Serum uric acid levels in optic neuritis.

Uric acid, an antioxidant, is reduced in multiple sclerosis (MS). Patients with gout have a reduced incidence of MS. Optic neuritis (ON), often the first manifestation of MS, is not known to be associated with reduced uric acid. Patients with recent onset of ON were investigated to determine whether uric acid levels were reduced at presentation. Twenty-one patients with ON were included, 17 females and 4 males. The mean (SD) serum uric acid in the ON female group was 184.4 ( +/-55.1) micromol/L (range, 116-309 micromol/L), whilst in the control group it was 235.2 (+/- 50.2) micromol/L (range, 172-381 micromol/L). The difference was statistically significant (chi2 = 8.93, P = 0.003). In the small male cohort, mean (SD) serum uric acid was 305 (+/- 52.1) micromol/L, whilst in the control group it was 328 (+/- 80.4) micromol/L. These differences were not statistically significant. Reduced antioxidant reserve is possibly an early pathogenic mechanism in inflammatory demyelination, and raises the possibility that low uric acid levels could be an indicator of disease activity. Since optic neuropathies of other causes were not investigated, future research needs to determine whether low uric acid represents a unique feature of optic neuritis or is seen in other optic neuropathies.

Restoration of myocardial blood flow following percutaneous coronary balloon dilatation and stent implantation: assessment with qualitative and quantitative contrast-enhanced magnetic resonance imaging.

AIM: To examine the serial use of magnetic resonance imaging (MRI) to evaluate regional myocardial perfusion changes following percutaneous coronary angioplasty and stent implantation (PTCA). MATERIALS AND METHODS: Six patients with single vessel coronary artery disease (CAD) underwent contrast-enhanced first pass MRI immediately prior to (visit A) and within 7 days after (visit B) PTCA. Three sequential short axis slices were obtained after gadodiamide (Gd) bolus (0.025 mmol/kg(-1)) at rest and during adenosine. Each short axis was divided radially into eight regions of interest (ROIs). ROIs were anatomically assigned to a coronary artery territory (CAT). Stress and rest qualitative and quantitative (unidirectional extraction fraction constant (K(i)); index of myocardial perfusion reserve (MPRI) = stressK(i) / restK(i)) perfusion parameters were determined for ROI supplied by remote and stenosed/stented vessels for each visit. RESULTS: In stented ROIs the number of ROIs demonstrating normal perfusion, as opposed to reversible perfusion deficits, increased. Qualitative perfusion assessment in remote CATs was unchanged. MPRI in stenotic CATs was lower than in remote CATs at visit A (P < 0.001). Following PTCA, MPRI increased in stented CATs (P < 0.001) but was unchanged in remote CATs. CONCLUSION: Restoration of myocardial perfusion following PTCA can be delineated with qualitative and quantitative perfusion MRI. Although at present the investigation is technically complex and not perfectly sensitive or specific, MRI has the potential to be a valuable tool for patient follow-up and evaluation of revascularization strategy efficacy.

Magnetic resonance imaging of metastatic disease to the brain with gadobenate dimeglumine.

Seventy-four patients with one to eight proven intraaxial brain metastases received a total cumulative dose of 0.2 mmol/kg bodyweight gadobenate dimeglumine, administered as sequential injections of 0.05, 0.05 and 0.1 m mol/kg over a 20-min period. MR imaging was performed before the first administration (T2- and T1-weighted sequences) and after each injection of contrast agent (T1-weighted sequences only). Quantitative assessment of images revealed significant (P <0.01) dose-related increases in lesion-to-brain (L/B) ratio and percent enhancement of lesion signal intensity. Qualitative assessment by two independent, blinded assessors revealed additional lesions in 22%, 25% and 38% (assessor 1) and 29%, 32% and 34% (assessor 2) of patients after each cumulative dose when compared with combined T1- and T2-weighted pre-contrast images. Significantly more lesions (P < 0.01) were noted by both assessors after the first injection and by one assessor after each subsequent injection. For patients with just one lesion observed on unenhanced T1- and T2-weighted images, additional lesions were noted in 12%, 16% and 28% of patients by assessor 1 following each dose and in 24%, 27% and 30% of patients by assessor 2. Contemporaneously, diagnostic confidence was increased and lesion conspicuity improved over unenhanced MRI. For patients with one lesion observed after an initial dose of 0.05 mmol/kg, additional lesions were noted by assessors 1 and 2 in 9.1% and 11.8% of patients, respectively, after a cumulative dose of 0.1 mmol/kg and in a further 9.1% and 5.9% of patients, respectively, after a cumulative dose of 0.2 mmol/kg. No safety concerns were apparent.

