Patch-Probe Excitation for Ultrahigh Magnetic Field Wide-Bore MRI

Bluem, P.; Kiruluta, Andrew J.M.; Moortele, Pierre-François Van de; Duh, Allison; Adriany, Gregor; Popović, Zoya

doi:10.1109/tmtt.2017.2656084

Cited by 7 publications

(7 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other boundary structures that can affect field uniformity are electrically hard and soft surfaces as shown previously in [22]. Electrically hard surfaces are longitudinal corrugations used in horn antennas, to increase aperture efficiency by distributing the field more uniformly across the aperture, characterized by H lon =0 along the boundary [27], [26].…”

Section: Boundary Condition Modificationsmentioning

confidence: 96%

“…A quadrature circular patch is an effective traveling-wave MR probe [11]. The circular spatial current density distribution on the probe excites a circularly polarized field in the cylindrical bore as shown in [22]. A similar coaxially fed patch is designed on a Rogers 3010 substrate, ε r = 11.2 and 1.27 mm thick, shown in Fig.…”

Section: A Circular Patch Probementioning

confidence: 99%

“…Typical | B 1 + | shimming can only partially improve the field homogeneity [15]. Additionally, the complex structure of biological tissues can further complicate the excited field profile which can be manipulated using specially designed high permittivity [25] or metallic structures [22]. Three basic passive field modifiers are explored in this paper: (1) an undriven quadrifilar helix, (2) electrically hard surfaces, and (3) electrically soft surfaces [26].…”

Section: Boundary Condition Modificationsmentioning

confidence: 99%

See 2 more Smart Citations

Excitation and RF Field Control of a Human-Size 10.5-T MRI System

Bluem

Moortele

Adriany

et al. 2019

IEEE Trans. Microwave Theory Techn.

Self Cite

View full text Add to dashboard Cite

This paper presents an investigation of methods for improving homogeneity inside various dielectric phantoms situated in a 10.5 T human-sized MRI. The transmit B 1 (B 1 +) field is excited with a quadrature fed circular patch-probe and a 12 element capacitively-loaded microstrip array. Both simulations and measurements show improved homogeneity in a cylindrical water phantom, an inhomogeneous phantom (pineapple), and a NIST standard phantom. The simulations are performed using a full-wave finite-difference time-domain solver (Sim4Life) in order to find the B 1 + field distribution and compared to the gradient recalled echo image and efficiency result. For additional field uniformity, the wall electromagnetic boundary conditions are modified with a passive quadrifilar helix. Finally, these methods are applied in simulation to head imaging of an anatomically correct human body model (Duke, IT'IS Virtual Population) showing improved homogeneity and specific absorption rate for various excitations.

show abstract

Section: Boundary Condition Modificationsmentioning

confidence: 96%

Section: A Circular Patch Probementioning

confidence: 99%

Section: Boundary Condition Modificationsmentioning

confidence: 99%

See 1 more Smart Citation

Excitation and RF Field Control of a Human-Size 10.5-T MRI System

Bluem

Moortele

Adriany

et al. 2019

IEEE Trans. Microwave Theory Techn.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Schematics of RF coil arrays with multiple elements used to acquire images of lower limbs with whole-body MR imagers: (d), 12 (e), 13 (f), 14 (g), 15 and (h) two standard birdcage coils for lower limbs 17 The traveling-wave (tw) MRI approach provides an alternative to coil arrays with a larger number of coil elements. 40 This method is based on the use of a waveguide and a transmitter antenna, in order to acquire images with larger fields of view, such as at 7 T, 41 9.4 T, 42 and 10.5 T. 43 The viability of twMRI at ultrahigh fields (UHFs) using small-bore systems has also been demonstrated. [44][45][46] We have previously demonstrated that a parallel-plate waveguide (PPWG) can transmit an RF signal at 3 T 47,48 without dielectric materials, and that the waveguide dimensions play no role in the twMRI experiments.…”

Section: Introductionmentioning

confidence: 99%

External waveguide magnetic resonance imaging for lower limbs at 3 T

et al. 2021

View full text Add to dashboard Cite

Purpose. We report a method based on the traveling-wave MRI approach, in order to acquire images of human lower limbs with an external waveguide at 3 T. Methods. We use a parallel-plate waveguide and an RF surface coil for reception, while a whole-body birdcage is used for transmission. The waveguide and the surface coil are located right outside the magnet, in the magnetic resonance (MR) conditional devices zone. We ran numerical simulations to investigate the B 1 field generated by the surface coil located at one of the waveguides, as well as a saline-solution phantom positioned on the opposite side (150 cm away) inside the magnet. Results. We obtained phantom images by varying the distance between the coil and the phantom, in order to investigate the signal-to-noise ratio and to validate our numerical simulations. Lower limb images of a healthy volunteer were also acquired, demonstrating the viability of this approach. Standard pulse sequences were used and no physical modifications were made to the MR imager. Conclusions. These numerical and experimental results show that travelingwave MRI can produce high-quality images with only a simple waveguide and an RF coil located outside the magnet. This can be particularly favorable when acquiring images of lower limbs requiring a larger field of view.

show abstract

“…However, because of problems with excitation, DR probes have been used only for very small samples such as zebra fish. To resolve the problem of B1 uniformity in large volumes, authors of [56][57][58] proposed to employ travelling waves within the bores, which could perform as waveguides. However, small bores of UHF MRI scanners, operating at higher frequencies could not be used as waveguides because of supporting only evanescent waves.…”

Section: Rf Probes For Ultrahigh Field Mri Scannersmentioning

confidence: 99%

Employing Dielectric-Based Media for Controlling Field Patterns and Wave Propagation in Advanced Electromagnetic Devices

Gandji¹

View full text Add to dashboard Cite

Patch-Probe Excitation for Ultrahigh Magnetic Field Wide-Bore MRI

Cited by 7 publications

References 31 publications

Excitation and RF Field Control of a Human-Size 10.5-T MRI System

Excitation and RF Field Control of a Human-Size 10.5-T MRI System

External waveguide magnetic resonance imaging for lower limbs at 3 T

Employing Dielectric-Based Media for Controlling Field Patterns and Wave Propagation in Advanced Electromagnetic Devices

Contact Info

Product

Resources

About