Whole-body radiofrequency coil for<sup>31</sup>P MRSI at 7 T

Löring, J.; Kemp, Wybe J. M. van der; Almujayyaz, Salam; Oorschot, Joep W. M. van; Luijten, Peter R.; Klomp, Dennis W. J.

doi:10.1002/nbm.3517

Cited by 28 publications

(44 citation statements)

References 46 publications

(78 reference statements)

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“…B 1 + field homogeneity was assessed from designs by Löring as our design is merely scaled to the bore size. The homogeneity of the insert was shown from the use of B 1 maps from 3 T proton MRI, which have identical diameter and coil layout to the present 31 P body coil and are tuned to almost the same frequency …”

Section: Discussionsupporting

confidence: 81%

“…19 In another recent publication, Löring et al showed an insertable 31 P birdcage body coil that can produce uniform B 1 fields, thus allowing the use of rectangular RF pulse excitations. 20 This birdcage coil is wide enough to accommodate the human torso, allowing 31 In this work, we demonstrate that the permanent installation of a 31 P body coil behind the covers of the patient tube, ie without sacrificing patient space, while interfacing to a high power RF amplifier, increases its usability. The reduction in SAR with this body coil allows the use of rectangular and even multiple rectangular composite pulses.…”

Section: Introductionmentioning

confidence: 80%

“…The space requirements for such setup may be comparable to those of conventional clinical MRI receiver arrays, where 16‐channel body arrays are being used on a regular basis. The 31 P receivers, as demonstrated here, can be merged with the relatively thin dipole antennas as can be seen in Figure A and aB, without efficiency losses …”

Section: Discussionmentioning

confidence: 99%

“…In another recent publication, Löring et al showed an insertable 31 P birdcage body coil that can produce uniform B 1 fields, thus allowing the use of rectangular RF pulse excitations . This birdcage coil is wide enough to accommodate the human torso, allowing 31 P MRSI of the human body, yet occupies space from the bore limiting inclusion of heavy patients and reduces space for receiver coils.…”

Section: Introductionmentioning

confidence: 99%

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Low SAR ³¹P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

et al. 2019

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Phosphorus (31P) MRSI provides opportunities to monitor potential biomarkers. However, current applications of 31P MRS are generally restricted to relatively small volumes as small coils are used. Conventional surface coils require high energy adiabatic RF pulses to achieve flip angle homogeneity, leading to high specific absorption rates (SARs), and occupy space within the MRI bore. A birdcage coil behind the bore cover can potentially reduce the SAR constraints massively by use of conventional amplitude modulated pulses without sacrificing patient space. Here, we demonstrate that the integrated 31P birdcage coil setup with a high power RF amplifier at 7 T allows for low flip angle excitations with short repetition time (T R) for fast 3D chemical shift imaging (CSI) and 3D T 1‐weighted CSI as well as high flip angle multi‐refocusing pulses, enabling multi‐echo CSI that can measure metabolite T 2, over a large field of view in the body. B 1 + calibration showed a variation of only 30% in maximum B 1 in four volunteers. High signal‐to‐noise ratio (SNR) MRSI was obtained in the gluteal muscle using two fast in vivo 3D spectroscopic imaging protocols, with low and high flip angles, and with multi‐echo MRSI without exceeding SAR levels. In addition, full liver MRSI was achieved within SAR constraints. The integrated 31P body coil allowed for fast spectroscopic imaging and successful implementation of the multi‐echo method in the body at 7 T. Moreover, no additional enclosing hardware was needed for 31P excitation, paving the way to include larger subjects and more space for receiver arrays. The increase in possible number of RF excitations per scan time, due to the improved B 1 + homogeneity and low SAR, allows SNR to be exchanged for spatial resolution in CSI and/or T 1 weighting by simply manipulating T R and/or flip angle to detect and quantify ratios from different molecular species.