Coronary artery disease: combined stress MR imaging protocol-one-stop evaluation of myocardial perfusion and function.

The authors developed and tested a dual stress magnetic resonance (MR) imaging protocol to evaluate myocardial perfusion, function, and hibernation. The technique was well tolerated, and high-quality images were achieved. The comprehensive information obtained can be used to guide clinical management decisions regarding coronary artery revascularization procedures. This protocol offers a one-stop assessment of patients with coronary artery disease with use of a clinical MR imager.

A myocardial perfusion reserve index in humans using first-pass contrast-enhanced magnetic resonance imaging.

OBJECTIVES: The purpose of this study was to evaluate a myocardial perfusion reserve index (MPRI) derived from a quantitative magnetic resonance imaging (MRI) technique in normal human volunteers and patients with coronary artery disease and to relate MPRI to coronary artery stenosis severity measured with quantitative arteriography. BACKGROUND: Magnetic resonance imaging could be a useful noninvasive tool in the investigation of ischemic heart disease. However, there have been few studies in humans to quantify myocardial perfusion and myocardial perfusion reserve using MRI and none in patients with coronary disease. METHODS: Twenty patients with angiographically proven coronary artery disease and five normal volunteers underwent both resting and stress (adenosine 140 microg/kg(-1)/min(-1)) first-pass contrast-enhanced MRI examinations (using 0.05 mmol/kg 1 of gadopentetate dimeglumine. Using a tracer kinetic model, the unidirectional transfer constant (K(i)), a perfusion marker for the myocardial uptake of contrast, was computed in each coronary arterial territory. The ratio of K(i) for the rest and stress scans was used to calculate the MPRI. Percent reduction in luminal diameter of coronary lesions was measured using an automated edge-detection algorithm. RESULTS: Myocardial perfusion reserve index was significantly reduced in patients compared with normal subjects (2.02+/-0.7 vs. 4.21+/-1.16, p < 0.02). For regions supplied by individual vessels, there was a significant negative correlation of MPRI with percent diameter stenosis (r = -0.81, p < 0.01). Importantly, regions supplied by vessels with <40% diameter stenosis (non-flow limiting) had a significantly higher MPRI than regions supplied by stenoses of "intermediate" severity, that is, >40% to 59% diameter stenosis (2.80+/-0.77 and 1.93+/-0.38, respectively, p < 0.02). However, even regions supplied by vessels with <40% diameter stenosis had a significantly lower MPRI than volunteers (p < 0.01). CONCLUSIONS: A myocardial perfusion reserve index derived from first-pass MRI studies can distinguish between normal subjects and patients with coronary artery disease. Furthermore, it provides useful functional information on coronary lesions, particularly where the physiologic significance cannot be predicted accurately from the angiogram.

Mechanism and clinical significance of precordial ST depression in inferior myocardial infarction: evaluation by contrast-enhanced dynamic myocardial perfusion magnetic resonance imaging.

We elucidated the mechanism and clinical significance of precordial ST depression in patients with an inferior myocardial infarction using first-pass, contrast-enhanced, myocardial perfusion magnetic resonance imaging (MRI). Forty-seven patients with acute inferior myocardial infarction underwent first-pass contrast-enhanced MR studies within 2-6 days postinfarction. Patients were followed-up for a minimum of 1 year after infarct (range, 12-32 months). Total perfusion deficit scores derived qualitatively from MRIs were compared in patients with (group 1, n = 30) and without (group 2, n = 17) ST depression precordially. Perfusion remote from the infarct zone was also compared. The combined end points of adverse clinical events and/or the need for further intervention were assessed for each group. Total perfusion deficit scores were significantly higher in group 1 than group 2 (medians 9.7 versus 4.5, p < 0.005). Posterolateral basal extension of hypoperfusion was greater in group 1 versus group 2 (1.23 versus 0.42, p < 0.02), with no evidence of remote anterior perfusion abnormalities. There were more patients with an adverse clinical end point in group 1 versus group 2 (18 versus 1, p < 0.01). Furthermore, in patients with ST depression (group 1), there was a significant increase in number of adverse clinical end points in patients with a global deficit score > 15 versus 0-5 (7/7 versus 1/7, p < 0.01). MRI shows that precordial ST depression in inferior myocardial infarction is a marker for a larger global perfusion abnormality with posterolateral basal extension and an increase in adverse clinical end points. Furthermore, the magnitude of the perfusion deficit correlates with an increase in the number of adverse clinical end points, highlighting the potential of MRI perfusion studies as a research and clinical tool in myocardial infarction.

