Grace Hutchinson, Jeromy Thotland, Pramod K Pisharady, Michael Garwood, Christophe Lenglet, Risto A Kauppinen
Understanding the effects of white matter (WM) axon fibre microstructure on T1 relaxation is important for neuroimaging. Here, we have studied the interrelationship between T1 and axon fibre configurations at 3T and 7T. T1 and S0 (=signal intensity at zero TI) were computed from MP2RAGE images acquired with six inversion recovery times. Multishell diffusion MRI images were analysed for fractional anisotropy (FA); MD; V1; the volume fractions for the first (f1), second (f2) and third (f3) fibre configuration; and fibre density cross-section images for the first (fdc1), second (fdc2) and third (fdc3) fibres. T1 values were plotted as a function of FA, f1, f2, f3, fdc1, fdc2 and fdc3 to examine interrelationships between the longitudinal relaxation and the diffusion MRI microstructural measures. T1 values decreased with increasing FA, f1 and f2 in a nonlinear fashion. At low FA values (from 0.2 to 0.4), a steep shortening of T1 was followed by a shallow shortening by 6%-10% at both fields. The steep shortening was associated with decreasing S0 and MD. T1 also decreased with increasing fdc1 values in a nonlinear fashion. Instead, only a small T1 change as a function of either f3 or fdc3 was observed. In WM areas selected by fdc1 only masks, T1 was shorter than in those with fdc2/fdc3. In WM areas with high single fibre populations, as delineated by f1/fdc1 masks, T1 was shorter than in tissue with high complex fibre configurations, as segmented by f2/fdc2 or f3/fdc3 masks. T1 differences between these WM areas are attributable to combined effects by T1 anisotropy and lowered FA. The current data show strong interrelationships between T1, axon fibre configuration and orientation in healthy WM. It is concluded that diffusion MRI microstructural measures are essential in the effort to interpret quantitative T1 images in terms of tissue state in health and disease.
{"title":"T1 relaxation and axon fibre configuration in human white matter.","authors":"Grace Hutchinson, Jeromy Thotland, Pramod K Pisharady, Michael Garwood, Christophe Lenglet, Risto A Kauppinen","doi":"10.1002/nbm.5234","DOIUrl":"https://doi.org/10.1002/nbm.5234","url":null,"abstract":"<p><p>Understanding the effects of white matter (WM) axon fibre microstructure on T1 relaxation is important for neuroimaging. Here, we have studied the interrelationship between T1 and axon fibre configurations at 3T and 7T. T1 and S0 (=signal intensity at zero TI) were computed from MP2RAGE images acquired with six inversion recovery times. Multishell diffusion MRI images were analysed for fractional anisotropy (FA); MD; V1; the volume fractions for the first (f<sub>1</sub>), second (f<sub>2</sub>) and third (f<sub>3</sub>) fibre configuration; and fibre density cross-section images for the first (fdc<sub>1</sub>), second (fdc<sub>2</sub>) and third (fdc<sub>3</sub>) fibres. T1 values were plotted as a function of FA, f<sub>1</sub>, f<sub>2</sub>, f<sub>3</sub>, fdc<sub>1</sub>, fdc<sub>2</sub> and fdc<sub>3</sub> to examine interrelationships between the longitudinal relaxation and the diffusion MRI microstructural measures. T1 values decreased with increasing FA, f<sub>1</sub> and f<sub>2</sub> in a nonlinear fashion. At low FA values (from 0.2 to 0.4), a steep shortening of T1 was followed by a shallow shortening by 6%-10% at both fields. The steep shortening was associated with decreasing S0 and MD. T1 also decreased with increasing fdc<sub>1</sub> values in a nonlinear fashion. Instead, only a small T1 change as a function of either f<sub>3</sub> or fdc<sub>3</sub> was observed. In WM areas selected by fdc<sub>1</sub> only masks, T1 was shorter than in those with fdc<sub>2</sub>/fdc<sub>3</sub>. In WM areas with high single fibre populations, as delineated by f<sub>1</sub>/fdc<sub>1</sub> masks, T1 was shorter than in tissue with high complex fibre configurations, as segmented by f<sub>2</sub>/fdc<sub>2</sub> or f<sub>3</sub>/fdc<sub>3</sub> masks. T1 differences between these WM areas are attributable to combined effects by T1 anisotropy and lowered FA. The current data show strong interrelationships between T1, axon fibre configuration and orientation in healthy WM. It is concluded that diffusion MRI microstructural measures are essential in the effort to interpret quantitative T1 images in terms of tissue state in health and disease.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141889867","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}
Jonathan Stelter, Kilian Weiss, Lisa Steinhelfer, Veronika Spieker, Elizabeth Huaroc Moquillaza, Weitong Zhang, Marcus R Makowski, Julia A Schnabel, Bernhard Kainz, Rickmer F Braren, Dimitrios C Karampinos
Purpose: To develop and validate a data acquisition scheme combined with a motion-resolved reconstruction and dictionary-matching-based parameter estimation to enable free-breathing isotropic resolution self-navigated whole-liver simultaneous water-specific ( ) and ( ) mapping for the characterization of diffuse and oncological liver diseases.
Methods: The proposed data acquisition consists of a magnetization preparation pulse and a two-echo gradient echo readout with a radial stack-of-stars trajectory, repeated with different preparations to achieve different and contrasts in a fixed acquisition time of 6 min. Regularized reconstruction was performed using self-navigation to account for motion during the free-breathing acquisition, followed by water-fat separation. Bloch simulations of the sequence were applied to optimize the sequence timing for insensitivity at 3 T, to correct for relaxation-induced blurring, and to map and using a dictionary. The proposed method was validated on a water-fat phantom with varying relaxation properties and in 10 volunteers against imaging and spectroscopy reference values. The performance and robustness of the proposed method were evaluated in five patients with abdominal pathologies.
