Pre- and Postcontrast 3D Double Inversion Recovery Sequence in Multiple Sclerosis: A Simple and Effective MR Imaging Protocol

BACKGROUND AND PURPOSE:The double inversion recovery sequence is known to be very sensitive and specific for MS-related lesions. Our aim was to compare the sensitivity of pre- and postcontrast images of 3D double inversion recovery and conventional 3D T1-weighted images for the detection of contrast-enhancing MS-related lesions in the brain to analyze whether double inversion recovery could be as effective as T1WI.MATERIALS AND METHODS:A postcontrast 3D double inversion recovery sequence was acquired in addition to the standard MR imaging protocol at 3T, including pre- and postcontrast 3D T1WI sequences as well as precontrast double inversion recovery of 45 consecutive patients with MS or clinically isolated syndrome between June and December 2013. Two neuroradiologists independently assessed precontrast, postcontrast, and subtraction images of double inversion recovery as well as T1WI to count the number of contrast-enhancing lesions. Afterward, a consensus reading was performed. Lin concordance was calculated between both radiologists, and differences in lesion detectability were assessed with the Student t test. Additionally, the contrast-to-noise ratio was calculated.RESULTS:Significantly more contrast-enhancing lesions could be detected with double inversion recovery compared with T1WI (16%, 214 versus 185, P = .007). The concordance between both radiologists was almost perfect (ρ_c = 0.94 for T1WI and ρ_c = 0.98 for double inversion recovery, respectively). The contrast-to-noise ratio was significantly higher in double inversion recovery subtraction images compared with T1-weighted subtraction images (double inversion recovery, 14.3 ± 5.5; T1WI, 6.3 ± 7.1; P < .001).CONCLUSIONS:Pre- and postcontrast double inversion recovery enables better detection of contrast-enhancing lesions in MS in the brain compared with T1WI and may be considered an alternative to the standard MR imaging protocol.

Since the introduction of the double inversion recovery (DIR) sequence in 1994 by Redpath and Smith,^1,2 many studies have investigated the usefulness of DIR for the detection of inflammatory lesions in the brain in multiple sclerosis. In this sequence, the signals from both the CSF and normal white matter are suppressed simultaneously; thus, differentiation between gray matter and white matter is facilitated. Additionally, inflammatory lesions remain unsuppressed and appear hyperintense. The studies concluded that DIR is very sensitive and specific for MS lesions in the brain,^3–5 especially for intracortical lesions.^6–8 One group could also show that DIR provides the highest sensitivity in the detection of MS lesions in the infratentorial region compared with FLAIR and T2WI.⁴ A similar benefit was found for an adapted DIR sequence in the spinal cord.⁹ Due to the high sensitivity and specificity as well as the increasing availability of the DIR sequence, it is more often included in routine MR imaging protocols.The standard MR imaging protocol for the examination of patients with MS commonly includes the intravenous administration of gadolinium-based contrast agents (GBCAs). The presence of contrast-enhancing lesions is important for the diagnosis and therapeutic strategies of MS and is listed in the revised McDonald criteria from 2010¹⁰ and the magnetic resonance imaging in multiple sclerosis consensus guidelines¹¹ for the criteria of dissemination in time. Because the best sensitivity for enhancing lesions is achieved about 5–10 minutes after injection of a GBCA,¹² further sequences, usually T2WI, are performed for bridging the waiting time. However, these sequences should be carefully selected because the signal of contrast-enhancing lesions might be changed in modified T2WI sequences such as FLAIR^13,14 or DIR.^15,16One group found that contrast-enhancing parts of tumors appear hypointense in postcontrast DIR.¹⁵ Furthermore, it has been shown recently that there is an altered signal intensity of active enhancing inflammatory MS lesions in postcontrast DIR of the brain.¹⁶ This observation led to the recommendation to acquire DIR sequences before GBCA administration.Here, we test the hypothesis that the signal loss on DIR images after GBCA administration can be used to detect active enhancing lesions. In particular, the aim was to compare the sensitivity of pre- and postcontrast images of 3D double inversion recovery and conventional 3D T1WI for the detection of contrast-enhancing MS-related lesions in the brain to analyze whether DIR could be as effective as T1WI.     

A Spiral Spin-Echo MR Imaging Technique for Improved Flow Artifact Suppression in T1-Weighted Postcontrast Brain Imaging: A Comparison with Cartesian Turbo Spin-Echo

BACKGROUND AND PURPOSE:A challenge with the T1-weighted postcontrast Cartesian spin-echo and turbo spin-echo brain MR imaging is the presence of flow artifacts. Our aim was to develop a rapid 2D spiral spin-echo sequence for T1-weighted MR imaging with minimal flow artifacts and to compare it with a conventional Cartesian 2D turbo spin-echo sequence.MATERIALS AND METHODS:T1-weighted brain imaging was performed in 24 pediatric patients. After the administration of intravenous gadolinium contrast agent, a reference Cartesian TSE sequence with a scanning time of 2 minutes 30 seconds was performed, followed by the proposed spiral spin-echo sequence with a scanning time of 1 minutes 18 seconds, with similar spatial resolution and volumetric coverage. The results were reviewed independently and blindly by 3 neuroradiologists. Scores from a 3-point scale were assigned in 3 categories: flow artifact reduction, subjective preference, and lesion conspicuity, if any. The Wilcoxon signed rank test was performed to evaluate the reviewer scores. The t test was used to evaluate the SNR. The Fleiss κ coefficient was calculated to examine interreader agreement.RESULTS:In 23 cases, spiral spin-echo was scored over Cartesian TSE in flow artifact reduction (P < .001). In 21 cases, spiral spin-echo was rated superior in subjective preference (P < .001). Ten patients were identified with lesions, and no statistically significant difference in lesion conspicuity was observed between the 2 sequences. There was no statistically significant difference in SNR between the 2 techniques. The Fleiss κ coefficient was 0.79 (95% confidence interval, 0.65–0.93).CONCLUSIONS:The proposed spiral spin-echo pulse sequence provides postcontrast images with minimal flow artifacts at a faster scanning time than its Cartesian TSE counterpart.

