Pub Date : 2025-02-01DOI: 10.1016/j.zemedi.2024.07.002
Lukas Nierer , Florian Kamp , Michael Reiner , Stefanie Corradini , Moritz Rabe , Olaf Dietrich , Katia Parodi , Claus Belka , Christopher Kurz , Guillaume Landry
{"title":"Erratum to “Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout” [Z Med. Phys. 32 (2022) 312–325]","authors":"Lukas Nierer , Florian Kamp , Michael Reiner , Stefanie Corradini , Moritz Rabe , Olaf Dietrich , Katia Parodi , Claus Belka , Christopher Kurz , Guillaume Landry","doi":"10.1016/j.zemedi.2024.07.002","DOIUrl":"10.1016/j.zemedi.2024.07.002","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 1","pages":"Page 118"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142127875","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}
Pub Date : 2025-02-01DOI: 10.1016/j.zemedi.2024.07.005
Nicholas M. Brisson , Martin Krämer , Leonie A.N. Krahl , Alexander Schill , Georg N. Duda , Jürgen R. Reichenbach
{"title":"Erratum to “A novel multipurpose device for guided knee motion and loading during dynamic magnetic resonance imaging” [Z Med Phys 32 (2022) 500–513]","authors":"Nicholas M. Brisson , Martin Krämer , Leonie A.N. Krahl , Alexander Schill , Georg N. Duda , Jürgen R. Reichenbach","doi":"10.1016/j.zemedi.2024.07.005","DOIUrl":"10.1016/j.zemedi.2024.07.005","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 1","pages":"Page 116"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142127871","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}
Pub Date : 2025-02-01DOI: 10.1016/j.zemedi.2024.12.004
Christian Licht , Efe Ilicak , Fernando E. Boada , Maxime Guye , Frank G. Zöllner , Lothar R. Schad , Stanislas Rapacchi
Purpose
To develop an improved post-processing pipeline for noise-robust accelerated phase-cycled Cartesian Single (SQ) and Triple Quantum (TQ) sodium (23Na) Magnetic Resonance Imaging (MRI) of in vivo human brain at 7 T.
Theory and Methods
Our pipeline aims to tackle the challenges of 23Na Multi-Quantum Coherences (MQC) MRI including low Signal-to-Noise Ratio (SNR) and time-consuming Radiofrequency (RF) phase-cycling. Our method combines low-rank k-space denoising for SNR enhancement with Dynamic Mode Decomposition (DMD) to robustly separate SQ and TQ signal components. This separation is crucial for computing the TQ/SQ ratio, a key parameter of 23Na MQC MRI. We validated our pipeline in silico, in vitro and in vivo in healthy volunteers, comparing it with conventional denoising and Fourier transform (FT) methods. Additionally, we assessed its robustness through ablation experiments simulating a corrupted RF phase-cycle step.
Results
Our denoising algorithm doubled SNR compared to non-denoised images and enhanced SNR by up to 29% compared to Wavelet denoising. The low-rank approach produced high-quality images even at later echo times, allowing reduced signal averaging. DMD effectively separated the SQ and TQ signals, even with missing RF phase cycle steps, resulting in superior Structural Similarity (SSIM) of and lower Root Mean Squared Error (RMSE) of compared to conventional FT methods (SSIM=, RMSE=). This pipeline enabled high-quality 8x8x15mm3 in vivo 23Na MQC MRI, with a reduction in acquisition time from 48 to 10 min at 7 T.
Conclusion
The proposed pipeline improves robustness in 23Na MQC MRI by exploiting low-rank properties to denoise signals and DMD to effectively separate SQ and TQ signals. This approach ensures high-quality MR images of both SQ and TQ components, even in accelerated and incomplete RF phase-cycling cases.