Results: Simulations demonstrate good insensitivity of the proposed method in measuring
{"title":"<ArticleTitle xmlns:ns0=\"http://www.w3.org/1998/Math/MathML\">Simultaneous whole-liver water <ns0:math> <ns0:semantics> <ns0:mrow><ns0:msub><ns0:mtext>T</ns0:mtext> <ns0:mtext>1</ns0:mtext></ns0:msub> </ns0:mrow> <ns0:annotation>$$ {mathrm{T}}_1 $$</ns0:annotation></ns0:semantics> </ns0:math> and <ns0:math> <ns0:semantics> <ns0:mrow><ns0:msub><ns0:mtext>T</ns0:mtext> <ns0:mtext>2</ns0:mtext></ns0:msub> </ns0:mrow> <ns0:annotation>$$ {mathrm{T}}_2 $$</ns0:annotation></ns0:semantics> </ns0:math> mapping with isotropic resolution during free-breathing.","authors":"Jonathan Stelter, Kilian Weiss, Lisa Steinhelfer, Veronika Spieker, Elizabeth Huaroc Moquillaza, Weitong Zhang, Marcus R Makowski, Julia A Schnabel, Bernhard Kainz, Rickmer F Braren, Dimitrios C Karampinos","doi":"10.1002/nbm.5216","DOIUrl":"https://doi.org/10.1002/nbm.5216","url":null,"abstract":"<p><strong>Purpose: </strong>To develop and validate a data acquisition scheme combined with a motion-resolved reconstruction and dictionary-matching-based parameter estimation to enable free-breathing isotropic resolution self-navigated whole-liver simultaneous water-specific <math> <semantics> <mrow><msub><mtext>T</mtext> <mtext>1</mtext></msub> </mrow> <annotation>$$ {mathrm{T}}_1 $$</annotation></semantics> </math> ( <math> <semantics> <mrow><msub><mtext>wT</mtext> <mtext>1</mtext></msub> </mrow> <annotation>$$ {mathrm{wT}}_1 $$</annotation></semantics> </math> ) and <math> <semantics> <mrow><msub><mtext>T</mtext> <mtext>2</mtext></msub> </mrow> <annotation>$$ {mathrm{T}}_2 $$</annotation></semantics> </math> ( <math> <semantics> <mrow><msub><mtext>wT</mtext> <mtext>2</mtext></msub> </mrow> <annotation>$$ {mathrm{wT}}_2 $$</annotation></semantics> </math> ) mapping for the characterization of diffuse and oncological liver diseases.</p><p><strong>Methods: </strong>The proposed data acquisition consists of a magnetization preparation pulse and a two-echo gradient echo readout with a radial stack-of-stars trajectory, repeated with different preparations to achieve different <math> <semantics> <mrow><msub><mtext>T</mtext> <mtext>1</mtext></msub> </mrow> <annotation>$$ {mathrm{T}}_1 $$</annotation></semantics> </math> and <math> <semantics> <mrow><msub><mtext>T</mtext> <mtext>2</mtext></msub> </mrow> <annotation>$$ {mathrm{T}}_2 $$</annotation></semantics> </math> contrasts in a fixed acquisition time of 6 min. Regularized reconstruction was performed using self-navigation to account for motion during the free-breathing acquisition, followed by water-fat separation. Bloch simulations of the sequence were applied to optimize the sequence timing for <math> <semantics> <mrow> <msub><mrow><mi>B</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {B}_1 $$</annotation></semantics> </math> insensitivity at 3 T, to correct for relaxation-induced blurring, and to map <math> <semantics> <mrow><msub><mtext>T</mtext> <mtext>1</mtext></msub> </mrow> <annotation>$$ {mathrm{T}}_1 $$</annotation></semantics> </math> and <math> <semantics> <mrow><msub><mtext>T</mtext> <mtext>2</mtext></msub> </mrow> <annotation>$$ {mathrm{T}}_2 $$</annotation></semantics> </math> using a dictionary. The proposed method was validated on a water-fat phantom with varying relaxation properties and in 10 volunteers against imaging and spectroscopy reference values. The performance and robustness of the proposed method were evaluated in five patients with abdominal pathologies.</p><p><strong>Results: </strong>Simulations demonstrate good <math> <semantics> <mrow> <msub><mrow><mi>B</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {B}_1 $$</annotation></semantics> </math> insensitivity of the proposed method in measuring <math> <semantics> <mrow><msub><mtext>T</mtext> <mtext>1</mtext></msub> </mrow> <annotation>$$ {mathrm{T}}_1 $$</annotation></semantics> ","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141889864","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}
Pub Date : 2024-08-01Epub Date: 2024-03-15DOI: 10.1002/nbm.5130
Rohith Saai Pemmasani Prabakaran, Se Weon Park, Joseph H C Lai, Kexin Wang, Jiadi Xu, Zilin Chen, Abdul-Mojeed Olabisi Ilyas, Huabing Liu, Jianpan Huang, Kannie W Y Chan
Chemical exchange saturation transfer (CEST) MRI is a molecular imaging tool that provides physiological information about tissues, making it an invaluable tool for disease diagnosis and guided treatment. Its clinical application requires the acquisition of high-resolution images capable of accurately identifying subtle regional changes in vivo, while simultaneously maintaining a high level of spectral resolution. However, the acquisition of such high-resolution images is time consuming, presenting a challenge for practical implementation in clinical settings. Among several techniques that have been explored to reduce the acquisition time in MRI, deep-learning-based super-resolution (DLSR) is a promising approach to address this problem due to its adaptability to any acquisition sequence and hardware. However, its translation to CEST MRI has been hindered by the lack of the large CEST datasets required for network development. Thus, we aim to develop a DLSR method, named DLSR-CEST, to reduce the acquisition time for CEST MRI by reconstructing high-resolution images from fast low-resolution acquisitions. This is achieved by first pretraining the DLSR-CEST on human brain T1w and T2w images to initialize the weights of the network and then training the network on very small human and mouse brain CEST datasets to fine-tune the weights. Using the trained DLSR-CEST network, the reconstructed CEST source images exhibited improved spatial resolution in both peak signal-to-noise ratio and structural similarity index measure metrics at all downsampling factors (2-8). Moreover, amide CEST and relayed nuclear Overhauser effect maps extrapolated from the DLSR-CEST source images exhibited high spatial resolution and low normalized root mean square error, indicating a negligible loss in Z-spectrum information. Therefore, our DLSR-CEST demonstrated a robust reconstruction of high-resolution CEST source images from fast low-resolution acquisitions, thereby improving the spatial resolution and preserving most Z-spectrum information.
