Magnetic Resonance Imaging Artifacts Research Articles

ARTIFACTS IN MAGNETIC RESONANCE IMAGING CAUSED BY DENTAL MATERIALS: A SYSTEMATIC REVIEW.

Bohner L, Hanisch M, Sesma N, Blanck-Lubarsch M, Kleinheinz J. Artifacts in magnetic resonance imaging caused by dental materials: a systematic review. Dentomaxillofac Radiol (2022) 10.1259/dmfr.20210450. Non-profit, Foundations: Open access funding enabled by Projekt DEAL, Germany. Systematic review.

Reducing cardiac implantable electronic device–induced artefacts in cardiac magnetic resonance imaging

ObjectivesCardiac implantable electronic device (CIED)–induced metal artefacts possibly significantly diminish the diagnostic value of magnetic resonance imaging (MRI), particularly cardiac MR (CMR). Right-sided generator implantation, wideband late-gadolinium enhancement (LGE) technique and raising the ipsilateral arm to the generator during CMR scanning may reduce the CIED-induced image artefacts. We assessed the impact of generator location and the arm-raised imaging position on the CIED-induced artefacts in CMR.MethodsWe included all clinically indicated CMRs performed on patients with normal cardiac anatomy and a permanent CIED with endocardial pacing leads between November 2011 and October 2019 in our institution (n = 171). We analysed cine and LGE sequences using the American Heart Association 17-segment model for the presence of artefacts.ResultsRight-sided generator implantation and arm-raised imaging associated with a significantly increased number of artefact-free segments. In patients with a right-sided pacemaker, the median percentage of artefact-free segments in short-axis balanced steady-state free precession LGE was 93.8% (IQR 9.4%, n = 53) compared with 78.1% (IQR 20.3%, n = 58) for left-sided pacemaker (p < 0.001). In patients with a left-sided implantable cardioverter-defibrillator, the median percentage of artefact-free segments reached 87.5% (IQR 6.3%, n = 9) using arm-raised imaging, which fell to 62.5% (IQR 34.4%, n = 9) using arm-down imaging in spoiled gradient echo short-axis cine (p = 0.02).ConclusionsArm-raised imaging represents a straightforward method to reduce CMR artefacts in patients with left-sided generators and can be used alongside other image quality improvement methods. Right-sided generator implantation could be considered in CIED patients requiring subsequent CMR imaging to ensure sufficient image quality.Key Points• Cardiac implantable electronic device (CIED)–induced metal artefacts may significantly diminish the diagnostic value of an MRI, particularly in cardiac MRIs.• Raising the ipsilateral arm relative to the CIED generator is a cost-free, straightforward method to significantly reduce CIED-induced artefacts on cardiac MRIs in patients with a left-sided generator.• Right-sided generator implantation reduces artefacts compared with left-sided implantation and could be considered in CIED patients requiring subsequent cardiac MRIs to ensure adequate image quality in the future.

True location of deep brain stimulation electrodes differs from what is seen on postoperative magnetic resonance images: An anthropomorphic phantom study.

Deep brain stimulation (DBS) is an established yet growing treatment for a range of neurological and psychiatric disorders. Over the last decade, numerous studies have underscored the effect of electrode placement on the clinical outcome of DBS. As a result, imaging is now extensively used for DBS electrode localization, even though the accuracy of different modalities in determining the true coordinates of DBS electrodes is less explored. Postoperative magnetic resonance imaging (MRI) is a gold standard method for DBS electrode localization, however, the geometrical distortion induced by the lead's artifact could limit the accuracy. In this work, we investigated to what degree the difference between the true location of the lead's tip and the location of the tip estimated from the MRI artifact varies depending on the MRI sequence parameters, acquisition plane, phase encoding direction, and the implant"s extracranial trajectory. Clinical Relevance- Results will help researchers and clinicians to estimate the true location of DBS leads and contacts from postoperative MRI scans.

