Whole body 3T MRI system with eight parallel RF transmit/receive channels and dual operation modes

Graesslin, I.; Vernickel, P.; Schmidt, John C.; Findeklee, Christian; Röschmann, P.; Leussler, Christoph; Haaker, P.; Laudan, H.; Luedeke, K. M.; Scholz, J.; Buller, S.; Keupp, Jochen; Börnert, Peter; Dingemans, H.; Mens, Giel; Vissers, G.; Blom, Kevin; Heijden, Jvd; Swennen, N.; Mollevanger, L.; Harvey, Paul R.; Katscher, Ulrich

doi:10.1055/s-2007-972138

Cited by 23 publications

(28 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Each bottle had a square cross-section of 5 Â 5 cm 2 , yielding an overall phantom size of 25 Â 25 cm 2 . This phantom was used to determine the spatial transmit sensitivity distributions S n (r) of the N ¼ 8 elements of a multichannel body coil (20), integrated in a Philips 3T Achieva (Philips Medical System, Best, The Netherlands) (13). The transmit sensitivities were measured by actual flip angle imaging (17), including RF spoiling (21) (TR1/ TR2/echo time ¼ 40/200/2 ms, a ¼ 60 , spatial resolution 20 Â 20 Â 10 mm 3 ).…”

Section: Determination Of Encoding Functionsmentioning

confidence: 99%

“…To resolve two spatial dimensions via backprojection-like techniques, a rotation of the object (5), a rotation of the surface transmit coil around the object (7), or the application of orthogonal RF gradients (6,8) was proposed. Parallel transmit systems (11)(12)(13)(14), supporting multiple individual transmit channels, facilitate the mentioned rotations in an electronic, nonmechanical manner. This new hardware concept, originally developed to cope with spatial B 1 inhomogeneities, can find interesting applications in RF encoding and might enable even three-dimensional spatial resolution.…”

mentioning

confidence: 99%

See 1 more Smart Citation

RF encoding using a multielement parallel transmit system

Katscher

Lisinski

Börnert

2010

Magnetic Resonance in Med

View full text Add to dashboard Cite

Radiofrequency (RF) encoding using spatially variant RF transmission fields represents an alternative to the conventional signal-encoding techniques applied in MRI, which are based on main field gradients. Thus, RF encoding might allow omitting the use of all main field gradients, alleviating acoustic noise and other main field gradient-related problems. This study investigates the potential of RF transmit encoding using spatially nonlinear RF fields generated by an eight-channel parallel transmit system equipped with the corresponding transmit array. Appropriate spatial encoding functions are determined iteratively by randomized superposition of the array element sensitivities and judging their performance. Besides RF amplitude-based signal encoding, the possibility of RF phase-dominated encoding is investigated to allow future fast imaging applications. The theoretical background is given and experimental phantom results are compared with predictions from corresponding simulations to prove the basic feasibility of the approach for low-resolution MRI. Deviations of roughly 10-15% between main field and RF encoded images were found for an in-plane resolution of 5 3 5 mm 2 . The approach of RF encode MRI does not seem to be able to replace standard main field gradient encoding completely, but a suitable combination of both concepts could find promising applications.

show abstract

Section: Determination Of Encoding Functionsmentioning

confidence: 99%

mentioning

confidence: 99%

RF encoding using a multielement parallel transmit system

Katscher

Lisinski

Börnert

2010

Magnetic Resonance in Med

View full text Add to dashboard Cite

show abstract

“…107 Left: Transmit-receive RF coil with eight cylindrically arranged transverse electromagnetic elements, 105 and quality phantom. Center: Corresponding cabinets showing eight RF amplifiers, two circulator boxes (central cabinet) and the fully integrated spectrometer (right cabinet).…”

Section: Figmentioning

confidence: 99%

Parallel Magnetic Resonance Imaging

Katscher

Börnert

2007

Neurotherapeutics

View full text Add to dashboard Cite

Summary: Parallel MRI started with the introduction of coil arrays in improving radiofrequency (RF) acquisition (what is called parallel imaging) and continued with an analogous development for RF transmission (parallel transmission). Based on differences in the spatial sensitivity distributions of the involved array elements, both techniques try to shorten the respective k-space trajectory. Parallel imaging refers to the acquisition of k-space data, whereas parallel transmission is dealing with the deposition of RF energy packages in the excitation k-space.However, parallel transmission is not simply the reciprocal of parallel imaging. The main goal of parallel imaging is the shortening of the acquisition time. The main goal of parallel transmission is the shortening of the pulse duration of spatially selective RF pulses. The present article describes the basic concept, the state of the art, and the similarities and differences of both technologies.

show abstract

“…More recently, researchers have designed eight-channel parallel excitation systems and demonstrated slice-selective and 2D spatial excitations (5,9).…”

Section: Introductionmentioning

confidence: 99%

Comparison of three algorithms for solving linearized systems of parallel excitation RF waveform design equations: Experiments on an eight‐channel system at 3 Tesla

Zelinski

Wald

Setsompop

et al. 2007

Concepts Magn Reson

View full text Add to dashboard Cite

Three algorithms for solving linearized systems of RF waveform design equations for calculating accelerated spatially-tailored excitations on parallel excitation MRI systems are presented. Their artifact levels, computational speed, and RF peak and root-mean-square (RMS) voltages are analyzed. An SVD-based inversion method is compared with conjugate gradient least squares (CGLS) and least squares QR (LSQR), two iterative algorithms designed to solve large linear systems. The excitation pulses calculated using these methods are used in both Bloch simulations and imaging experiments on an actual eight-channel parallel excitation coil array implemented on a 3T human scanner. Specifically, RF waveforms are designed for accelerated 2D spiral k-space trajectories to produce a variety of 2D target excitations and for a 3D spokes trajectory to produce a uniform thin-slice excitation. Overall, these experiments show that waveforms designed using LSQR and CGLS have significantly lower peak and RMS waveform voltages and produce excitations with fewer artifacts than those generated by the SVDbased method.

show abstract

Whole body 3T MRI system with eight parallel RF transmit/receive channels and dual operation modes

Cited by 23 publications

References 0 publications

RF encoding using a multielement parallel transmit system

RF encoding using a multielement parallel transmit system

Parallel Magnetic Resonance Imaging

Comparison of three algorithms for solving linearized systems of parallel excitation RF waveform design equations: Experiments on an eight‐channel system at 3 Tesla

Contact Info

Product

Resources

About