The brightness and other characteristics of the image produced by the changes in the magnetic field in magnetic resonance depend both on the concentration of the hydrogen nuclei in the tissue called the proton density or spin density and the weight given to the T 1 and T 2 components of the image, which is determined by the radiofrequency pulse sequence. When a radiofrequency pulse sequence with a long time between pulses milliseconds and 2 echos at milliseconds and milliseconds is used, the first echo produces a proton-density image that contrasts MS lesions hyperintense with the cerebrospinal fluid hypointense , while the second echo produces an image in which MS lesions are clearly contrasted with normal brain tissue, while the cerebrospinal fluid and brain tissue contrast is diminished.
As shown in Figure 1 , the plaques of MS appear as multiple, periventricular, rounded, or oval areas of increased signal intensity on T 2 -weighted MR images. Three types of lesions have been described: new lesions, reappearing lesions, and enlarging lesions. In serial MRI studies, lesion activity was greater than clinical activity in all cases. In studies using Gd-DTPA enhancement, new lesions typically appear first on Gd-DTPA—enhanced T 1 -weighted images, indicating that blood-brain barrier impairment is an early event in the process of lesion formation.
Correlations between the pathological appearance of MS lesions demyelination, perivascular inflammation, edema, macrophage infiltration, gliosis, axon loss, and necrosis 25 , 31 and MRI findings were first demonstrated in by Stewart et al.
Some insights into the pathophysiological correlates of lesion evolution were provided in a serial MRI study in which lesion development was followed with both Gd-DTPA—enhanced T 1 -weighted images and proton-density images.
This pattern subsequently changed to one of ring hyperintensity, usually within 1 month of first appearance. The ring hyperintensity gradually faded over time. The MRI studies can provide quantitative information about MS lesions with respect to lesion number 15 , 16 , 18 , 32 , 34 , 37 - 42 and lesion volume. Lesion volume may be calculated in various ways, but 2 general approaches are common: manual tracing of lesion outlines 4 , 31 , 51 and semiautomatic lesion detection based on signal intensity.
One study 48 recently addressed the problem of standardizing data reported from multiple centers using a technique in which digitized images, stored on tape or film, are analyzed at a central processing center following a standard image analysis and segmentation procedure. Multiparametric segmentation techniques, which require integration of 2 or more MRI sequences, are the newest method.
Although quantitative measures based on MRI scans are now standard in many MS studies, the method remains imperfect. As Filippi et al 13 observed in a recent review of quantitative MRI, the quantitative assessment of brain abnormalities by MRI is reliable and reproducible, but further refinements are needed to improve the correlation between MRI abnormalities and clinical progression. Although the diagnosis of MS is generally made on clinical grounds, 57 MRI evidence may be used to support or suggest a diagnosis in cases that do not meet all clinical criteria.
Several sets of MRI diagnostic criteria have been developed. The criteria of Fazekas et al 59 require the presence of 2 of 3 findings: lesion size greater than 6 mm, lesions abutting the lateral ventricles, and lesions in the posterior fossa. These criteria 60 have a higher specificity and a lower false-positive rate. In the Optic Neuritis Treatment Trial, 61 which enrolled patients with optic neuritis but without definite or probable MS, the strongest indicator of risk for development of definite MS was MRI scan grade at study entry Table 1 , with 27 Similar results were reported by the MS Nuclear Magnetic Resonance Research Group 62 in a 5-year follow-up study of 89 of patients who initially presented with an acute, clinically isolated syndrome of the optic nerve, brainstem, or spinal cord.
Brain lesions at initial presentation were associated with a relative risk of 6. It is thus apparent that MRI lesion data at presentation are useful in predicting the subsequent development of MS in patients with clinically isolated syndromes and may identify patients who will benefit most from early treatment, with monitoring of their course. Patients with chronic-progressive MS generally have a higher mean lesion load overall than those with benign MS. Establishment of a usable relationship of MRI-quantified MS lesion load to the clinical status of patients with MS is influenced by a number of methodological difficulties.
The correlation between lesion load, measured by unenhanced MRI, and clinical disability was studied in 53 patients with suspected MS. Double-echo images with automatic segmentation and image registration were used to extract lesion volumes and counts in a recent serial study of 45 patients with MS. The correlation between increased activity on MRI scans and clinical worsening in 9 patients with relapsing-remitting MS during 24 to 37 months was assessed with a logistic regression analysis model.