Adjustable and Magnetic Resonance Imaging Conditional Implantation of a Licox Brain Tissue Oxygenation Probe in Neurosurgery: Technical Note

Continuous bedside brain tissue oxygen monitoring is an essential part of managing comatose patients with acute brain injury. Maintenance of adequate brain oxygenation has been established as an important goal in neurocritical care to prevent patients from secondary ischemia. As patients with subarachnoid hemorrhage and traumatic brain injury often require early magnetic resonance imaging, conventionally implanted metal bolts are disadvantageous due to massive artifacts. We hereby report a novel technique of magnetic resonance imaging conditional bedside implantation of a brain tissue oxygenation probe. We performed bedside implantation of a Licox brain tissue oxygenation probe with a peripheral venous cannula that is placed through a plastic bolt placed on a burr hole. Bedside implantation of a Licox brain tissue oxygenation probe was successfully performed in a novel fashion. This article describes the feasibility of a novel technique of bedside implantation of a Licox brain tissue oxygenation probe, resulting in a length-adjustable insertion and rigid fixation without metal artifacts in early magnetic resonance imaging.

Qualitative Assessment of Titanium versus Carbon Fiber/Polyetheretherketone Pedicle Screw–Related Artifacts: A Cadaveric Study

Dorsal instrumentation and decompression are the mainstays of spinal tumor treatment. Replacing titanium screws with carbon fiber-reinforced polyetheretherketone (CFRP) screws can reduce imaging artifacts on neural structures and perturbations of radiation dose. Further reduction of metal content in such screws might enhance the benefit. The aim of this study was to assess the artifacts produced by all-titanium screws (Ti-Ti), CFRP thread-titanium screw heads (C-Ti), and all-CFRP screws (C-C). A cadaveric spine was used to place Ti-Ti, C-Ti, and C-C consecutively from T2 to S1. Computed tomography and 1.5T and 3T magnetic resonance imaging were performed for each screw system. Axial T1- and T2-weighted sequences of representative thoracic and lumbar regions were assessed for artifacts. The artifacts were classified as not relevant, considerable, or severe. We evaluated 92 screws and made 178 artifact assessments. The artifacts were clearly visible in computed tomography scans but did not influence the visualization of intraspinal structures. Severe magnetic resonance imaging artifacts were found in 28% (17/60, mostly in the thoracic spine) of Ti-Ti, 2% (1/60, all T1 sequences) of C-Ti, and 0% of C-C, and considerable artifacts were found in 47% (28/60) of Ti-Ti, 10% (6/60, only 1 T2 sequence) of C-Ti, and 0% of C-C screws (P < 0.001). CFRP pedicle screws reduced the artifact intensity in spinal structures compared with titanium screws, and may be beneficial for planning radiotherapy and for follow-up imaging. C-C demonstrated an enhanced effect on dorsal structures.

Attenuation Coefficient Estimation for PET/MRI With Bayesian Deep Learning Pseudo-CT and Maximum-Likelihood Estimation of Activity and Attenuation.

A major remaining challenge for magnetic resonance-based attenuation correction methods (MRAC) is their susceptibility to sources of magnetic resonance imaging (MRI) artifacts (e.g., implants and motion) and uncertainties due to the limitations of MRI contrast (e.g., accurate bone delineation and density, and separation of air/bone). We propose using a Bayesian deep convolutional neural network that in addition to generating an initial pseudo-CT from MR data, it also produces uncertainty estimates of the pseudo-CT to quantify the limitations of the MR data. These outputs are combined with the maximum-likelihood estimation of activity and attenuation (MLAA) reconstruction that uses the PET emission data to improve the attenuation maps. With the proposed approach uncertainty estimation and pseudo-CT prior for robust MLAA (UpCT-MLAA), we demonstrate accurate estimation of PET uptake in pelvic lesions and show recovery of metal implants. In patients without implants, UpCT-MLAA had acceptable but slightly higher root-mean-squared-error (RMSE) than Zero-echotime and Dixon Deep pseudo-CT when compared to CTAC. In patients with metal implants, MLAA recovered the metal implant; however, anatomy outside the implant region was obscured by noise and crosstalk artifacts. Attenuation coefficients from the pseudo-CT from Dixon MRI were accurate in normal anatomy; however, the metal implant region was estimated to have attenuation coefficients of air. UpCT-MLAA estimated attenuation coefficients of metal implants alongside accurate anatomic depiction outside of implant regions.

