Saba Elias

Four-Dimensional Phase Contrast Magnetic Resonance Imaging Protocol Optimization Using Patient-Specific 3-Dimensional Printed Replicas for In Vivo Imaging Before and After Flow Diverter Placement

OBJECTIVE Hemodynamics in cerebral aneurysms are currently investigated toward clinical efficacy using nonstandardized computational simulation techniques. At the same time, flow patterns and velocities are accessible by 4-dimensional phase contrast magnetic resonance imaging (4D pcMRI). Complexity of protocol design and imaging duration has limited the use of this technique in clinical imaging. A new approach is presented to overcome these limitations. METHODS Three-dimensional (3D) replicas of 2 cerebral aneurysms were fabricated by fused deposition prototyping (3D printing) and imaged using 4D pcMRI while connected to a magnetic resonance imaging-compatible continuous flow loop. Acquisition parameters were optimized with imaging times not to exceed 10 minutes. Six patients harboring cerebral aneurysms with sizes ranging from 4.7 to 13.8 mm were imaged with the optimized 4D pcMRI protocol. After treatment with the pipeline embolization device (PED), 4D pcMRI examinations were repeated in 3 patients. RESULTS In all cases, major flow patterns were visualized well; smaller aneurysms posed a challenge because of limited spatial resolution, whereas larger aneurysms contained regions of low velocity resulting in limited contrast in the flow-sensitive images. After PED placement, ordered aneurysmal flow was disrupted and intra-aneurysmal velocity was reduced on average by 24.5% (range, 12.9-31.5%). Exploratory statistical analysis yielded a positive significant correlation (P < 0.01) between changes in inflow velocity and posttreatment intra-aneurysmal flow velocity. CONCLUSIONS 4D pcMRI flow imaging in cerebral aneurysms within a time frame suitable for clinical imaging applications is feasible with optimized acquisition parameters, thereby enabling quantification of intra-aneurysmal flow changes after flow diverter device treatment.

Augmented Reality with Virtual Cerebral Aneurysms: A Feasibility Study

OBJECTIVE Advanced magnetic resonance imaging (MRI) acquisition methods such as 4D phase contrast magnetic resonance imaging (4D pcMRI) have found widespread applications in assessing hemodynamics in cerebral aneurysms. One of the goals is the identification of a hemodynamic scenario predictive of aneurysm rupture. Because of the technical complexity the 4D pcMRI technology, challenges exist in extracting and communicating the wealth of information contained in the MRI image data, in particular, to a multidisciplinary team of health professionals and basic scientists. METHODS Here we introduce a new resource in the form of a commercially available optical see-through head-mounted display, which allows augmenting the real world by computer-generated virtual objects. RESULTS An image processing algorithm was presented for integrating 3D surface models derived from 3D rotational angiography data, 3D time-of-flight MRI data, and 4D pcMRI data into the augmented reality environment. This new approach was successfully evaluated on blood flow data acquired before and after flow diverter treatment in 6 patients harboring a cerebral aneurysm. CONCLUSIONS Augmented reality may become an additional means for visualizing complex medical data, in particular complex flows as illustrated here.

Higher Neural Correlates in Multiple Sclerosis Patients with Neurogenic Overactive Bladder Following Treatment with Intradetrusor Injection of OnabotulinumtoxinA

Purpose: OnabotulinumtoxinA is a well described treatment of neurogenic overactive bladder. While motor effects on the detrusor muscle have been extensively studied, the sensory effects have not. The aim of this study was to evaluate the impact of intradetrusor onabotulinumtoxinA injection on brain activity in female patients with multiple sclerosis and neurogenic overactive bladder. Materials and Methods: We prospectively studied 12 women with stable multiple sclerosis and neurogenic overactive bladder using concurrent functional magnetic resonance imaging and urodynamic studies prior to and 6 to 10 weeks following onabotulinumtoxinA injection. Individual functional magnetic resonance imaging activation maps at the time of strong urgency were averaged before and after onabotulinumtoxinA injection where areas of significant activation were identified. Results: After onabotulinumtoxinA injection functional magnetic resonance imaging activation increased in the right cingulate body (p = 0.0012), the left posterior cingulate (p = 0.02), the left anterior cingulate (p = 0.0015), the right prefrontal cortex (p = 0.0015), the insula (p = 0.0138) and the pons micturition center (p = 0.05). Sparse areas showed decreased activity, including the left cerebellum (p = 0.001), the left fusiform gyrus (p = 0.065) and the bilateral lentiform nucleus (p = 0.026). Conclusions: Intradetrusor injection of onabotulinumtoxinA appeared to increase the activity of most brain regions known to be involved in the sensation and process of urinary urgency in female patients with multiple sclerosis and neurogenic overactive bladder. To our knowledge this is the first study of its kind to evaluate the possible effects of onabotulinumtoxinA at the human brain level where sensory awareness is located. This activation pattern may be used to further phenotype patients to optimize therapy or determine the sensory effects of onabotulinumtoxinA beyond the bladder.

