Improved T2* imaging without increase in scan time: SWI processing of 2D gradient echo

Acquired hydrocephalus following hypoxic ischemic encephalopathy without intraventricular hemorrhage: A case report

The most common cause of acquired hydrocephalus in infants is hemorrhage, most often as a consequence of prematurity. Other important causes include neoplasm and infection, usually bacterial meningitis. Hypoxic ischemic encephalopathy (HIE) in term infants usually results in secondary microcephaly. We report an infant with severe HIE at birth treated by therapeutic hypothermia who developed progressive acquired hydrocephalus over 2 months, although no cause of the hydrocephalus was identified. Although hydrocephalus, even intraventricular hemorrhage, is uncommon in term infants with HIE, careful follow-up of the head circumference is important, even if no findings indicating possible causes of hydrocephalus, such as hemorrhage, are detected on ultrasound or magnetic resonance imaging.

Clinical significance of asymmetric venous vasculature on minimum-intensity projection in patients with moyamoya disease

This study analyzed the clinical significance and characteristics of asymmetric venous blood flow in patients with Moyamoya disease (MMD) using minimum intensity projection (minIP) susceptibility-weighted imaging. The minIP views of 30 patients diagnosed with MMD were retrospectively analyzed using clinical features, brain magnetic resonance angiography, electroencephalography, and brain single-photon emission computed tomography (SPECT). Simultaneously, differences between patients with acute cerebral infarction and non-MMD causes were analyzed. Twelve (40.0%) of the 30 patients had asymmetrical venous flow, which is usually seen in patients with acute cerebral infarction (P = .146). They also had significantly higher Suzuki stages than symmetric patients (P = .014), with five (41.7%) and three (25.0%) of them in stages 4 and 5, respectively. When the Suzuki stages of both hemispheres were different, more veins were found in the stenotic hemisphere (88.9%). Brain SPECT showed more severe hypoperfusion on the side with prominent vascularity in the minIP view (100.0%). Additionally, asymmetric blood flow was observed in 66.7% of the patients with cerebral infarction caused by MMD, whereas only 11.1% of the children with cerebral infarction caused by non-MMD had asymmetry (P = .005). Patients with MMD showed asymmetric hypointensity of the cortical veins with a minIP appearance. The venous structure showed greater signal loss on SWI and was more prominent in the hemisphere where stenosis was advanced or infarction occurred in other examinations. Cerebral infarction in patients with MMD tended to occur with asymmetrically prominent venous patterns with damaged areas in minIP images, which had distinct characteristics from those of patients without MMD.

Susceptibility-weighted Imaging: Technical Essentials and Clinical Neurologic Applications

Susceptibility-weighted imaging (SWI) evolved from simple two-dimensional T2*-weighted sequences to three-dimensional sequences with improved spatial resolution and enhanced susceptibility contrast. SWI is an MRI sequence sensitive to compounds that distort the local magnetic field (eg, calcium and iron), in which the phase information can differentiate. But the term SWI is colloquially used to denote high-spatial-resolution susceptibility-enhanced sequences across different MRI vendors and sequences even when phase information is not used. The imaging appearance of SWI and related sequences strongly depends on the acquisition technique. Initially, SWI and related sequences were mostly used to improve the depiction of findings already known from standard two-dimensional T2*-weighted neuroimaging: more microbleeds in patients who are aging or with dementia or mild brain trauma; increased conspicuity of superficial siderosis in Alzheimer disease and amyloid angiopathy; and iron deposition in neurodegenerative diseases or abnormal vascular structures, such as capillary telangiectasia. But SWI also helps to identify findings not visible on standard T2*-weighted images: the nigrosome 1 in Parkinson disease and dementia with Lewy bodies, the central vein and peripheral rim signs in multiple sclerosis, the peripheral rim sign in abscesses, arterial signal loss related to thrombus, asymmetrically prominent cortical veins in stroke, and intratumoral susceptibility signals in brain neoplasms.

Diagnostic value of alternative techniques to gadolinium-based contrast agents in MR neuroimaging-a comprehensive overview

Gadolinium-based contrast agents (GBCAs) increase lesion detection and improve disease characterization for many cerebral pathologies investigated with MRI. These agents, introduced in the late 1980s, are in wide use today. However, some non-ionic linear GBCAs have been associated with the development of nephrogenic systemic fibrosis in patients with kidney failure. Gadolinium deposition has also been found in deep brain structures, although it is of unclear clinical relevance. Hence, new guidelines from the International Society for Magnetic Resonance in Medicine advocate cautious use of GBCA in clinical and research practice. Some linear GBCAs were restricted from use by the European Medicines Agency (EMA) in 2017.