化学交换饱和转移(CEST)磁共振成像是一种分子成像工具,可提供有关组织的生理信息,是疾病诊断和指导治疗的宝贵工具。其临床应用要求获取高分辨率图像,能够准确识别体内细微的区域变化,同时保持较高的光谱分辨率。然而,获取这种高分辨率图像非常耗时,给临床实际应用带来了挑战。在为缩短磁共振成像采集时间而探索的几种技术中,基于深度学习的超分辨率(DLSR)因其对任何采集序列和硬件的适应性,是一种很有希望解决这一问题的方法。然而,由于缺乏网络开发所需的大型 CEST 数据集,该方法在 CEST MRI 中的应用受到了阻碍。因此,我们旨在开发一种名为 DLSR-CEST 的 DLSR 方法,通过从快速低分辨率采集中重建高分辨率图像来缩短 CEST MRI 的采集时间。为此,我们首先在人脑 T1w 和 T2w 图像上对 DLSR-CEST 进行预训练,初始化网络权重,然后在非常小的人脑和小鼠脑 CEST 数据集上训练网络,对权重进行微调。使用训练有素的 DLSR-CEST 网络,重建的 CEST 源图像在所有下采样因子(2-8)下的峰值信噪比和结构相似性指数度量指标上都显示出更高的空间分辨率。此外,从 DLSR-CEST 源图像推断出的酰胺 CEST 和中继核 Overhauser 效应图显示出较高的空间分辨率和较低的归一化均方根误差,表明 Z 光谱信息的损失可以忽略不计。因此,我们的 DLSR-CEST 展示了从快速低分辨率采集到的高分辨率 CEST 源图像的稳健重建,从而提高了空间分辨率并保留了大部分 Z 光谱信息。
{"title":"Deep-learning-based super-resolution for accelerating chemical exchange saturation transfer MRI.","authors":"Rohith Saai Pemmasani Prabakaran, Se Weon Park, Joseph H C Lai, Kexin Wang, Jiadi Xu, Zilin Chen, Abdul-Mojeed Olabisi Ilyas, Huabing Liu, Jianpan Huang, Kannie W Y Chan","doi":"10.1002/nbm.5130","DOIUrl":"10.1002/nbm.5130","url":null,"abstract":"<p><p>Chemical exchange saturation transfer (CEST) MRI is a molecular imaging tool that provides physiological information about tissues, making it an invaluable tool for disease diagnosis and guided treatment. Its clinical application requires the acquisition of high-resolution images capable of accurately identifying subtle regional changes in vivo, while simultaneously maintaining a high level of spectral resolution. However, the acquisition of such high-resolution images is time consuming, presenting a challenge for practical implementation in clinical settings. Among several techniques that have been explored to reduce the acquisition time in MRI, deep-learning-based super-resolution (DLSR) is a promising approach to address this problem due to its adaptability to any acquisition sequence and hardware. However, its translation to CEST MRI has been hindered by the lack of the large CEST datasets required for network development. Thus, we aim to develop a DLSR method, named DLSR-CEST, to reduce the acquisition time for CEST MRI by reconstructing high-resolution images from fast low-resolution acquisitions. This is achieved by first pretraining the DLSR-CEST on human brain T1w and T2w images to initialize the weights of the network and then training the network on very small human and mouse brain CEST datasets to fine-tune the weights. Using the trained DLSR-CEST network, the reconstructed CEST source images exhibited improved spatial resolution in both peak signal-to-noise ratio and structural similarity index measure metrics at all downsampling factors (2-8). Moreover, amide CEST and relayed nuclear Overhauser effect maps extrapolated from the DLSR-CEST source images exhibited high spatial resolution and low normalized root mean square error, indicating a negligible loss in Z-spectrum information. Therefore, our DLSR-CEST demonstrated a robust reconstruction of high-resolution CEST source images from fast low-resolution acquisitions, thereby improving the spatial resolution and preserving most Z-spectrum information.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140140511","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}
Pub Date : 2024-08-01Epub Date: 2024-03-05DOI: 10.1002/nbm.5135
Rushdi Zahid Rusho, Abdul Haseeb Ahmed, Stanley Kruger, Wahidul Alam, David Meyer, David Howard, Brad Story, Mathews Jacob, Sajan Goud Lingala
This work develops and evaluates a self-navigated variable density spiral (VDS)-based manifold regularization scheme to prospectively improve dynamic speech magnetic resonance imaging (MRI) at 3 T. Short readout duration spirals (1.3-ms long) were used to minimize sensitivity to off-resonance. A custom 16-channel speech coil was used for improved parallel imaging of vocal tract structures. The manifold model leveraged similarities between frames sharing similar vocal tract postures without explicit motion binning. The self-navigating capability of VDS was leveraged to learn the Laplacian structure of the manifold. Reconstruction was posed as a sensitivity-encoding-based nonlocal soft-weighted temporal regularization scheme. Our approach was compared with view-sharing, low-rank, temporal finite difference, extra dimension-based sparsity reconstruction constraints. Undersampling experiments were conducted on five volunteers performing repetitive and arbitrary speaking tasks at different speaking rates. Quantitative evaluation in terms of mean square error over moving edges was performed in a retrospective undersampling experiment on one volunteer. For prospective undersampling, blinded image quality evaluation in the categories of alias artifacts, spatial blurring, and temporal blurring was performed by three experts in voice research. Region of interest analysis at articulator boundaries was performed in both experiments to assess articulatory motion. Improved performance with manifold reconstruction constraints was observed over existing constraints. With prospective undersampling, a spatial resolution of 2.4 × 2.4 mm2/pixel and a temporal resolution of 17.4 ms/frame for single-slice imaging, and 52.2 ms/frame for concurrent three-slice imaging, were achieved. We demonstrated implicit motion binning by analyzing the mechanics of the Laplacian matrix. Manifold regularization demonstrated superior image quality scores in reducing spatial and temporal blurring compared with all other reconstruction constraints. While it exhibited faint (nonsignificant) alias artifacts that were similar to temporal finite difference, it provided statistically significant improvements compared with the other constraints. In conclusion, the self-navigated manifold regularized scheme enabled robust high spatiotemporal resolution dynamic speech MRI at 3 T.