Similarity of functional connectivity patterns in patients with multiple sclerosis who void spontaneously versus patients with voiding dysfunction

To investigate if Multiple Sclerosis (MS) lesion characteristics affect functional brain connectivity (FC) during bladder voiding.

F161. Evolution of EEG-rfMRI bold activation maps during a focal seizure in a patient with medically refractory epilepsy

Introduction Simultaneous EEG recordings during MRI have been used as a research tool to define the epileptogenic zone. Most of the data available has relied on MRI blood oxygenation level dependent signal (BOLD) changes during interictal spikes. The literature is limited regarding BOLD changes during ictal activity. We analyzed the BOLD activation maps during a focal onset electrographic seizure in a patient with medically refractory epilepsy. In addition, limited data is available regarding evolution of changes in functional connectivity maps compared to the resting state. Methods A patient with known medically refractory focal epilepsy underwent a resting fMRI-EEG study. Our protocol includes two twenty-minute resting state scanning sessions (3 T, Philips Ingenia) with simultaneous electroencephalography recorded with a Brain Vision fMRI EEG compatible system. Post-acquisition processing was performed to eliminate MRI artifact and EEG data was reviewed. A focal seizure was identified on EEG lasting approximately 6 min. The EEG was reviewed by 2 independent epileptologists who were in agreement regarding onset and duration of seizure. Twenty-four second blocks of rfMRI data were processed using AFNI (Analysis of Functional NeuroImages) program that corresponded to the identified seizure that was recorded with simultaneous EEG recordings. Sequential 12 s delays from onset were used to evaluate seizure propagation. Utilizing general linear model (GLM) fMRI Blood-Oxygen-Level Dependent (BOLD) activation maps were created. The differences in BOLD activation maps were compared to period of baseline fMRI recording when no EEG ictal or interictal changes were identified. Results Prior presurgical workup with video EEG monitoring in our patient demonstrated seizure onset in the left frontal region. High resolution 3T MRI was normal. rfMRI BOLD activation maps revealed focal changes in the left precentral gyrus. Seizure propagation was analyzed and images reviewed. Conclusion fMRI is widely available for evaluation of patients with epilepsy and is more readily available than other technologies such as MEG. As demonstrated by our patient, simultaneous EEG and fMRI recordings may be helpful in patients in defining the epileptogenic zone and planning for implantation and respective surgery.

Multiple Aneurysms AnaTomy CHallenge 2018 (MATCH): Phase I: Segmentation

PurposeAdvanced morphology analysis and image-based hemodynamic simulations are increasingly used to assess the rupture risk of intracranial aneurysms (IAs). However, the accuracy of those results strongly depends on the quality of the vessel wall segmentation.MethodsTo evaluate state-of-the-art segmentation approaches, the Multiple Aneurysms AnaTomy CHallenge (MATCH) was announced. Participants carried out segmentation in three anonymized 3D DSA datasets (left and right anterior, posterior circulation) of a patient harboring five IAs. Qualitative and quantitative inter-group comparisons were carried out with respect to aneurysm volumes and ostia. Further, over- and undersegmentation were evaluated based on highly resolved 2D images. Finally, clinically relevant morphological parameters were calculated.ResultsBased on the contributions of 26 participating groups, the findings reveal that no consensus regarding segmentation software or underlying algorithms exists. Qualitative similarity of the aneurysm representations was obtained. However, inter-group differences occurred regarding the luminal surface quality, number of vessel branches considered, aneurysm volumes (up to 20%) and ostium surface areas (up to 30%). Further, a systematic oversegmentation of the 3D surfaces was observed with a difference of approximately 10% to the highly resolved 2D reference image. Particularly, the neck of the ruptured aneurysm was overrepresented by all groups except for one. Finally, morphology parameters (e.g., undulation and non-sphericity) varied up to 25%.ConclusionsMATCH provides an overview of segmentation methodologies for IAs and highlights the variability of surface reconstruction. Further, the study emphasizes the need for careful processing of initial segmentation results for a realistic assessment of clinically relevant morphological parameters.