Magnetic Resonance in Medicine最新文献

{"title":"Microstructure-Informed Myelin Mapping (MIMM) from routine multi-echo gradient echo data using multiscale physics modeling of iron and myelin effects and QSM.","authors":"Mert Şişman, Thanh D Nguyen, Alexandra G Roberts, Dominick J Romano, Alexey V Dimov, Ilhami Kovanlikaya, Pascal Spincemaille, Yi Wang","doi":"10.1002/mrm.30369","DOIUrl":"10.1002/mrm.30369","url":null,"abstract":"<p><strong>Purpose: </strong>Myelin quantification is used in the study of demyelination in neurodegenerative diseases. A novel noninvasive MRI method, Microstructure-Informed Myelin Mapping (MIMM), is proposed to quantify the myelin volume fraction (MVF) from a routine multi-gradient echo sequence (mGRE) using a multiscale biophysical signal model of the effects of microstructural myelin and iron.</p><p><strong>Theory and methods: </strong>In MIMM, the effects of myelin are modeled based on the Hollow Cylinder Fiber Model accounting for anisotropy, while iron is considered as an isotropic paramagnetic point source. This model is used to create a dictionary of mGRE magnitude signal evolution and total voxel susceptibility using finite elements of size 0.2 μm. Next, voxel-by-voxel stochastic matching pursuit between acquired mGRE data (magnitude+QSM) and the pre-computed dictionary generates quantitative MVF and iron susceptibility maps. Dictionary matching was evaluated under three conditions: (1) without fiber orientation (basic), (2) with fiber orientation obtained using DTI, and (3) with fiber orientation obtained using an atlas (atlas). MIMM was compared with the three-pool complex fitting (3PCF) using T2-relaxometry myelin water fraction (MWF) map as reference.</p><p><strong>Results: </strong>The DTI MIMM and atlas MIMM approaches were equally effective in reducing the overestimation of MVF in certain white matter tracts observed in the basic MIMM approach, and they both showed good agreement with T2-relaxometry MWF. MIMM MVF reduced myelin overestimation of globus pallidus observed in 3PCF MWF.</p><p><strong>Conclusion: </strong>MIMM processing of mGRE data can provide MVF maps from routine clinical scans without requiring special sequences.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142648383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of an integrated variable flip angle protocol to estimate coil B₁ for hyperpolarized MRI.","authors":"Kylie Yeung, Kher Lik Ng, Jordan J McGing, Aaron Axford, Sarah Birkhoelzer, Ayaka Shinozaki, Mattia Ricchi, Noemi Sgambelluri, Fulvio Zaccagna, Rebecca Mills, Andrew J M Lewis, Jennifer J Rayner, Zack Ravetz, Lise Berner, Kenneth Jacob, Anthony McIntyre, Marianne Durrant, Oliver J Rider, Rolf F Schulte, Fergus V Gleeson, Damian J Tyler, James T Grist","doi":"10.1002/mrm.30378","DOIUrl":"https://doi.org/10.1002/mrm.30378","url":null,"abstract":"<p><strong>Purpose: </strong>The purpose of this work is to validate a simple and versatile integrated variable flip angle (VFA) method for mapping B₁ in hyperpolarized MRI, which can be used to correct signal variations due to coil inhomogeneity.</p><p><strong>Theory and methods: </strong>Simulations were run to assess performance of the VFA B₁ mapping method compared to the currently used constant flip angle (CFA) approach. Simulation results were used to inform the design of VFA sequences, validated in four volunteers for hyperpolarized xenon-129 imaging of the lungs and another four volunteers for hyperpolarized carbon-13 imaging of the human brain. B₁ maps obtained were used to correct transmit and receive inhomogeneity in the images.</p><p><strong>Results: </strong>Simulations showed improved performance of the VFA approach over the CFA approach with reduced sensitivity to T₁. For xenon-129, the B₁ maps accurately reflected the variation of signal depolarization, but in some cases could not be used to correct for coil receive inhomogeneity due to a lack of transmit-receive reciprocity resulting from suboptimal coil positioning. For carbon-13, the B₁ maps showed good agreement with a separately acquired B₁ map of a phantom and were effectively used to correct coil-induced signal inhomogeneity.</p><p><strong>Conclusion: </strong>A simple, versatile, and effective VFA B₁ mapping method was implemented and evaluated. Inclusion of the B₁ mapping method in hyperpolarized imaging studies can enable more robust signal quantification.