Jan Rieger

Modular 32-channel transceiver coil array for cardiac MRI at 7.0T

To design and evaluate a modular transceiver coil array with 32 independent channels for cardiac MRI at 7.0T.

Two-Dimensional Sixteen Channel Transmit/Receive Coil Array for Cardiac MRI at 7.0 T: Design, Evaluation, and Application

To design, evaluate, and apply a 2D 16‐channel transmit/receive (TX/RX) coil array tailored for cardiac magnetic resonance imaging (MRI) at 7.0 T.

Design and application of a four-channel transmit/receive surface coil for functional cardiac imaging at 7T.

To design and evaluate a four‐channel cardiac transceiver coil array for functional cardiac imaging at 7T.

Skin sodium measured with 23Na MRI at 7.0 T

Skin sodium (Na+) storage, as a physiologically important regulatory mechanism for blood pressure, volume regulation and, indeed, survival, has recently been rediscovered. This has prompted the development of MRI methods to assess Na+ storage in humans (23Na MRI) at 3.0 T. This work examines the feasibility of high in‐plane spatial resolution 23Na MRI in skin at 7.0 T. A two‐channel transceiver radiofrequency (RF) coil array tailored for skin MRI at 7.0 T (f = 78.5 MHz) is proposed. Specific absorption rate (SAR) simulations and a thorough assessment of RF power deposition were performed to meet the safety requirements. Human skin was examined in an in vivo feasibility study using two‐dimensional gradient echo imaging. Normal male adult volunteers (n = 17; mean ± standard deviation, 46 ± 18 years; range, 20–79 years) were investigated. Transverse slices of the calf were imaged with 23Na MRI using a high in‐plane resolution of 0.9 × 0.9 mm2. Skin Na+ content was determined using external agarose standards covering a physiological range of Na+ concentrations. To assess the intra‐subject reproducibility, each volunteer was examined three to five times with each session including a 5‐min walk and repositioning/preparation of the subject. The age dependence of skin Na+ content was investigated. The 23Na RF coil provides improved sensitivity within a range of 1 cm from its surface versus a volume RF coil which facilitates high in‐plane spatial resolution imaging of human skin. Intra‐subject variability of human skin Na+ content in the volunteer population was <10.3%. An age‐dependent increase in skin Na+ content was observed (r = 0.78). The assignment of Na+ stores with 23Na MRI techniques could be improved at 7.0 T compared with current 3.0 T technology. The benefits of such improvements may have the potential to aid basic research and clinical applications designed to unlock questions regarding the Na+ balance and Na+ storage function of skin. Copyright

16-channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla

To design, evaluate, and apply a bow tie antenna transceiver radiofrequency (RF) coil array tailored for cardiac MRI at 7.0 Tesla (T).

Assessment of the right ventricle with cardiovascular magnetic resonance at 7 Tesla

BackgroundFunctional and morphologic assessment of the right ventricle (RV) is of clinical importance. Cardiovascular magnetic resonance (CMR) at 1.5T has become gold standard for RV chamber quantification and assessment of even small wall motion abnormalities, but tissue analysis is still hampered by limited spatial resolution. CMR at 7T promises increased resolution, but is technically challenging. We examined the feasibility of cine imaging at 7T to assess the RV.MethodsNine healthy volunteers underwent CMR at 7T using a 16-element TX/RX coil and acoustic cardiac gating. 1.5T served as gold standard. At 1.5T, steady-state free-precession (SSFP) cine imaging with voxel size (1.2x1.2x6) mm3 was used; at 7T, fast gradient echo (FGRE) with voxel size (1.2x1.2x6) mm3 and (1.3x1.3x4) mm3 were applied. RV dimensions (RVEDV, RVESV), RV mass (RVM) and RV function (RVEF) were quantified in transverse slices. Overall image quality, image contrast and image homogeneity were assessed in transverse and sagittal views.ResultsAll scans provided diagnostic image quality. Overall image quality and image contrast of transverse RV views were rated equally for SSFP at 1.5T and FGRE at 7T with voxel size (1.3x1.3x4)mm3. FGRE at 7T provided significantly lower image homogeneity compared to SSFP at 1.5T. RVEDV, RVESV, RVEF and RVM did not differ significantly and agreed close between SSFP at 1.5T and FGRE at 7T (p=0.5850; p=0.5462; p=0.2789; p=0.0743). FGRE at 7T with voxel size (1.3x1.3x4) mm3 tended to overestimate RV volumes compared to SSFP at 1.5T (mean difference of RVEDV 8.2±9.3ml) and to FGRE at 7T with voxel size (1.2x1.2x6) mm3 (mean difference of RVEDV 9.3±8.6ml).ConclusionsFGRE cine imaging of the RV at 7T was feasible and provided good image quality. RV dimensions and function were comparable to SSFP at 1.5T as gold standard.

