MRI in multiple sclerosis of the spinal cord: evaluation of fast short-tan inversion-recovery and spin-echo sequences

Comparison of Sagittal FSE T2, STIR, and T1-Weighted Phase-Sensitive Inversion Recovery in the Detection of Spinal Cord Lesions in MS at 3T

BACKGROUND AND PURPOSE

Determining the diagnostic accuracy of different MR sequences is essential to design MR imaging protocols. The purpose of the study was to compare 3T sagittal FSE T2, STIR, and T1-weighted phase-sensitive inversion recovery in the detection of spinal cord lesions in patients with suspected or definite MS.

MATERIALS AND METHODS

We performed a retrospective analysis of 38 patients with suspected or definite MS. Involvement of the cervical and thoracic cord segments was recorded on sagittal FSE T2, STIR, and T1-weighted phase-sensitive inversion recovery sequences independently by 2 readers. A consensus criterion standard read was performed with all sequences available. Sensitivity, specificity, and interobserver agreement were calculated for each sequence.

RESULTS

In the cervical cord, the sensitivity of T1-weighted phase-sensitive inversion recovery (96.2%) and STIR (89.6%) was significantly higher (P < .05) than that of FSE T2 (50.9%), but no significant difference was found between T1-weighted phase-sensitive inversion recovery and STIR. In the thoracic cord, sensitivity values were 93.8% for STIR, 71.9% for FSE T2, and 50.8% for T1-weighted phase-sensitive inversion recovery. Significant differences were found for all comparisons (P < .05). No differences were detected in specificity. Poor image quality and lower sensitivity of thoracic T1-weighted phase-sensitive inversion recovery compared with the other 2 sequences were associated with a thicker back fat pad.

CONCLUSIONS

The use of an additional sagittal sequence other than FSE T2 significantly increases the detection of cervical and thoracic spinal cord lesions in patients with MS at 3T. In the cervical segment, both STIR and T1-weighted phase-sensitive inversion recovery offer high sensitivity and specificity, whereas in the thoracic spine, STIR performs better than T1-weighted phase-sensitive inversion recovery, particularly in patients with a thick dorsal fat pad.

Proton Density MRI Increases Detection of Cervical Spinal Cord Multiple Sclerosis Lesions Compared with T2-Weighted Fast Spin-Echo

BACKGROUND AND PURPOSE

There is a paucity of literature that supports the Consortium of Multiple Sclerosis Centers guideline that proton density MR imaging is a core spinal cord sequence. We hypothesized that proton density fast spin-echo imaging is superior to T2 fast spin-echo MR imaging for the detection of cervical cord MS lesions. This study compared the detection rate and conspicuity of cervical cord MS lesions on sagittal 1.5T proton density fast spin-echo and T2 fast spin-echo MR imaging.

MATERIALS AND METHODS

One hundred consecutive patients with MS imaged with 1.5T sagittal proton density fast spin-echo and T2 fast spin-echo cervical cord MR imaging between September 2012 and October 2013 were retrospectively included. The number of MS lesions detected on each sequence was recorded; conspicuity was assessed quantitatively with the lesion-to-cord contrast ratio and lesion-contrast-to-noise ratio. Statistical analysis was performed by using the Wilcoxon signed rank test.

RESULTS

Seventy-eight patients had MS cord lesions detected. Proton density fast spin-echo imaging detected a greater number of lesions (n = 181) compared with T2 fast spin-echo imaging (n = 137, P < .001). Fifteen patients (19%) with abnormal findings on proton density fast spin-echo imaging had normal findings on T2 fast spin-echo imaging; no patient with abnormal T2 fast spin-echo imaging findings had normal proton density fast spin-echo imaging findings. Although proton density fast spin-echo and T2 fast spin-echo imaging had similar lesion-to-cord contrast ratios (proton density fast spin-echo, 0.32 ± 0.01, versus T2 fast spin-echo, 0.33 ± 0.01; P = .43), proton density fast spin-echo had greater lesion-contrast-to-noise ratio (proton density fast spin-echo, 82 ± 3.0, versus T2 fast spin-echo, 64 ± 2.6; P < .001).