Stacked U-Nets with self-assisted priors towards robust correction of rigid motion artifact in brain MRI

Magnetic Resonance Imaging (MRI) is sensitive to motion caused by patient movement due to the relatively long data acquisition time. This could cause severe degradation of image quality and therefore affect the overall diagnosis. In this paper, we develop an efficient retrospective 2D deep learning method called stacked U-Nets with self-assisted priors to address the problem of rigid motion artifacts in 3D brain MRI. The proposed work exploits the usage of additional knowledge priors from the corrupted images themselves without the need for additional contrast data. The proposed network learns the missed structural details through sharing auxiliary information from the contiguous slices of the same distorted subject. We further design a refinement stacked U-Nets that facilitates preserving the spatial image details and improves the pixel-to-pixel dependency. To perform network training, simulation of MRI motion artifacts is inevitable. The proposed network is optimized by minimizing the loss of structural similarity (SSIM) using the synthesized motion-corrupted images from 83 real motion-free subjects. We present an intensive analysis using various types of image priors: the proposed self-assisted priors and priors from other image contrast of the same subject. The experimental analysis proves the effectiveness and feasibility of our self-assisted priors since it does not require any further data scans. The overall image quality of the motion-corrected images via the proposed motion correction network significantly improves SSIM from 71.66% to 95.03% and declines the mean square error from 99.25 to 29.76. These results indicate the high similarity of the brain's anatomical structure in the corrected images compared to the motion-free data. The motion-corrected results of both the simulated and real motion data showed the potential of the proposed motion correction network to be feasible and applicable in clinical practices.

The Development of Monolithic Silicon Carbide Intracortical Neural Interfaces for Long-Term Human Implantation

Silicon Carbide (SiC) has been demonstrated as both a bio- and neuro-compatible wide-band-gap semiconductor with a high thermal conductivity and magnetic susceptibility and may be potentially compatible with human brain tissue. Two single-crystal, solid-state forms of SiC have been used to create monolithic intracortical neural implants (INI) without using physiologically exposed metals or polymers, thus eliminating many known reliability challenges in-vivo through a single, homogenous material. Amorphous SiC (a-SiC) was used to insulate 16-channel functional INI and the electrochemical and MRI compatibility (7T) performance were measured. 4H-SiC interfaces were fabricated using homoepitaxy,alternating epitaxial films of n-type and p-type forming an isolating PN junction which prevents substrate leakage current between the 16 adjacent electrodes and traces fabricated which were formed using deep-reactive ion etching (DRIE). 3C-SiC interfaces were fabricated in a similar fashion, but the epitaial conductive layers were grown on on both bulk crystalline (100) silicon and SOI wafers. In both cases a conformal coating of a-SiC was used as the top-side insulator and windows opened using RIE to allow electrochemical interaction. Electrochemical charaterization achieved through electrochemcial impedance spectroscopy (EIS) and cyclic voltammetry (CV) indicates performance on par, or exceeding, that of Pt reference electrodes with the same form fit. While magnetic resonance imaging (MRI) is an essential, non-contact method used to investigate issues with the nervous system, the high field MRI (e.g., 3 T and higher) necessary for proper diagnosis can be a safety issue for patients with INI due to inductive coupling between the powerful electromagnetic fields and the implanted device. This results in having to use lower electromagnetic field power (less than 1.5T), and therefore lower resolution, which hinders diagnostic prognosis for these patients. In this work the MRI compliance of epitaxial, monolithic SiC INI was studied. The specific absorption rate (SAR), induced heating, and image artifacts caused by the portion of the implant within a brain tissue phantom located in a 7 T small animal MRI machine were estimated and measured via finite element method (FEM) and Fourier-based simulations. Both the simulation and experimental results revealed that free-standing 3C-SiC films had no observable image artifacts compared to silicon and platinum reference materials inside the MRI at 7 T while FEM simulations predicted an ~30% SAR reduction for 3C-SiC compared to Pt. These initial simulations and experiments indicate a SiC monolithic INI may effectively reduce MRI induced heating and image artifacts in high field MRI.

Segmenting electroencephalography wires reduces radiofrequency shielding artifacts in simultaneous electroencephalography and functional magnetic resonance imaging at 7 T.