T1-weighted MR imaging after the injection of gadolinium-based contrast agent is widely used in the diagnosis of many neurologic diseases, such as tumors, infections, and inflammatory conditions. 2D multisection Cartesian spin-echo (SE) and turbo spin-echo–based pulse sequences are the clinically preferred methods for postcontrast T1WI. A challenge with these Cartesian images is the presence of ghosting artifacts due to flowing blood from the venous sinuses. These artifacts can obscure the visualization of lesions and reduce image quality. With contrast-agent enhancement, these flow artifacts are further exacerbated by bright-blood signals. Gradient flow compensation and spatial saturation bands are helpful in alleviating, but not eliminating, these flow-induced artifacts in Cartesian acquisitions.Spiral MR imaging, a non-Cartesian acquisition technique, has several advantages over its Cartesian counterpart.^1,2 A primary benefit is the ability of the spiral to traverse k-space more efficiently per unit of time than Cartesian trajectories, thus providing a higher scan speed. With spiral acquisitions, motion- and flow-induced errors are manifest as incoherent artifacts in the image domain. As a result, spiral acquisition reduces the sensitivity of the pulse sequence to structured artifacts.³ The spiral trajectory also inherently provides zero gradient moments at the origin of k-space, which substantially decreases the sensitivity of the sequence to in-plane flow-related artifacts.⁴ Spiral SE MR imaging has been reported in pelvic imaging,⁵ black-blood imaging of peripheral vasculature,⁶ and functional MR imaging.⁷The purpose of this work was to develop a 2D spiral SE technique for T1-weighted brain imaging with minimal flow artifacts and faster scanning speed and compare it with a conventional 2D Cartesian TSE pulse sequence, with comparable spatial resolution and volumetric coverage. We prospectively evaluated the performance of the 2D spiral SE technique and its subsequent image quality in a cohort of pediatric patients.     

3D Quantitative Synthetic MRI in the Evaluation of Multiple Sclerosis Lesions

BACKGROUND AND PURPOSE:Synthetic MR imaging creates multiple contrast-weighted images based on a single time-efficient quantitative scan, which has been mostly performed for 2D acquisition. We assessed the utility of 3D synthetic MR imaging in patients with MS by comparing its diagnostic image quality and lesion volumetry with conventional MR imaging.MATERIALS AND METHODS:Twenty-four patients with MS prospectively underwent 3D quantitative synthetic MR imaging and conventional T1-weighted, T2-weighted, FLAIR, and double inversion recovery imaging, with acquisition times of 9 minutes 3 seconds and 18 minutes 27 seconds for the synthetic MR imaging and conventional MR imaging sequences, respectively. Synthetic phase-sensitive inversion recovery images and those corresponding to conventional MR imaging contrasts were created for synthetic MR imaging. Two neuroradiologists independently assessed the image quality on a 5-point Likert scale. The numbers of cortical lesions and lesion volumes were quantified using both synthetic and conventional image sets.RESULTS:The overall diagnostic image quality of synthetic T1WI and double inversion recovery images was noninferior to that of conventional images (P = .23 and .20, respectively), whereas that of synthetic T2WI and FLAIR was inferior to that of conventional images (both Ps < .001). There were no significant differences in the number of cortical lesions (P = .17 and .53 for each rater) or segmented lesion volumes (P = .61) between the synthetic and conventional image sets.CONCLUSIONS:Three-dimensional synthetic MR imaging could serve as an alternative to conventional MR imaging in evaluating MS with a reduced scan time.

MS is a chronic, immune-mediated, demyelinating disorder of the CNS that usually affects young adults and leads to chronic disability.^1,2 The diagnostic criteria for MS are based on the lesion number, size, and location.³ Although diffuse periventricular lesions are most commonly observed, previous studies have shown that the cortical and juxtacortical lesion load is associated with cognitive impairment.^4,5 Additionally, the detection of cortical and juxtacortical lesions may contribute to early diagnosis because these lesions are characteristic of MS. MR imaging plays an integral role in the diagnosis and management of patients with MS through the in vivo detection and characterization of lesions. Although MR imaging is highly sensitive in detecting periventricular lesions and is considered as a standard biomarker in the monitoring of treatment response,⁶ conventional MR imaging techniques have a relatively low sensitivity for detecting (juxta)cortical lesions. Phase-sensitive inversion recovery (PSIR) and double inversion recovery (DIR) are recently developed imaging techniques useful for detecting MS lesions, especially (juxta)cortical ones.^7,8 The PSIR preserves the positive and negative polarities of tissues as they recover from the inversion pulse, thus providing a T1-weighted contrast with higher SNR and GM-WM contrast. DIR is an imaging technique that suppresses both WM and CSF signals, thus significantly increasing lesion conspicuity in both GM and WM compared with FLAIR or T2-weighted images. PSIR and DIR have been shown to improve sensitivity compared with FLAIR or T2-weighted images in the detection of cortical lesions. However, the additional scanning time associated with PSIR and DIR has hindered the use of these techniques in clinical practice. Thus, a rapid imaging technique that can acquire these contrast-weighted images with high spatial resolution is desired.Quantitative synthetic MR imaging is a time-efficient MR imaging technique that enables simultaneous quantification of T1 and T2 relaxation times and proton attenuation and allows the creation of any contrast-weighted image, including DIR and PSIR, without additional scanning time.^9–13 Previous studies have shown that synthetic MR imaging is useful for detecting and characterizing MS lesions.^10,11,14 However, these studies were based on a multisection 2D acquisition, providing a relatively low resolution in the section direction. 3D quantitative synthetic MR imaging, enabling the simultaneous quantification of T1, T2, and proton attenuation of the whole brain in 3D,^15–17 with smaller section thickness, should allow for more detailed delineation of MS lesions. With the combination of high spatial resolution 3D acquisition and DIR as well as PSIR contrasts, 3D quantitative synthetic MR imaging could serve as a clinically useful technique for monitoring MS lesions.Here, we assessed the utility of the recently developed 3D quantitative synthetic MR imaging for evaluating MS lesions by comparing the synthetic and conventional MR image sets. We hypothesized that 3D synthetic MR imaging would have a comparable diagnostic quality with that of a conventional image set (including 3D FLAIR and DIR) while shortening the total acquisition time.     

