magnetic resonance imaging (MRI) study with the demonstration of intraspinal serpentine areas of low signal intensity (flow voids). The presence of other MRI findings believed to represent spinal cord ischemia included multisegmental swelling of the cord associated with T1 and T2 prolongation and gadolinium enhancement. The location of the malformation, as well as arterial supply and venous drainage, were defined on selective spinal arterial digital subtraction angiography (DSA). Following surgical resection, the clinical condition stabilized, but with poor return of lost function. The repeat MRI 6 months after surgery demonstrated diffuse thoracic cord atrophy.

MR imaging of spinal lymphoma

Fourteen patients with spinal lymphoma examined by MR imaging were reviewed. Thirteen of them also had extraspinal lymphoma. Vertebral involvement was found in 12 patients, epidural in 10, and paraspinal in 8 patients. On the basis of MR imaging at 0.3 T, spinal lymphoma may be divided into three types of growth pattern according to the main location: paraspinal, vertebral, and epidural. Most frequently, all three locations were found simultaneously on MR (7/14). In one patient the location was vertebral with epidural extension, in one paraspinal with vertebral extension, in 3 it was entirely vertebral, and in 2 entirely epidural. Multiple plane T1-weighted imaging gave complete information about the extent of spinal lymphoma. The signal intensity was lower than or equal to muscle and lower than bone marrow in paraspinal and vertebral lesions on T1-weighted images and high on T2-weighted images. Epidural lesions showed a hypo- or isointense signal relative to the cord on T1-weighted images except in one case and a hyperintense signal on T2-weighted images. Compression of the cord and cauda equina due to bulging of diseased vertebral bodies and epidural lesions was well demonstrated. MR imaging was also found useful in the follow-up of treatment.

MR imaging of intradural extramedullary tumors

Thirty-one consecutive intradural extramedullary spinal tumors examined with MR at 0.3 T were reviewed. In 13 of the patients myelography had been performed. There were 11 patients with meningeoma, 14 with neuroma, one ependymoma, 3 metastases, and 2 lipomas. All tumors were surgically removed and verified by histology. The intradural extramedullary location of the tumors was accurately assessed by MR imaging in all patients and by myelography in 10 of 13. The MR diagnoses were in accordance with the histologic findings in 74% of cases. Compression of the spinal cord or cauda equina with widening of the subarachnoid space above and below the mass or outward displacement of epidural fat was characteristic of the intradural extramedullary tumors. The signal intensity of meningeoma as well as of neuroma was slightly lower or equal to that of the cord on T1-weighted images, and equal to or higher than cord signal on T2-weighted images. Neuroma had a lower signal intensity on T1-weighted images and a higher signal intensity on T2-weighted images than meningeoma. Meningeoma appeared more homogeneous than neuroma and had a broad base towards the dura.

Improved receiver coil for upper thoracic spine imaging in a vertical magnetic field

To improve image quality in the upper thoracic spine, an anatomically shaped copper wire loop coil, made to fit over the patient's shoulders, was constructed. The coil was permanently mounted on a foam-rubber vest to facilitate attachment to the patient. Phantom and in vivo studies of the performance of the coil in healthy volunteers showed as much as a two times greater signal-to-noise ratio relative to that of standard coils for the upper thoracic spine. In a patient with lesions in the upper thoracic cord, the coil gave better image quality in the region of interest than did the standard coils. The coil has been integrated into the authors' routine imaging equipment and has been the coil of choice for imaging of the upper thoracic spine on their 0.3-T vertical field system.

Venous infarction of the spinal cord resulting from dural arteriovenous fistula: MR imaging findings

Three patients with spinal dural arteriovenous fistula presented with acute and/or progressive myelopathy. The thoracic cord was focally enlarged and poorly defined on MR images in two of the patients. One individual showed focal cord atrophy, and one demonstrated abnormal intrathecal vessels. In all patients MR studies revealed cord enhancement after IV administration of gadopentetate dimeglumine. The MR findings are believed to represent disruption of the blood-cord barrier associated with cord ischemia and/or infarction, which, in turn, is caused by venous stasis resulting from the fistula. The diagnosis in each case was confirmed by the combined results of myelography, spinal arteriography, and surgery. Surgical excision or embolization of the fistula produced a poor return of lost function but an arrest in the progression of paresis. One of the patients had constant severe back and leg pain postoperatively, and a follow-up MR study 5 months after surgery showed focal atrophy and persistent enhancement of the thoracic cord. The patient with preoperative focal cord atrophy had an MR examination 1 year prior to surgery, which revealed enhancement of the cord similar to that seen on the immediate preoperative MR study. This patient also had severe pain in the back and lower extremities preoperatively, which accompanied her progressive paraparesis. It is believed that long-standing enhancement of the spinal cord in patients with dural arteriovenous fistula probably results from chronic progressive venous ischemia, which may be irreversible and cause pain of a central type.

