<sup>1</sup><scp>H MR</scp> spectroscopic imaging of the prostate at 7<scp>T</scp> using spectral‐spatial pulses

Lagemaat, Miriam W.; Breukels, Vincent; Vos, Eline K.; Kerr, Adam B.; Uden, Mark J. van; Orzada, Stephan; Bitz, Andreas K.; Maas, Marnix C.; Scheenen, Tom W. J.

doi:10.1002/mrm.25569

Cited by 16 publications

(28 citation statements)

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“…The reason is that the combined spectral‐spatial pulses for refocusing are not as selective for the signals of interest as the separate volume‐selective pulses and frequency‐selective suppression pulses, used at 1.5 and 3T in the other groups. In combination with the difficulties at 7T to obtain homogeneous flip angles over the whole prostate, this leads to areas with low SNR and with large lipid contamination in the prostate …”

Section: Discussionmentioning

confidence: 99%

“…It was necessary to reset the Q ratio threshold for QC of 7T MR spectra because of dominant spermine signals at this field strength, specifically in healthy tissue . Thus, if a large signal overlaps with specific peaks included in the Q ratio , its classification threshold will need adaptation.…”

Section: Discussionmentioning

confidence: 99%

“…For PRESS (point resolved spectroscopy) and semi‐LASER (localized by adiabatic selective refocusing) sequences, water and lipid signals were suppressed by dual‐frequency selective pulses and by outer‐volume suppression slabs placed around the prostate. In the double spin‐echo sequence at 7T, only spins of relevant metabolites inside the prostate were refocused, using spectral‐spatial pulses, whereas dephasing those of water and periprostatic lipids …”

Section: Methodsmentioning

confidence: 99%

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Simple and broadly applicable automatic quality control for 3D ¹H MR spectroscopic imaging data of the prostate

Tayari

Obels

Kobus

et al. 2018

Magnetic Resonance in Med

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Purpose Quality control (QC) is a prerequisite for clinical MR spectroscopic imaging (MRSI) to avoid that bad spectra hamper data interpretation. The aim of this work was to present a simple automatic QC for prostate 1H MRSI that can handle data obtained with different commonly used pulse sequences, echo times, field strengths, and MR platforms. Methods A QC method was developed with a ratio (Qratio) where the numerator and the denominator are functions of several signal heights, logically combined for their positive or negative contribution to spectral quality. This Qratio was tested on 4 data sets obtained at 1.5, 3, and 7T, with and without endorectal coil and different localization sequences and echo times. Spectra of 25,248 voxels in 26 prostates were labeled as acceptable or unacceptable by MRS experts as gold standard. A threshold value was determined for Qratio from a subset of voxels, labeled in consensus by 4 experts, for an optimal accuracy to separate spectra. Results Applying this Qratio threshold to the remaining test voxels, an automatic separation of good and bad spectra was possible with an accuracy of 0.88, similar to manual separation between the 2 classes. Qratio values were used to generate maps representing spectral quality on a binary or continuous scale. Conclusion Automated QC of prostate 1H MRSI by Qratio is fast, simple, easily transferable and more practical than supervised feature extraction methods and therefore easy to integrate into different clinical MR systems. Moreover, quality maps can be generated to read the reliability of spectra in each voxel.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Simple and broadly applicable automatic quality control for 3D ¹H MR spectroscopic imaging data of the prostate

Tayari

Obels

Kobus

et al. 2018

Magnetic Resonance in Med

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“…Proton MRSI was performed using a PRESS‐like sequence with RF refocusing pulses that are both spectrally and spatially selective, such that the signal of a volume of interest (VOI) is received only from the spectral region of interest (2.3–3.3 ppm) . 31 P MRSI was performed using a 3D phase‐encoded pulse‐acquire sequence with a nonselective BIR‐4 excitation pulse (see Table for further imaging and spectroscopy details).…”

Section: Methodsmentioning

confidence: 99%

A multitransmit external body array combined with a ¹H and ³¹P endorectal coil to enable a multiparametric and multimetabolic MRI examination of the prostate at 7T