This review focuses on non-contrast-enhanced MRI techniques that can serve as alternatives for the use of GBCAs. Clinical studies on the diagnostic performance of non-contrast-enhanced as well as contrast-enhanced MRI methods, both well established and newly proposed, were included. Advantages and disadvantages together with the diagnostic performance of each method are detailed. Non-contrast-enhanced MRIs discussed in this review are arterial spin labeling (ASL), time of flight (TOF), phase contrast (PC), diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS), susceptibility weighted imaging (SWI), and amide proton transfer (APT) imaging.

Ten common diseases were identified for which studies reported comparisons of non-contrast-enhanced and contrast-enhanced MRI. These specific diseases include primary brain tumors, metastases, abscess, multiple sclerosis, and vascular conditions such as aneurysm, arteriovenous malformation, arteriovenous fistula, intracranial carotid artery occlusive disease, hemorrhagic, and ischemic stroke.

In general, non-contrast-enhanced techniques showed comparable diagnostic performance to contrast-enhanced MRI for specific diagnostic questions. However, some diagnoses still require contrast-enhanced imaging for a complete examination.

Clinical Significance of Asymmetric Minimum Intensity Projection Images of Brain Magnetic Resonance Imaging in Children

Background and Purpose

The susceptibility-weighted imaging form of brain MRI using minimum intensity projection (mIP) is useful for assessing traumatic brain injuries because it readily reveals deoxyhemoglobin or paramagnetic compounds. We investigated the efficacy of using this methodology in nontraumatic patients.

Methods

We retrospectively analyzed the asymmetric mIP findings in nontraumatic patients. Asymmetric mIP images were first verified visually and then using ImageJ software. We enrolled patients with a difference of >5% between hemispheres in ImageJ analysis. All patients underwent detailed history-taking and EEG, and asymmetric mIP findings were compared.

Results

The visual analysis identified 54 pediatric patients (37 males and 17 females) with asymmetric mIP findings. Ten patients were excluded because they did not meet the ImageJ verification criteria. The 44 patients with asymmetry comprised 36 with epilepsy, 6 with headache, and 2 with cerebral infarction. Thirty-one of the 36 epileptic patients showed definite partial seizure activities in semiology, while the remaining patients did not demonstrate a history of partial seizure manifestations. The MRI findings were normal in all patients except for five with periventricular leukomalacia unrelated to seizure symptoms. There was agreement between mIP images and semiology in 29 (93.5%) of the 31 epileptic patients with focal signs, while the other 2 demonstrated discordance. Twenty (64.5%) of the 31 patients showed consistent EEG abnormalities.

Conclusions

Our data suggest that asymmetric mIP findings are an excellent lateralizing indicator in pediatric patients with partial epilepsy.

Use of magnetic resonance imaging in severe pediatric traumatic brain injury: assessment of current practice

OBJECTIVE

There is no consensus on the optimal timing and specific brain MRI sequences in the evaluation and management of severe pediatric traumatic brain injury (TBI), and information on current practices is lacking. The authors performed a survey of MRI practices among sites participating in a multicenter study of severe pediatric TBI to provide information for designing future clinical trials using MRI to assess brain injury after severe pediatric TBI.

METHODS

Information on current imaging practices and resources was collected from 27 institutions participating in the Approaches and Decisions after Pediatric TBI Trial. Multiple-choice questions addressed the percentage of patients with TBI who have MRI studies, timing of MRI, MRI sequences used to investigate TBI, as well as the magnetic field strength of MR scanners used at the participating institutions and use of standardized MRI protocols for imaging after severe pediatric TBI.

RESULTS

Overall, the reported use of MRI in pediatric patients with severe TBI at participating sites was high, with 40% of sites indicating that they obtain MRI studies in > 95% of this patient population. Differences were observed in the frequency of MRI use between US and international sites, with the US sites obtaining MRI in a higher proportion of their pediatric patients with severe TBI (94% of US vs 44% of international sites reported MRI in at least 70% of patients with severe TBI). The reported timing and composition of MRI studies was highly variable across sites. Sixty percent of sites reported typically obtaining an MRI study within the first 7 days postinjury, with the remainder of responses distributed throughout the first 30-day postinjury period. Responses indicated that MRI sequences sensitive for diffuse axonal injury and ischemia are frequently obtained in patients with TBI, whereas perfusion imaging and spectroscopy techniques are less common.