水激发三维VIBE肩关节MR造影对Bankart病变的评价

目的评价肩关节MR造影水激发三维容积内插梯度回波(volumetric interpolated breath-hold examination,VIBE)序列对Bankart病变的诊断价值。资料与方法由2名影像诊断医师独立回顾99例肩关节MR造影常规序列和三维VIBE重建图像,判定有无Bankart病变以及骨性Bankart病变,计算其敏感性和特异性。采用McNemar检验评价常规序列与三维VIBE的诊断价值差异是否存在统计学意义。结果 99例患者中,关节镜证实前下方盂唇完整41例,Bankart病变58例,其中26例为骨性Bankart病变。三维VIBE对Bankart病变的敏感性、特异性分别为91.38%～93.10%和95.12%～97.56%;对骨性Bankart病变分别为96.15%和95.89%～97.26%。常规序列对Bankart病变的敏感性、特异性分别为91.38%～96.55%和97.56%;对骨性Bankart病变分别为42.31%～50%和97.26%～100%。三维VIBE和常规序列对于Bankart病变的诊断性能差异无统计学意义,但前者判断骨性Ban-kart病变的敏感性显著优于后者。结论在肩关节MR造影中,水激发三维VIBE序列可全面评价Bankart病变。     

MR Arthrographic 3D VIBE Sequence for Bankart Lesions at 3.0-T

目的 评价肩关节MR造影水激发三维容积内插梯度回波(volumetric interpolated breath-hold examination,VIBE)序列对Bankart病变的诊断价值.资料与方法 由2名影像诊断医师独立回顾99例肩关节MR造影常规序列和三维VIBE重建图像,判定有无Bankart病变以及骨性Bankart病变,计算其敏感性和特异性.采用McNemar 检验评价常规序列与三维VIBE的诊断价值差异是否存在统计学意义.结果 99例患者中,关节镜证实前下方盂唇完整41例,Bankart病变58例,其中26例为骨性Bankart病变.三维VIBE对Bankart病变的敏感性、特异性分别为91.38％ ～93.10％和95.12％～ 97.56％;对骨性Bankart病变分别为96.15％和95.89％ ～ 97.26％.常规序列对Bankart病变的敏感性、特异性分别为91.38％ ～96.55％和97.56％;对骨性Bankart病变分别为42.31％ ～50％和97.26％ ～ 100％.三维VIBE和常规序列对于Bankart病变的诊断性能差异无统计学意义,但前者判断骨性Bankart病变的敏感性显著优于后者.结论 在肩关节MR造影中,水激发三维VIBE序列可全面评价Bankart病变.     

Cumulative Dose of Macrocyclic Gadolinium-Based Contrast Agent Improves Detection of Enhancing Lesions in Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE:Gadolinium-enhanced MR imaging is currently the reference standard for detecting active inflammatory lesions in patients with multiple sclerosis. The sensitivity of MR imaging for this purpose may vary according to the physicochemical characteristics of the contrast agent used and the acquisition strategy. The purpose of this study was to compare detection of gadolinium-enhancing lesions or active disease following a single or cumulative dose of a macrocyclic gadolinium-based contrast agent with different image acquisition delays in patients with clinically isolated syndrome or relapsing multiple sclerosis.MATERIALS AND METHODS:All patients received a first dose (0.1 mmol/kg) of gadobutrol and, 20 minutes later, a second dose (0.1 mmol/kg), with a cumulative dose of 0.2 mmol/kg. Two contrast-enhanced T1-weighted sequences were performed at 5 and 15 minutes after the first contrast administration, and 2 additional T1-weighted sequences at 5 and 15 minutes after the second contrast administration with a 3T magnet.RESULTS:One hundred fifteen patients were considered evaluable. A significantly larger number of lesions were detected in scans obtained at 5 and 15 minutes after the second contrast injection compared with scans obtained at 5 and 15 minutes after the first injection (P < .001). The number of patients with active lesions on MR imaging was significantly higher after the second dose administration (52.0%, first dose versus 59.2%, second dose; P < .001).CONCLUSIONS:Cumulative dosing of a macrocyclic gadolinium-based contrast agent increases detection of enhancing lesions and patients with active lesions. These data could be considered in the design of MR imaging protocols aimed at detecting active multiple sclerosis lesions.

Gadolinium-enhanced MR imaging is currently the reference standard for detecting inflammatory demyelinating lesions associated with increased permeability of the blood-brain barrier in patients with multiple sclerosis, and is commonly used as a marker of acute focal inflammatory activity.^1,2 The sensitivity of the technique for this purpose may vary according to the physicochemical characteristics of the contrast agent used and the acquisition strategy (eg, delay between injection and image acquisition, contrast dose, field strength, and parameters of the postinjection T1-weighted sequence).^3–12 A large body of evidence has indicated that various approaches can increase the visibility of contrast-enhancing lesions and lead to a notable improvement in sensitivity.^{3,4,8,9,12–15} One potential strategy that has not yet been explored is the combination of an increased contrast dose and a longer delay time at 3T MR imaging with a 2D gradient recalled-echo (GRE) T1-weighted sequence. To examine this option, we designed the present open-label, prospective study to assess the advantages of combining a high-field-strength MR imaging magnet (3T) and a cumulative gadolinium dose (0.1 mmol/kg + 0.1 mmol/kg) at different delay times compared with a single dose (0.1 mmol/kg) to detect active lesions in patients with clinically isolated syndrome (CIS) or relapsing MS. The hypothesis was that the combined advantages of a cumulative gadolinium dose and a longer delay time would significantly increase the detection rate of active lesions and the percentage of patients showing disease activity, measures that have a strong impact for the diagnosis of the disease, therapy optimization, and predicting disease course and treatment response.^1,2,16     

Evaluation of Focal Cervical Spinal Cord Lesions in Multiple Sclerosis: Comparison of White Matter–Suppressed T1 Inversion Recovery Sequence versus Conventional STIR and Proton Density–Weighted Turbo Spin-Echo Sequences

