Magnetic Resonance Materials in Physics, Biology and Medicine最新文献

{"title":"Comparing repeatability metrics for quantitative susceptibility mapping in the head and neck.","authors":"Matthew T Cherukara, Karin Shmueli","doi":"10.1007/s10334-025-01229-3","DOIUrl":"https://doi.org/10.1007/s10334-025-01229-3","url":null,"abstract":"<p><strong>Objective: </strong>Quantitative susceptibility mapping (QSM) is a technique that has been demonstrated to be highly repeatable in the brain. As QSM is applied to other parts of the body, it is necessary to investigate metrics for quantifying repeatability, to enable optimization of repeatable QSM reconstruction pipelines beyond the brain.</p><p><strong>Materials and methods: </strong>MRI data were acquired in the head and neck (HN) region in ten healthy volunteers, who underwent six acquisitions across two sessions. QSMs were reconstructed using six representative state-of-the-art techniques. Repeatability of the susceptibility values was compared using voxel-wise metrics (normalized root mean squared error and XSIM) and ROI-based metrics (within-subject and between-subject standard deviation, coefficient of variation (CV), intraclass correlation coefficient (ICC)).</p><p><strong>Results: </strong>Both within-subject and between-subject variations were smaller than the variation between QSM dipole inversion methods, in most ROIs. autoNDI produced the most repeatable susceptibility values, with ICC > 0.75 in three of six HN ROIs with an average ICC of 0.66 across all ROIs. Joint consideration of standard deviation and ICC offered the best metric of repeatability for comparisons between QSM methods, given typical distributions of positive and negative QSM values.</p><p><strong>Discussion: </strong>Repeatability of QSM in the HN region is highly dependent on the dipole inversion method chosen, but the most repeatable methods (autoNDI, QSMnet, TFI) are only moderately repeatable in most HN ROIs.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143537442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anatomical zone and tissue type impacts the repeatability of quantitative MRI parameters and radiomic features for longitudinal monitoring of treatment response in the prostate.","authors":"Yu-Feng Wang, Sirisha Tadimalla, Lois Holloway, Niluja Thiruthaneeswaran, Annette Haworth","doi":"10.1007/s10334-025-01231-9","DOIUrl":"https://doi.org/10.1007/s10334-025-01231-9","url":null,"abstract":"<p><strong>Objective: </strong>To (1) establish the repeatability coefficient (%RC) of region of interest (ROI) and voxel-wise measurements of a comprehensive range of quantitative MRI (qMRI) parameters and radiomic features in the prostate, and (2) assess the impact of different tissue types (benign vs tumor) and anatomical zones (peripheral, PZ, and non-peripheral, nPZ) on the %RCs.</p><p><strong>Methods: </strong>Test-retest qMRI was acquired in ten prostate cancer patients and six healthy volunteers. Parametric maps of apparent diffusion coefficient (ADC), diffusion coefficient (D), perfusion fraction (f), hypoxia score (HS), longitudinal relaxation time (T1), and observed transverse relaxation rate (R2*) were calculated. Fifty-nine radiomic feature maps were calculated from each of the parametric maps and T2-weighted images. The %RCs between tissue type and anatomical zones were compared using the Student's t test at 95% significance level.</p><p><strong>Results: </strong>The %RC of ADC, D and HS, and up to 118 (out of all 413) radiomic features was significantly different between either anatomical zones, or between tumor and benign tissue, or both.</p><p><strong>Conclusions: </strong>DWI-derived parameters and a portion of their radiomic features require %RCs to be established specifically for anatomical zones, tumor and benign tissues. The remaining qMRI parameters and features can have a single threshold for the whole prostate.