CONCLUSIONS

Proton density fast spin-echo imaging is superior to T2 fast spin-echo MR imaging for the detection of cervical cord MS lesions. Proton density fast spin-echo detects cord lesions in patients in whom T2 fast spin-echo findings appear normal. This study forms the evidentiary base for the current Consortium of Multiple Sclerosis Centers guideline that proton density imaging is a core spinal cord sequence.

Comparison of two fat-suppressed magnetic resonance imaging pulse sequences to standard t2-weighted images for brain parenchymal contrast and lesion detection in dogs with inflammatory intracranial disease

T2-weighted (T2w) sequences are commonly relied upon in magnetic resonance imaging protocols for the detection of brain lesions in dogs. Previously, the effect of fluid suppression via fluid-attenuated inversion recovery (FLAIR) has been compared to T2-weighting with mixed results. Short tau inversion recovery (STIR) has been reported to increase the detection of some CNS lesions in people. The purpose of the current study was to evaluate the effect of fat suppression on brain parenchymal contrast resolution and lesion detection in dogs. We compared three sequences: T2w images, STIR, and T2w FLAIR with chemical fat suppression (T2-FLAIR-FS) in dogs with meningoencephalitis. Dogs with meningoencephalitis and dogs with idiopathic epilepsy were retrospectively identified and anonymized. Evaluators recorded the presence or absence of lesions within 12 predetermined brain regions on randomized sequences, viewing and scoring each sequence individually. Additionally, signal-to-noise ratios, contrast-to-noise ratios, and relative contrast (RC) were measured in a reference population. Short tau inversion recovery sequences had the highest RC between gray and white matter. While descriptively more lesions were identified by evaluators on T2-FLAIR-FS images, there was no statistical difference in the relative sensitivity of lesion detection between the sequences. Nor was there a statistical difference in false lesion detection within our reference population. Short tau inversion recovery may be favored for enhanced anatomic contrast depiction in brain imaging. No benefit of the inclusion of a fat-suppressed T2-FLAIR sequence was found.

A comparison of sagittal short T1 inversion recovery and T2-weighted FSE sequences for detection of multiple sclerosis spinal cord lesions

PURPOSE

Multiple sclerosis (MS) is the most common disabling CNS disease of young adults. MRI is routinely used for the detection of MS plaques in the brain and spinal cord. A significant portion of patients with MS demonstrates spinal cord lesions at the time of initial workup, and these lesions are an important part of the McDonald criteria for diagnosis. However, whereas brain imaging sequences are now fairly standardized, there continues to be debate about the optimal sequences for imaging the spinal cord. The short T1 inversion recovery (STIR) sequence has been shown in the current literature to improve lesion detection with its additive T1/T2 weighting, but current spinal cord imaging protocols from the Consortium on MS Center Consensus Guidelines do not include the STIR sequence. We demonstrate that not only do STIR sequences improve lesion detection when compared directly with conventional T2-weighted sequences, but that they also significantly improve lesion conspicuity, facilitating earlier positive diagnosis and management.

MATERIALS AND METHODS

Dedicated MR spinal cord imaging of twenty-nine sequential patients with clinically confirmed multiple sclerosis was retrospectively analyzed by two independent neuroradiologists in a novel study design. Sagittal T2-weighted and STIR sequence images from the same study for each patient were examined for MS plaques using a double-blinded review of individual images 'separated in time and space', such that STIR and T2 image pairs were never analyzed simultaneously. Number of lesions and lesion conspicuity for each lesion, using a subjective scale (1-5), were tallied for each sequence. Averages for each observer were compared using a paired t-test analysis for statistical significance, and assessment of inter-rater agreement was assessed using Cohen's kappa index.