CONCLUSIONS

Results from this survey suggest that despite the lack of consensus or guidelines, MRI is commonly obtained during the acute clinical setting after severe pediatric TBI. The variation in MRI practices highlights the need for additional studies to determine the utility, optimal timing, and composition of clinical MRI studies after TBI. The information in this survey describes current clinical MRI practices in children with severe TBI and identifies important challenges and objectives that should be considered when designing future studies.

Cerebral Microbleeds: Imaging and Clinical Significance

Cerebral microbleeds (CMBs), also referred to as microhemorrhages, appear on magnetic resonance (MR) images as hypointense foci notably at T2*-weighted or susceptibility-weighted (SW) imaging. CMBs are detected with increasing frequency because of the more widespread use of high magnetic field strength and of newer dedicated MR imaging techniques such as three-dimensional gradient-echo T2*-weighted and SW imaging. The imaging appearance of CMBs is mainly because of changes in local magnetic susceptibility and reflects the pathologic iron accumulation, most often in perivascular macrophages, because of vasculopathy. CMBs are depicted with a true-positive rate of 48%-89% at 1.5 T or 3.0 T and T2*-weighted or SW imaging across a wide range of diseases. False-positive "mimics" of CMBs occur at a rate of 11%-24% and include microdissections, microaneurysms, and microcalcifications; the latter can be differentiated by using phase images. Compared with postmortem histopathologic analysis, at least half of CMBs are missed with premortem clinical MR imaging. In general, CMB detection rate increases with field strength, with the use of three-dimensional sequences, and with postprocessing methods that use local perturbations of the MR phase to enhance T2* contrast. Because of the more widespread availability of high-field-strength MR imaging systems and growing use of SW imaging, CMBs are increasingly recognized in normal aging, and are even more common in various disorders such as Alzheimer dementia, cerebral amyloid angiopathy, stroke, and trauma. Rare causes include endocarditis, cerebral autosomal dominant arteriopathy with subcortical infarcts, leukoencephalopathy, and radiation therapy. The presence of CMBs in patients with stroke is increasingly recognized as a marker of worse outcome. Finally, guidelines for adjustment of anticoagulant therapy in patients with CMBs are under development. ^© RSNA, 2018.

Brain Injury Lesion Imaging Using Preconditioned Quantitative Susceptibility Mapping without Skull Stripping

BACKGROUND AND PURPOSE

Identifying cerebral microhemorrhage burden can aid in the diagnosis and management of traumatic brain injury, stroke, hypertension, and cerebral amyloid angiopathy. MR imaging susceptibility-based methods are more sensitive than CT for detecting cerebral microhemorrhage, but methods other than quantitative susceptibility mapping provide results that vary with field strength and TE, require additional phase maps to distinguish blood from calcification, and depict cerebral microhemorrhages as bloom artifacts. Quantitative susceptibility mapping provides universal quantification of tissue magnetic property without these constraints but traditionally requires a mask generated by skull-stripping, which can pose challenges at tissue interphases. We evaluated the preconditioned quantitative susceptibility mapping MR imaging method, which does not require skull-stripping, for improved depiction of brain parenchyma and pathology.

MATERIALS AND METHODS

Fifty-six subjects underwent brain MR imaging with a 3D multiecho gradient recalled echo acquisition. Mask-based quantitative susceptibility mapping images were created using a commonly used mask-based quantitative susceptibility mapping method, and preconditioned quantitative susceptibility images were made using precondition-based total field inversion. All images were reviewed by a neuroradiologist and a radiology resident.

RESULTS

Ten subjects (18%), all with traumatic brain injury, demonstrated blood products on 3D gradient recalled echo imaging. All lesions were visible on preconditioned quantitative susceptibility mapping, while 6 were not visible on mask-based quantitative susceptibility mapping. Thirty-one subjects (55%) demonstrated brain parenchyma and/or lesions that were visible on preconditioned quantitative susceptibility mapping but not on mask-based quantitative susceptibility mapping. Six subjects (11%) demonstrated pons artifacts on preconditioned quantitative susceptibility mapping and mask-based quantitative susceptibility mapping; they were worse on preconditioned quantitative susceptibility mapping.