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143476821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Field-cycling imaging yields repeatable brain R₁ dispersion measurement at fields strengths below 0.2 Tesla with optimal fitting routine.","authors":"Nicholas Senn, P James Ross, Reina Ayde, Vasiliki Mallikourti, Adarsh Krishna, Charly James, Clarisse F de Vries, Lionel M Broche, Gordon D Waiter, Mary Joan MacLeod","doi":"10.1007/s10334-025-01230-w","DOIUrl":"https://doi.org/10.1007/s10334-025-01230-w","url":null,"abstract":"<p><strong>Objectives: </strong>By rapidly changing magnetic field strength between 0.2 and 200 mT during the pulse sequence Field-Cycling Imaging (FCI) makes it possible to identify and evaluate new quantitative markers of pathology derived from dispersion of spin-lattice relaxation rate (R₁) in vivo. The aim of this work was to determine the most effective approach to reliably estimate multi-field R₁ dispersion measurements in brain tissue using FCI.</p><p><strong>Materials and methods: </strong>This repeatability study consisted of twenty participants with moderate or severe small vessel disease. Each participant underwent 3 T MRI and FCI scans, repeated 30 days apart. After R₁ maps were generated at 0.2, 2, 20, and 200 mT, co-registered tissue labels generated from 3 T MRI were used to extract tissue averaged values of R₁ dispersion from regions of white matter (WM) and WM hyperintensities (WMHs).</p><p><strong>Results: </strong>The fitted model which yielded best overall image contrast between WM and WMH regions and R₁ dispersion model adherence was determined. Tissue averaged values of R₁ (0.2 mT) and R₁ dispersion slope exhibited Cohen's d effect sizes of 3.07 and 1.48, respectively, between regions of WM and WMH. The cohort study results were repeatable between study visits.</p><p><strong>Discussion: </strong>Differences in R₁ measurements could repeatably be discerned between normal and abnormal appearing brain tissues.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143425724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A method to measure renal inner medullary perfusion using MR renography.","authors":"A de Boer, K Sharma, B Alhummiany, S P Sourbron","doi":"10.1007/s10334-025-01225-7","DOIUrl":"https://doi.org/10.1007/s10334-025-01225-7","url":null,"abstract":"<p><strong>Objective: </strong>In the kidney, the medulla is most susceptible to damage in case of hampered perfusion or oxygenation. Due to separate regulation of cortical and medullary perfusion, measurement of both is crucial to improve the understanding of renal pathophysiology. We aim to develop and evaluate a physiologically accurate model to measure renal inner medullary (F_med) and cortical perfusion (F_cor) separately.</p><p><strong>Materials and methods: </strong>We developed a 7-compartment model of renal perfusion and used an iterated approach to fit 10 free parameters. Model stability and accuracy were tested on both patient data and simulations. Cortical perfusion and F_T (tubular flow or glomerular filtration rate per unit of tissue volume) were compared to a conventional 2-compartment filtration model.</p><p><strong>Results: </strong>Average (standard deviation) F_med was 37(23)mL/100 mL/min. Fitting stability as expressed by the median (interquartile range) coefficient of variation between fits was 0.0(0.0-5.8)%, with outliers up to 81%. In simulations, F_med was underestimated by around 8%. Intra-class correlation coefficients for F_cor and F_T as measured with the 2- and 7- compartment model were 0.87 and 0.63, respectively.</p><p><strong>Discussion: </strong>We developed a pharmacokinetic model closely following renal physiology. Although the results were vulnerable for overfitting, relatively stable results could be obtained even for F_med.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143425658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Brain tumor detection and segmentation using deep learning.","authors":"Rafia Ahsan, Iram Shahzadi, Faisal Najeeb, Hammad Omer","doi":"10.1007/s10334-024-01203-5","DOIUrl":"10.1007/s10334-024-01203-5","url":null,"abstract":"<p><strong>Objectives: </strong>Brain tumor detection, classification and segmentation are challenging due to the heterogeneous nature of brain tumors. Different deep learning-based algorithms are available for object detection; however, the performance of detection algorithms on brain tumor data has not been widely explored. Therefore, we aim to compare different object detection algorithms (Faster R-CNN, YOLO & SSD) for brain tumor detection on MRI data. Furthermore, the best-performing detection network is paired with a 2D U-Net for pixel-wise segmentation of abnormal tumor cells.