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142648332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A bootstrapping residuals approach to determine the error in quantitative functional lung imaging.","authors":"Anne Slawig, Andreas Max Weng, Simon Veldhoen, Herbert Köstler","doi":"10.1002/mrm.30367","DOIUrl":"https://doi.org/10.1002/mrm.30367","url":null,"abstract":"<p><strong>Purpose: </strong>To implement and validate an algorithm to determine the statistical errors in self-gated non-contrast-enhanced functional lung imaging.</p><p><strong>Methods: </strong>A bootstrapping residuals approach to determine the error in quantitative functional lung imaging is proposed. Precision and accuracy of the median error over the lungs, as well as reproducibility of the approach were investigated in 7 volunteers. The algorithm was additionally applied to data acquired in a patient with cystic fibrosis.</p><p><strong>Results: </strong>The obtained bootstrapping error maps appear comparable to the error maps determined from repeated measurements, and median absolute error values for both methods show comparable median errors when reducing the number of averages. In a volunteer in whom 10 consecutive measurements were carried out, the median functional parameters were ventilation = 0.22 mL gas/mL lung tissue, perfusion amplitude = 0.028, perfusion timing = -82 ms, whereas precision and accuracy of the median error were below 3.2 × 10^-3 mL gas/mL lung for ventilation tissue, 4.4 × 10^-4 for perfusion amplitude, and 11 ms for perfusion timing. In the measurement of the patient, low errors in areas with reduced ventilation support the assessment as real defects.</p><p><strong>Conclusion: </strong>Using a bootstrapping residuals method, the error of functional lung MRI could be determined without the need for repeated measurements. The error values can be determined reproducibly and can be used as a future means of quality control for functional lung MRI.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142648355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectrally selective and interleaved water imaging and fat imaging (siWIFI).","authors":"Soo Hyun Shin, Qingbo Tang, Michael Carl, Jiyo S Athertya, Arya Suprana, Yajun Ma","doi":"10.1002/mrm.30366","DOIUrl":"https://doi.org/10.1002/mrm.30366","url":null,"abstract":"<p><strong>Purpose: </strong>To develop a novel imaging sequence that independently acquires water and fat images while being inherently insensitive to motion.</p><p><strong>Methods: </strong>The new sequence, termed spectrally selective and interleaved water imaging and fat imaging (siWIFI), uses a narrow bandwidth RF pulse for selective excitation of water and fat separately. The interleaved acquisition method ensures that the obtained water and fat images are inherently coregistered. A radial sampling strategy further reduces motion-induced artifacts. Phantoms with lipid concentrations ranging from 0% to 50% were scanned to measure fat fraction. Moreover, healthy volunteers were scanned to assess the in vivo feasibility of fat fraction measurement at the hip, knee, and liver. In vivo fat fraction measurements were compared with those from vendor-provided iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) scans. Furthermore, a magnetization transfer (MT) preparation module was incorporated to demonstrate the feasibility of simultaneous measurement of fat fraction and MT ratio utilizing the siWIFI framework.</p><p><strong>Results: </strong>The phantom fat fractions measured by siWIFI showed excellent correlation with lipid concentrations (R² = 0.9995, p < 0.0001). In vivo studies demonstrated that the fat fractions obtained from siWIFI were comparable to those from IDEAL. Additionally, siWIFI demonstrates reduced motion artifacts from pulsatile flow in knee imaging compared to IDEAL scans and exhibits less sensitivity to respiratory motion in liver imaging compared to IDEAL scans without breath-hold. The knee imaging study demonstrated that MT-prepared siWIFI is capable of generating fat fraction and MT ratio maps simultaneously.</p><p><strong>Conclusion: </strong>The proposed siWIFI sequence allows selective water-fat imaging and quantification with reduced motion artifacts.