这项研究开发并评估了一种基于自导航可变密度螺旋(VDS)的流形正则化方案,用于前瞻性地改进 3 T 动态语音磁共振成像(MRI)。采用了读出持续时间较短的螺旋(1.3 毫秒长),以最大限度地降低对非共振的敏感性。定制的 16 通道语音线圈用于改进声道结构的平行成像。流形模型利用了具有相似声道姿态的帧之间的相似性,而无需明确的运动分选。VDS 的自导航功能可用于学习流形的拉普拉卡结构。重构是一种基于灵敏度编码的非局部软加权时间正则化方案。我们的方法与视图共享、低秩、时间有限差分、基于额外维度的稀疏性重建约束进行了比较。在五名志愿者身上进行了欠采样实验,他们以不同的语速执行重复和任意的说话任务。在对一名志愿者进行的回顾性欠采样实验中,对移动边缘的均方误差进行了定量评估。对于前瞻性欠采样,由三位语音研究专家对别名伪影、空间模糊和时间模糊进行了盲法图像质量评估。两次实验都对发音器边界进行了感兴趣区分析,以评估发音运动。与现有的限制条件相比,流形重建限制条件的性能有所提高。通过前瞻性欠采样,单片成像的空间分辨率为 2.4 × 2.4 mm2/像素,时间分辨率为 17.4 ms/帧,三片同时成像的时间分辨率为 52.2 ms/帧。我们通过分析拉普拉斯矩阵的力学原理,证明了隐式运动分档。与所有其他重建约束相比,Mifold 正则化在减少空间和时间模糊方面的图像质量得分更高。虽然它表现出与时间有限差分类似的微弱(不显著)别离伪影,但与其他约束相比,它在统计上有显著改善。总之,自导航流形正则化方案能在 3 T 下实现稳健的高时空分辨率动态语音磁共振成像。
{"title":"Prospectively accelerated dynamic speech magnetic resonance imaging at 3 T using a self-navigated spiral-based manifold regularized scheme.","authors":"Rushdi Zahid Rusho, Abdul Haseeb Ahmed, Stanley Kruger, Wahidul Alam, David Meyer, David Howard, Brad Story, Mathews Jacob, Sajan Goud Lingala","doi":"10.1002/nbm.5135","DOIUrl":"10.1002/nbm.5135","url":null,"abstract":"<p><p>This work develops and evaluates a self-navigated variable density spiral (VDS)-based manifold regularization scheme to prospectively improve dynamic speech magnetic resonance imaging (MRI) at 3 T. Short readout duration spirals (1.3-ms long) were used to minimize sensitivity to off-resonance. A custom 16-channel speech coil was used for improved parallel imaging of vocal tract structures. The manifold model leveraged similarities between frames sharing similar vocal tract postures without explicit motion binning. The self-navigating capability of VDS was leveraged to learn the Laplacian structure of the manifold. Reconstruction was posed as a sensitivity-encoding-based nonlocal soft-weighted temporal regularization scheme. Our approach was compared with view-sharing, low-rank, temporal finite difference, extra dimension-based sparsity reconstruction constraints. Undersampling experiments were conducted on five volunteers performing repetitive and arbitrary speaking tasks at different speaking rates. Quantitative evaluation in terms of mean square error over moving edges was performed in a retrospective undersampling experiment on one volunteer. For prospective undersampling, blinded image quality evaluation in the categories of alias artifacts, spatial blurring, and temporal blurring was performed by three experts in voice research. Region of interest analysis at articulator boundaries was performed in both experiments to assess articulatory motion. Improved performance with manifold reconstruction constraints was observed over existing constraints. With prospective undersampling, a spatial resolution of 2.4 × 2.4 mm<sup>2</sup>/pixel and a temporal resolution of 17.4 ms/frame for single-slice imaging, and 52.2 ms/frame for concurrent three-slice imaging, were achieved. We demonstrated implicit motion binning by analyzing the mechanics of the Laplacian matrix. Manifold regularization demonstrated superior image quality scores in reducing spatial and temporal blurring compared with all other reconstruction constraints. While it exhibited faint (nonsignificant) alias artifacts that were similar to temporal finite difference, it provided statistically significant improvements compared with the other constraints. In conclusion, the self-navigated manifold regularized scheme enabled robust high spatiotemporal resolution dynamic speech MRI at 3 T.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140028539","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}
Pub Date : 2024-08-01Epub Date: 2024-03-31DOI: 10.1002/nbm.5140
Marc Jonuscheit, Celina Uhlemeyer, Benedict Korzekwa, Marten Schouwink, Soner Öner-Sieben, Regina Ensenauer, Michael Roden, Bengt-Frederik Belgardt, Vera B Schrauwen-Hinderling
Maternal obesity and hyperglycemia are linked to an elevated risk for obesity, diabetes, and steatotic liver disease in the adult offspring. To establish and validate a noninvasive workflow for perinatal metabolic phenotyping, fixed neonates of common mouse strains were analyzed postmortem via magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS) to assess liver volume and hepatic lipid (HL) content. The key advantage of nondestructive MRI/MRS analysis is the possibility of further tissue analyses, such as immunohistochemistry, RNA extraction, and even proteomics, maximizing the data that can be gained per individual and therefore facilitating comprehensive correlation analyses. This study employed an MRI and 1H-MRS workflow to measure liver volume and HL content in 65 paraformaldehyde-fixed murine neonates at 11.7 T. Liver volume was obtained using semiautomatic segmentation of MRI acquired by a RARE sequence with 0.5-mm slice thickness. HL content was measured by a STEAM sequence, applied with and without water suppression. T1 and T2 relaxation times of lipids and water were measured for respective correction of signal intensity. The HL content, given as CH2/(CH2 + H2O), was calculated, and the intrasession repeatability of the method was tested. The established workflow yielded robust results with a variation of ~3% in repeated measurements for HL content determination. HL content measurements were further validated by correlation analysis with biochemically assessed triglyceride contents (R2 = 0.795) that were measured in littermates. In addition, image quality also allowed quantification of subcutaneous adipose tissue and stomach diameter. The highest HL content was measured in C57Bl/6N (4.2%) and the largest liver volume and stomach diameter in CBA (53.1 mm3 and 6.73 mm) and NMRI (51.4 mm3 and 5.96 mm) neonates, which also had the most subcutaneous adipose tissue. The observed effects were independent of sex and litter size. In conclusion, we have successfully tested and validated a robust MRI/MRS workflow that allows assessment of morphology and HL content and further enables paraformaldehyde-fixed tissue-compatible subsequent analyses in murine neonates.