</p><p><strong>Materials and methods: </strong>The proposed model was evaluated on the Brain Tumor Figshare (BTF) dataset, and the best-performing detection network cascaded with 2D U-Net for pixel-wise segmentation of tumors. The best-performing detection network was also fine-tuned on BRATS 2018 data to detect and classify the glioma tumor.</p><p><strong>Results: </strong>For the detection of three tumor types, YOLOv5 achieved the highest mAP of 89.5% on test data compared to other networks. For segmentation, YOLOv5 combined with 2D U-Net achieved a higher DSC compared to the 2D U-Net alone (DSC: YOLOv5 + 2D U-Net = 88.1%; 2D U-Net = 80.5%). The proposed method was compared with the existing detection and segmentation network i.e. Mask R-CNN and achieved a higher mAP (YOLOv5 + 2D U-Net = 89.5%; Mask R-CNN = 67%) and DSC (YOLOv5 + 2D U-Net = 88.1%; Mask R-CNN = 44.2%).</p><p><strong>Conclusion: </strong>In this work, we propose a deep-learning-based method for multi-class tumor detection, classification and segmentation that combines YOLOv5 with 2D U-Net. The results show that the proposed method not only detects different types of brain tumors accurately but also delineates the tumor region precisely within the detected bounding box.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":"13-22"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142133157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep learning for efficient reconstruction of highly accelerated 3D FLAIR MRI in neurological deficits.","authors":"Luka C Liebrand, Dimitrios Karkalousos, Émilie Poirion, Bart J Emmer, Stefan D Roosendaal, Henk A Marquering, Charles B L M Majoie, Julien Savatovsky, Matthan W A Caan","doi":"10.1007/s10334-024-01200-8","DOIUrl":"10.1007/s10334-024-01200-8","url":null,"abstract":"<p><strong>Objective: </strong>To compare compressed sensing (CS) and the Cascades of Independently Recurrent Inference Machines (CIRIM) with respect to image quality and reconstruction times when 12-fold accelerated scans of patients with neurological deficits are reconstructed.</p><p><strong>Materials and methods: </strong>Twelve-fold accelerated 3D T2-FLAIR images were obtained from a cohort of 62 patients with neurological deficits on 3 T MRI. Images were reconstructed offline via CS and the CIRIM. Image quality was assessed in a blinded and randomized manner by two experienced interventional neuroradiologists and one experienced pediatric neuroradiologist on imaging artifacts, perceived spatial resolution (sharpness), anatomic conspicuity, diagnostic confidence, and contrast. The methods were also compared in terms of self-referenced quality metrics, image resolution, patient groups and reconstruction time. In ten scans, the contrast ratio (CR) was determined between lesions and white matter. The effect of acceleration factor was assessed in a publicly available fully sampled dataset, since ground truth data are not available in prospectively accelerated clinical scans. Specifically, 451 FLAIR scans, including scans with white matter lesions, were adopted from the FastMRI database to evaluate structural similarity (SSIM) and the CR of lesions and white matter on ranging acceleration factors from four-fold up to 12-fold.</p><p><strong>Results: </strong>Interventional neuroradiologists significantly preferred the CIRIM for imaging artifacts, anatomic conspicuity, and contrast. One rater significantly preferred the CIRIM in terms of sharpness and diagnostic confidence. The pediatric neuroradiologist preferred CS for imaging artifacts and sharpness. Compared to CS, the CIRIM reconstructions significantly improved in terms of imaging artifacts and anatomic conspicuity (p < 0.01) for higher resolution scans while yielding a 28% higher SNR (p = 0.001) and a 5.8% lower CR (p = 0.04). There were no differences between patient groups. Additionally, CIRIM was five times faster than CS was. An increasing acceleration factor did not lead to changes in CR (p = 0.92), but led to lower SSIM (p = 0.002).</p><p><strong>Discussion: </strong>Patients with neurological deficits can undergo MRI at a range of moderate to high acceleration. DL reconstruction outperforms CS in terms of image resolution, efficient denoising with a modest reduction in contrast and reduced reconstruction times.