BACKGROUND AND PURPOSE:Conventional MR imaging of the cervical spinal cord in MS is challenged by numerous artifacts and interreader variability in lesion counts. This study compares the relatively novel WM-suppressed T1 inversion recovery sequence with STIR and proton density–weighted TSE sequences in the evaluation of cervical cord lesions in patients with MS.MATERIALS AND METHODS:Retrospective blinded analysis of cervical cord MR imaging examinations of 50 patients with MS was performed by 2 neuroradiologists. In each patient, the number of focal lesions and overall lesion conspicuity were measured in the STIR/proton density–weighted TSE and WM-suppressed T1 inversion recovery sequence groups. Independent side-by-side comparison was performed to categorize the discrepant lesions as either “definite” or “spurious.” Lesion contrast ratio and edge sharpness were independently calculated in each sequence.RESULTS:Substantial interreader agreement was noted on the WM-suppressed T1 inversion recovery sequence (κ = 0.82) compared with STIR/proton density–weighted TSE (κ = 0.52). Average lesion conspicuity was better on the WM-suppressed T1 inversion recovery sequence (conspicuity of 3.1/5.0 versus 3.7/5.0, P < .01, in the WM-suppressed T1 inversion recovery sequence versus STIR/proton density–weighted TSE, respectively). Spurious lesions were more common on STIR/proton density–weighted TSE than on the WM-suppressed T1 inversion recovery sequence (23 and 30 versus 3 and 4 by readers 1 and 2, respectively; P < .01). More “definite” lesions were missed on STIR/proton density–weighted TSE compared with the WM-suppressed T1 inversion recovery sequence (37 and 38 versus 3 and 6 by readers 1 and 2, respectively). Lesion contrast ratio and edge sharpness were highest on the WM-suppressed T1 inversion recovery sequence.CONCLUSIONS:There is better interreader consistency in the lesion count on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density–weighted TSE sequences. The focal cord lesions are visualized with better conspicuity due to better contrast ratio and edge sharpness. There are fewer spurious lesions on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density–weighted TSE. The WM-suppressed T1 inversion recovery sequence could potentially be substituted for either STIR or proton density–weighted TSE sequences in routine clinical protocols.

The cervical spinal cord is commonly affected in multiple sclerosis, which is often associated with an increase in clinical disability.^1–3 A focal form of involvement is more common in the relapsing-remitting variant of MS compared with the other less common MS subtypes.⁴ MS lesions undergo complex cycles of inflammation, followed by variable extent of repair and, therefore, have heterogeneity in the prolongation of T1 and T2 relaxation times, which influence their conspicuity on the standard MR imaging sequences such as STIR and proton density–weighted TSE (PDWTSE).The PDWTSE sequence with a lower TE is better than the longer TE T2-weighted sequences in the detection of focal MS lesions in the spinal cord.^5,6 STIR has intrinsic sensitivity to T1 shortening effects in addition to T2 prolongation effects and improves the lesion contrast compared with T2-weighted sequences, translating to a better interreader agreement in the assessment of the extent of disease.⁷ Nevertheless, artifacts and lower lesion conspicuity prevalent on these sequences may cause variability in the clinical evaluation of lesion burden, which is difficult to resolve in the absence of a true reference standard.⁸ Reliable characterization of the lesion burden on follow-up examinations is therefore important for assessing treatment efficacy and optimizing treatment strategies.Many novel sequences have been devised attempting to improve imaging quality and lesion conspicuity with fewer artifacts and with a reasonable acquisition time. In a smaller study population, the WM-suppressed T1 inversion recovery (WMS) sequence has shown improvement in lesion conspicuity over STIR and dual-echo fast spin-echo.⁹ While the principles of the contrast mechanism on WMS are similar to those on STIR, the sequence parameters of WMS are optimized for better intramedullary imaging. In WMS, the section-selective inversion pulse is applied at 385 ms to suppress the background signal from white matter, whereas in STIR, it is applied at 160 ms to optimize fat suppression.¹⁰ A shorter TE is used in WMS compared with STIR or PDWTSE, which further increases the T1-weighting of the sequence, which acts as the main contrast mechanism in this long TR/short TE sequence.^11,12 MS lesions have increased T1 relaxation times and thus are not suppressed with a white matter selective inversion recovery suppression pulse. There is a need for larger scale evaluation of WMS for clinical utility in routine practice against the standard sequences (STIR and PDWTSE) in the detection of MS cord lesions. The purpose of this retrospective study was to compare the utility of WMS compared with routinely used STIR and PDWTSE sequences in the evaluation of focal cervical cord lesions is MS.     

3D-STIR序列增强扫描在腰骶丛神经成像中的应用研究

目的探讨3.0T磁共振三维短恢复时间反转恢复(3D-STIR)序列增强扫描在腰骶丛神经成像中的可行性及其实际应用的效果和价值。资料与方法对20名健康自愿者及21例腰骶丛神经病变患者行常规扫描序列、3D-STIR序列平扫及3D-STIR序列增强扫描,观察所得图像,评价显示情况和对比噪声比。结果 3D-STIR序列及其增强扫描可清楚、明确地显示所有自愿者腰骶丛神经的构成、走行、连续性、形态、信号;3D-STIR序列增强扫描能明显改善背景抑制效果,可清楚显示肿瘤、外伤及椎间盘突出累及腰骶丛神经所致各种征象。结论 3D-STIR序列增强扫描可以更清楚地显示腰骶丛神经解剖结构,并且能获得更好的背景抑制效果,在腰骶丛神经损伤的定位定性诊断和损伤程度判定方面有广阔的应用前景。     

Multicenter Validation of Mean Upper Cervical Cord Area Measurements from Head 3D T1-Weighted MR Imaging in Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE:Spinal cord atrophy is a common and clinically relevant characteristic in multiple sclerosis. We aimed to perform a multicenter validation study of mean upper cervical cord area measurements in patients with multiple sclerosis and healthy controls from head MR images and to explore the effect of gadolinium administration on mean upper cervical cord area measurements.MATERIALS AND METHODS:We recruited 97 subjects from 3 centers, including 60 patients with multiple sclerosis of different disease types and 37 healthy controls. Both cervical cord and head 3D T1-weighted images were acquired. In 11 additional patients from 1 center, head images before and after gadolinium administration and cervical cord images after gadolinium administration were acquired. The mean upper cervical cord area was compared between cervical cord and head images by using intraclass correlation coefficients (ICC) for both consistency (ICC_consist) and absolute (ICC_abs) agreement.RESULTS:There was excellent agreement of mean upper cervical cord area measurements from head and cervical cord images in the entire group (ICC_abs = 0.987) and across centers and disease subtypes. The mean absolute difference between the mean upper cervical cord area measured from head and cervical cord images was 2 mm² (2.3%). Additionally, excellent agreement was found between the mean upper cervical cord area measured from head images with and without gadolinium administration (ICC_abs = 0.991) and between the cervical cord and head images with gadolinium administration (ICC_abs = 0.992).CONCLUSIONS:Excellent agreement between mean upper cervical cord area measurements on head and cervical cord images was observed in this multicenter study, implying that upper cervical cord atrophy can be reliably measured from head images. Postgadolinium head or cervical cord images may also be suitable for measuring mean upper cervical cord area.