Normal pituitary gland: coronal MR imaging of infundibular tilt

To determine the prevalence of pituitary infundibular deviation or tilt as a normal variant, coronal magnetic resonance (MR) images of 50 patients who had been examined for reasons other than pituitary disease were evaluated retrospectively. Forty-six percent of the patients had a more or less pronounced tilt of the pituitary stalk. This tilt was due to developmental lateral eccentricity of the pituitary gland in relationship to the midline of the brain in 34% and to ontogenic eccentric insertion of the pituitary infundibulum off the midline of the gland in the other 12%. This high frequency of stalk deviation in patients without pituitary disease suggests that such displacement by itself should not be used to support the presence of pituitary microadenoma on MR images or computed tomograms.

Low flip angle gradient echo magnetic resonance imaging of the cervical spine at 0.3 tesla

The influence of flip angle and TR on signal to noise ratio and contrast between cerebrospinal fluid (CSF) and cord was evaluated in cervical spine imaging in 5 volunteers, using gradient echo technique. All experiments were performed on a 0.3 tesla Fonar beta-3000 M scanner using solenoidal surface coils. The most useful sequence was considered to be TR/TE = 300/12 ms and 10 degrees flip angle. This sequence provided images with a 'myelographic appearance' with good delineation of cord, CSF and epidural space. The grey and white matter was also regularly visualized. The acquisition time was considerably shorter than would have been necessary if a long TR/TE spin echo sequence had been used to obtain the same contrast pattern and the sequence was not as sensitive to motion as was the spin echo sequence. The sequence was also evaluated in 10 patients with degenerative disease and in 5 with lesions in the cord. The gradient echo sequence was found to be equal to or better than short and long TR/TE spin echo sequences in demonstrating narrowing of the spinal canal and cord lesion. The drawback is the limited signal to noise ratio.

Comparison of myelography, CT myelography and magnetic resonance imaging in cervical spondylosis and disk herniation. Pre- and postoperative findings

Twenty-six patients with cervical radiculopathy and/or myelopathy caused by spondylosis or disk herniation were examined with myelography, CT myelography and MR. Fourteen of the patients were operated upon and 11 of them underwent postoperative MR and CT. The three radiologic methods provided comparable information about narrowing of the subarachnoid space and compression of the spinal cord. It was more difficult to distinguish bone from soft tissue with MR only, but the combination of MR and conventional radiography gave sufficient information for this differentiation. When radiologic nerve root sheath deformity was compared with clinical radiculopathy, myelography, CT myelography and MR had similar sensitivity and accuracy. Postoperative MR could reveal remaining indentation on the thecal sac and the cord but CT without contrast medium was useful as a complement to determine the aetiology of the indentation. Because MR has several practical advantages, it is well suited as the primary imaging modality, together with conventional radiography, for the preoperative radiologic evaluation of patients with cervical radiculopathy and/or myelopathy. Postoperative MR is useful in patients with persistent or new symptoms.

Pre- and postoperative MR imaging of the craniocervical junction in rheumatoid arthritis

Ten patients with severe chronic rheumatoid arthritis with atlantoaxial subluxation were examined with conventional radiography and MR imaging of the cervical spine before and at an average of 6 months after posterior occipitocervical fusion. Periodontoid pannus formation was revealed by MR preoperatively in nine patients, all with mobile horizontal atlantoaxial subluxation. Compression of the medulla and/or upper cervical cord, due to subluxation and periodontoid pannus bulging into the spinal canal, was seen in seven patients. After the stabilizing surgery the periodontoid pannus had decreased in size in all patients with preoperative pannus. This reduction in the pannus seems to be the result of the atlantoaxial immobility achieved by the posterior fusion. Postoperatively, three patients had some remaining compression of the medulla and/or cord secondary to immobile subluxation, while the pannus posterior to the odontoid process had disappeared. Artifacts from the surgical stainless steel fixation material were confined to the posterior part of the neck on short TR/short TE MR images and did not interfere with the evaluation of the periodontoid region and the anterior part of the medulla/cervical cord. We found that flexion and extension lateral radiographs, combined with sagittal short TR/short TE MR images in the neutral position, enable preoperative evaluation of patients with rheumatoid arthritis in the cervical spine. Postoperative MR should be performed only if there are residual or new symptoms.