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Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Low SAR ³¹P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

et al. 2019

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“…The combination of the receive sensitivity of modern coil-arrays with the transmit power, B 1 homogeneity, and volume coverage of volume coils, e.g., the recently proposed volume coil for 7 T [28], could, in the future, constitute a prime tool for 31 P-MR at ultra-high fields.…”

Section: Introductionmentioning

confidence: 99%

In-vivo 31P-MRS of skeletal muscle and liver: A way for non-invasive assessment of their metabolism

Valkovič

Chmelík

Krššák

2017

Analytical Biochemistry

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In addition to direct assessment of high energy phosphorus containing metabolite content within tissues, phosphorus magnetic resonance spectroscopy (31P-MRS) provides options to measure phospholipid metabolites and cellular pH, as well as the kinetics of chemical reactions of energy metabolism in vivo. Even though the great potential of 31P-MR was recognized over 30 years ago, modern MR systems, as well as new, dedicated hardware and measurement techniques provide further opportunities for research of human biochemistry. This paper presents a methodological overview of the 31P-MR techniques that can be used for basic, physiological, or clinical research of human skeletal muscle and liver in vivo. Practical issues of 31P-MRS experiments and examples of potential applications are also provided. As signal localization is essential for liver 31P-MRS and is important for dynamic muscle examinations as well, typical localization strategies for 31P-MR are also described.

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³¹P MR Spectroscopy in the Pancreas: Repeatability, Comparison With Liver, and Pilot Pancreatic Cancer Data

Seelen,

van den Wildenberg,

Gursan

et al. 2024

Magnetic Resonance Imaging

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BackgroundNon‐invasive evaluation of phosphomonoesters (PMEs) and phosphodiesters (PDEs) by 31‐phosphorus MR spectroscopy (31P MRS) may have potential for early therapy (non‐)response assessment in cancer. However, 31P MRS has not yet been applied to investigate the human pancreas in vivo.PurposeTo assess the technical feasibility and repeatability of 31P MR spectroscopic imaging (MRSI) of the pancreas, compare 31P metabolite levels between pancreas and liver, and determine the feasibility of 31P MRSI in pancreatic cancer.Study TypeProspective cohort study.Population10 healthy subjects (age 34 ± 12 years, four females) and one patient (73‐year‐old female) with pancreatic ductal adenocarcinoma.Field Strength/Sequence7‐T, 31P FID‐MRSI, 1H gradient‐echo MRI.Assessment31P FID‐MRSI of the abdomen (including the pancreas and liver) was performed with a nominal voxel size of 20 mm (isotropic). For repeatability measurements, healthy subjects were scanned twice on the same day. The patient was only scanned once. Test–retest 31P MRSI data of pancreas and liver voxels (segmented on 1H MRI) of healthy subjects were quantified by fitting in the time domain and signal amplitudes were normalized to γ‐adenosine triphosphate. In addition, the PME/PDE ratio was calculated. Metabolite levels were averaged over all voxels within the pancreas, right liver lobe and left liver lobe, respectively.Statistical TestsRepeatability of test–retest data from healthy pancreas was assessed by paired t‐tests, Bland–Altman analyses, and calculation of the intrasubject coefficients of variation (CoVs). Significant differences between healthy pancreas and right and left liver lobes were assessed with a two‐way analysis of variance (ANOVA) for repeated measures. A P‐value <0.05 was considered statistically significant.ResultsThe intrasubject CoVs for PME, PDE, and PME/PDE in healthy pancreas were below 20%. Furthermore, PME and PME/PDE were significantly higher in pancreas compared to liver. In the patient with pancreatic cancer, qualitatively, elevated relative PME signals were observed in comparison with healthy pancreas.Data ConclusionIn vivo 31P MRSI of the human healthy pancreas and in pancreatic cancer may be feasible at 7 T.Evidence Level3Technical EfficacyStage 2

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Whole-body radiofrequency coil for³¹P MRSI at 7 T

Cited by 28 publications

References 46 publications

Low SAR ³¹P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

Low SAR ³¹P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

In-vivo 31P-MRS of skeletal muscle and liver: A way for non-invasive assessment of their metabolism

³¹P MR Spectroscopy in the Pancreas: Repeatability, Comparison With Liver, and Pilot Pancreatic Cancer Data

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Whole-body radiofrequency coil for31P MRSI at 7 T

Cited by 28 publications

References 46 publications

Low SAR 31P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

Low SAR 31P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

In-vivo 31P-MRS of skeletal muscle and liver: A way for non-invasive assessment of their metabolism

31P MR Spectroscopy in the Pancreas: Repeatability, Comparison With Liver, and Pilot Pancreatic Cancer Data

Contact Info

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Whole-body radiofrequency coil for³¹P MRSI at 7 T

Low SAR ³¹P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

Low SAR ³¹P (multi‐echo) spectroscopic imaging using an integrated whole‐body transmit coil at 7T

³¹P MR Spectroscopy in the Pancreas: Repeatability, Comparison With Liver, and Pilot Pancreatic Cancer Data