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White Matter Tractography Reconstruction Ability Increases as a Function of Distance from Artifact Border. The artifact masks derived from the diffusion-weighted image volume were dilated in 2 mm increments, and the volume of white matter tracts that intersected any component of the dilated mask was computed. Components of the uncinate fasciculus (loop from temporal to ventral frontal) and inferior fronto-occipital fasciculus (occipital to temporal) in both patients' left hemisphere can be resolved within 2 mm of the artifact border by visual inspection of the orange tractography pathways. Both views are sagittal left hemisphere where A, P, S, and I indicate anterior, posterior, superior and inferior directions.
Source publication
The application of advanced 3T MRI imaging techniques to study recovery after subarachnoid hemorrhage (SAH) is complicated by the presence of image artifacts produced by implanted aneurysm clips. To characterize the effect of these artifacts on image quality, we sought to: 1) quantify extent of image artifact in SAH patients with implanted aneurysm...
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Citations
... Ito et al. examined the artifacts caused by titanium clips on MR (magnetic resonance) images and detected the artifact sizes 200% larger than the size of the actual clips [11]. Another study by Khursheed et al. revealed that the largest artifact produced by titanium alloy aneurysm clip takes up 3.94% of brain volume, and the artifact/clip length ratio is 4.75 to 6.55 mm [12]. Based on the evidence presented, another material is considered for an aneurysm clip, and one of them is a polymer. ...
An aneurysm clip is an implant tool for assisting the neurosurgeon in treating acute hemorrhagic stroke and cerebral aneurysm. This equipment stops the blood flow of a ruptured or enlarged blood vessel or aneurysm. In the development of aneurysm clip production, titanium alloy is the most used material selection. Several researchers reported that this metal leads to artifacts during MR (magnetic resonance) or CT (computed tomography) imaging. Since several pieces of evidence polyurethane could be a good material selection for aneurysm clips, this paper aims to investigate the material properties of the polyurethane foam with an additional combination of magnesium and zinc. This study conducts magnesium and zinc composition variations of 1 wt.%, 2 wt.%, and 3 wt.%, respectively. The materials were tested using a compression test, a FTIR (fourier-transform-infrared), SEM (scanning-electron-microscope), DSC (differential-scanning-calorimetry), and TGA (thermogravimetric-analyzer) to determine the material properties. From all examinations, adding magnesium and zinc to polyurethane foam affected the compressive strength and porosity of the polyurethane foam. Therefore, all test results concluded that adding magnesium with a composition of 3wt.%, which has a compressive strength of 0.84 MPa, is the best mixture. The idea of finding other compositions that are compatible with the polyurethane will significantly increase the possibility of new materials for aneurysm clip construction.
... We select MRI-safe titanium clips as implants in order to produce minimal artifact (Khursheed, 2011). An advanced 3T MR scanner can successfully image brain tissue around implanted titanium aneurysm clips at different spatial ranges depending on the sequence type. ...
Aneurysmal subarachnoid hemorrhage (aSAH) is a common disease causing vascular dementia. Survivors often suffer from cognitive impairment especially working memory deficit. Currently, lack of theoretical support limits the improvement of cognitive intervention or rehabilitation. It is unclear how the large-scale network differs and to what extent is the brain network affected? Our study aims to provide novel information about the topological characteristics of brain organization, especially “small-world” property. A total of 62 aSAH patients are enrolled in this study. They are divided into two groups according to the syndrome of working memory deficit. Their working memory function is evaluated by TMT-B and AVLT (Chinese version). Functional MRI scan is also performed for detecting resting-state cortical plasticity. We utilized ICA to extract functional sub-networks including working memory network from imaging data. And then we establish binarized network and calculate the small-worldness property as well as local and global efficiency of networks. aSAH group with working memory deficit shows no significant difference of clustering coefficient with control group. Our study discovered significant decrease of characteristic path length indicating an increase of overall routing efficiency. We reason that patients with working memory deficit have to recruit more neuronal resources and thus develops higher overall routing efficiency of local network. This study provides novel information about the neural alterations of aSAH patients with working memory deficit. It might contribute to the understanding of neural mechanism and the improvement of current intervention for vascular dementia.