Spinal cord atrophy is recognized as a common and clinically relevant characteristic in patients with multiple sclerosis.¹ Differences in cervical cord volume and area among patients with different phenotypes of MS and healthy controls (HCs) measured by MR imaging have been identified in many studies.^2–4 Furthermore, a modest or strong correlation between spinal cord atrophy and disability has been demonstrated in numerous studies, suggesting that spinal cord atrophy is an essential determinant of clinical disability and a potential outcome measure to monitor MS disease progression.^5–7 The measurement of the upper cervical cord area is a well-established method for the assessment of spinal cord atrophy and has been applied in most studies so far.^2,3,5,8,9 Both image acquisition and spinal cord segmentation are technically feasible and more accurate in the upper cervical region compared with other parts of the cord or the entire cord.¹⁰ In addition, the upper cervical cord is more frequently affected by MS pathology than lower parts of the spinal cord.¹¹Mean upper cervical cord area (MUCCA) can be measured by using 3D T1-weighted MR images of the cervical cord.^3,4 The MUCCA also has been measured recently on 3D T1-weighted MR images of the head covering the upper cervical cord, which has yielded promising results showing associations between MUCCA and clinical disability and disease progression.^2,5 Measuring the MUCCA from head MR images offers the opportunity to analyze MUCCA retrospectively in datasets without dedicated cervical 3D T1-weighted images, and it can reduce costs and patient burden in prospective studies by eliminating the need for separate cervical cord image acquisitions if these are only acquired to measure the MUCCA. An MR imaging contrast agent is commonly used to detect the blood-brain barrier breakdown and inflammation in new lesions^12,13 in patients with MS, which might influence the MUCCA measurements by tissue-contrast changes. The effect of the MR imaging contrast agent on MUCCA measurement also has to be investigated to ease the implementation of MUCCA as an auxiliary measurement in clinical practice. Although MUCCA measurements based on head 3D T1-weighted images have been successfully used in a monocenter study,¹⁴ multicenter validation is lacking. In addition, the possible effect of intravenous contrast administration on MUCCA measurements has not been investigated.Therefore, the aim of the current study was to validate the measurement of the MUCCA on the basis of head compared with cervical cord 3D T1-weighted images in patients with MS and healthy controls on different MR imaging systems by using different acquisition parameters from multiple centers and to explore the effect of gadolinium (Gd) administration on MUCCA measurements.     

PD/T2 WI和FLAIR序列对多发性硬化患者病灶的对比研究

目的 研究不同MR扫描序列对多发性硬化(MS)患者病灶检出率的差异.资料与方法将符合2001年McDonald MS诊断标准且资料完整的74例有脑部病灶的MS患者纳入研究对象,采用国际MS中心推荐的MR扫描序列,比较液体衰减反转恢复(FLAIR)和质子密度双回波(PD/T2WI)序列对MS病灶的显示差别.结果 (1)皮质及皮质下病灶,FLAIR较T2WI的检出率差异有统计学意义(P＜0.05);幕下病灶,PD/T2WI较FLAIR的检出率稍高,但差异无统计学意义(P＞0.05);侧脑室周围以及深部白质区病灶的检出率比较,FLAIR、T2WI和PD之间差异无统计学意义(P＞0.05).(2)进展型MS较复发-缓解型MS幕上皮质的病灶数差异有统计学意义(P＜0.05).结论不同的扫描序列对MS患者不同部位的病灶检出率各有差异,针对受检部位选择合适的序列,可提高对病灶的检出率.     

Cervical Spinal Cord Lesions in Multiple Sclerosis: T1-weighted Inversion-Recovery MR Imaging with Phase-Sensitive Reconstruction

This magnetic resonance (MR) imaging study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained from all participants. The purpose of the study was to prospectively compare T1-weighted inversion recovery with short inversion time inversion recovery (STIR) and dual fast spin echo (FSE) for imaging cervical spinal cord lesions in patients with multiple sclerosis (MS). Twelve patients (eight men, four women; median age, 44 years) were imaged by using T1-weighted inversion recovery, STIR, and FSE. Contrast between lesions and normal cervical cord was measured for each sequence, and generalized estimating equation analysis was used to test statistical significance of the results. Normalized contrast between lesion and normal-appearing spinal cord was significantly higher for T1-weighted inversion recovery than for the other sequences (P < .0001). Use of phase-sensitive reconstruction improved lesion localization and boundary definition. These advantages of T1-weighted inversion recovery over STIR and dual-echo FSE suggest that it has potential in cervical spinal cord imaging of MS. (c) RSNA, 2007.     

Measurement of Cortical Thickness and Volume of Subcortical Structures in Multiple Sclerosis: Agreement between 2D Spin-Echo and 3D MPRAGE T1-Weighted Images