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":"1-12"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11790796/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142108914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphology of the human inner ear and vestibulocochlear nerve assessed using 7 T MRI.","authors":"Kingkarn Aphiwatthanasumet, Ketan Jethwa, Paul Glover, Gerard O'Donoghue, Dorothee Auer, Penny Gowland","doi":"10.1007/s10334-024-01213-3","DOIUrl":"10.1007/s10334-024-01213-3","url":null,"abstract":"<p><strong>Objective: </strong>To optimize high-resolution 7 T MRI of the cochlea and measure normal cochlea and the cochlear nerve morphometry in vivo.</p><p><strong>Materials and methods: </strong>Eight volunteers with normal hearing were scanned at 7 T using an optimized protocol. Two neuroradiologists independently scored image quality. The basal turn lumen diameter (BTLD), height, width, length and volume of the cochlear, long (LD) and short (SD) diameter the calculated cross-sectional area (CSA) of the cochlear nerve were measured. Intra and inter-observer reliability was assessed using intraclass correlation (ICC).</p><p><strong>Results: </strong>3D T2W DRIVE combined with dielectric pads, allowed acquisition of high-resolution images showing detailed structures, such as the crista ampullaris in the semicircular canals. The overall grading scores from neuroradiologists were excellent. In the left ear, averaging over all subjects gave BTLD of 2.6 ± 0.05 mm, height of 4.9 ± 0.1 mm, width of 4.4 ± 0.2 mm, length of 36.5 ± 0.4 mm, volume of 0.16 ± 0.02 ml, LD of 1.31 ± 0.1 mm, SD of 1.06 ± 0.1 mm, and CSA of 1.1 ± 0.1 mm². The right ear gave BTLD of 2.6 ± 0.04 mm, height of 4.9 ± 0.1 mm, width of 4.4 ± 0.3 mm, length of 35.5 ± 0.4 mm, volume of 0.16 ± 0.02 ml, LD of 1.29 ± 0.1 mm, SD of 1.07 ± 0.1 mm, and CSA of 1.10 ± 0.2 mm². No statistically significant difference was found between the sides of the head (p-value > 0.05). The intra-observer reliability was high (0.77-0.94), while the inter-observer reliability varied from moderate to high (0.55-0.81).</p><p><strong>Conclusion: </strong>7 T MRI can provide excellent visualization of the internal structure of the cochlear and of the vestibulocochlear nerve in vivo.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":"121-130"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11790716/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142623021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extraction of 3D trajectories of mandibular condyles from 2D real-time MRI.","authors":"Karyna Isaieva, Justine Leclère, Guillaume Paillart, Guillaume Drouot, Jacques Felblinger, Xavier Dubernard, Pierre-André Vuissoz","doi":"10.1007/s10334-024-01214-2","DOIUrl":"10.1007/s10334-024-01214-2","url":null,"abstract":"<p><strong>Objective: </strong>Computing the trajectories of mandibular condyles directly from MRI could provide a comprehensive examination, providing both anatomical and kinematic details. This study aimed to investigate the feasibility of extracting 3D condylar trajectories from 2D real-time MRI.</p><p><strong>Materials and methods: </strong>Twenty healthy subjects underwent real-time MRI while performing jaw opening and closing movements. One axial and two sagittal slices were segmented using a U-Net-based algorithm. After motion compensation, the centers of mass of the resulting masks were projected onto the coordinate system based on anatomical markers and temporally adjusted. The quality of the computed trajectories was evaluated using metrics designed to estimate movement reproducibility, head motion, and slice placement symmetry.</p><p><strong>Results: </strong>The segmentation of the axial slices demonstrated good-to-excellent quality; however, the segmentation of the sagittal slices required some fine-tuning. On average, the intercuspal position shifted by 0.6 mm after an opening-closing cycle. The difference in the superior-inferior coordinate of the condyles in the intercuspal position was 1.5 mm on average. Some subjects demonstrated a significant discrepancy between the axial and the sagittal trajectories.</p><p><strong>Discussion: </strong>Real-time MRI enables the extraction of condylar trajectories for evaluating some clinically relevant parameters. However, attention is required during patient installation and image acquisition.