... Resting-state functional magnetic resonance imaging (fMRI) data were obtained with a single-shot gradient-recalled echo planar imaging (EPI) sequence with the following parameters: interleaved scanning order, An MRI-safe clipping method was used to treat the enrolled patients (Khursheed, 2011). An advanced 3T MR scanner can successfully image brain tissue around implanted titanium aneurysm clips at different spatial ranges depending on the sequence type. ...
Introduction
Aneurysmal subarachnoid hemorrhage (aSAH), caused by rupture of an intracranial aneurysm and bleeding into the subarachnoid space, is a life-threatening cerebrovascular disease. Because of improvements in clinical interventions, the mortality rate of aSAH is gradually decreasing. Thus, many survivors recover from aSAH but still have sequelae. Working memory (WM) deficit is one of the most common and severe sequelae after aSAH. Interestingly, the severity of WM deficit is not identical to the extent or localization of brain damage, which implies an underlying mechanism of WM deficit other than direct hemorrhagic brain damage. Previous studies have revealed altered neural activity of several brain regions during stimulus tasks. However, the behaviors and functional organization of these corresponding areas in the resting state remain unclear. Insights into the organization of the WM network could reveal novel information about the mechanism of WM deficits, which will be of great value in developing new therapeutic strategies.
Methods
In this study, we recruited 50 aSAH patients consisting of survivors with either impaired or intact WM (two groups). Independent component analysis was performed on resting state data to extract the WM network. Dynamic causal modeling was then performed to assess the intrinsic coupling between key regions of the WM network. A model describing the neural activity and functional organization of the WM network was established, although some connections were not consistent in the resting state.
Results
We found that effective connectivity of the precuneus (PCUN)-middle temporal gyrus (MTG), MTG-PCUN, and middle frontal gyrus-inferior parietal lobule was significantly decreased in the impaired WM group, which suggests a vital and central role of affected regions or connections and provides new targets for brain stimulation.
Conclusions
The results of this study may contribute to new therapeutic or rehabilitation strategies for aSAH patients with WM deficits.
... of aneurysm rupture has been successfully performed using diffusion tensor imaging; this also suggests secondary and more diffuse changes leading to inefficient neuronal function that may impact cognitive function more than any focal structural damage. 29 Limited description of functional network integrity after aSAH exists. The clinical heterogeneity and diffuse effects of aSAH suggest that functional connections can be important to understand persistent cognitive dysfunction. ...
... Time-series data were reconstructed from AAL locations using vector beamforming (linearly constrained minimum variance; LCMV) for each subject and filtered into five bandwidths: Theta (4-7 Hz), Alpha (8-14 Hz), Beta (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), Gamma (30-80 Hz) and High-Gamma (80-150 Hz). Beamforming applied an adaptive spatial filter allowing accurate source-level activity reconstruction and artefact suppression 4 . ...
Background and purpose:
Neurocognitive deficits are common among survivors of aneurysmal subarachnoid hemorrhage, even among those with good outcomes and no structural lesions. This study aims to probe the neurophysiological underpinnings of cognitive dysfunction among patients with ruptured intracranial aneurysms using magnetoencephalography (MEG).
Methods:
Thirteen patients who had undergone uncomplicated coiling for aneurysmal subarachnoid hemorrhage and 13 matched controls were enrolled. Neuropsychological tests were done before magnetoencephalography scans. Magnetoencephalography data were acquired in a 151-channel, whole-head magnetoencephalography system for resting state and 2 cognitive tasks (go-no-go and set-shifting). Mean time from treatment to test was 18.8 months.
Results:
Cognitive tasks of inhibition (go-no-go) indicated greater activation in the right anterior cingulate and inferior frontal gyrus, and cognitive set-shifting tasks (mental flexibility) indicated greater activity in the bilateral anterior cingulate cortex and right medial frontal gyrus among aneurysmal subarachnoid hemorrhage patients, with significantly different timing of activation between groups. Resting-state, beta-band connectivity of the anterior cingulate correlated negatively with Montreal Cognitive Assessment scores (left: r=-0.56; P<0.01 and right: r=-0.55; P<0.01): higher connectivity of this region was linked to poorer cognitive test performance.