{"title":"Post mortem analysis of hepatic volume and lipid content by magnetic resonance imaging and spectroscopy in fixed murine neonates.","authors":"Marc Jonuscheit, Celina Uhlemeyer, Benedict Korzekwa, Marten Schouwink, Soner Öner-Sieben, Regina Ensenauer, Michael Roden, Bengt-Frederik Belgardt, Vera B Schrauwen-Hinderling","doi":"10.1002/nbm.5140","DOIUrl":"10.1002/nbm.5140","url":null,"abstract":"<p><p>Maternal obesity and hyperglycemia are linked to an elevated risk for obesity, diabetes, and steatotic liver disease in the adult offspring. To establish and validate a noninvasive workflow for perinatal metabolic phenotyping, fixed neonates of common mouse strains were analyzed postmortem via magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS) to assess liver volume and hepatic lipid (HL) content. The key advantage of nondestructive MRI/MRS analysis is the possibility of further tissue analyses, such as immunohistochemistry, RNA extraction, and even proteomics, maximizing the data that can be gained per individual and therefore facilitating comprehensive correlation analyses. This study employed an MRI and <sup>1</sup>H-MRS workflow to measure liver volume and HL content in 65 paraformaldehyde-fixed murine neonates at 11.7 T. Liver volume was obtained using semiautomatic segmentation of MRI acquired by a RARE sequence with 0.5-mm slice thickness. HL content was measured by a STEAM sequence, applied with and without water suppression. T<sub>1</sub> and T<sub>2</sub> relaxation times of lipids and water were measured for respective correction of signal intensity. The HL content, given as CH<sub>2</sub>/(CH<sub>2</sub> + H<sub>2</sub>O), was calculated, and the intrasession repeatability of the method was tested. The established workflow yielded robust results with a variation of ~3% in repeated measurements for HL content determination. HL content measurements were further validated by correlation analysis with biochemically assessed triglyceride contents (R<sup>2</sup> = 0.795) that were measured in littermates. In addition, image quality also allowed quantification of subcutaneous adipose tissue and stomach diameter. The highest HL content was measured in C57Bl/6N (4.2%) and the largest liver volume and stomach diameter in CBA (53.1 mm<sup>3</sup> and 6.73 mm) and NMRI (51.4 mm<sup>3</sup> and 5.96 mm) neonates, which also had the most subcutaneous adipose tissue. The observed effects were independent of sex and litter size. In conclusion, we have successfully tested and validated a robust MRI/MRS workflow that allows assessment of morphology and HL content and further enables paraformaldehyde-fixed tissue-compatible subsequent analyses in murine neonates.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140331881","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}
Pub Date : 2024-08-01Epub Date: 2024-03-12DOI: 10.1002/nbm.5138
Gurcan Taspinar, Nalan Ozkurt
Attention deficit hyperactivity disorder (ADHD) is a common mental health condition that significantly affects school-age children, causing difficulties with learning and daily functioning. Early identification is crucial, and reliable and objective diagnostic tools are necessary. However, current clinical evaluations of behavioral symptoms can be inconsistent and subjective. Functional magnetic resonance imaging (fMRI) is a non-invasive technique that has proven effective in detecting brain abnormalities in individuals with ADHD. Recent studies have shown promising outcomes in using resting state fMRI (rsfMRI)-based brain functional networks to diagnose various brain disorders, including ADHD. Several review papers have examined the detection of other diseases using fMRI data and machine learning or deep learning methods. However, no review paper has specifically addressed ADHD. Therefore, this study aims to contribute to the literature by reviewing the use of rsfMRI data and machine learning methods for detection of ADHD. The study provides general information about fMRI databases and detailed knowledge of the ADHD-200 database, which is commonly used for ADHD detection. It also emphasizes the importance of examining all stages of the process, including network and atlas selection, feature extraction, and feature selection, before the classification stage. The study compares the performance, advantages, and disadvantages of previous studies in detail. This comprehensive approach may be a useful starting point for new researchers in this area.