RESULTS

Significantly, more MS lesions were detected on STIR than on T2-weighted sequences for both observers (P = 0.001 and P = 0.005). In seven patients, the conventional T2 sequence detected no lesions at all, whereas STIR sequences showed significant cord involvement. Lesion conspicuity was also significantly better on STIR for both observers (P < 0.0005). This improved conspicuity leads to more uniform lesion detection. On the conventional T2-weighted sequence, there was a statistically significant difference in the number of lesions detected between the two observers (P = 0.003), but there was no statistically significant difference on STIR (P = 0.43). The kappa index showed greater interobserver agreement in both lesion count and lesion conspicuity on the STIR sequence as compared with T2.

CONCLUSIONS

Short T1 inversion recovery sequence imaging not only significantly improves detection of MS lesions within the spinal cord, but also provides better contrast and conspicuity of visible lesions, creating a more confident diagnostic measure of MS extent and progression. Short T1 inversion recovery sequences of the spinal cord should be routinely obtained during initial and routine follow-up of MS.

Standardized magnetic resonance imaging acquisition and reporting in pediatric multiple sclerosis

Magnetic resonance (MR) imaging is one of the most important paraclinical tools for the diagnosis of multiple sclerosis (MS), and monitoring of disease progression and treatment response. This article provides clinicians and neuroradiologists caring for children with demyelinating disorders with a suggested standard MR imaging acquisition and reporting protocol, and defines a standard lexicon for lesion features typical of MS in children. As there is considerable overlap between the MR imaging features of pediatric- and adult-onset MS, the recommendations provided herein may be of relevance to radiologists and clinicians caring for adults with multiple sclerosis.

[Imaging of non-traumatic and non-tumoral cord lesions]

There is a wide range of spinal cord pathologies (vascular, inflammatory, infectious, metabolic, degenerative). They present clinically as acute partial or complete cord syndromes, or chronic myelopathies (more than 4 weeks in duration). MRI examination should be undertaken with a very strict protocol. Spinal cord lesions should be evaluated with regards to their T1W and T2W signal characteristics, involvement of grey and/or white matter, axial and sagittal extension, cord volume changes, contrast uptake and associated lesions (perimedullary, radicular or brain). The correlation of MR imaging features with clinical and biological data (blood and CSF) should suggest a differential diagnosis.

Spinal-cord MRI in multiple sclerosis: conventional and nonconventional MR techniques

Multiple sclerosis is a diffuse disease of the central nervous system, and MRI of the spinal cord is highly recommended in the clinical evaluation of patients suspected of having multiple sclerosis. Within the new diagnostic criteria, spinal cord MRI increases sensitivity and possibly specificity for MS, but further work is needed to investigate other criteria that may give greater weight to the presence of cord lesions in patients with clinically isolated syndromes or suspected relapsing-remitting multiple sclerosis. Techniques should be further studied and validated in studies comparing these techniques with clinical status and histopathology, however.

Demyelinating and infectious diseases of the spinal cord

Spinal cord diseases generally have distinctive clinical findings that reflect dysfunction of particular sensory or motor tracts. The abnormalities on MR images reflect the pathologic changes that occur in the affected pathways. The complexity and the wide spectrum of diseases affecting the spinal cord require a profound knowledge of neuropathology and exactly tuned imaging strategies. This article describes and illustrates the clinical and imaging characteristics in various demyelinating and infectious conditions of the spinal cord.