{"title":"A noise-robust post-processing pipeline for accelerated phase-cycled 23Na Multi-Quantum Coherences MRI","authors":"Christian Licht , Efe Ilicak , Fernando E. Boada , Maxime Guye , Frank G. Zöllner , Lothar R. Schad , Stanislas Rapacchi","doi":"10.1016/j.zemedi.2024.12.004","DOIUrl":"10.1016/j.zemedi.2024.12.004","url":null,"abstract":"<div><h3><strong>Purpose</strong></h3><div>To develop an improved post-processing pipeline for noise-robust accelerated phase-cycled Cartesian Single (SQ) and Triple Quantum (TQ) sodium (<sup>23</sup>Na) Magnetic Resonance Imaging (MRI) of in vivo human brain at 7 T.</div></div><div><h3><strong>Theory and Methods</strong></h3><div>Our pipeline aims to tackle the challenges of <sup>23</sup>Na Multi-Quantum Coherences (MQC) MRI including low Signal-to-Noise Ratio (SNR) and time-consuming Radiofrequency (RF) phase-cycling. Our method combines low-rank k-space denoising for SNR enhancement with Dynamic Mode Decomposition (DMD) to robustly separate SQ and TQ signal components. This separation is crucial for computing the TQ/SQ ratio, a key parameter of <sup>23</sup>Na MQC MRI. We validated our pipeline in silico, in vitro and in vivo in healthy volunteers, comparing it with conventional denoising and Fourier transform (FT) methods. Additionally, we assessed its robustness through ablation experiments simulating a corrupted RF phase-cycle step.</div></div><div><h3><strong>Results</strong></h3><div>Our denoising algorithm doubled SNR compared to non-denoised images and enhanced SNR by up to 29% compared to Wavelet denoising. The low-rank approach produced high-quality images even at later echo times, allowing reduced signal averaging. DMD effectively separated the SQ and TQ signals, even with missing RF phase cycle steps, resulting in superior Structural Similarity (SSIM) of <span><math><mrow><mn>0.89</mn><mo>±</mo><mn>0.024</mn></mrow></math></span> and lower Root Mean Squared Error (RMSE) of <span><math><mrow><mn>0.055</mn><mo>±</mo><mn>0.008</mn></mrow></math></span> compared to conventional FT methods (SSIM=<span><math><mrow><mn>0.71</mn><mo>±</mo><mn>0.061</mn></mrow></math></span>, RMSE=<span><math><mrow><mn>0.144</mn><mo>±</mo><mn>0.036</mn></mrow></math></span>). This pipeline enabled high-quality 8x8x15mm<sup>3</sup> in vivo <sup>23</sup>Na MQC MRI, with a reduction in acquisition time from 48 to 10 min at 7 T.</div></div><div><h3><strong>Conclusion</strong></h3><div>The proposed pipeline improves robustness in <sup>23</sup>Na MQC MRI by exploiting low-rank properties to denoise signals and DMD to effectively separate SQ and TQ signals. This approach ensures high-quality MR images of both SQ and TQ components, even in accelerated and incomplete RF phase-cycling cases.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 1","pages":"Pages 98-108"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143026272","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}
Pub Date : 2025-02-01DOI: 10.1016/j.zemedi.2023.08.005
Agilo Luitger Kern , Marcel Gutberlet , Regina Rumpel , Inga Bruesch , Jens M. Hohlfeld , Frank Wacker , Bennet Hensen
129Xe hyperpolarized gas chemical exchange saturation transfer (HyperCEST) MRI has been suggested as molecular imaging modality but translation to in vivo imaging has been slow, likely due to difficulties of synthesizing suitable molecules. Cucurbit[6]uril–either in readily available non-functionalized or potentially in functionalized form–may, combined with 129Xe HyperCEST MRI, prove useful as a switchable 129Xe MR contrast agent but the likely differential properties of contrast generation in individual chemical compartments as well as the influence of 129Xe signal drifts encountered in vivo on HyperCEST MRI are unknown. Here, HyperCEST z spectroscopy and chemical shift imaging with compartment-specific analysis are performed in a total of 10 rats using cucurbit[6]uril injected i.v. and under a protocol employing spontaneous respiration. Differences in intensity of the HyperCEST effect between chemical compartments and anatomical regions are investigated. Strategies to mitigate influence of signal instabilities associated with drifts in physiological parameters are developed. It is shown that presence of cucurbit[6]uril can be readily detected under spontaneous 129Xe inhalation mostly in aqueous tissues further away from the lung. Differences of effect intensity in individual regions and compartments must be considered in HyperCEST data interpretation. In particular, there seems to be almost no effect in lipids. 129Xe HyperCEST MR measurements utilizing spontaneous respiration protocols and extended measurement times are feasible. HyperCEST MRI of non-functionalized cucurbit[6]uril may create contrast between anatomical structures in vivo.