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142623034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<ArticleTitle xmlns:ns0=\"http://www.w3.org/1998/Math/MathML\">Improving <ns0:math> <ns0:semantics> <ns0:mrow><ns0:msubsup><ns0:mi>B</ns0:mi> <ns0:mn>1</ns0:mn> <ns0:mo>+</ns0:mo></ns0:msubsup> </ns0:mrow> <ns0:annotation>$$ {B}_1^{+} $$</ns0:annotation></ns0:semantics> </ns0:math> -inhomogeneity tolerance by resolving non-bijection in MP2RAGE R₁ mapping: A 2D look-up table approach demonstrated at 3 T.","authors":"Lenno Ruijters, Torben Ellegaard Lund, Mads Sloth Vinding","doi":"10.1002/mrm.30363","DOIUrl":"https://doi.org/10.1002/mrm.30363","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Purpose: &lt;/strong&gt;Regarding in vivo, robust longitudinal relaxation rate (R&lt;sub&gt;1&lt;/sub&gt;) mapping, the goal of the present paper is two-fold. First, to verify that non-bijective mapping in magnetization-prepared 2 rapid gradient echo (MP2RAGE) imaging can be resolved through a two-dimensional look-up table approach. Second, that the expanded parameter space from this can be used to improve &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -inhomogeneity tolerance without other prerequisites.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Theory: &lt;/strong&gt;By deriving a second contrast from the magnitude images of the MP2RAGE acquisition, ambiguities in the original MP2RAGE image resulting from non-bijective transfer curves can be resolved. Such ambiguities may occur when protocols are optimized, such as for higher &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -inhomogeneity tolerance. A 2D look-up table approach combines the available information to resolve these ambiguities during mapping.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;At 3 T, we acquired MP2RAGE images with standard acquisition parameters and (non-bijective) parameters optimized for &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -inhomogeneity tolerance. From 3 subjects across multiple sessions, we assessed the &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -inhomogeneity tolerance through excitation-pulse amplitude scalings.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;The R&lt;sub&gt;1&lt;/sub&gt; maps resulting from the &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -optimized protocols showed greatly reduced &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; effects across images but without additional scanner time. Meanwhile, these maps could only successfully be derived by a 2D look-up table approach.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;We show that it is possible to optimize for &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -inhomogeneity tolerance in MP2RAGE through sequence-parameter settings, while still successfully estimating the R&lt;sub&gt;1&lt;/sub&gt; map with a two-dimensional look-up table approach. This without the need for an additional &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; map. The increased parameter space enabled by the two-dimensional look-up table ","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simultaneous monitoring of glycogen, creatine, and phosphocreatine in type II glycogen storage disease using saturation transfer MRI.","authors":"Chongxue Bie, Shaowei Bo, Nirbhay N Yadav, Peter C M van Zijl, Tao Wang, Lin Chen, Jiadi Xu, Chao Zou, Hairong Zheng, Yang Zhou","doi":"10.1002/mrm.30371","DOIUrl":"10.1002/mrm.30371","url":null,"abstract":"<p><strong>Purpose: </strong>There is a need for non-invasive approaches to assess the progression of glycogen storage diseases (GSD). Here, we use saturation transfer (ST) MRI via relayed nuclear Overhauser effects (glycoNOE) to detect abnormal changes in muscle glycogen of a GSD II mouse model. In addition to glycogen, the energy metabolites phosphocreatine (PCr) and creatine (Cr) were studied to assess the muscle disease.</p><p><strong>Methods: </strong>Water saturation (Z-spectra) and ¹H MRS were acquired at 9.4 T on the skeletal muscle of healthy control mice and homozygous acid <math> <semantics><mrow><mi>α</mi></mrow> <annotation>$$ upalpha $$</annotation></semantics> </math> -glucosidase (GAA) knock-out mice (ages of 2-48 weeks). The glycoNOE (-1 ppm), total creatine (tCr)* (+2 ppm, = a × [Cr] + b × [PCr]), and PCr (+2.5 ppm) from Z-spectra and the ratio between tCr and taurine signals (tCr/Tau) from ¹H MRS spectra were quantified by using multi-pool Lorentzian fitting methods. The concentrations of the metabolites were also measured via tissue assays.</p><p><strong>Results: </strong>The postnatal GSD II mice (age <12 weeks) showed a continued accumulation of muscle glycoNOE signal. GlycoNOE in adult GSD II mice (age ≥12 weeks) reached a plateau, at a level above 400% of that in normal mice. PCr, tCr*, and tCr/Tau gradually decreased in GSD II mice during the postnatal stage, then stabilized at levels comparable to adult control, yet PCr in adult GSD II mice was lower than that in controls.