CONCLUSIONS

Preconditioned quantitative susceptibility mapping MR imaging can bring the benefits of quantitative susceptibility mapping imaging to clinical practice without the limitations of mask-based quantitative susceptibility mapping, especially for evaluating cerebral microhemorrhage-associated pathologies, such as traumatic brain injury.

Diagnostic Performance of a 10-Minute Gadolinium-Enhanced Brain MRI Protocol Compared with the Standard Clinical Protocol for Detection of Intracranial Enhancing Lesions

BACKGROUND AND PURPOSE

The development of new MR imaging scanners with stronger gradients and improvement in coil technology, allied with emerging fast imaging techniques, has allowed a substantial reduction in MR imaging scan times. Our goal was to develop a 10-minute gadolinium-enhanced brain MR imaging protocol with accelerated sequences and to evaluate its diagnostic performance compared with the standard clinical protocol.

MATERIALS AND METHODS

Fifty-three patients referred for brain MR imaging with contrast were scanned with a 3T scanner. Each MR image consisted of 5 basic fast precontrast sequences plus standard and accelerated versions of the same postcontrast T1WI sequences. Two neuroradiologists assessed the image quality and the final diagnosis for each set of postcontrast sequences and compared their performances.

RESULTS

The acquisition time of the combined accelerated pre- and postcontrast sequences was 10 minutes and 15 seconds; and of the fast postcontrast sequences, 3 minutes and 36 seconds, 46% of the standard sequences. The 10-minute postcontrast axial T1WI had fewer image artifacts (P < .001) and better overall diagnostic quality (P < .001). Although the 10-minute MPRAGE sequence showed a tendency to have more artifacts than the standard sequence (P = .08), the overall diagnostic quality was similar (P = .66). Moreover, there was no statistically significant difference in the diagnostic performance between the protocols. The sensitivity, specificity, and accuracy values for the 10-minute protocol were 100.0%, 88.9%, and 98.1%.

CONCLUSIONS

The 10-minute brain MR imaging protocol with contrast is comparable in diagnostic performance with the standard protocol in an inpatient motion-prone population, with the additional benefits of reducing acquisition times and image artifacts.

Simultaneous Multislice-Based 5-Minute Lumbar Spine MRI Protocol: Initial Experience in a Clinical Setting

BACKGROUND AND PURPOSE

Previous studies have used parallel imaging (PI) techniques to decrease spine magnetic resonance imaging (MRI) protocol acquisition times. Recently developed MRI sequences allow even faster acquisitions. Our purpose was to develop a lumbar spine MRI protocol using PI with GRAPPA (generalized autocalibrating partially parallel acquisition) and a simultaneous multislice (SMS)-based sequence and to evaluate its diagnostic performance compared to a standard lumbar spine MRI protocol.

METHODS

Ten patients were scanned in a 3-Tesla scanner (MAGNETOM Skyra, Siemens Healthcare). Each patient was imaged using a standard protocol and an optimized fast protocol acquiring the same contrasts and planes. The fast protocol included sagittal T1, T2, and fat suppressed T2 sequences accelerated with GRAPPA and an SMS-based axial T2-weighted sequence using a high-density spine coil (Siemens MR, 30 channel spine). Two blinded neuroradiologists independently assessed image quality and diagnostic accuracy for clinically relevant imaging findings.

RESULTS

The fast protocol acquisition time was 5:28 minutes, compared with 16:30 minutes for the standard protocol. Both protocols had a similar performance for definition of anatomical structures, diagnostic quality, and identification of clinically relevant imaging findings. There were more artifacts in the SMS Turbo Spin Echo (P = .014) sequence without compromising diagnostic performance. Artifacts in the remaining non-SMS sequences were similar in both protocols (P > .180). The sensitivity, specificity, and accuracy of the 5-minute protocol were 92.3%, 100.0%, and 99.6%, respectively, for the clinically relevant findings (P = 1.0, interrater agreement .57).

CONCLUSIONS

A 5-minute SMS-based MRI protocol for lumbar spine imaging is feasible and can be achieved without significant impact in the overall diagnostic quality.

Susceptibility-Based Neuroimaging: Standard Methods, Clinical Applications, and Future Directions

The evaluation of neuropathologies using MRI methods that leverage tissue susceptibility have become standard practice, especially to detect blood products or mineralization. Additionally, emerging MRI techniques have the ability to provide new information based on tissue susceptibility properties in a robust and quantitative manner. This paper discusses these advanced susceptibility imaging techniques and their clinical applications.