Idiopathic inflammatory-demyelinating diseases of the central nervous system

Idiopathic inflammatory-demyelinating diseases (IIDDs) include a broad spectrum of central nervous system disorders that can usually be differentiated on the basis of clinical, imaging, laboratory and pathological findings. However, there can be a considerable overlap between at least some of these disorders, leading to misdiagnoses or diagnostic uncertainty. The relapsing-remitting and secondary progressive forms of multiple sclerosis (MS) are the most common IIDDs. Other MS phenotypes include those with a progressive course from onset (primary progressive and progressive relapsing) or with a benign course continuing for years after onset (benign MS). Uncommon forms of IIDDs can be classified clinically into: (1) fulminant or acute IIDDs, such as the Marburg variant of MS, Baló's concentric sclerosis, Schilder's disease, and acute disseminated encephalomyelitis; (2) monosymptomatic IIDDs, such as those involving the spinal cord (transverse myelitis), optic nerve (optic neuritis) or brainstem and cerebellum; and (3) IIDDs with a restricted topographical distribution, including Devic's neuromyelitis optica, recurrent optic neuritis and relapsing transverse myelitis. Other forms of IIDD, which are classified clinically and radiologically as pseudotumoral, can have different forms of presentation and clinical courses. Although some of these uncommon IIDDs are variants of MS, others probably correspond to different entities. MR imaging of the brain and spine is the imaging technique of choice for diagnosing these disorders, and together with the clinical and laboratory findings can accurately classify them. Precise classification of these disorders may have relevant prognostic and treatment implications, and might be helpful in distinguishing them from tumoral or infectious lesions, avoiding unnecessary aggressive diagnostic or therapeutic procedures.

Volumetric quantitation by MRI in primary progressive multiple sclerosis: volumes of plaques and atrophy correlated with neurological disability

In primary progressive multiple sclerosis (PPMS) abnormalities in brain magnetic resonance imaging (MRI) differ from abnormalities in other subtypes of multiple sclerosis (MS). It was investigated whether the extent of brain and spinal cord MRI abnormalities is reflected in the neurological disability in PPMS. Focal and diffuse changes and atrophy in central nervous system (CNS) in patients with PPMS (n = 28) and healthy controls (n = 20) were assessed by semi-automatic MRI segmentation and volumetric analysis. The measurements were related to neurological disability as expressed by the expanded disability status scale (EDSS), the regional functional scoring system (RFSS), the arm index and the ambulation index. Plaques in T1- and/or T2-weighted images were seen in all brains, while spinal plaques were detected in 23 of 28 patients (82%). The total volumes of brain and spinal cord were significantly smaller in patients than in controls (P = 0.001 and 0.000, respectively). The volumes of T1 or T2 lesions in the brain correlated to the ambulation index (r = 0.51, P = 0.005 and r = 0.53, P = 0.004, respectively). No correlations were detected between MRI measurements and total EDSS score, but relative brain atrophy correlated inversely with the total RFSS scores, poor arm index and higher cerebral disturbances (r = -0.53, P = 0.004; r = -0.53, P = 0.004; and r = -0.52, P = 0.005, respectively). Although the number of spinal T2 lesions correlated with sensory disturbances (r = 0.60, P = 0.001), no correlations were found between EDSS subscores and spinal cord atrophy. These findings show that marked atrophy of brain and spinal cord detected by volumetric quantitation correlates with neurological disability. This observation indicates the importance of neurodegenerative events in PPMS.

The clinico-radiological paradox in multiple sclerosis revisited

The use of magnetic resonance imaging as a surrogate outcome measure in clinical trials, or even as a prognosticator in the assessment of the natural evolution, assumes a close relationship between extent and rate of development of magnetic resonance imaging abnormalities with the clinical status and rate of development of disability. While it may seem obvious that patients who develop new lesions are worse off than those without new lesions, the association between clinical findings and radiological extent of involvement is generally poor. In this review, various confounders are discussed, including inappropriate clinical rating, lack of histopathological specificity (especially for axonal loss), neglect of spinal cord involvement, underestimation of damage to the normal appearing brain tissue (both white and gray matter), and masking effects of cortical adaptation. It is concluded that much progression has been made in magnetic resonance techniques so that the clinico-radiological dissociation has indeed proved to be a paradox. Thus, the relevance of normal appearing brain tissue damage, residual brain volume, spinal cord damage and cerebral plasticity had to be reiterated. The increased awareness of the subtle interplay between these dimensions should be kept in mind when magnetic resonance is used as a surrogate outcome measure. This corroborates with conventional wisdom that one should not rely on a single magnetic resonance measure, but take full advantage of the fact that magnetic resonance is able to provide multidimensional information.