PurposeSimultaneous scalp electroencephalography and functional magnetic resonance imaging (EEG‐fMRI) enable noninvasive assessment of brain function with high spatial and temporal resolution. However, at ultra‐high field, the data quality of both modalities is degraded by mutual interactions. Here, we thoroughly investigated the radiofrequency (RF) shielding artifact of a state‐of‐the‐art EEG‐fMRI setup, at 7 T, and design a practical solution to limit this issue.MethodsElectromagnetic field simulations and MR measurements assessed the shielding effect of the EEG setup, more specifically the EEG wiring. The effectiveness of segmenting the wiring with resistors to reduce the transmit field disruption was evaluated on a wire‐only EEG model and a simulation model of the EEG cap.ResultsThe EEG wiring was found to exert a dominant effect on the disruption of the transmit field, whose intensity varied periodically as a function of the wire length. Breaking the electrical continuity of the EEG wires into segments shorter than one quarter RF wavelength in air (25 cm at 7 T) reduced significantly the RF shielding artifacts. Simulations of the EEG cap with segmented wires indicated similar improvements for a moderate increase of the power deposition.ConclusionWe demonstrated that segmenting the EEG wiring into shorter lengths using commercially available nonmagnetic resistors is effective at reducing RF shielding artifacts in simultaneous EEG‐fMRI. This prevents the formation of RF‐induced standing waves, without substantial specific absorption rate (SAR) penalties, and thereby enables benefiting from the functional sensitivity boosts achievable at ultra‐high field.

LSTM-Based RNN Framework to Remove Motion Artifacts in Dynamic Multicontrast MR Images with Registration Model

Today, many people under the age of 10 are being examined for brain-related issues, including tumours, without displaying any symptoms. It is not unusual for children to develop brain-related concerns such as tumours and central nervous system disorders, which may affect 15% of the population. Medical experts believe that the irregular eating habits (junk food) and the consumption of pesticide-tainted fruits and vegetables are to blame. The human body is naturally resistant to harmful gears, but only up to a point. If it exceeds the limit, a cell manipulation process is automatically initiated that can remove dangerous inactive tissues from the cell membrane and later grows into tumour blockage in the human body. Thus, the adoption of an advanced computer-based diagnostic system is highly recommended in order to generate visually enhanced images for anomaly identification and infectious tissue segmentation. In most cases, an MR image is chosen since it is easier to distinguish between affected and nonaffected tissue. Conventional convolution neural network (CCNN) mapping and feature extraction are difficult because of the vast volume of data. In addition, it takes a lengthy time for the MRI scanning process to obtain diverse positions for anomaly identification. Aside from the discomfort, the patient may experience motion abnormalities. Recurrent neural network (RNN) classifies tumour regions into several isolated portions much faster and more accurately, so that it can be prevented. To remove motion artefacts from dynamic multicontrast MR images, a novel long short-term memory- (LSTM-) based RNN framework is introduced in this research. With this method, the MR image’s visual quality is improved over CCNN while simultaneously mapping a larger volume and extracting more quiet characteristics than CCNN can. DC-CNN, SMSR-CNN, FMSI-CNN, and DRCA-CNN results are compared. For both low and high signal-to-noise ratios, the suggested LSTM-based RNN framework has gained reasonable feature intelligibility (SNRs). In comparison to previous approaches, it requires less computing and has higher accuracy when it comes to detecting infected portions.

MR Imaging Artifacts in the Head and Neck Region: Pitfalls and Solutions.

MR Imaging artifacts are features appearing in MR images that are not present in the original anatomy. MR imaging artifacts can be patient-related, hardware-related, or signal-processing-related and affect diagnostic quality or mimic pathology. It is necessary to take MR imaging artifacts into consideration when interpreting images. A basic knowledge of MR imaging physics and the potential origin of MR imaging artifacts can help to find solutions to eliminate or reduce the influence of artifacts on image quality by adjusting acquisition parameters appropriately for a better diagnosis.

High-resolution simulation of B0 field conditions in the human heart from segmented computed tomography images.

B0 inhomogeneity leads to imaging artifacts in cardiac magnetic resonance imaging (MRI), in particular dark band artifacts with steady-state free precession pulse sequences. The limited spatial resolution of MR-derived in vivo B0 maps and the lack of population data prevent systematic analysis of the problem at hand and the development of optimized B0 shim strategies. We used readily available clinical computed tomography (CT) images to simulate the B0 conditions in the human heart at high spatial resolution. Calculated B0 fields showed consistency with MRI-based B0 measurements. The B0 maps for both the simulations and in vivo measurements showed local field inhomogeneities in the vicinity of lung tips with dominant Z3 spherical harmonic terms in the field distribution. The presented simulation approach allows for the derivation of B0 field conditions at high spatial resolution from CT images and enables the development of subject- and population-specific B0 shim strategies for the human heart.

Primer on Commonly Occurring MRI Artifacts and How to Overcome Them.