Coil selection for magnetic resonance imaging of the cervical and thoracic spine using a vertical magnetic field

In order to optimize the coil selection for cervical and thoracic spine imaging the signal characteristics of two different solenoidal surface coils (15 cm and 30 cm diameter, respectively) as well as the head coil and body coil were determined using a 0.3 T MR scanner with a vertical magnetic field. Signal-to-noise ratio curves were obtained for each coil using tube phantoms and a human-like phantom. The findings were compared with images obtained in two healthy volunteers. The head coil was found to be superior for imaging of the cranio-cervical junction while the 15 cm surface coil gave better results in the remaining part of the cervical spine and the upper thoracic spine. The body coil was superior for imaging of the thoracic region at the level of the shoulders (T4-T6) but the 30 cm surface coil was better for the more caudal part of the thoracic spine. Combined phantom and in vivo studies are also recommended for evaluation of future, improved coils.

Gd-DTPA-enhanced MR of suspected spinal multiple sclerosis

A prospective study was undertaken to evaluate the potential of Gd-DTPA-enhanced MR to differentiate active from inactive demyelinating lesions of the cervical spinal cord. Five patients with elongated high-signal-intensity lesions in the cervical cord on long TR/TE spin-echo MR images and a clinical suspicion of demyelinating disease had MR before and after IV Gd-DTPA. Delayed contrast enhancement (after 45-60 min) of the lesions was seen on short TR/TE images in two patients with clinically active disease, but no enhancement could be detected in three patients with stable disease. The patients with active disease underwent repeated MR examinations until the enhancement disappeared. The decrease in Gd-DTPA enhancement paralleled a decrease in clinical signs and symptoms of cervical myelopathy. MR is useful in evaluating patients suspected of having demyelinating disease. The MR finding of asymptomatic lesions in the brain lends support to the diagnosis of multiple sclerosis. Other possible causes of myelopathy, such as spinal cord compression and intramedullary tumor, can be excluded with the use of MR.

Comparison of MR imaging and CT in patients with intracranial aneurysm clips

CT and MR imaging of the brain were performed without complications in 16 patients who had undergone surgery for a ruptured aneurysm with the use of nonferromagnetic Yasargil 316 or Sugita Elgiloy clips. MR was performed on a 0.3-T Fonar beta-3000M imaging system. The artifacts caused by the clips were smaller on MR than on CT, and, therefore, anatomic structures such as the brainstem and temporal lobes were better visualized on MR. Brain-tissue lesions corresponding to the frontotemporal surgical approach were seen with MR in seven patients and with CT in six. In three patients temporal-lobe lesions seen on MR were not seen on CT because of beam-hardening artifacts. Lesions unrelated to the region of surgery were seen with MR in nine patients and with CT in five. In conclusion, MR was safe and superior to CT both in demonstrating anatomic details and in detecting tissue lesions in patients with aneurysm clips.

Emergency magnetic resonance examination of patients with spinal cord symptoms

Eighteen consecutive patients with spinal cord symptoms of sudden or relatively sudden onset were examined with magnetic resonance imaging (MRI). The examinations were performed on a 0.3 tesla permanent/resistive imaging system using solenoidal surface coils. MRI revealed epidural tumour in five patients, intramedullary tumour in one, epidural abscess in one, myelitis in two, spontaneous intraspinal epidural haematoma in two, disc herniation in two, traumatic lesions in four and no abnormality in one patient. MRI was found to be capable of non-invasively and painlessly detecting and exactly defining the extent of intraspinal and paraspinal lesions. In some cases the nature of the lesion could be inferred from specific signal characteristics, which is a unique property of MRI. The results strongly suggest that MRI is superior to myelography and other imaging methods and should be regarded as the examination of choice in the emergency examination of patients with spinal cord symptoms.