{"title":"Compartment-specific 129Xe HyperCEST z spectroscopy and chemical shift imaging of cucurbit[6]uril in spontaneously breathing rats","authors":"Agilo Luitger Kern , Marcel Gutberlet , Regina Rumpel , Inga Bruesch , Jens M. Hohlfeld , Frank Wacker , Bennet Hensen","doi":"10.1016/j.zemedi.2023.08.005","DOIUrl":"10.1016/j.zemedi.2023.08.005","url":null,"abstract":"<div><div><sup>129</sup>Xe hyperpolarized gas chemical exchange saturation transfer (HyperCEST) MRI has been suggested as molecular imaging modality but translation to in vivo imaging has been slow, likely due to difficulties of synthesizing suitable molecules. Cucurbit[6]uril–either in readily available non-functionalized or potentially in functionalized form–may, combined with <sup>129</sup>Xe HyperCEST MRI, prove useful as a switchable <sup>129</sup>Xe MR contrast agent but the likely differential properties of contrast generation in individual chemical compartments as well as the influence of <sup>129</sup>Xe signal drifts encountered in vivo on HyperCEST MRI are unknown. Here, HyperCEST z spectroscopy and chemical shift imaging with compartment-specific analysis are performed in a total of 10 rats using cucurbit[6]uril injected i.v. and under a protocol employing spontaneous respiration. Differences in intensity of the HyperCEST effect between chemical compartments and anatomical regions are investigated. Strategies to mitigate influence of signal instabilities associated with drifts in physiological parameters are developed. It is shown that presence of cucurbit[6]uril can be readily detected under spontaneous <sup>129</sup>Xe inhalation mostly in aqueous tissues further away from the lung. Differences of effect intensity in individual regions and compartments must be considered in HyperCEST data interpretation. In particular, there seems to be almost no effect in lipids. <sup>129</sup>Xe HyperCEST MR measurements utilizing spontaneous respiration protocols and extended measurement times are feasible. HyperCEST MRI of non-functionalized cucurbit[6]uril may create contrast between anatomical structures in vivo.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 1","pages":"Pages 33-45"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10136802","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}
Pub Date : 2025-02-01DOI: 10.1016/j.zemedi.2024.07.004
Simon Schröer , Daniel Düx , Josef Joaquin Löning Caballero , Julian Glandorf , Thomas Gerlach , Dominik Horstmann , Othmar Belker , Moritz Gutt , Frank Wacker , Oliver Speck , Bennet Hensen , Marcel Gutberlet
Magnetic Resonance (MR) thermometry is used for the monitoring of MR-guided microwave ablations (MWA), and for the intraoperative evaluation of ablation regions. Nevertheless, the accuracy of temperature mapping may be compromised by electromagnetic interference emanating from the microwave (MW) generator. This study evaluated different setups for improving magnetic resonance imaging (MRI) during MWA with a modified MW generator.
MWA was performed in 15 gel phantoms comparing three setups: The MW generator was placed outside the MR scanner room, either connected to the MW applicator using a penetration panel with a radiofrequency (RF) filter and a 7 m coaxial cable (Setup 1), or through a waveguide using a 5 m coaxial cable (Setup 2). Setup 3 employed the MW generator within the MR scan room, connected by a 5 m coaxial cable. The coaxial cables in setups 2 and 3 were modified with custom shielding to reduce interference. The setups during ablation (active setup) were compared to a reference setup without the presence of the MW system. Thermometry and thermal dose maps (CEM43 model) were compared for the three configurations. Primary endpoints for assessment were signal-to-noise ratio (SNR), temperature precision, Sørensen-Dice-Coefficient (DSC), and RF-noise spectra.