{"title":"A review of ADHD detection studies with machine learning methods using rsfMRI data.","authors":"Gurcan Taspinar, Nalan Ozkurt","doi":"10.1002/nbm.5138","DOIUrl":"10.1002/nbm.5138","url":null,"abstract":"<p><p>Attention deficit hyperactivity disorder (ADHD) is a common mental health condition that significantly affects school-age children, causing difficulties with learning and daily functioning. Early identification is crucial, and reliable and objective diagnostic tools are necessary. However, current clinical evaluations of behavioral symptoms can be inconsistent and subjective. Functional magnetic resonance imaging (fMRI) is a non-invasive technique that has proven effective in detecting brain abnormalities in individuals with ADHD. Recent studies have shown promising outcomes in using resting state fMRI (rsfMRI)-based brain functional networks to diagnose various brain disorders, including ADHD. Several review papers have examined the detection of other diseases using fMRI data and machine learning or deep learning methods. However, no review paper has specifically addressed ADHD. Therefore, this study aims to contribute to the literature by reviewing the use of rsfMRI data and machine learning methods for detection of ADHD. The study provides general information about fMRI databases and detailed knowledge of the ADHD-200 database, which is commonly used for ADHD detection. It also emphasizes the importance of examining all stages of the process, including network and atlas selection, feature extraction, and feature selection, before the classification stage. The study compares the performance, advantages, and disadvantages of previous studies in detail. This comprehensive approach may be a useful starting point for new researchers in this area.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140110846","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}
Pub Date : 2024-08-01Epub Date: 2024-02-29DOI: 10.1002/nbm.5123
Simone Poli, Ahmed F Emara, Naomi F Lange, Edona Ballabani, Angeline Buser, Michele Schiavon, David Herzig, Chiara Dalla Man, Lia Bally, Roland Kreis
The liver plays a central role in metabolic homeostasis, as exemplified by a variety of clinical disorders with hepatic and systemic metabolic disarrays. Of particular interest are the complex interactions between lipid and carbohydrate metabolism in highly prevalent conditions such as obesity, diabetes, and fatty liver disease. Limited accessibility and the need for invasive procedures challenge direct investigations in humans. Hence, noninvasive dynamic evaluations of glycolytic flux and steady-state assessments of lipid levels and composition are crucial for basic understanding and may open new avenues toward novel therapeutic targets. Here, three different MR spectroscopy (MRS) techniques that have been combined in a single interleaved examination in a 7T MR scanner are evaluated. 1H-MRS and 13C-MRS probe endogenous metabolites, while deuterium metabolic imaging (DMI) relies on administration of deuterated tracers, currently 2H-labelled glucose, to map the spatial and temporal evolution of their metabolic fate. All three techniques have been optimized for a robust single-session clinical investigation and applied in a preliminary study of healthy subjects. The use of a triple-channel 1H/2H/13C RF coil enables interleaved examinations with no need for repositioning. Short-echo-time STEAM spectroscopy provides well resolved spectra to quantify lipid content and composition. The relative benefits of using water saturation versus metabolite cycling and types of respiratory synchronization were evaluated. 2H-MR spectroscopic imaging allowed for registration of time- and space-resolved glucose levels following oral ingestion of 2H-glucose, while natural abundance 13C-MRS of glycogen provides a dynamic measure of hepatic glucose storage. For DMI and 13C-MRS, the measurement precision of the method was estimated to be about 0.2 and about 16 mM, respectively, for 5 min scanning periods. Excellent results were shown for the determination of dynamic uptake of glucose with DMI and lipid profiles with 1H-MRS, while the determination of changes in glycogen levels by 13C-MRS is also feasible but somewhat more limited by signal-to-noise ratio.
{"title":"Interleaved trinuclear MRS for single-session investigation of carbohydrate and lipid metabolism in human liver at 7T.","authors":"Simone Poli, Ahmed F Emara, Naomi F Lange, Edona Ballabani, Angeline Buser, Michele Schiavon, David Herzig, Chiara Dalla Man, Lia Bally, Roland Kreis","doi":"10.1002/nbm.5123","DOIUrl":"10.1002/nbm.5123","url":null,"abstract":"<p><p>The liver plays a central role in metabolic homeostasis, as exemplified by a variety of clinical disorders with hepatic and systemic metabolic disarrays. Of particular interest are the complex interactions between lipid and carbohydrate metabolism in highly prevalent conditions such as obesity, diabetes, and fatty liver disease. Limited accessibility and the need for invasive procedures challenge direct investigations in humans. Hence, noninvasive dynamic evaluations of glycolytic flux and steady-state assessments of lipid levels and composition are crucial for basic understanding and may open new avenues toward novel therapeutic targets. Here, three different MR spectroscopy (MRS) techniques that have been combined in a single interleaved examination in a 7T MR scanner are evaluated. <sup>1</sup>H-MRS and <sup>13</sup>C-MRS probe endogenous metabolites, while deuterium metabolic imaging (DMI) relies on administration of deuterated tracers, currently <sup>2</sup>H-labelled glucose, to map the spatial and temporal evolution of their metabolic fate. All three techniques have been optimized for a robust single-session clinical investigation and applied in a preliminary study of healthy subjects. The use of a triple-channel <sup>1</sup>H/<sup>2</sup>H/<sup>13</sup>C RF coil enables interleaved examinations with no need for repositioning. Short-echo-time STEAM spectroscopy provides well resolved spectra to quantify lipid content and composition. The relative benefits of using water saturation versus metabolite cycling and types of respiratory synchronization were evaluated. <sup>2</sup>H-MR spectroscopic imaging allowed for registration of time- and space-resolved glucose levels following oral ingestion of <sup>2</sup>H-glucose, while natural abundance <sup>13</sup>C-MRS of glycogen provides a dynamic measure of hepatic glucose storage. For DMI and <sup>13</sup>C-MRS, the measurement precision of the method was estimated to be about 0.2 and about 16 mM, respectively, for 5 min scanning periods. Excellent results were shown for the determination of dynamic uptake of glucose with DMI and lipid profiles with <sup>1</sup>H-MRS, while the determination of changes in glycogen levels by <sup>13</sup>C-MRS is also feasible but somewhat more limited by signal-to-noise ratio.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139996995","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}
Pub Date : 2024-08-01Epub Date: 2024-03-15DOI: 10.1002/nbm.5145
Siyuan Dong, Annabella Shewarega, Julius Chapiro, Zhuotong Cai, Fahmeed Hyder, Daniel Coman, James S Duncan
Noninvasive extracellular pH (pHe) mapping with Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) using MR spectroscopic imaging (MRSI) has been demonstrated on 3T clinical MR scanners at 8 mm3 spatial resolution and applied to study various liver cancer treatments. Although pHe imaging at higher resolution can be achieved by extending the acquisition time, a postprocessing method to increase the resolution is preferable, to minimize the duration spent by the subject in the MR scanner. In this work, we propose to improve the spatial resolution of pHe mapping with BIRDS by incorporating anatomical information in the form of multiparametric MRI and using an unsupervised deep-learning technique, Deep Image Prior (DIP). Specifically, we used high-resolution , , and diffusion-weighted imaging (DWI) MR images of rabbits with VX2 liver tumors as inputs to a U-Net architecture to provide anatomical information. U-Net parameters were optimized to minimize the difference between the output super-resolution image and the experimentally acquired low-resolution pHe image using the mean-absolute error. In this way, the super-resolution pHe image would be consistent with both anatomical MR images and the low-resolution pHe measurement from the scanner. The method was developed based on data from 49 rabbits implanted with VX2 liver tumors. For evaluation, we also acquired high-resolution pHe images from two rabbits, which were used as ground truth. The results indicate a good match between the spatial characteristics of the super-resolution images and the high-resolution ground truth, supported by the low pixelwise absolute error.