Conclusions:
We have shown increased activation in areas of the anterior cingulate gyrus and frontobasal regions during the execution of more demanding tasks in good grade. The degree of activation in the anterior cingulate gyrus has a negative correlation with cognitive (Montreal Cognitive Assessment) scores. These subtle differences may be related to the common neurocognitive and behavioral complaints seen in this patient population.
... While 316L stainless steel contains a larger amount of nickel, which stabilizes iron in its nonmagnetic state and reduces its magnetic susceptibility, its magnetic susceptibility remains larger relative to titanium, resulting in larger perturbations of the magnetic field and more extensive artifacts. 14,15 In addition, the Certas programmable valve (Codman & Shurtleff, Raynham, Massachusetts) contains neodymium magnets, which caused extensive signal loss 13,16,17 and likely contributed to the large artifact volume (139.6 cm 3 ) relative to other VP shunts evaluated (64.0 and 83.5 cm 3 ). ...
Blood oxygenation level-dependent MR imaging is increasingly used clinically to noninvasively assess cerebrovascular reactivity and/or language and motor function. However, many patients have metallic implants, which will induce susceptibility artifacts, rendering the functional information uninformative. Here, we calculate and interpret blood oxygenation level-dependent MR imaging artifact impact arising from surgically implanted hardware.
A retrospective analysis of all blood oxygenation level-dependent MRIs (n = 343; B0 = 3T; TE = 35 ms; gradient echo EPI) acquired clinically (year range = 2006-2014) at our hospital was performed. Blood oxygenation level-dependent MRIs were most commonly prescribed for patients with cerebrovascular disease (n = 80) or patients undergoing language or motor localization (n = 263). Artifact volume (cubic centimeters) and its impact on clinical interpretation were determined by a board-certified neuroradiologist.
Mean artifact volume associated with intracranial hardware was 4.3 ± 3.2 cm(3) (range = 1.1-9.4 cm(3)). The mean artifact volume from extracranial hardware in patients with cerebrovascular disease was 28.4 ± 14.0 cm(3) (range = 6.1-61.7 cm(3)), and in patients with noncerebrovascular disease undergoing visual or motor functional mapping, it was 39.9 (3)± 27.0 cm(3) (range = 6.9-77.1 cm(3)). The mean artifact volume for ventriculoperitoneal shunts was 95.7 ± 39.3 cm(3) (range = 64.0-139.6 cm(3)). Artifacts had no-to-mild effects on clinical interpretability in all patients with intracranial implants. Extracranial hardware artifacts had no-to-moderate impact on clinical interpretability, with the exception of 1 patient with 12 KLS-Martin maxDrive screws with severe artifacts precluding clinical interpretation. All examined ventriculoperitoneal shunts resulted in moderate-to-severe artifacts, limiting clinical interpretation.
Blood oxygenation level-dependent MR imaging yields interpretable functional maps in most patients beyond a small (30-40 cm(3)) artifact surrounding the hardware. Exceptions were ventriculoperitoneal shunts, particularly those with programmable valves and siphon gauges, and large numbers of KLS-Martin maxDrive screws.
© 2015 American Society of Neuroradiology.
... In part this may part be secondary to the technical difficulties of performing MRI in patients with extensive extra-vascular blood products and the need to ensure that any clips and coils are MRI safe. The presence of such clips causes artifacts that may impact image quality (101). A recent study has found cerebral micro-bleeds (on T2* GE) related to the presence of DWI lesions in almost 46% of patients imaged within 7 days of ictus (102). ...