BACKGROUND AND PURPOSE:Gray matter pathology is known to occur in multiple sclerosis and is related to disease outcomes. FreeSurfer and the FMRIB Integrated Registration and Segmentation Tool (FIRST) have been developed for measuring cortical and subcortical gray matter in 3D-gradient-echo T1-weighted images. Unfortunately, most historical MS cohorts do not have 3D-gradient-echo, but 2D-spin-echo images instead. We aimed to evaluate whether cortical thickness and the volume of subcortical structures measured with FreeSurfer and FIRST could be reliably measured in 2D-spin-echo images and to investigate the strength and direction of clinicoradiologic correlations.MATERIALS AND METHODS:Thirty-eight patients with MS and 2D-spin-echo and 3D-gradient-echo T1-weighted images obtained at the same time were analyzed by using FreeSurfer and FIRST. The intraclass correlation coefficient between the estimates was obtained. Correlation coefficients were used to investigate clinicoradiologic associations.RESULTS:Subcortical volumes obtained with both FreeSurfer and FIRST showed good agreement between 2D-spin-echo and 3D-gradient-echo images, with 68.8%–76.2% of the structures having either a substantial or almost perfect agreement. Nevertheless, with FIRST with 2D-spin-echo, 18% of patients had mis-segmentation. Cortical thickness had the lowest intraclass correlation coefficient values, with only 1 structure (1.4%) having substantial agreement. Disease duration and the Expanded Disability Status Scale showed a moderate correlation with most of the subcortical structures measured with 3D-gradient-echo images, but some correlations lost significance with 2D-spin-echo images, especially with FIRST.CONCLUSIONS:Cortical thickness estimates with FreeSurfer on 2D-spin-echo images are inaccurate. Subcortical volume estimates obtained with FreeSurfer and FIRST on 2D-spin-echo images seem to be reliable, with acceptable clinicoradiologic correlations for FreeSurfer.

Gray matter pathology in patients with multiple sclerosis is present from the very early stages of the disease and has been related to long-term disability.^1,2 Therefore, in recent years, research has focused on obtaining accurate markers of GM damage, and different software packages have been developed or optimized for measuring it in MS. FreeSurfer software (http://surfer.nmr.mgh.harvard.edu)^3,4 allows automatic calculation of cortical thickness and the volume of subcortical GM structures by using 3D T1-weighted images. Briefly, the image-processing pipeline includes Talairach transformation of the 3D T1-weighted images and segmentation of the subcortical white matter and deep GM structures, relying on the gray and white matter boundaries and pial surfaces. The FMRIB Integrated Registration and Segmentation Tool (FIRST; http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FIRST) software package⁵ automatically segments subcortical GM structures also on the basis of 3D T1-weighted images. Briefly, FIRST is a model-based segmentation and registration program that uses shape and appearance models constructed from manually segmented images. On the basis of the learned models, FIRST searches through linear combinations of shape modes of variation for the most probable shape instance, given the observed intensities in the 3D T1-weighted input images. Both software packages have been shown to be accurate and reproducible.^6–11The study of cortical pathology in patients with MS by using FreeSurfer has shown cortical thinning in patients with MS compared with healthy controls,^12,13 which has been related to lesion volume, disease duration, disability,¹² and cognitive impairment.¹⁴ Also, cortical thinning of the superior frontal gyrus, thalamus, and cerebellum significantly predicted conversion to MS in patients presenting with clinically isolated syndromes,¹⁵ and global cortical thinning for 6 years was significantly associated with a more aggressive disease evolution.¹⁶ The volume of deep GM structures (measured with both FreeSurfer and FIRST) has also been shown to be lower in patients with MS compared with healthy controls,^17–19 and it has been related to different clinical disease outcomes such as fatigue,²⁰ cognitive impairment,^17–19,21 disability,¹⁹ and walking function.²²Both FreeSurfer and FIRST have been optimized for 3D T1-weighted gradient-echo images that incorporate a magnetization-prepared inversion pulse that increases the T1-weighting.²³ Unfortunately, for most of the historical MS cohorts with long-term clinical and radiologic follow-up, only 2D spin-echo (2D-SE) T1-weighted images were acquired, a sequence that does not provide an optimal contrast between gray and white matter, particularly when acquired with high-field magnets.²⁴ The objectives of this work were the following: 1) to evaluate whether cortical thickness and subcortical volumes obtained with FreeSurfer could be reliably measured with 2D-SE T1-weighted images by using as the criterion standard the same measures obtained with 3D gradient-echo (3D-GE) T1-weighted sequences, 2) to investigate whether subcortical volumes obtained with FIRST could be reliably measured in 2D-SE T1-weighted images by using as the criterion standard the same measures obtained with 3D-GE T1-weighted images, and 3) to assess whether the correlations between clinical outcomes and subcortical normalized volumes obtained with 3D-GE and 2D-SE T1-weighted images had a similar strength and direction.     

Improved Automatic Detection of New T2 Lesions in Multiple Sclerosis Using Deformation Fields

BACKGROUND AND PURPOSE:Detection of disease activity, defined as new/enlarging T2 lesions on brain MR imaging, has been proposed as a biomarker in MS. However, detection of new/enlarging T2 lesions can be hindered by several factors that can be overcome with image subtraction. The purpose of this study was to improve automated detection of new T2 lesions and reduce user interaction to eliminate inter- and intraobserver variability.MATERIALS AND METHODS:Multiparametric brain MR imaging was performed at 2 time points in 36 patients with new T2 lesions. Images were registered by using an affine transformation and the Demons algorithm to obtain a deformation field. After affine registration, images were subtracted and a threshold was applied to obtain a lesion mask, which was then refined by using the deformation field, intensity, and local information. This pipeline was compared with only applying a threshold, and with a state-of-the-art approach relying only on image intensities. To assess improvements, we compared the results of the different pipelines with the expert visual detection.RESULTS:The multichannel pipeline based on the deformation field obtained a detection Dice similarity coefficient close to 0.70, with a false-positive detection of 17.8% and a true-positive detection of 70.9%. A statistically significant correlation (r = 0.81, P value = 2.2688e-09) was found between visual detection and automated detection by using our approach.CONCLUSIONS:The deformation field–based approach proposed in this study for detecting new/enlarging T2 lesions resulted in significantly fewer false-positives while maintaining most true-positives and showed a good correlation with visual detection annotations. This approach could reduce user interaction and inter- and intraobserver variability.