Accuracy of SWI sequences compared to T2*-weighted gradient echo sequences in the detection of cerebral cavernous malformations in the familial form

PURPOSE

The purpose of this study was to assess the accuracy of susceptibility-weighted imaging (SWI), compared with T2*-weighted gradient echo (GRE) imaging in assessing cerebral cavernous malformations.

MATERIALS AND METHODS

We retrospectively evaluated 21 patients with a familial form of cavernous malformation. Magnetic resonance (MR) protocol included non-enhanced and contrast-enhanced fast-spin echo (FSE) T1-weighted sequences, FSE T2-weighted sequences, fluid-attenuated inversion-recovery (FLAIR), GRE T2*-weighted and SWI sequences. Images were reviewed in consensus by two expert neuroradiologists to assess the location, number, size and conspicuity of the lesions on T2*-weighted GRE and SWI sequences. Statistical differences in the number, size and conspicuity of the lesions seen on the SWI images and the T2*-weighted GRE images were assessed with the nonparametric Wilcoxon signed rank test.

RESULTS

The number of cavernous malformations was significantly higher (p < .001) on the SWI images (n = 152) than on T2*-weighted GRE images (n = 56). Lesion size was significantly higher (p < .001) on SWI images (mean: 0.4 cm, SD ± 0.55) than on T2*-weighted GRE sequences (mean: 0.2 cm, SD ± 0.51) and the differences were statistically significant (p < .001). Lesion conspicuity was significant higher (p < .001) on SWI than on T2*-weighted GRE images. In one patient who underwent a 2-month follow-up for the onset of neurologic symptoms related to cerebral hemorrhage, a cerebral hematoma was identified at the site of a cerebral cavernous malformation that was demonstrated only on the SWI images in the previous MR examination.

CONCLUSIONS

The SWI sequence, being more sensitive to substances which distort the local magnetic field than the GRE T2*W sequence, showed a higher sensitivity in identifying cerebral cavernous malformations. Thus, routine clinical neuroimaging protocol should contain SWI sequences to evaluate patients with (or suspected) cerebral cavernous malformations.

Iron and Non-Iron-Related Characteristics of Multiple Sclerosis and Neuromyelitis Optica Lesions at 7T MRI

BACKGROUND AND PURPOSE

Characterization of iron deposition associated with demyelinating lesions of multiple sclerosis and neuromyelitis optica has not been well studied. Our aim was to investigate the potential of ultra-high-field MR imaging to distinguish MS from neuromyelitis optica and to characterize tissue injury associated with iron pathology within lesions.

MATERIALS AND METHODS

Twenty-one patients with MS and 21 patients with neuromyelitis optica underwent 7T high-resolution 2D-gradient-echo-T2* and 3D-susceptibility-weighted imaging. An in-house-developed algorithm was used to reconstruct quantitative susceptibility mapping from SWI. Lesions were classified as "iron-laden" if they demonstrated hypointensity on gradient-echo-T2*-weighted images and/or SWI and hyperintensity on quantitative susceptibility mapping. Lesions were considered "non-iron-laden" if they were hyperintense on gradient-echo-T2* and isointense or hyperintense on quantitative susceptibility mapping.

RESULTS

Of 21 patients with MS, 19 (90.5%) demonstrated at least 1 quantitative susceptibility mapping-hyperintense lesion, and 11/21 (52.4%) had iron-laden lesions. No quantitative susceptibility mapping-hyperintense or iron-laden lesions were observed in any patients with neuromyelitis optica. Iron-laden and non-iron-laden lesions could each be further characterized into 2 distinct patterns based on lesion signal and morphology on gradient-echo-T2*/SWI and quantitative susceptibility mapping. In MS, most lesions (n = 262, 75.9% of all lesions) were hyperintense on gradient-echo T2* and isointense on quantitative susceptibility mapping (pattern A), while a small minority (n = 26, 7.5% of all lesions) were hyperintense on both gradient-echo-T2* and quantitative susceptibility mapping (pattern B). Iron-laden lesions (n = 57, 16.5% of all lesions) were further classified as nodular (n = 22, 6.4%, pattern C) or ringlike (n = 35, 10.1%, pattern D).

CONCLUSIONS

Ultra-high-field MR imaging may be useful in distinguishing MS from neuromyelitis optica. Different patterns related to iron and noniron pathology may provide in vivo insight into the pathophysiology of lesions in MS.