HomeRadioGraphicsVol. 42, No. 3 PreviousNext PhysicsRadioGraphics FundamentalsPrimer on Commonly Occurring MRI Artifacts and How to Overcome ThemChikara Noda, Bharath Ambale Venkatesh, Jennifer D. Wagner, Yoko Kato, Jason M. Ortman, João A. C. Lima Chikara Noda, Bharath Ambale Venkatesh, Jennifer D. Wagner, Yoko Kato, Jason M. Ortman, João A. C. Lima Author AffiliationsFrom the Divisions of Cardiology (C.N., Y.K., J.M.O., J.A.C.L.) and Radiology (B.A.V.), Johns Hopkins University School of Medicine, 600 N Wolfe St, Blalock 524, Baltimore, MD 21287; and Canon Medical Research USA, Cleveland, Ohio (J.D.W.).Address correspondence to J.A.C.L. (e-mail: [email protected]).Chikara NodaBharath Ambale VenkateshJennifer D. WagnerYoko KatoJason M. OrtmanJoão A. C. Lima Published Online:Apr 22 2022https://doi.org/10.1148/rg.210021MoreSectionsFull textPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In AbstractVarious artifacts occur at MRI, and MRI technologists and radiologists must know how to identify and avoid these artifacts so they can consistently produce high-quality images.Suggested Readings Hirokawa Y, Isoda H, Maetani YS, Arizono S, Shimada K, Togashi K. MRI artifact reduction and quality improvement in the upper abdomen with PROPELLER and prospective acquisition correction (PACE) technique. AJR Am J Roentgenol 2008;191(4):1154–1158. Crossref, Medline, Google Scholar Huang SY, Seethamraju RT, Patel P, Hahn PF, Kirsch JE, Guimaraes AR. Body MR Imaging: Artifacts, k-Space, and Solutions. RadioGraphics 2015;35(5):1439–1460. Link, Google Scholar Runge M, Ibrahim EH, Bogun F, et al. Metal Artifact Reduction in Cardiovascular MRI for Accurate Myocardial Scar Assessment in Patients With Cardiac Implantable Electronic Devices. AJR Am J Roentgenol 2019;213(3):555–561. Crossref, Medline, Google Scholar Stadler A, Schima W, Ba-Ssalamah A, Kettenbach J, Eisenhuber E. Artifacts in body MR imaging: their appearance and how to eliminate them. Eur Radiol 2007;17(5):1242–1255. Crossref, Medline, Google Scholar Tsuchihashi T. Artifact of MRI [in Japanese]. Nippon Hoshasen Gijutsu Gakkai Zasshi 2003;59(11):1370–1377. Crossref, Medline, Google ScholarArticle HistoryReceived: Feb 1 2021Revision requested: Apr 20 2021Revision received: June 29 2021Accepted: July 9 2021Published online: Apr 22 2022Published in print: May 2022 FiguresReferencesRelatedDetailsCited ByPostsurgical Evaluation of the Pediatric Foot and AnkleMaria PilarAparisi Gómez, AlbertoBazzocchi, PaoloSimoni, Emilio J.Inarejos Clemente2022 | Seminars in Musculoskeletal Radiology, Vol. 26, No. 06Accompanying This ArticlePrimer on Commonly Occurring MRI Artifacts and How to Overcome ThemApr 22 2022Default Digital Object SeriesRecommended Articles Respiratory Motion Management in Abdominal MRI: Radiology In TrainingRadiology2022Volume: 306Issue: 1pp. 47-53Invited Commentary on “Optimizing Diffusion-Tensor Imaging Acquisition for Spinal Cord Assessment,” with Response from Dr Martín Noguerol et alRadioGraphics2020Volume: 40Issue: 2pp. 428-431Impact of Data-driven Respiratory Gating in Clinical PETRadiology2016Volume: 281Issue: 1pp. 229-238Validation of Software Gating: A Practical Technology for Respiratory Motion Correction in PETRadiology2016Volume: 281Issue: 1pp. 239-248MR Neurography of Peripheral Nerve Injury in the Presence of Orthopedic Hardware: Technical ConsiderationsRadiology2021Volume: 300Issue: 2pp. 246-259See More RSNA Education Exhibits A Primer on Commonly Occurring MRI Artifacts and How to Overcome ThemDigital Posters2020Up-to-Date Technique for Improvement of CT and MRI Imaging Quality in the Head and Neck: Theory, Clinical ApplicationsDigital Posters2019Pulse Sequences Used in Musculoskeletal MRI Exams: A Review for Residents and FellowsDigital Posters2018 RSNA Case Collection Orbital blowout fractureRSNA Case Collection2020Metastatic invasive lobular breast carcinomaRSNA Case Collection2021Pulmonary SequestrationRSNA Case Collection2022 Vol. 42, No. 3 Slide PresentationMetrics Altmetric Score PDF download