{"title":"High-resolution extracellular pH imaging of liver cancer with multiparametric MR using Deep Image Prior.","authors":"Siyuan Dong, Annabella Shewarega, Julius Chapiro, Zhuotong Cai, Fahmeed Hyder, Daniel Coman, James S Duncan","doi":"10.1002/nbm.5145","DOIUrl":"10.1002/nbm.5145","url":null,"abstract":"<p><p>Noninvasive extracellular pH (pH<sub>e</sub>) mapping with Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) using MR spectroscopic imaging (MRSI) has been demonstrated on 3T clinical MR scanners at 8 <math><mo>×</mo> <mn>8</mn> <mo>×</mo> <mn>10</mn></math> mm<sup>3</sup> spatial resolution and applied to study various liver cancer treatments. Although pH<sub>e</sub> imaging at higher resolution can be achieved by extending the acquisition time, a postprocessing method to increase the resolution is preferable, to minimize the duration spent by the subject in the MR scanner. In this work, we propose to improve the spatial resolution of pH<sub>e</sub> mapping with BIRDS by incorporating anatomical information in the form of multiparametric MRI and using an unsupervised deep-learning technique, Deep Image Prior (DIP). Specifically, we used high-resolution <math><msub><mi>T</mi> <mn>1</mn></msub> </math> , <math><msub><mi>T</mi> <mn>2</mn></msub> </math> , and diffusion-weighted imaging (DWI) MR images of rabbits with VX2 liver tumors as inputs to a U-Net architecture to provide anatomical information. U-Net parameters were optimized to minimize the difference between the output super-resolution image and the experimentally acquired low-resolution pH<sub>e</sub> image using the mean-absolute error. In this way, the super-resolution pH<sub>e</sub> image would be consistent with both anatomical MR images and the low-resolution pH<sub>e</sub> measurement from the scanner. The method was developed based on data from 49 rabbits implanted with VX2 liver tumors. For evaluation, we also acquired high-resolution pH<sub>e</sub> images from two rabbits, which were used as ground truth. The results indicate a good match between the spatial characteristics of the super-resolution images and the high-resolution ground truth, supported by the low pixelwise absolute error.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140132215","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}
Magnetic resonance electrical propert tomography promises to retrieve electrical properties (EPs) quantitatively and non-invasively in vivo, providing valuable information for tissue characterization and pathology diagnosis. However, its clinical implementation has been hindered by, for example, B1 measurement accuracy, reconstruction artifacts resulting from inaccuracies in underlying models, and stringent hardware/software requirements. To address these challenges, we present a novel approach aimed at accurate and high-resolution EPs reconstruction based on water content maps by using a physics-informed network (PIN-wEPT). The proposed method utilizes standard clinical protocols and conventional multi-channel receive arrays that have been routinely equipped in clinical settings, thus eliminating the need for specialized RF sequence/coil configurations. Compared with the original wEPT method, the network generates accurate water content maps that effectively eliminate the influence of and by incorporating data mismatch with electrodynamic constraints derived from the Helmholtz equation. Subsequent regression analysis develops a broad relationship between water content and EPs across various types of brain tissue. A series of numerical simulations was conducted at 7 T to assess the feasibility and performance of the method, which encompassed four normal head models and models with tumorous tissues incorporated, and the results showed normalized mean square error below 1.0% in water content, below 11.7% in conductivity, and below 1.1% in permittivity reconstructions for normal brain tissues. Moreover, in vivo validations conducted over five healthy subjects at both 3 and 7 T showed reasonably good consistency with empirical EPs values across the white matter, gray matter, and cerebrospinal fluid. The PIN-wEPT method, with its demonstrated efficacy, flexibility, and compatibility with current MRI scanners, holds promising potential for future clinical application.