Much progress has been made over the past two decades in the treatment of severe acute brain injury, including traumatic brain injury and subarachnoid hemorrhage, resulting in a higher proportion of patients surviving with better outcomes. This has arisen from a combination of factors. These include improvements in procedures at the scene (pre-hospital) and in the hospital emergency department, advances in neuromonitoring in the intensive care unit, both continuously at the bedside and intermittently in scans, evolution and refinement of protocol-driven therapy for better management of patients, and advances in surgical procedures and rehabilitation. Nevertheless, many patients still experience varying degrees of long-term disabilities post-injury with consequent demands on carers and resources, and there is room for improvement. Biomarkers are a key aspect of neuromonitoring. A broad definition of a biomarker is any observable feature that can be used to inform on the state of the patient, e.g., a molecular species, a feature on a scan, or a monitoring characteristic, e.g., cerebrovascular pressure reactivity index. Biomarkers are usually quantitative measures, which can be utilized in diagnosis and monitoring of response to treatment. They are thus crucial to the development of therapies and may be utilized as surrogate endpoints in Phase II clinical trials. To date, there is no specific drug treatment for acute brain injury, and many seemingly promising agents emerging from pre-clinical animal models have failed in clinical trials. Large Phase III studies of clinical outcomes are costly, consuming time and resources. It is therefore important that adequate Phase II clinical studies with informative surrogate endpoints are performed employing appropriate biomarkers. In this article, we review some of the available systemic, local, and imaging biomarkers and technologies relevant in acute brain injury patients, and highlight gaps in the current state of knowledge.
... The factors associated with CTA image quality include the clip material (cobalt is worse than titanium alloy clips) [69,70], clip orientation (within the scan plane), and the number of clips on the same aneurysm [64,69]. Metal artefact reduction algorithms using flatpanel detector CT [71,72], subtraction three-dimensional CTA with the orbital synchronised helical scan technique [65], and advanced 3 T MRI imaging techniques [73] are some of the new modalities applied to reduce artefacts generated by the metallic clips, which can in turn improve the quality of the image. ...
Neuroimaging is a key element in the management of patients suffering from subarachnoid haemorrhage (SAH). In this article, we review the current literature to provide a summary of the existing neuroimaging methods available in clinical practice. Noncontrast computed tomography is highly sensitive in detecting subarachnoid blood, especially within 6 hours of haemorrhage. However, lumbar puncture should follow a negative noncontrast computed tomography scan in patients with symptoms suspicious of SAH. Computed tomography angiography is slowly replacing digital subtraction angiography as the first-line technique for the diagnosis and treatment planning of cerebral aneurysms, but digital subtraction angiography is still required in patients with diffuse SAH and negative initial computed tomography angiography. Delayed cerebral ischaemia is a common and serious complication after SAH. The modern concept of delayed cerebral ischaemia monitoring is shifting from modalities that measure vessel diameter to techniques focusing on brain perfusion. Lastly, evolving modalities applied to assess cerebral physiological, functional and cognitive sequelae after SAH, such as functional magnetic resonance imaging or positron emission tomography, are discussed. These new techniques may have the advantage over structural modalities due to their ability to assess brain physiology and function in real time. However, their use remains mainly experimental and the literature supporting their practice is still scarce.
Electronic supplementary material
The online version of this article (doi:10.1186/s13054-014-0557-2) contains supplementary material, which is available to authorized users.
... Oral production is strongly left-lateralized (Laine & Martin, 2006). It probably continued to be subserved by the spared left inferior frontal gyrus (IFG) in AA, albeit the present MRI evidence is not fully conclusive due to the aneurysm clip close by that introduced small distortions to MRI signal (Khursheed, Rohlffs, Suzuki, Kim, & Ellmore, 2011 ). AA's reading-related activations suggest that the connection from reading to oral production was established through a route from the right temporo-parietal areas to the right frontal premotor regions, with intercallosal transfer to the left premotor areas and further to Broca's area. ...
p>Multiple studies have been conducted to properly elucidate the various tools available to help enhance the resection of tumor tissue, aneurysms, and arteriovenous malformations (AVM). Diffusion tensor imaging (DTI) tractography is useful in providing a map of the tumor borders, allowing the optimal preservation of function and structure of specific regions of the brain. During neurosurgery, especially craniotomies, the possibility of the brain shifting due to swelling or gravity is high. Thus, tools for intraoperative imaging such as high-frequency linear array ultrasound transducers and doppler ultrasonography are utilized for high resolution images and detecting frequency shifts. 4D-digital subtraction angiography (DSA) is another technique used to create spatial resolutions and 3D maps for aneurysms. These similar techniques can also be utilized to assess the integrity of white matter in AVM. By implementing effective evaluation strategies, healthcare professionals can make informed decisions regarding treatment options, preventive measures, and long-term care plans tailored to individual patients. </p