Realignment and surgical fixation of atlanto-axial and subaxial dislocations in rheumatoid arthritis (RA) patients

One hundred consecutive patients with atlanto-axial dislocation(s) were subjected to posterior occipito-cervical fusion and followed up to 16 1/2 years postoperatively (mean: 4 1/2 years). The mean age at surgery was 60.3 years. At the time of follow-up, 45 patients had died, mostly due to cardiopulmonary disease. Out of the 100 patients, 67% showed a major improvement and in an additional 14% there was a slight or moderate improvement. Some patients with a stable fusion later developed subaxial dislocation(s) necessitating an anterior fusion which in patients with RA is difficult due to poor bone quality. MRI revealed pannus formation around the odontoid peg in many patients, in several to such a degree that cord compression was evident. Following the posterior fixation, the pannus disappeared or was reduced which may at least partly explain the generally favourable operative outcome following the fixation procedure. Early occipito-cervical fusion appears to prevent further vertical dislocation or upwards migration of the odontoid which is a more severe condition, and does not appear to result in increased incidence of subsequent subaxial dislocation(s). Such luxation(s) pose a technically difficult problem since the quality of the patients' own bone usually does not permit a common anterior fusion procedure with autologous graft. In such cases with cord compression, acrylic cement may be used to obtain a normalized realignment.

MR imaging of the cervical spine in rheumatoid arthritis

The cervical spine was examined with MR imaging and conventional radiography in 23 patients with severe rheumatoid arthritis. All patients had neck pain and 17 also had neurologic symptoms. MR provided detailed information about soft-tissue lesions, vertebral dislocation, and narrowing of the spinal canal. Pannus surrounding the odontoid process was revealed in 14 patients, all with horizontal atlantoaxial subluxation. Compression of the medulla and/or spinal cord, caused by dislocated vertebrae and/or the soft-tissue mass around the odontoid process, was seen in 15 patients. When there was more than one dislocation the most important level could be determined. Posterior occipitocervical fusion had been performed in six of the patients, and in only two of these was adequate analysis of the upper cervical spine impossible because of artifacts from metal (stainless steel wires and pins). Sagittal MR in the neutral position combined with conventional radiography, including lateral views in flexion and extension, provided all the information necessary for further clinical management of rheumatoid arthritis of the cervical spine.

Reduction of rheumatoid periodontoid pannus following posterior occipito-cervical fusion visualised by magnetic resonance imaging

Nine patients (four females and five males) with chronic rheumatoid arthritis (RA) and atlanto-axial (AA) instability subjected to occipito-cervical fusion were evaluated clinically and radiologically. All of them had soft tissue formation (pannus) around the odontoid peg. The age ranged from 50 to 79 years (mean: 66). The duration of the RA disease was 3-48 years (mean: 18.5). All patients were seropositive. Both conventional radiography and magnetic resonance imaging (MR) were performed pre- and postoperatively. All fusions except one were stable. One patient was re-fused after 2 months because of wire break. With regard to pain all patients had improved and eight were pain free. Six patients who experienced signs of myelopathy prior to the fusion had improved at follow up. MR revealed reduction of pannus in all nine cases. This was obvious in one patient within 6 weeks postoperatively. The MR findings of a reduction or even disappearance of pannus following posterior fusion should decrease the need for transoral surgery.

Myelopathy patients studied with magnetic resonance for multiple sclerosis plaques

Seven patients with isolated spinal cord symptoms, and with evoked potential (EP) recordings and/or cerebrospinal fluid (CSF) findings supporting a demyelinating cause for their myelopathy, were examined with cervical and cranial magnetic resonance imaging (MRI). Lesions in the cervical spinal cord were detected in 6 of the patients, including 2 who also had disseminated lesions in the brain compatible with multiple sclerosis (MS). In one patient MRI of the cervical spinal cord was normal, while plaques were seen in the periventricular region of the brain and in the brain stem. Thus, in the 3 patients with cerebral plaques, MRI supported the diagnosis of MS by showing dissemination in space. In the remaining 4 patients MRI provided support for the diagnosis of MS by demonstrating the cervical spinal cord plaques while excluding other potential causes of myelopathy, such as spinal cord compression and intramedullary tumor.

Persisting intraventricular fat-fluid levels following surgery on a ruptured dermoid cyst of the posterior fossa

Intracranial dermoid cysts occasionally rupture spontaneously into the ventricles or into the subarachnoid space. In such cases, intraventricular fat-fluid levels are invariably evident at computed tomography and may even be visible on a conventional radiograph of the skull. A case is described in which fat was observed to remain in the ventricles long after surgical removal of a dermoid cyst. We think that this fat, by causing obstruction of the cerebrospinal fluid pathways, should be regarded as a potential cause of intermittent elevation of intracranial pressure.