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":"131-140"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142909832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Free-breathing qRF-MRF with pilot tone respiratory motion navigator for T₁, T₂, T₂*, and off-resonance mapping of the human body at 3 T.","authors":"Madison E Kretzler, Sherry S Huang, Jessie E P Sun, Leonardo K Bittencourt, Yong Chen, Mark A Griswold, Rasim Boyacioglu","doi":"10.1007/s10334-024-01209-z","DOIUrl":"10.1007/s10334-024-01209-z","url":null,"abstract":"<p><p>Standard quantitative abdominal MRI techniques are time consuming, require breath-holds, and are susceptible to patient motion artifacts. Magnetic resonance fingerprinting (MRF) is naturally multi-parametric and quantifies multiple tissue properties, including T₁ and T₂. This work includes T₂* and off-resonance mapping into a free-breathing MRF framework utilizing a pilot tone navigator. The new acquisition and reconstruction are compared to current clinical standards. Prospective. Ten volunteers. 3 T scanner, Quadratic-RF MRF, Balanced SSFP, Inversion recovery spin-echo, LiverLab. MRI ROIs were evaluated in the liver, spleen, pancreas, kidney (cortex and medulla), and paravertebral muscle by two abdominal imaging investigators for ten healthy adult volunteers for clinical standard, breath-Hold (BH) qRF-MRF, and free-breathing qRF-MRF with pilot-tone (PT) acquisitions. Bland-Altman analysis as well as Student's T tests were used to evaluate and compare the respective ROI analyses. Quantitative values between breath-Hold (BH) and free-breathing qRF-MRF with pilot-tone (PT) results show good agreement with clinical standard T1 and T2 quantitative mapping, and Dixon q-VIBE (acquired using the Siemens LiverLAB). In this work, we show free-breathing abdominal MRF (T₁, T₂) with T₂* results that are quantitatively comparable to current breath-hold MRF and clinical techniques.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":"85-95"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Signal-to-noise trade-offs between magnet diameter and shield-to-coil distance for cylindrical Halbach-based portable MRI systems for neuroimaging.","authors":"Javad Parsa, Andrew Webb","doi":"10.1007/s10334-024-01210-6","DOIUrl":"10.1007/s10334-024-01210-6","url":null,"abstract":"<p><strong>Objective: </strong>To investigate the trade-off between magnet bore diameter and the distance between the conductive Faraday shield and RF head coil for low-field point-of-care neuroimaging systems.</p><p><strong>Methods: </strong>Electromagnetic simulations were performed for three different Faraday shield geometries and two commonly used RF coil designs (spiral and solenoid) to assess the effects of a close-fitting shield on the RF coil's transmit and receive efficiencies. Experimental measurements were performed to confirm the accuracy of the simulations. Parallel simulations were performed to assess the static magnet ( <math><msub><mi>B</mi> <mn>0</mn></msub> </math> ) field as a function of the magnet bore diameter. The obtainable SNR was then calculated as a function of these two related variables.</p><p><strong>Results: </strong>Simulations of the RF coil characteristics and <math><msubsup><mi>B</mi> <mrow><mn>1</mn></mrow> <mo>+</mo></msubsup> </math> transmit efficiencies agreed well with corresponding experimentally determined parameters. Overall, the RF coil transmit efficiency was, as expected, higher when the gap between the shield and coil increased. The calculated intrinsic SNR showed that maximum SNR would be obtained for a cylindrical shield of diameter 310 mm with an inner diameter of the magnet of 320 mm (assuming 10 mm for the gradient coils).</p><p><strong>Conclusion: </strong>This work presents an overview of the trade-offs in transmit efficiencies for RF coils used for POC MRI neuroimaging as a function of coil-to-shield distance and inner diameter of the Halbach magnet. Results show that there is a relatively shallow optimum between a magnet diameter of 290 and 330 mm, with values falling more than 10% if either smaller or larger magnets are used.</p>","PeriodicalId":18067,"journal":{"name":"Magnetic Resonance Materials in Physics, Biology and Medicine","volume":" ","pages":"97-105"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11790726/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}