MR imaging has become a core paraclinical tool for diagnosing and predicting long-term disability and treatment response in patients with multiple sclerosis. Of particular note, several criteria and strategies have been proposed for prompt identification of suboptimal response in individual patients based on a combination of clinical and MR imaging measures assessed during the first 6–12 months after treatment initiation.^1–6 These criteria are related to detection of disease activity on follow-up brain MR imaging studies compared with baseline scans, defined as either gadolinium-enhancing lesions or new/enlarging T2 lesions. However, detection of active T2 lesions in patients with MS can be hindered by several factors, such as a high burden of inactive T2 lesions, the presence of small and confluent lesions, inadequate repositioning, and high interobserver variability.⁷ Image subtraction after image registration can overcome these issues by visually cancelling stable disease (lesions that stay the same over time) and providing good visualization and quantification of active T2 lesions (either positively or negatively).^8,9Techniques for automatic detection of active T2 lesions can be classified into 2 categories: intensity-based and deformation-based approaches.¹⁰ In the former, successive scans are analyzed by point-to-point (voxel-to-voxel) comparison, whereas in the latter, deformation fields obtained by nonrigid registration of the 2 scans are analyzed.Most of the proposed techniques to detect changes on follow-up images use an image-subtraction process that identifies new T2 lesions^11–13 and include statistical models of intensity changes between scans or other, more complex, supervised strategies. Although segmentation of subtraction images enables quantification of new, enlarging, and resolving MS lesions, automated image analysis that differentiates a true lesion change and noise or artifacts would save considerable time and effort.Nonrigid registration techniques usually provide a discrete vector field that defines deformations occurring between 2 different images. This vector field can be used to detect evolving processes, including new T2 lesions. Several approaches that use deformation fields (DF) to detect positive changes occurring in longitudinal MR studies have been reported.^14,15 These approaches focus on detecting and explaining processes undergoing change (ie, lesions shrinking or growing), but not on detecting new lesions, a measure that is now under consideration as a biomarker for monitoring and predicting treatment response.¹⁶The purpose of this study was to improve automated detection of new T2 lesions on successive brain MR images, by using a novel approach that combines subtraction and DF analysis. This new pipeline will be compared with other approaches, in which a threshold is applied or a postprocessing step is incorporated on the basis of intensity rules.     

Dedicated 3D-T2-STIR-ZOOMit Imaging Improves Demyelinating Lesion Detection in the Anterior Visual Pathways of Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE:Demyelinating lesions in the anterior visual pathways represent an underestimated marker of disease dissemination in patients with MS. We prospectively investigated whether a dedicated high-resolution MR imaging technique, the 3D-T2-STIR-ZOOMit, improves demyelinating lesion detection compared with the current clinical standard sequence, the 2D-T2-STIR.MATERIALS AND METHODS:3T MR imaging of the anterior visual pathways (optic nerves, chiasm, and tracts) was performed using 3D-T2-STIR-ZOOMit and 2D-T2-STIR, in patients with MS and healthy controls. Two experienced neuroradiologists assessed, independently, demyelinating lesions using both sequences separately. 3D-T2-STIR-ZOOMit scan-rescan reproducibility was tested in 12 patients. The Cohen κ was used for interrater agreement, and the intraclass correlation coefficient for reproducibility. Between-sequence detection differences and the effects of location and previous acute optic neuritis were assessed using a binomial mixed-effects model.RESULTS:Forty-eight patients with MS with (n = 19) or without (n = 29) past optic neuritis and 19 healthy controls were evaluated. Readers'' agreement was strong (3D-T2-STIR-ZOOMit: 0.85; 2D-T2-STIR: 0.90). The 3D-T2-STIR-ZOOMit scan-rescan intraclass correlation coefficient was 0.97 (95% CI, 0.96–0.98; P < .001), indicating excellent reproducibility. Overall, 3D-T2-STIR-ZOOMit detected more than twice the demyelinating lesions (n = 89) than 2D-T2-STIR (n = 43) (OR = 2.7; 95% CI, 1.7–4.1; P < .001). In the intracranial anterior visual pathway segments, 33 of the 36 demyelinating lesions (91.7%) detected by 3D-T2-STIR-ZOOMit were not disclosed by 2D-T2-STIR. 3D-T2-STIR-ZOOMit increased detection of demyelinating lesion probability by 1.8-fold in patients with past optic neuritis (OR = 1.8; 95% CI, 1.2–3.1; P = .01) and 5.9-fold in patients without past optic neuritis (OR = 5.9; 95% CI, 2.5–13.8; P < .001). No false-positive demyelinating lesions were detected in healthy controls.CONCLUSIONS:Dedicated 3D-T2-STIR-ZOOMit images improved substantially the detection of MS disease dissemination in the anterior visual pathways, particularly in the intracranial segments and in patients without past optic neuritis.

MS is the most common immune-mediated demyelinating disease in young adults,¹ with frequent involvement of the visual pathways.² Pathologic investigations demonstrated a high prevalence of demyelinating lesions (DLs) in the anterior visual pathways (aVPs), including the optic nerve, chiasm (OC), and tract (OT), in patients either with or without previous episodes of acute optic neuritis (AON).³ Accordingly, ophthalmologic studies showed frequent occurrence of subclinical visual impairment in MS, even in patients without previous AON.⁴ Nevertheless and despite a previous proposal,⁵ the aVPs are currently not included among the sites investigated by MR imaging to demonstrate disease dissemination in space, due to the lack of supportive data about DL prevalence and MR imaging characteristics.⁶ Including highly sensitive examinations in the diagnostic workflow may potentially lead to earlier diagnosis and start of treatment⁵ and provide structural correlates for patients'' asymptomatic visual loss.⁴ Furthermore, in the monitoring phase, an improved detection of new-onset lesions may help tailor treatment in individual patients.⁷In a group of patients with MS with and without a history of AON and in a group of healthy controls (HC), we tested whether a dedicated inversion-recovery (STIR)-prepared T2-weighted technique, combining high spatial resolution and tissue contrast characteristics, the “3D-T2-STIR-ZOOMit” (Siemens), may improve DL diagnostic performance in the aVPs with respect to 2D-T2-STIR, the current standard technique.⁸     