磁共振电特性断层成像有望在体内无创定量检索电特性,为组织特征描述和病理诊断提供有价值的信息。然而,B1 测量精度、基础模型不准确导致的重建伪影以及严格的硬件/软件要求等因素阻碍了其临床应用。为了应对这些挑战,我们提出了一种新方法,旨在通过使用物理信息网络(PIN-wEPT),根据含水量图重建精确的高分辨率 EPs。所提出的方法利用了标准临床方案和临床上常规配备的传统多通道接收阵列,因此无需专门的射频序列/线圈配置。与原始的 wEPT 方法相比,该网络生成的精确含水量图有效消除了 B → 1 + $$ {overrightarrow{B}}_1^{+} $$ 和 B → 1 - $$ {overrightarrow{B}}_1^{-} $$ 的影响。通过将数据错配与亥姆霍兹方程得出的电动约束结合起来,得出了 $$。随后的回归分析在各类脑组织的含水量和 EPs 之间建立了广泛的关系。结果显示,正常脑组织的含水量归一化均方误差低于 1.0%,电导率低于 11.7%,介电常数重建低于 1.1%。此外,在 3 T 和 7 T 下对五名健康受试者进行的活体验证显示,白质、灰质和脑脊液的 EPs 值与经验值具有相当好的一致性。PIN-wEPT 方法的有效性、灵活性以及与当前磁共振成像扫描仪的兼容性均已得到证实,在未来的临床应用中大有可为。
{"title":"MR-based electrical property tomography using a physics-informed network at 3 and 7 T.","authors":"Mengxuan Zheng, Feiyang Lou, Yiman Huang, Sihong Pan, Xiaotong Zhang","doi":"10.1002/nbm.5137","DOIUrl":"10.1002/nbm.5137","url":null,"abstract":"<p><p>Magnetic resonance electrical propert tomography promises to retrieve electrical properties (EPs) quantitatively and non-invasively in vivo, providing valuable information for tissue characterization and pathology diagnosis. However, its clinical implementation has been hindered by, for example, B<sub>1</sub> measurement accuracy, reconstruction artifacts resulting from inaccuracies in underlying models, and stringent hardware/software requirements. To address these challenges, we present a novel approach aimed at accurate and high-resolution EPs reconstruction based on water content maps by using a physics-informed network (PIN-wEPT). The proposed method utilizes standard clinical protocols and conventional multi-channel receive arrays that have been routinely equipped in clinical settings, thus eliminating the need for specialized RF sequence/coil configurations. Compared with the original wEPT method, the network generates accurate water content maps that effectively eliminate the influence of <math> <msubsup><mover><mi>B</mi> <mo>→</mo></mover> <mn>1</mn> <mo>+</mo></msubsup> </math> and <math> <msubsup><mover><mi>B</mi> <mo>→</mo></mover> <mn>1</mn> <mo>-</mo></msubsup> </math> by incorporating data mismatch with electrodynamic constraints derived from the Helmholtz equation. Subsequent regression analysis develops a broad relationship between water content and EPs across various types of brain tissue. A series of numerical simulations was conducted at 7 T to assess the feasibility and performance of the method, which encompassed four normal head models and models with tumorous tissues incorporated, and the results showed normalized mean square error below 1.0% in water content, below 11.7% in conductivity, and below 1.1% in permittivity reconstructions for normal brain tissues. Moreover, in vivo validations conducted over five healthy subjects at both 3 and 7 T showed reasonably good consistency with empirical EPs values across the white matter, gray matter, and cerebrospinal fluid. The PIN-wEPT method, with its demonstrated efficacy, flexibility, and compatibility with current MRI scanners, holds promising potential for future clinical application.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140028538","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}
Pub Date : 2024-08-01Epub Date: 2024-03-27DOI: 10.1002/nbm.5146
Junghwan Kim, Changyu Sun, Chan Hong Moon, Hoby Hetherington, Jullie Pan
The decoupled 8 × 2 transceiver array has been shown to achieve a mean B1+ of 11.7 uT with a coefficient of variation of ~11% over the intracranial brain volume for 7-T MR imaging. However, this array may be thought to give lower signal-to-noise ratio (SNR) and higher g-factors for parallel imaging compared with a radio frequency (RF) receive-only coil due to the latter's higher coil count and use of coil overlap to reduce the mutual impedance. Nonetheless, because the transceiver's highly decoupled design (pertinent for transmission) should also be constructive for reception, we measured the noise correlation, g-factors, and SNR for the decoupled transceiver in comparison with a commercial reference coil. We found that although the transceiver has half the number of receive elements in comparison with the reference coil (16 vs. 32), comparable g-factors and SNR over the head were obtained. From five subjects, the transceiver versus reference coil SNR was 65 ± 10 versus 67 ± 15. The mean noise correlation for all coil pairs was 10% ± 5% and 12% ± 9% (transceiver and reference coil, respectively). As changes in load impedance may alter the S parameters, we also examined the performance of the transceiver with tuned and matched (TM) versus untuned and unmatched (UTM) conditions on five subjects. We found that the noise correlation and SNR are robust to load variation; a noise correlation of 10% ± 5% and 10% ± 6% was determined with TM versus UTM conditions (SNRUTM/SNRTM = 0.97 ± 0.08). Finally, we demonstrate the performance of the array in human brain using T2-weighted turbo spin echo imaging, finding excellent SNR performance in both caudal and rostral brain regions.
{"title":"Evaluation of the performance of a 7-T 8 × 2 transceiver array.","authors":"Junghwan Kim, Changyu Sun, Chan Hong Moon, Hoby Hetherington, Jullie Pan","doi":"10.1002/nbm.5146","DOIUrl":"10.1002/nbm.5146","url":null,"abstract":"<p><p>The decoupled 8 × 2 transceiver array has been shown to achieve a mean B<sub>1</sub> <sup>+</sup> of 11.7 uT with a coefficient of variation of ~11% over the intracranial brain volume for 7-T MR imaging. However, this array may be thought to give lower signal-to-noise ratio (SNR) and higher g-factors for parallel imaging compared with a radio frequency (RF) receive-only coil due to the latter's higher coil count and use of coil overlap to reduce the mutual impedance. Nonetheless, because the transceiver's highly decoupled design (pertinent for transmission) should also be constructive for reception, we measured the noise correlation, g-factors, and SNR for the decoupled transceiver in comparison with a commercial reference coil. We found that although the transceiver has half the number of receive elements in comparison with the reference coil (16 vs. 32), comparable g-factors and SNR over the head were obtained. From five subjects, the transceiver versus reference coil SNR was 65 ± 10 versus 67 ± 15. The mean noise correlation for all coil pairs was 10% ± 5% and 12% ± 9% (transceiver and reference coil, respectively). As changes in load impedance may alter the S parameters, we also examined the performance of the transceiver with tuned and matched (TM) versus untuned and unmatched (UTM) conditions on five subjects. We found that the noise correlation and SNR are robust to load variation; a noise correlation of 10% ± 5% and 10% ± 6% was determined with TM versus UTM conditions (SNR<sub>UTM</sub>/SNR<sub>TM</sub> = 0.97 ± 0.08). Finally, we demonstrate the performance of the array in human brain using T2-weighted turbo spin echo imaging, finding excellent SNR performance in both caudal and rostral brain regions.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140294074","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}