Echoplanar MRI in patients with an acute stroke syndrome.

An increasing number of patients with an acute stroke syndrome are being admitted to hospitals with on-site echoplanar MRI scanners. In this pictorial review, we describe our experience of an MRI protocol in the first 150 such patients scanned in our hospital. We illustrate some of the advantages of using echoplanar MRI. Diffusion and susceptibility weighted acquisitions may supplement conventional MR sequences by providing useful additional information about the age and location of the lesion, together with a high sensitivity to the presence of blood breakdown products.

Dynamic T1 measurement using snapshot-FLASH MRI.

The application of an inversion-recovery snapshot FLASH (fast low-angled shot) imaging sequence to the dynamic measurement of monoexponential T1 relaxation was investigated. The effect of (a) a reduction in the overall sequence repetition time, and (b) an increase of the read-pulse flip angle, on the measurement of T1 was analyzed. The error in T1 introduced by these factors is calculated, and a fuller analysis that takes them into account is presented. Data from a phantom are used to confirm this analysis. The magnitude of the errors is illustrated by measuring myocardial T1 in patients with acute ischaemic heart disease during the injection of a bolus of the contrast medium gadobenate dimeglumine. Overall, there was a 10% difference between the T1 values when the approximate and exact solutions were used; this was statistically significant. However, the difference was on average 25% for patients with a high heart rate (because of the shorter sequence-repetition time) in areas of infarcted myocardium (because of the longer T1).

[Comparative evaluation of computerized tomography/magnetic resonance (1.5 T) in the detection of brain metastasis]. / Valutazione comparativa tomografia computerizzata/risonanza magnetica (1,5 T) nell'identificazione delle metastasi cerebrali.

Forty-four patients with small cell carcinoma of the bronchus underwent CT and MR studies of the brain to detect cerebral metastases. All patients were studied with contrast-enhanced CT scans, short (T1-weighted) and long (T2-weighted), spin-echo (SE) and FLASH 90 degrees MR sequences. Gd-DTPA enhanced SE-T1 and FLASH 90 degrees sequences were also obtained. A quantitative comparison of the results was carried out to assess the sensitivity of the different techniques in the detection of brain metastases according to lesion diameter. Metastases were identified in 19/44 patients (43%). All techniques detected the lesions greater than 2 cm; of the metastases less than 2 cm, 63/124 (51%) were detected only by Gd-DTPA SE-T1 and FLASH sequences and 11 more (9%) only by Gd-DTPA SE-T1 scans. All the lesions identified on enhanced CT scans or on T2-weighted images were easily detected by Gd-DTPA scans. CT sensitivity was higher than that of pre-contrast SE-T1 and FLASH studies and only slightly lower than that of T2-weighted images. As for lesions less than 2 cm, Gd-DTPA T1-weighted sequences had the highest detection rate (124 lesions) versus Gd-DTPA FLASH 90 degrees scans (113 lesions) and precontrast T1-weighted scans (45 lesions). When comparing Gd-DTPA SE-T1 and FLASH 90 degrees sequences in the detection of lesions less than 1 cm, we observed that the latter missed 9% of metastases, mainly due to a high rate of magnetic susceptibility artifacts and to lower contrast resolution. Therefore, Gd-DTPA SE-T1 images still remain the most accurate technique in the assessment of cerebral metastases.

Cutaneous neuro-endocrine (Merkel cell) carcinoma.

Two cases of neuro-endocrine (Merkel cell) tumours of the skin are reported. There was evidence of distant relapse in both patients who eventually succumbed to the disease. The wide range of clinical and radiological manifestations of this rare tumour are discussed and the literature reviewed.

The role of computed tomography in the investigation of recurrent axillary disease in patients with carcinoma of the breast.