Inversion Recovery Ultrashort TE MR Imaging of Myelin is Significantly Correlated with Disability in Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE:MR imaging has been widely used for the noninvasive evaluation of MS. Although clinical MR imaging sequences are highly effective in showing focal macroscopic tissue abnormalities in the brains of patients with MS, they are not specific to myelin and correlate poorly with disability. We investigated direct imaging of myelin using a 2D adiabatic inversion recovery ultrashort TE sequence to determine its value in assessing disability in MS.MATERIALS AND METHODS:The 2D inversion recovery ultrashort TE sequence was evaluated in 14 healthy volunteers and 31 patients with MS. MPRAGE and T2-FLAIR images were acquired for comparison. Advanced Normalization Tools were used to correlate inversion recovery ultrashort TE, MPRAGE, and T2-FLAIR images with disability assessed by the Expanded Disability Status Scale.RESULTS:Weak correlations were observed between normal-appearing white matter volume (R = –0.03, P = .88), lesion load (R = 0.22, P = .24), and age (R = 0.14, P = .44), and disability. The MPRAGE signal in normal-appearing white matter showed a weak correlation with age (R = –0.10, P = .49) and disability (R = –0.19, P = .31). The T2-FLAIR signal in normal-appearing white matter showed a weak correlation with age (R = 0.01, P = .93) and disability (R = 0.13, P = .49). The inversion recovery ultrashort TE signal was significantly negatively correlated with age (R = –0.38, P = .009) and disability (R = –0.44; P = .01).CONCLUSIONS:Direct imaging of myelin correlates with disability in patients with MS better than indirect imaging of long-T2 water in WM using conventional clinical sequences.

MS is the most common demyelinating disease of the brain.¹ Demyelination affects many aspects of neurologic function, including speech, balance, and cognitive awareness. Across time, this frequently leads to severe and irreversible clinical disability. MR imaging has been widely used for accurate diagnosis of MS, with current techniques focused on imaging the long-T2 water components in WM and GM.^2-4 MS lesions often appear hypointense with T1-weighted gradient recalled-echo sequences² and hyperintense with T2-weighted FSE and T2-weighted FLAIR sequences.³ Active lesions can be highlighted with gadolinium-enhanced imaging.⁴ The magnetization transfer ratio has been used as an indirect marker of myelin disorder in regions of normal-appearing WM (NAWM).⁵ There are also several other advanced imaging techniques for indirect myelin imaging via assessment of myelin water, such as multicomponent T2 or T2* analysis^6,7 and direct visualization of components with short transverse relaxation times.^8,9While conventional MR imaging sequences are highly effective in detecting focal macroscopic brain tissue abnormalities, they are not specific for pathologic substrates of MS lesions such as demyelination and remyelination, and they may not correlate well with patients'' neurologic deficits. Current MR imaging techniques correlate only modestly with disability assessed by the Expanded Disability Status Scale (EDSS).^10-15 The total lesion load showed statistically significant-but-weak correlations with the EDSS score in several large-scale studies (R = 0.1–0.3).^10-12 Composite scores including relaxation times of different tissues and/or volumetric measures generally correlate more strongly with the EDSS score, with a maximum observed correlation of R = 0.34 (P < .001).¹³ Lesions seen with gadolinium-enhanced imaging are only moderately correlated with disability in the first 6 months and are not predictive of changes in the EDSS score in the subsequent 1 or 2 years.¹⁴ A large-scale multicenter study reported very limited correlation between the EDSS score and normalized brain volume (R = –0.18), cross-sectional area (R = –0.26), magnetization transfer ratio of whole-brain tissue (R = –0.16), and GM (R = –0.17).¹⁵The poor performance of conventional MR imaging sequences in assessing disability highlights the need for novel MR imaging techniques that can directly image myelin lipid and enable direct assessment of both myelin damage and repair. However, myelin has an extremely short transverse relaxation time and is not directly detectable with conventional MR images, which typically have TEs of several milliseconds or longer. Ultrashort TE (UTE) sequences can directly detect signal from myelin with ultrashort T2 (ie, excluding water with longer T2s).^16-21 In this study, we describe imaging of WM using a 2D adiabatic inversion recovery prepared UTE (IR-UTE) sequence in healthy volunteers and patients with MS and evaluate its performance in assessing disability in patients with MS compared with 2 conventional clinical sequences.     

膝关节半月板损伤的磁共振诊断:三维质子加权序列与二维序列的对比

目的 比较评估三维快速自旋回波(3D-SPACE)序列与传统二维快速自旋回波(2D-TSE)序列对于膝关节半月板损伤的诊断价值.方法 半月板撕裂病例共40例.对所有患者进行3D-SPACE序列及2D序列的扫描,根据所得图像对半月板撕裂进行分型诊断.分别计算半月板信噪比(SNR)、半月板/软骨对比噪声比(CNR)、半月板/韧带CNR、半月板/关节液CNR,比较两者是否有统计学差异;与关节镜或手术结果比较,计算诊断半月板撕裂的敏感度、特异度、阳性预测值、阴性预测值及准确率,比较两者诊断符合率是否有统计学差异.结果 3D序列对于复合撕裂的诊断准确率较高.两种序列所得图像半月板SNR间差异无统计学意义(P=0.736);两种序列所得图像半月板/软骨CNR差异无统计学意义(P=0.526),半月板/韧带CNR差异有统计学意义(P=0.029),半月板/关节液CNR差异无统计学意义(P=0.899).3D-PD-SPACE序列采集所得图像Kappa值为0.84,表示不同观察者之间具有较强的一致性.两种序列在诊断半月板撕裂的准确性上没有明显差异(P=0.576 ＞0.05).结论 3D-SPACE序列是一种新的MR成像序列,能进行各向同性的扫描及多平面薄层重组,对于某些半月板撕裂类型诊断准确性较高,在膝关节半月板损伤的诊断方面有潜在应用价值.     

Advanced Diffusion MR Imaging for Multiple Sclerosis in the Brain and Spinal Cord

Diffusion tensor imaging (DTI) has been established its usefulness in evaluating normal-appearing white matter (NAWM) and other lesions that are difficult to evaluate with routine clinical MRI in the evaluation of the brain and spinal cord lesions in multiple sclerosis (MS), a demyelinating disease. With the recent advances in the software and hardware of MRI systems, increasingly complex and sophisticated MRI and analysis methods, such as q-space imaging, diffusional kurtosis imaging, neurite orientation dispersion and density imaging, white matter tract integrity, and multiple diffusion encoding, referred to as advanced diffusion MRI, have been proposed. These are capable of capturing in vivo microstructural changes in the brain and spinal cord in normal and pathological states in greater detail than DTI.This paper reviews the current status of recent advanced diffusion MRI for assessing MS in vivo as part of an issue celebrating two decades of magnetic resonance in medical sciences (MRMS), an official journal of the Japanese Society of Magnetic Resonance in Medicine.