Thorpe and colleagues 18 followed up 10 patients with relapsing-remitting MS for 1 year with serial Gd-DTPA—enhanced MRI scans of the spinal cord and brain and evaluations of relapse and disability. Most recent studies that have found correlations between lesion activity on MRI scans and clinical disease progression have been serial studies Table 3 , an observation that suggests that cross-sectional studies may miss such correlations because of heterogeneity in the apparent lesion load between patients.
It is likely that the development of more refined imaging technologies will lead to the discovery of even stronger correlations between neurological activity and clinical outcome.
Multiple sclerosis affects cognitive as well as physical functioning, and the relationship between cognitive function and lesion load in patients with MS has been examined in several studies. Traditional measures of treatment outcome in MS involve clinical events such as relapse frequency or worsening of disability.
Because the course of MS is highly variable, trials using such end points must enroll large numbers of patients and follow them up for several years. In addition, available clinical scales are not entirely satisfactory with respect to interrater reliability and bias. For these reasons, there has been a great interest in developing an effective surrogate marker of MS activity. Of the available imaging and immunological measures that may provide MS marker data, MRI is the most widely used.
However, because lesion activity on MRI scans may not correlate with clinical findings, serial MRI is currently recommended as a secondary outcome measure of pathological progression in clinical trials involving patients with established MS. Two cyclosporine trials 75 , 76 have been conducted in patients with MS. In the first, 75 both MRI and clinical disability as measured by the EDSS were used to compare the effects of cyclosporine and azathioprine in 74 patients with definite MS; both treatments appeared to be equally effective, but neither halted neurological progression as evidenced by the appearance of new lesions.
In the second study, 76 MRI data were used to compare the efficacy of cyclosporine and placebo in patients with chronic-progressive MS; although a marked increase in lesion load was seen during the study period, treatment with cyclosporine did not affect lesion load. The efficacy of interferon alfa in the treatment of MS has been evaluated in 2 randomized, double-blind, placebo-controlled trials.
Serial scans obtained at 6-week intervals in 52 patients to determine lesion activity showed that the interferon beta-1B group had a median of 5. At 1 year, the proportion of positive scans dropped to The technical difficulties involved in imaging MS lesions reliably and reproducibly have led to the development of newer techniques with greater powers of discrimination than conventional MRI T 1 -weighted, T 2 -weighted, and proton-density images.
Fluid-attenuated inversion recovery uses a long inversion time to suppress the MRI signal from cerebrospinal fluid plus heavy T 2 weighting of the image obtained with a long echo time.
That includes performing lab tests that include cerebrospinal fluid samples and blood tests. You will also have your brain scanned. Is the white matter injury active or old? Our patients typically fall into two categories: those who worry that they may have MS, based on preliminary diagnosis by their physician, and those who already have MS and seek updates on their disease. For patients who already have the diagnosis, a magnetic resonance imaging scan MRI can help doctors study whether a therapy is working.
If a patient presents with new symptoms, Dr. While general brain scans are often performed using computerized tomography CT , MRIs are used to scan for MS; in the images, doctors are looking for abnormal white matter.
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Department of Radiology, Athinoula A. You can also search for this author in PubMed Google Scholar. Correspondence to Pascal Sati. This work is licensed under a Creative Commons Attribution 4. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material.
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Download PDF. Subjects Brain imaging Multiple sclerosis. Main At present, the diagnosis of multiple sclerosis MS relies heavily on the use of MRI, which can demonstrate disease dissemination in space and time 1 , 2 , 3 , 4. Permanently damaged areas of the brain appear as dark spots. These are also known as black holes or hypointense lesions. According to some researchers , chronic active lesions are very damaging to the brain.
These lesions require treatment as early as possible. A T-1 weighted scan without contrast dye can show hypointense lesions, which may indicate areas of permanent nerve damage. New MS lesions appear as bright spots on a T-2 scan. These are also known as hyperintense lesions. Typical lesions that appear on a T-2 scan are oval in shape.
Fluid-attenuated inversion recovery imaging reduces interference from the spinal fluid to help view the effects of MS. Anomalies remain bright, while normal brain fluid looks dark. Spinal cord imaging can show that damage has occurred in different parts of the central nervous system at different points in time. Learn about radiology tests for MS here. Radio waves then pulse through the body, causing the protons to spin out of order. Once the technician turns the radio waves off, the protons fall back to their original order.
As they return to their original positions, the protons release signals that transmit to a computer. The computer then converts these signals to detailed 2D and 3D images of body tissue and organs. Before undergoing an MRI scan, a person needs to remove any clothing or personal items that may contain metal.
The MRI machine makes loud knocking noises during the test. A person undergoing a scan will receive earplugs or earphones to help muffle the noise.
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