</p><p><strong>Conclusion: </strong>This study demonstrates that ST MRI of glycogen can provide in situ non-invasive biomarkers for GSD II disease progression, with the potential to study the progression and treatment response of GSDs.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142623028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reproducibility of liver ADC measurements using first moment optimized diffusion imaging.","authors":"Timothy J Allen, Rianne A van der Heijden, Gregory Simchick, Diego Hernando","doi":"10.1002/mrm.30372","DOIUrl":"https://doi.org/10.1002/mrm.30372","url":null,"abstract":"<p><strong>Purpose: </strong>Cardiac-induced liver motion can bias liver ADC measurements and compromise reproducibility. The purpose of this work was to enable motion-robust DWI on multiple MR scanners and assess reproducibility of the resulting liver ADC measurements.</p><p><strong>Methods: </strong>First moment-optimized diffusion imaging (MODI) was implemented on three MR scanners with various gradient performances and field strengths. MODI-DWI and conventional Stejskal-Tanner monopolar (MONO) DWI were acquired in eight (N = 8) healthy volunteers on each scanner, and DWI repetitions were combined using three different averaging methods. For each combination of scanner, acquisition, and averaging method, ADC measurements from each liver segment were collected. Systematic differences in ADC values between scanners and methods were assessed with linear mixed effects modeling, and reproducibility was quantified via reproducibility coefficients.</p><p><strong>Results: </strong>MODI reduced left-right liver lobe ADC bias from 0.43 × 10^-3 mm²/s (MONO) to 0.19 × 10^-3 mm²/s (MODI) when simple (unweighted) repetition averaging was used. The bias was reduced from 0.23 × 10^-3 mm²/s to 0.06 × 10^-3 mm²/s using weighted averaging, and 0.14 × 10^-3 mm²/s to 0.01 × 10^-3 mm²/s using squared weighted averaging. There was no significant difference in ADC measurements between field strengths or scanner gradient performance. MODI improved reproducibility coefficients compared to MONO: 0.84 × 10^-3 mm²/s vs. 0.63 × 10^-3 mm²/s (MODI vs. MONO) for simple averaging, 0.66 × 10^-3 mm²/s vs. 0.50 × 10^-3 mm²/s for weighted averaging, and 0.61 × 10^-3 mm²/s vs. 0.47 × 10^-3 mm²/s for squared weighted averaging.</p><p><strong>Conclusion: </strong>The feasibility of motion-robust liver DWI using MODI was demonstrated on multiple MR scanners. MODI improved interlobar agreement and reproducibility of ADC measurements in a healthy cohort.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142623008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design and operation of a whole-body MRI scanner without RF shielding.","authors":"Stephan Biber, Stephan Kannengiesser, Juergen Nistler, Markus Braun, Stefan Blaess, Matthias Gebhardt, David Grodzki, Dieter Ritter, Georg Seegerer, Markus Vester, Rainer Schneider","doi":"10.1002/mrm.30374","DOIUrl":"https://doi.org/10.1002/mrm.30374","url":null,"abstract":"<p><strong>Purpose: </strong>To investigate how a clinical MRI system can be operated without an RF cabin. Receive interference cancellation via signal processing and active transmit emission suppression are evaluated for mitigating image artifacts and achieving electromagnetic compatibility.</p><p><strong>Methods: </strong>A clinical whole-body MR scanner with B₀ = 0.55 T was placed in an environment without RF shielding. The signals of 16 additional auxiliary receive antenna elements outside the scanner bore were used to remove interference from the wanted MR signal via a dedicated sidelobe cancellation algorithm. In vivo measurements with different MR sequences were performed in the presence of ambient RF noise and additional artificial interferers, covering brain and abdominal applications. To investigate the transmit electromagnetic compatibility, simulations with different auxiliary transmit antenna arrangements and body coil loading conditions were performed, and their emission suppression performance in the far field was evaluated.</p><p><strong>Results: </strong>The MR sidelobe cancellation algorithm successfully removed interference artifacts up to more than 3 times of the wanted MR image energy; difference images carried little to no visibly removed wanted signal. According to the simulations, electromagnetic compliance can be achieved with 32 or more auxiliary transmit antennas. The number and placement of sensor points are essential.