The Influence of Magnetic Resonance Imaging Artifacts on CNN-Based Brain Cancer Detection Algorithms

The Influence of Magnetic Resonance Imaging Artifacts on CNN-Based Brain Cancer Detection Algorithms

Artifacts in magnetic resonance imaging caused by dental materials: a systematic review.

The purpose of this systematic review was to search in literature in which severity unintended effects are caused by dental materials in magnetic resonance imaging (MRI), such as to evaluate whether these artifacts hamper the diagnosis in the head and neck region. Clinical studies showing the severity of artifacts which dental materials are capable of causing in MRI of head and neck, such as their influence on diagnostic accuracy, were included in this review. The searches were conducted in four electronic databases (PubMed/Medline, Embase, Scopus and Web of Science), and a manual search was made in the reference lists of papers screened for full-text reading. Risk of bias was assessed using "Quality Assessment Tool for Diagnostic Accuracy Studies-2" (QUADAS-2). The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was used to assess the quality of evidence. From 151 studies selected for full-reading, 19 were considered eligible for this review. Artifacts caused by orthodontic appliances were well-documented, and stainless steel brackets were the materials most likely to cause artifacts in MR imaging of head and neck. The literature was scarce for dental implants and restorations. Diagnoses within the oral cavity, but also those of the brain and craniofacial structures, were affected. Artifacts caused by orthodontic appliances may affect the diagnosis in oral cavity and craniofacial structures. Data regarding dental implants and prosthodontics restorations were inconclusive. The severity of artifacts in MRI and their influence on diagnosis is dependent on dental material features, location in the oral cavity, and magnetic resonance parameters.

Analysis of Physicochemical Natures of Modern Artifacts in MRI

Magnetic resonance imaging (MRI) is very useful in the medical sector as it uses radio waves and robust magnetic fields to produce images of the inside of the human body. MRIs are so helpful in pathologies. However, artifacts in MRI occur due to the complex nature of MRI. Artifacts in MRI may reduce the examination quality and may also be confused with pathology. Failing to identify artifacts in MRI can bring troubles. Hence, it’s very important to reduce or avoid artifacts in MRI. The major reasons behind artifacts in MRI are improper action of the MRI scanner, magnetic susceptibility, motion, chemical shifts, variation in signal intensity, etc. Due to MRI artifacts, patients can suffer from serious problems. Therefore, we have analyzed the physicochemical natures of artifacts in MRI. The research has made attempts to identify various types of artifacts in MRI and find out the causes of these artifacts. There have been samples of various types of artifacts based on which the analyses have been done. Based on these identifications of artifacts, there have also been discussions and analyses on how to avoid artifacts in MRI.

Application of Radial Acquisition Multishot sequence in Multiparametric MRI of prostate

The purpose of our study is to evaluate the T2 weighted sequence with multishot radial sampling (Radial Acquisition Multi-shot) also known as Multivane sequence in Philips Healthcare, introduced by J.Pipe with the aim to minimize motion artifacts in Magnetic Resonance Imaging (MRI). In the field of prostate MRI the Multivane sequence is useful in non-cooperating patients and/or patients who, due to their clinical conditions (such as glaucoma, arrhythmia, and severe benign prostatic hypertrophy), have not been receiving intravenous antispasmodic agents, administered for limiting the motility of intestinal loops, particularly rectum. The Multivane sequence is based on the collection of data throughout parallel multiple lines in periodic rotation around the center of k-space and advanced mathematical reconstruction. As the data at the center of k-space (low frequency) containing signals with maximum amplitude will be continuously sampled, this trajectory will provide an excellent contrast-noise ratio (CNR) and spatial resolution, without motion artifacts responsible of "blurring" in the final image. Specifically, each given point of the periphery of the k-space will be sampled by a certain line and the next one and so on, and for the final image reconstruction, once multiple data will be estimated, different algorithms will be used to compensate for motion artifacts. In this study we compared the Radial Acquisition Multishot TSE Multivane (Philips Healthcare) with the classic T2W TSE sequences with linear Cartesian sampling. Multivane sequences have proven to be superior and therefore of greater utility compared to sequences with linear Cartesian data sampling, in patients who can not receiving spasmolytic agents.