Setup 3 showed highly significant electromagnetic interference during ablation with a SNR decrease by −60.4%±13.5% () compared to reference imaging. For setup 1 and setup 2 no significant decrease in SNR was measured with differences of −2.9%±9.8% () and −1.5%±12.8% (), respectively. SNR differences were significant between active setups 1 and 3 with −51.2%±16.1% () and between active setups 2 and 3 with −59.0%±15.5% () but not significant between active setups 1 and 2 with 19.0%±13.7% (). Furthermore, no significant differences were seen in temperature precision or DSCs between all setups, ranging from 0.33 °C ± 0.04 °C (Setup 1) to 0.38 °C ± 0.06 °C (Setup 3) () and from 87.0%±1.6% (Setup 3) to 88.1%±1.6% (Setup 2) (), respectively.
Both setups (1 and 2) with the MW generator outside the MR scanner room were beneficial to reduce electromagnetic interference during MWA. Moreover, provided that a shielded cable is utilized in setups 2 and 3, all configurations displayed negligible differences in temperature precision and DSCs, indicating that the location of the MW gener
{"title":"Reducing electromagnetic interference in MR thermometry: A comparison of setup configurations for MR-guided microwave ablations","authors":"Simon Schröer , Daniel Düx , Josef Joaquin Löning Caballero , Julian Glandorf , Thomas Gerlach , Dominik Horstmann , Othmar Belker , Moritz Gutt , Frank Wacker , Oliver Speck , Bennet Hensen , Marcel Gutberlet","doi":"10.1016/j.zemedi.2024.07.004","DOIUrl":"10.1016/j.zemedi.2024.07.004","url":null,"abstract":"<div><div>Magnetic Resonance (MR) thermometry is used for the monitoring of MR-guided microwave ablations (MWA), and for the intraoperative evaluation of ablation regions. Nevertheless, the accuracy of temperature mapping may be compromised by electromagnetic interference emanating from the microwave (MW) generator. This study evaluated different setups for improving magnetic resonance imaging (MRI) during MWA with a modified MW generator.</div><div>MWA was performed in 15 gel phantoms comparing three setups: The MW generator was placed outside the MR scanner room, either connected to the MW applicator using a penetration panel with a radiofrequency (RF) filter and a 7 m coaxial cable (Setup 1), or through a waveguide using a 5 m coaxial cable (Setup 2). Setup 3 employed the MW generator within the MR scan room, connected by a 5 m coaxial cable. The coaxial cables in setups 2 and 3 were modified with custom shielding to reduce interference. The setups during ablation (active setup) were compared to a reference setup without the presence of the MW system. Thermometry and thermal dose maps (CEM43 model) were compared for the three configurations. Primary endpoints for assessment were signal-to-noise ratio (SNR), temperature precision, Sørensen-Dice-Coefficient (DSC), and RF-noise spectra.</div><div>Setup 3 showed highly significant electromagnetic interference during ablation with a SNR decrease by −60.4%±13.5% (<span><math><mrow><mi>p</mi><mo><</mo><mn>0.001</mn></mrow></math></span>) compared to reference imaging. For setup 1 and setup 2 no significant decrease in SNR was measured with differences of −2.9%±9.8% (<span><math><mrow><mi>p</mi><mo>=</mo><mn>0.6</mn></mrow></math></span>) and −1.5%±12.8% (<span><math><mrow><mi>p</mi><mo>=</mo><mn>0.8</mn></mrow></math></span>), respectively. SNR differences were significant between active setups 1 and 3 with −51.2%±16.1% (<span><math><mrow><mi>p</mi><mo><</mo><mn>0.001</mn></mrow></math></span>) and between active setups 2 and 3 with −59.0%±15.5% (<span><math><mrow><mi>p</mi><mo><</mo><mn>0.001</mn></mrow></math></span>) but not significant between active setups 1 and 2 with 19.0%±13.7% (<span><math><mrow><mi>p</mi><mo>=</mo><mn>0.09</mn></mrow></math></span>). Furthermore, no significant differences were seen in temperature precision or DSCs between all setups, ranging from 0.33 °C ± 0.04 °C (Setup 1) to 0.38 °C ± 0.06 °C (Setup 3) (<span><math><mrow><mi>p</mi><mo>=</mo><mn>0.6</mn></mrow></math></span>) and from 87.0%±1.6% (Setup 3) to 88.1%±1.6% (Setup 2) (<span><math><mrow><mi>p</mi><mo>=</mo><mn>0.58</mn></mrow></math></span>), respectively.