</p><p><strong>Conclusions: </strong>A whole-body 0.55T MR scanner can be operated without RF shielding. Image artifacts from external interference can be removed, requiring only a modest number of auxiliary antennas. Electromagnetic compliance appears to be achievable using active transmit cancellation, but the required hardware efforts may not be practical.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EPI proton resonant frequency temperature mapping at 0.5T in the brain: Comparison to single-echo gradient recalled echo.","authors":"Diego F Martinez, Curtis N Wiens, Chad T Harris, William B Handler, Blaine A Chronik","doi":"10.1002/mrm.30373","DOIUrl":"https://doi.org/10.1002/mrm.30373","url":null,"abstract":"<p><strong>Purpose: </strong>Evaluate the use of both single-echo gradient recalled echo (SE-GRE) and EPI approaches to creating temperature maps on a mid-field head-only scanner, both in vivo and on a tissue mimicking gel.</p><p><strong>Methods: </strong>Three 2D protocols were investigated (an SE-GRE, single-shot EPI, and an averaged single-shot EPI). The protocols used either a gradient recalled acquisition or an echo planar acquisition, with EPI parameters optimized for the longer <math> <semantics> <mrow><msubsup><mi>T</mi> <mn>2</mn> <mo>*</mo></msubsup> </mrow> <annotation>$$ {mathrm{T}}_2^{ast } $$</annotation></semantics> </math> at lower field-strengths. Phantom experiments were conducted to evaluate temperature tracking while cooling, comparing protocol to measurements from an optical fiber thermometer. Studies were performed on a 0.5T head only MR scanner. Temperature stability maps were produced in vivo for the various protocols to evaluate precision.</p><p><strong>Results: </strong>The use of an EPI protocol for thermometry improved temperature precision in a temperature control phantom and provided an 18% improvement in temperature measurement precision in vivo. Temperature tracking using a fast (<2 s) update rate EPI thermometry sequence provided a similar precision to the slower SE-GRE protocol.</p><p><strong>Conclusion: </strong>While SE-GRE PRF thermometry shows good performance, EPI methods offer improved tracking precision or update rate, making them a better option for thermometry in the brain at mid-field.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142623000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simultaneous multi-slice cardiac real-time MRI at 0.55T.","authors":"Ecrin Yagiz, Parveen Garg, Steven Y Cen, Krishna S Nayak, Ye Tian","doi":"10.1002/mrm.30364","DOIUrl":"10.1002/mrm.30364","url":null,"abstract":"<p><strong>Purpose: </strong>To determine the feasibility of simultaneous multi-slice (SMS) real-time MRI (RT-MRI) at 0.55T for the evaluation of cardiac function.</p><p><strong>Methods: </strong>Cardiac CINE MRI is routinely used to evaluate left-ventricular (LV) function. The standard is sequential multi-slice balanced SSFP (bSSFP) over a stack of short-axis slices using electrocardiogram (ECG) gating and breath-holds. SMS has been used in CINE imaging to reduce the number of breath-holds by a factor of 2-4 at 1.5T, 3T, and recently at 0.55T. This work aims to determine if SMS is similarly effective in the RT-MRI evaluation of cardiac function. We used an SMS bSSFP pulse sequence with golden-angle spirals at 0.55T with an SMS factor of three. We cover the LV with three acquisitions for SMS, and nine for single-band (SB). Imaging was performed on 9 healthy volunteers and 1 patient with myocardial fibrosis and sternal wires. A spatio-temporal constrained reconstruction is used, with regularization parameters selected by a board-certified cardiologist. Images were quantitatively analyzed with a normalized contrast and an Edge Sharpness (ES) score.</p><p><strong>Results: </strong>There was a statistically significant 2-fold difference in contrast between SMS and SB and no significant difference in ES score. The contrast for SMS and SB were 13.38/29.05 at mid-diastole and 10.79/22.26 at end-systole; the ES scores for SMS and SB were 1.77/1.83 at mid-diastole and 1.50/1.72 at end-systole.</p><p><strong>Conclusions: </strong>SMS cardiac RT-MRI at 0.55T is feasible and provides sufficient blood-myocardium contrast to evaluate LV function in three slices simultaneously without any gating or periodic motion assumptions.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142591044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}