Carcinoma of the breast commonly recurs in the axilla. A nodal mass may be palpable and computed tomography (CT) is frequently requested in order to differentiate recurrent tumour from the longer term effects of surgery and radiotherapy. We have reviewed the CT scans of 35 such patients referred consecutively to our CT unit. CT only detected the presence of recurrent tumour in one patient in whom a mass could not be palpated. This patient had a previously irradiated 'wooden' axilla making clinical examination impossible. CT failed to diagnose recurrence in two patients; one with disease in normal sized nodes and the other with axillary vein thrombosis. We conclude that CT of the axilla only appears to be of value when the axilla is impossible to palpate due to previous treatment. The key to the diagnosis of axillary tumour recurrence is careful palpation supplemented by aspiration cytology of any mass. When no mass is evident on clinical examination, CT is unlikely to demonstrate disease.

Bladder cancer: staging with CT and MR imaging.

Magnetic resonance (MR) imaging and computed tomography (CT) were compared in 30 patients with histologically proved bladder cancer. MR imaging was accurate in depicting the presence or absence of extravesical spread in 22 patients (accuracy, 73%; sensitivity, 82%; specificity, 62%), and CT was accurate in 24 patients (accuracy, 80%; sensitivity, 94%; specificity, 62%). The MR examinations of two patients were of undiagnostic quality and therefore considered to be technical failures. Each technique resulted in five false-positive and one false-negative examination for the diagnosis of extravesical tumor spread. In 28 patients the integrity of the bladder wall was assessed with MR imaging. In 22 patients the bladder wall was disrupted, and 18 of these patients had deep muscle invasion. In six patients the bladder wall was intact, and none of these patients had evidence of deep muscle invasion at pathologic examination. In this study MR imaging was slightly inferior to CT in the delineation of invasive tumors beyond the bladder wall. However, if one excludes from analysis the two patients with undiagnostic studies, there is no significant difference in accuracy between the two techniques.

Magnetic resonance imaging in recurrent carcinoma of the cervix.

Twenty patients with suspected recurrent cervical carcinoma were evaluated with computed tomography (CT) and high-field magnetic resonance imaging (MRI). Histological verification of the imaging findings were available in all cases. Computed tomography and MRI were equally effective in making the diagnosis of disease recurrence. The extent of vaginal recurrence and involvement of pelvic floor muscles was better shown on MRI than on CT.

Magnetic resonance imaging in suspected metastatic spinal cord compression.

This study describes high field magnetic resonance imaging (MRI), in 55 patients with suspected metastatic spinal cord compression. MRI, principally using T1-weighted sagittal surface coil images, showed evidence of cord compression in 29 patients, and intramedullary masses in three patients. MRI clearly showed the site, nature and extent of the cord compression and gave useful additional information about the presence of bone marrow metastases and paravertebral soft-tissue masses. Comparison with conventional myelography was possible in 21 patients and MRI was superior or equivalent to myelography in 18 patients and inferior in three patients. MRI is the method of choice for the investigation of patients with suspected metastatic spinal cord compression.

Significance of thoracic disc herniation demonstrated by MR imaging.

The thoracic spines of a group of 48 oncology patients were examined with high field (1.5 T) magnetic resonance (MR) imaging. Sagittal T1-weighted sections were obtained in all patients. Even using this single sequence an unexpectedly high prevalence of thoracic disk herniation (14.5%) was demonstrated. Thoracic disk herniation shown by MR may not be related to the patients' symptoms.

Fast magnetic resonance imaging of intracerebral metastatic disease.

The appearance of intracerebral metastases imaged with a multi-slice fast imaging sequence (FLASH) is described. Images were obtained using a Siemens 2.0 T Magnetom operating at 1.5 T. Results of the FLASH imaging sequence at different values of repetition time, different values of "flip angle" and different numbers of acquisitions are described both qualitatively and quantitatively. At low flip angles, both tumour and oedema appear brighter than surrounding white matter. Increasing the flip angle tends to make oedema brighter than both tumour and white matter and increasing the flip angle still further makes tumour and oedema darker than white matter. A major limitation of this technique is that the low flip angle images, in particular, suffer from low signal-to-noise ratios. High flip angle FLASH images have higher signal-to-noise ratios but show similar contrast behaviour to T1-weighted spin-echo images and are likely to be no better as a screening sequence for intracerebral metastases. All the FLASH sequences showed a sensitivity to changes in magnetic susceptibility. This made small intratumoral haemorrhages and basal ganglia "calcification" easier to detect than on spin-echo images but also caused susceptibility artefacts in images around the base of the skull.