</div><div>Both setups (1 and 2) with the MW generator outside the MR scanner room were beneficial to reduce electromagnetic interference during MWA. Moreover, provided that a shielded cable is utilized in setups 2 and 3, all configurations displayed negligible differences in temperature precision and DSCs, indicating that the location of the MW gener","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 1","pages":"Pages 59-68"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141918507","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}
Pub Date : 2025-02-01DOI: 10.1016/j.zemedi.2024.07.010
Uwe Schneider , Jürgen Besserer
{"title":"Erratum to “Tumour volume distribution can yield information on tumour growth and tumour control” [Z Med Phys 32 (2022) 143–148]","authors":"Uwe Schneider , Jürgen Besserer","doi":"10.1016/j.zemedi.2024.07.010","DOIUrl":"10.1016/j.zemedi.2024.07.010","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 1","pages":"Page 111"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142117030","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}
Pub Date : 2025-02-01DOI: 10.1016/j.zemedi.2024.12.001
Grzegorz Bauman , Roya Afshari , Oliver Bieri
Purpose
This study aims to evaluate the feasibility of structural sub-millimeter isotropic brain MRI at 0.55 T using a 3D half-radial dual-echo balanced steady-state free precession sequence, termed bSTAR and to assess its potential for high-resolution magnetization transfer imaging.
Methods
Phantom and in-vivo imaging of three healthy volunteers was performed on a low-field 0.55 T MR-system with isotropic bSTAR resolution settings of 0.87 × 0.87 × 0.87 mm3 and 0.69 × 0.69 × 0.69 mm3. Furthermore, off-resonance mapping was performed using 3D double-echo spoiled gradient imaging. For magnetization transfer (MT) MRI, the RF pulse duration of the 0.87 mm bSTAR scan was modified. Data were reconstructed using a GPU-accelerated compressed sensing algorithm. Magnetization transfer ratio (MTR) maps were calculated from two bSTAR scans with and without RF pulse prolongation. The MTR scan took 5 minutes and the reproducibility was assessed through repeated scans.
Results
Off-resonance mapping revealed that bSSFP brain imaging with TR < 5ms is essentially free of off-resonance-related artifacts even near the nasal cavities. Phantom and in-vivo scans demonstrated the feasibility of sub-millimeter isotropic bSTAR imaging. MTR maps obtained with high isotropic resolution bSTAR showed contrast between white and gray matter in agreement with expectations from high-field studies. The MTR measurements were highly reproducible with an average inter-scan MTR peak value of 43.3 ± 0.3 percent units.
Conclusions
This study demonstrated the potential of sub-millimeter and artifact-free morphologic brain imaging at 0.55 T using bSTAR leveraging the advantages of low-field MRI, such as reduced susceptibility artifacts and improved radio-frequency field homogeneity. Furthermore, MT-sensitized bSTAR brain MRI enabled whole-brain MTR assessment within clinically feasible times and with high reproducibility.