Ophthalmic Magnetic Resonance Imaging at 7 T Using a 6-Channel Transceiver Radiofrequency Coil Array in Healthy Subjects and Patients With Intraocular Masses

ObjectivesThis study was designed to examine the feasibility of ophthalmic magnetic resonance imaging (MRI) at 7 T using a local 6-channel transmit/receive radiofrequency (RF) coil array in healthy volunteers and patients with intraocular masses. Materials and MethodsA novel 6-element transceiver RF coil array that makes uses of loop elements and that is customized for eye imaging at 7 T is proposed. Considerations influencing the RF coil design and the characteristics of the proposed RF coil array are presented. Numerical electromagnetic field simulations were conducted to enhance the RF coil characteristics. Specific absorption rate simulations and a thorough assessment of RF power deposition were performed to meet the safety requirements. Phantom experiments were carried out to validate the electromagnetic field simulations and to assess the real performance of the proposed transceiver array. Certified approval for clinical studies was provided by a local notified body before the in vivo studies. The suitability of the RF coil to image the human eye, optical nerve, and orbit was examined in an in vivo feasibility study including (a) 3-dimensional (3D) gradient echo (GRE) imaging, (b) inversion recovery 3D GRE imaging, and (c) 2D T2-weighted fast spin-echo imaging. For this purpose, healthy adult volunteers (n = 17; mean age, 34 ± 11 years) and patients with intraocular masses (uveal melanoma, n = 5; mean age, 57 ± 6 years) were investigated. ResultsAll subjects tolerated all examinations well with no relevant adverse events. The 6-channel coil array supports high-resolution 3D GRE imaging with a spatial resolution as good as 0.2 × 0.2 × 1.0 mm3, which facilitates the depiction of anatomical details of the eye. Rather, uniform signal intensity across the eye was found. A mean signal-to-noise ratio of approximately 35 was found for the lens, whereas the vitreous humor showed a signal-to-noise ratio of approximately 30. The lens-vitreous humor contrast-to-noise ratio was 8, which allows good differentiation between the lens and the vitreous compartment. Inversion recovery prepared 3D GRE imaging using a spatial resolution of 0.4 × 0.4 × 1.0 mm3 was found to be feasible. T2-weighted 2D fast spin-echo imaging with the proposed RF coil afforded a spatial resolution of 0.25 × 0.25 × 0.7 mm3. ConclusionsThis work provides valuable information on the feasibility of ophthalmic MRI at 7 T using a dedicated 6-channel transceiver coil array that supports the acquisition of high-contrast, high–spatial resolution images in healthy volunteers and patients with intraocular masses. The results underscore the challenges of ocular imaging at 7 T and demonstrate that these issues can be offset by using tailored RF coil hardware. The benefits of such improvements would be in positive alignment with explorations that are designed to examine the potential of MRI for the assessment of spatial arrangements of the eye segments and their masses with the ultimate goal to provide imaging means for guiding treatment decisions in ophthalmological diseases.

W(h)ither human cardiac and body magnetic resonance at ultrahigh fields? technical advances, practical considerations, applications, and clinical opportunities

The objective of this study was to document and review advances and groundbreaking progress in cardiac and body MR at ultrahigh fields (UHF, B0 ≥ 7.0 T) with the goal to attract talent, clinical adopters, collaborations and resources to the biomedical and diagnostic imaging communities.

On the subjective acceptance during cardiovascular magnetic resonance imaging at 7.0 Tesla

Purpose This study examines the subjective acceptance during UHF-CMR in a cohort of healthy volunteers who underwent a cardiac MR examination at 7.0T. Methods Within a period of two-and-a-half years (January 2012 to June 2014) a total of 165 healthy volunteers (41 female, 124 male) without any known history of cardiac disease underwent UHF-CMR. For the assessment of the subjective acceptance a questionnaire was used to examine the participants experience prior, during and after the UHF-CMR examination. For this purpose, subjects were asked to respond to the questionnaire in an exit interview held immediately after the completion of the UHF-CMR examination under supervision of a study nurse to ensure accurate understanding of the questions. All questions were answered with “yes” or “no” including space for additional comments. Results Transient muscular contraction was documented in 12.7% of the questionnaires. Muscular contraction was reported to occur only during periods of scanning with the magnetic field gradients being rapidly switched. Dizziness during the study was reported by 12.7% of the subjects. Taste of metal was reported by 10.1% of the study population. Light flashes were reported by 3.6% of the entire cohort. 13% of the subjects reported side effects/observations which were not explicitly listed in the questionnaire but covered by the question about other side effects. No severe side effects as vomiting or syncope after scanning occurred. No increase in heart rate was observed during the UHF-CMR exam versus the baseline clinical examination. Conclusions This study adds to the literature by detailing the subjective acceptance of cardiovascular magnetic resonance imaging examinations at a magnetic field strength of 7.0T. Cardiac MR examinations at 7.0T are well tolerated by healthy subjects. Broader observational and multi-center studies including patient cohorts with cardiac diseases are required to gain further insights into the subjective acceptance of UHF-CMR examinations.

Sodium MRI of the human heart at 7.0 T: preliminary results.

The objective of this work was to examine the feasibility of three‐dimensional (3D) and whole heart coverage 23Na cardiac MRI at 7.0 T including single‐cardiac‐phase and cinematic (cine) regimes.