et al. 2019

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Purpose In vivo 1H and 31P magnetic resonance spectroscopic imaging (MRSI) provide complementary information on the biology of prostate cancer. In this work we demonstrate the feasibility of performing multiparametric imaging (mpMRI) and 1H and 31P spectroscopic imaging of the prostate using a 31P and 1H endorectal radiofrequency coil (ERC) in combination with a multitransmit body array at 7 Tesla (T).MethodsAn ERC with a 31P transceiver loop coil and 1H receive (Rx) asymmetric microstrip (31P/1H ERC) was designed, constructed and tested in combination with an external 8‐channel 1H transceiver body array coil (8CH). Electromagnetic field simulations and measurements and in vivo temperature measurements of the ERC were performed for safety validation. In addition, the signal‐to‐noise (SNR) benefit of the 1H microstrip with respect to the 8CH was evaluated. Finally, the feasibility of the setup was tested in one volunteer and three patients with prostate cancer by performing T2‐weighted and diffusion‐weighted imaging in combination with 1H and 31P spectroscopic imaging.ResultsElectromagnetic field simulations of the 31P loop coil showed no differences in the E‐ and B‐fields of the 31P/1H ERC compared with a previously safety validated ERC without 1H microstrip. The hotspot of the specific absorption rate (SAR) at the feed point of the 31P/1H ERC loop coil was 9.42 W/kg when transmitting on 31P at 1 W. Additional in vivo measurements showed a maximum temperature increase at the SAR hotspot of 0.7°C over 6 min on 31P at 1.9 W transmit (Tx) power, indicating safe maximum power levels. When transmitting with the external 1H body array at 40W for 2:30 min, the temperature increase around the ERC was < 0.3°C. Up to 3.5 cm into the prostate the 1H microstrip of the ERC provided higher SNR than the 8CH. The total coil combination allowed acquisition of an mpMRI protocol and the assessment of 31P and 1H metabolites of the prostate in all test subjects.ConclusionWe developed a setup with a 31P transceiver and 1H Rx endorectal coil in combination with an 8‐channel transceiver external body array coil and demonstrated its safety and feasibility for obtaining multiparametric imaging and 1H and 31P MRSI at 7T in patients with prostate cancer within one MR examination.

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“…Improvements in pulse sequence design have enabled the acquisition of metabolic information from the entire prostate at high resolution within less than 10 min with voxel sizes ranging from 0.2 to 0.5 cm 3 , making 1H-MRSI a clinically feasible technique [139,140]. These include using flyback echo-planar readout gradients to improve efficiency and robustness to errors and non-uniform undersampling, and compressed sensing to accelerate the acquisition [141,142]. A number of techniques have been used to reduce the negative effects of periprostatic fat, including outer volume saturation (OVS) with very selective suppression (VSS) pulses [143], band selective inversion with gradient dephasing (BASING) [144,145], and spectral-spatial radiofrequency pulses [146,147].…”

Section: Proton Magnetic Resonance Spectroscopic Imagingmentioning

confidence: 99%

Practical aspects of prostate MRI: hardware and software considerations, protocols, and patient preparation

et al. 2015

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The use of multiparametric MRI scans for the evaluation of men with prostate cancer has increased dramatically and is likely to continue expanding as new developments come to practice. However, it has not yet gained the same level of acceptance of other imaging tests. Partly, this is because of the use of suboptimal protocols, lack of standardization, and inadequate patient preparation. In this manuscript, we describe several practical aspects of prostate MRI that may facilitate the implementation of new prostate imaging programs or the expansion of existing ones.

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¹H MR spectroscopic imaging of the prostate at 7T using spectral‐spatial pulses

Abstract: It is possible to perform prostate (1)H-MRSI at 7T with a SPSP-MRSI sequence while using separate transmit and receive coils. This low-SAR MRSI concept provides the opportunity to increase spatial resolution of MRSI within reasonable scan times.

Cited by 16 publications

References 50 publications

Simple and broadly applicable automatic quality control for 3D ¹H MR spectroscopic imaging data of the prostate

Simple and broadly applicable automatic quality control for 3D ¹H MR spectroscopic imaging data of the prostate

A multitransmit external body array combined with a ¹H and ³¹P endorectal coil to enable a multiparametric and multimetabolic MRI examination of the prostate at 7T

Practical aspects of prostate MRI: hardware and software considerations, protocols, and patient preparation

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1H MR spectroscopic imaging of the prostate at 7T using spectral‐spatial pulses

Abstract: It is possible to perform prostate (1)H-MRSI at 7T with a SPSP-MRSI sequence while using separate transmit and receive coils. This low-SAR MRSI concept provides the opportunity to increase spatial resolution of MRSI within reasonable scan times.

Cited by 16 publications

References 50 publications

Simple and broadly applicable automatic quality control for 3D 1H MR spectroscopic imaging data of the prostate

Simple and broadly applicable automatic quality control for 3D 1H MR spectroscopic imaging data of the prostate

A multitransmit external body array combined with a 1H and 31P endorectal coil to enable a multiparametric and multimetabolic MRI examination of the prostate at 7T

Practical aspects of prostate MRI: hardware and software considerations, protocols, and patient preparation

Contact Info

Product

Resources

About

¹H MR spectroscopic imaging of the prostate at 7T using spectral‐spatial pulses

Simple and broadly applicable automatic quality control for 3D ¹H MR spectroscopic imaging data of the prostate

Simple and broadly applicable automatic quality control for 3D ¹H MR spectroscopic imaging data of the prostate

A multitransmit external body array combined with a ¹H and ³¹P endorectal coil to enable a multiparametric and multimetabolic MRI examination of the prostate at 7T