Contrast-enhanced FLAIR (fluid-attenuated inversion recovery) for evaluating mild traumatic brain injury

PURPOSE

To evaluate whether adding a contrast-enhanced fluid-attenuated inversion recovery (FLAIR) sequence to routine magnetic resonance imaging (MRI) can detect additional abnormalities in the brains of symptomatic patients with mild traumatic brain injury.

MATERIALS AND METHODS

Fifty-four patients with persistent symptoms following mild closed head injury were included in our retrospective study (M ∶ F =  32 ∶ 22, mean age: 59.8 ± 16.4, age range: 26-84 years). All MRI examinations were obtained within 14 days after head trauma (mean: 3.2 ± 4.1 days, range: 0.2-14 days). Two neuroradiologists recorded (1) the presence of traumatic brain lesions on MR images with and without contrast-enhanced FLAIR images and (2) the pattern and location of meningeal enhancement depicted on contrast-enhanced FLAIR images. The number of additional traumatic brain lesions diagnosed with contrast-enhanced FLAIR was recorded. Correlations between meningeal enhancement and clinical findings were also evaluated.

RESULTS

Traumatic brain lesions were detected on routine image sequences in 25 patients. Three additional cases of brain abnormality were detected with the contrast-enhanced FLAIR images. Meningeal enhancement was identified on contrast-enhanced FLAIR images in 9 cases while the other routine image sequences showed no findings of traumatic brain injury. Overall, the additional contrast-enhanced FLAIR images revealed more extensive abnormalities than routine imaging in 37 cases (p<0.001). In multivariate logistic regression analysis, subdural hematoma and posttraumatic loss of consciousness showed a significant association with meningeal enhancement on contrast-enhanced FLAIR images, with odds ratios 13.068 (95% confidence interval 2.037 to 83.852), and 15.487 (95% confidence interval 2.545 to 94.228), respectively.

CONCLUSION

Meningeal enhancement on contrast-enhanced FLAIR images can help detect traumatic brain lesions as well as additional abnormalities not identified on routine unenhanced MRI. Therefore contrast-enhanced FLAIR MR imaging is recommended when a contrast MR study is indicated in a patient with a symptomatic prior closed mild head injury.

T2* "susceptibility vessel sign" demonstrates clot location and length in acute ischemic stroke

OBJECTIVES

The aim of our study was to evaluate, in acute ischemic stroke patients, the diagnostic accuracy of the MRI susceptibility vessel sign (SVS) against catheter angiography (DSA) for the detection of the clot and its value in predicting clot location and length.

MATERIALS AND METHODS

We identified consecutive patients (2006-2012) admitted to our center, where 1.5 T MRI is systematically implemented as first-line diagnostic work-up, with: (1) pre-treatment 6-mm-thick multislice 2D T2* sequence; (2) delay from MRI-to-DSA <3 hrs; (3) no fibrinolysis between MRI and DSA. The location and length of SVS on T2* was independently assessed by three readers, and compared per patient, per artery and per segment, to DSA findings, obtained by two different readers. Clot length measured on T2* and DSA were compared using intra-class correlation coefficient (ICC), Bland & Altman test and Passing & Bablok regression analysis.

RESULTS

On DSA, a clot was present in 85 patients, in 126 of 1190 (10.6%) arteries and 175 of 1870 (9.4%) segments. Sensitivity of the SVS, as sensed by the used protocol at 1.5 T, was 81.1% (69 of 85 patients) and was higher in anterior (55 of 63, 87.3%), than in posterior circulation stroke (14 of 22, 63.6%, p=0.02). Sensitivity/specificity was 69.8/99.6% (per artery) and 76.6/99.7% (per segment). Positive (PPV) and negative predictive value (NPV) and accuracy were all >94%. Inter- and intra-observer ICC was excellent for clot length as measured on T2* (ĸ ≥ 0.97) and as measured on DSA (ĸ ≥ 0.94). Correlation between T2* and DSA for clot length was excellent (ICC: 0.88, 95%CI: 0.81-0.92; Bland & Altman: mean bias of 1.6% [95%CI: -4.7 to 7.8%], Passing & Bablok: 0.91).

CONCLUSIONS

SVS is a specific marker of clot location in the anterior and posterior circulation. Clot length greater than 6 mm can be reliably measured on T2*.