Whole brain MP2RAGE-based mapping of the longitudinal relaxation time at 9.4T

Hagberg, Gisela E.; Bause, J; Ethofer, Thomas; Ehses, P; Dresler, Thomas; Herbert, Cornelia; Pohmann, R; Shajan, G; Fallgatter, Andreas J.; Pavlova, Marina; Scheffler, Klaus

doi:10.1016/j.neuroimage.2016.09.047

Cited by 42 publications

(54 citation statements)

References 61 publications

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“…Both data sets were reconstructed offline including a recovery of the skipped part of k‐space because of partial Fourier acquisition using POCS. Afterward, T 1 and MP2RAGE images were calculated from the individual contrasts with a correction of residual transmit field influences …”

Section: Methodssupporting

confidence: 91%

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Double‐row 18‐loop transceive–32‐loop receive tight‐fit array provides for whole‐brain coverage, high transmit performance, and SNR improvement near the brain center at 9.4T

Avdievich

Giapitzakis

Bause

et al. 2018

Magnetic Resonance in Med

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Purpose To improve the transmit (Tx) and receive (Rx) performance of a human head array and provide whole‐brain coverage at 9.4T, a novel 32‐element array design was developed, constructed, and tested. Methods The array consists of 18 transceiver (TxRx) surface loops and 14 Rx‐only vertical loops all placed in a single layer. The new design combines benefits of both TxRx and transmit‐only–receive‐only (ToRo) designs. The general idea of the design is that the total number of array elements (both TxRx and Rx) should not exceed the number of required Rx elements. First, the necessary number of TxRx loops is placed around the object tightly to optimize the Tx performance. The rest of the elements are loops, which are used only for reception. We also compared the performance of the new array with that of a state‐of‐the‐art ToRo array consisting of 16 Tx‐only loops and 31 Rx‐only loops. Results The new array provides whole‐brain coverage, ~1.5 times greater Tx efficiency and 1.3 times higher SNR near the brain center as compared to the ToRo array, while the latter delivers higher (up to 1.5 times) peripheral SNR. Conclusion In general, the new approach of constructing a single‐layer array consisting of both TxRx‐ and Rx‐only elements simplifies the array construction by minimizing the total number of elements and makes the entire design more robust and, therefore, safe. Overall, our work provides a recipe for a Tx‐ and Rx‐efficient head array coil suitable for parallel transmission and reception as well as whole‐brain imaging at UHF.

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Section: Methodssupporting

confidence: 91%

“…Afterward, T 1 and MP2RAGE images were calculated from the individual contrasts with a correction of residual transmit field influences. 36…”

Section: Experimental Evaluationmentioning

confidence: 99%

Double‐row 18‐loop transceive–32‐loop receive tight‐fit array provides for whole‐brain coverage, high transmit performance, and SNR improvement near the brain center at 9.4T

Avdievich

Giapitzakis

Bause

et al. 2018

Magnetic Resonance in Med

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show abstract

“…Note: the fitted baseline has been subtracted from the presented spectrum, fit, and macromolecular basis set data [Colour figure can be viewed at wileyonlinelibrary.com] of different water tissues at 9.4T (GM: 2000 ms, WM: 1300 ms, and CSF: 4000 ms) were taken from Ref. 29. The assumption for the T 2 relaxation times of water at 9.4T (GM: 45 ms, WM: 37 ms, and CSF: 311 ms) was made utilizing published values from human brain measured with a STEAM sequence at 7T 30 because, to the best of our knowledge, values are not yet available for 9.4T.…”

Section: Mrs Data Quantificationmentioning

confidence: 99%

Investigation of the influence of macromolecules and spline baseline in the fitting model of human brain spectra at 9.4T

Giapitzakis

Borbáth

Murali‐Manohar

et al. 2018

Magnetic Resonance in Med

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Purpose In this study, the influence of experimentally measured macromolecules and spline baseline on the quantification results of proton MRS data was investigated. Methods Proton MRS spectra from the left parietal lobe and the occipital lobe were acquired at 9.4T in the human brain using metabolite‐cycled semi‐LASER. Then, the left parietal lobe data, along with the occipital lobe, spectra were quantified and the influence of the inclusion of experimentally measured macromolecular basis sets in the fitting model was evaluated. Furthermore, the effect of the stiffness of the fitted spline baselines on the resulting metabolite concentrations was evaluated. Results In general, concentrations were higher for metabolites in occipital lobe than the left parietal lobe. The inclusion of an experimentally acquired measured macromolecular basis set from another brain region neither affected the quantification results nor the resulting spline baselines significantly. A highly flexible spline baseline led to overestimation or underestimation of metabolite concentrations. Differences of above 15% in the quantification of metabolite levels for both lobes were observed for several metabolites using LCModel default settings for spline baselines and macromolecules in comparison to stiffer spline baselines. Conclusion Fitting with the default LCModel macromolecular basis set and spline baseline model had significant influence in the resulting spline baselines, leading to large deviations both in the concentrations and fitted macromolecular components. The number of knots in the spline may create overflexible baselines, which can potentially lead to quantification errors. Interestingly, the interchange of macromolecular basis set between occipital lobe and left parietal lobe spectra had less influence on the quantification results compared to the default LCModel settings.

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“…100,101 Furthermore, T 1 -based methods are cross-validated with histological myelin staining 102 and postmortem myeloarchitecture 103 and show robust longitudinal reproducibility. 104,105 To our knowledge, this method is yet to be applied in the study of ARMS and other prepsychotic states.…”

Section: The Role Of Myelin In Morphometrymentioning

confidence: 99%