APPLICATION OF RADIAL ACQUISITION MULTISHOT SEQUENCE IN MULTIPARAMETRIC MRI OF PROSTATE

The purpose of our study is to evaluate the T2 weighted sequence with multishot radial sampling (Radial AcquisitionMulti-shot) also known as Multivane sequence in Philips Healthcare, introduced by J.Pipe with the aim to minimizemotion artifacts in Magnetic Resonance Imaging (MRI).In the field of prostate MRI the Multivane sequence is useful in non-cooperating patients and/or patients who, dueto their clinical conditions (such as glaucoma, arrhythmia, and severe benign prostatic hypertrophy), have not beenreceiving intravenous antispasmodic agents, administered for limiting the motility of intestinal loops, particularlyrectum.The Multivane sequence is based on the collection of data throughout parallel multiple lines in periodic rotationaround the center of k-space and advanced mathematical reconstruction. As the data at the center of k-space (lowfrequency) containing signals with maximum amplitude will be continuously sampled, this trajectory will provide anexcellent contrast-noise ratio (CNR) and spatial resolution, without motion artifacts responsible of “blurring” in thefinal image. Specifically, each given point of the periphery of the k-space will be sampled by a certain line and thenext one and so on, and for the final image reconstruction, once multiple data will be estimated, different algorithmswill be used to compensate for motion artifacts.In this study we compared the Radial Acquisition Multishot TSE Multivane (Philips Healthcare) with the classic T2WTSE sequences with linear Cartesian sampling. Multivane sequences have proven to be superior and therefore ofgreater utility compared to sequences with linear Cartesian data sampling, in patients who can not receiving spasmolytic agents.

Effect of head motion-induced artefacts on the reliability of deep learning-based whole-brain segmentation

Due to their robustness and speed, recently developed deep learning-based methods have the potential to provide a faster and hence more scalable alternative to more conventional neuroimaging analysis pipelines in terms of whole-brain segmentation based on magnetic resonance (MR) images. These methods were also shown to have higher test–retest reliability, raising the possibility that they could also exhibit superior head motion tolerance. We investigated this by comparing the effect of head motion-induced artifacts in structural MR images on the consistency of segmentation performed by FreeSurfer and recently developed deep learning-based methods to a similar extent. We used state-of-the art neural network models (FastSurferCNN and Kwyk) and developed a new whole-brain segmentation pipeline (ReSeg) to examine whether reliability depends on choice of deep learning method. Structural MRI scans were collected from 110 participants under rest and active head motion and were evaluated for image quality by radiologists. Compared to FreeSurfer, deep learning-based methods provided more consistent segmentations across different levels of image quality, suggesting that they also have the advantage of providing more reliable whole-brain segmentations of MR images corrupted by motion-induced artifacts, and provide evidence for their practical applicability in the study of brain structural alterations in health and disease.

Influence of head orientation and implantation site of a novel transcutaneous bone conduction implant on MRI metal artifact reduction sequence

PurposeThe use of magnetic resonance imaging (MRI) is often limited in patients with auditory implants because of the presence of metallic components and magnets. The aim of this study was to evaluate the clinical usefulness of a customized MRI sequence for metal artifact suppression in patients with BONEBRIDGETM BCI 602 implants (MED-EL, Innsbruck, Austria), the successor of the BCI 601 model.MethodsUsing our in-house developed and customized metal artifact reduction sequence (SEMAC-VAT WARP), MRI artifacts were evaluated qualitatively and quantitatively. MRI sequences were performed with and without artifact reduction on two whole head specimens with and without the BCI 602 implant. In addition, the influence of two different implantation sites (mastoid versus retrosigmoid) and head orientation on artifact presence was investigated.ResultsArtifact volume was reduced by more than the 50%. Results were comparable with those obtained with the BCI 601, showing no significant differences in the dimensions of artifacts caused by the implant.ConclusionSEMAC-VAT WARP was once more proved to be efficient at reducing metal artifacts on MR images. The dimensions of artifacts associated with the BCI 602 are not smaller than those caused by the BCI 601.