目的：本研究旨在评估在0.55 T下使用三维半径向双回波平衡稳态自由进动序列（bSTAR）进行结构亚毫米各向同性脑MRI的可行性，并评估其在高分辨率磁化转移成像方面的潜力。方法:幻影和体内成像的三个健康的志愿者进行低场0.55 T mr系统各向同性bSTAR分辨率设置为0.87 × 0.87×0.87 mm3和0.69×0.69 ×0.69 mm3。此外，使用三维双回波破坏梯度成像进行非共振成像。对于磁化转移（MT） MRI，修改了0.87 mm bSTAR扫描的RF脉冲持续时间。数据重构采用gpu加速压缩感知算法。磁化传递比（MTR）图由两次bSTAR扫描计算，有和没有RF脉冲延长。MTR扫描耗时5分钟，通过重复扫描评估再现性。结果：非共振成像显示，即使在鼻腔附近，当TR < 5ms时，bSSFP脑成像基本上没有与非共振相关的伪影。幻影和活体扫描证明了亚毫米各向同性bSTAR成像的可行性。用高各向同性分辨率bSTAR获得的MTR地图显示了白质和灰质之间的对比，与高场研究的预期一致。MTR测量具有高重复性，平均扫描间MTR峰值为43.3 ± 0.3%单位。结论：本研究证明了在0.55 T时使用bSTAR进行亚毫米和无伪影的脑形态成像的潜力，利用低场MRI的优势，如减少敏感性伪影和改善射频场均匀性。此外，mt致敏的bSTAR脑MRI能够在临床可行的时间内进行全脑MTR评估，并且具有高重复性。
{"title":"Ultra-high-resolution brain MRI at 0.55T: bSTAR and its application to magnetization transfer ratio imaging","authors":"Grzegorz Bauman , Roya Afshari , Oliver Bieri","doi":"10.1016/j.zemedi.2024.12.001","DOIUrl":"10.1016/j.zemedi.2024.12.001","url":null,"abstract":"<div><h3>Purpose</h3><div>This study aims to evaluate the feasibility of structural sub-millimeter isotropic brain MRI at 0.55 T using a 3D half-radial dual-echo balanced steady-state free precession sequence, termed bSTAR and to assess its potential for high-resolution magnetization transfer imaging.</div></div><div><h3>Methods</h3><div>Phantom and in-vivo imaging of three healthy volunteers was performed on a low-field 0.55 T MR-system with isotropic bSTAR resolution settings of 0.87 × 0.87 × 0.87 mm<sup>3</sup> and 0.69 × 0.69 × 0.69 mm<sup>3</sup>. Furthermore, off-resonance mapping was performed using 3D double-echo spoiled gradient imaging. For magnetization transfer (MT) MRI, the RF pulse duration of the 0.87 mm bSTAR scan was modified. Data were reconstructed using a GPU-accelerated compressed sensing algorithm. Magnetization transfer ratio (MTR) maps were calculated from two bSTAR scans with and without RF pulse prolongation. The MTR scan took 5 minutes and the reproducibility was assessed through repeated scans.</div></div><div><h3>Results</h3><div>Off-resonance mapping revealed that bSSFP brain imaging with TR < 5ms is essentially free of off-resonance-related artifacts even near the nasal cavities. Phantom and in-vivo scans demonstrated the feasibility of sub-millimeter isotropic bSTAR imaging. MTR maps obtained with high isotropic resolution bSTAR showed contrast between white and gray matter in agreement with expectations from high-field studies. The MTR measurements were highly reproducible with an average inter-scan MTR peak value of 43.3 ± 0.3 percent units.</div></div><div><h3>Conclusions</h3><div>This study demonstrated the potential of sub-millimeter and artifact-free morphologic brain imaging at 0.55 T using bSTAR leveraging the advantages of low-field MRI, such as reduced susceptibility artifacts and improved radio-frequency field homogeneity. Furthermore, MT-sensitized bSTAR brain MRI enabled whole-brain MTR assessment within clinically feasible times and with high reproducibility.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 1","pages":"Pages 78-86"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143019466","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}
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