Dipole arrays
For precision imaging at ultra-high field, multi-channel arrays of radiative dipole antennas1,2 provide an optimal solution. We offer dipole arrays for different imaging targets. Dipoles have proven to be a good choice to be integrated with high density receive loop arrays for accelerated imaging. Previous solutions have been successfully applied in cardiac imaging3, prostate imaging4, breast imaging5, and brain imaging6. We have extensive experience with safety validation of dipole antennas at ultrahigh field (7T and 10.5T).
Current portfolio of dipole array coils:
Dipole body array
Imaging target: abdomen, heart, prostate
Geometry: flexible leather former
Tx channels: 8
Rx channels: 8-64
Field strengths: 3T, 7T, 10.5T and beyond
Dipole breast array
Imaging target: breast
Geometry: rigid former, prone position
Tx channels: 5, can be modified for single Tx mode
Rx channels: 30
Field strength: 7T and 10.5T (MIRACLE project FETOPEN)
References
1Raaijmakers, The Fractionated Dipole Antenna: A New Antenna for Body Imaging at 7 Tesla MRM 2016.
2Steensma et al., Optimization and validation of dipole antenna geometry for 10.5T, ISMRM 2018.
3Steensma, An 8‑channel Tx/Rx dipole array combined with 16 Rx loops for high‑resolution functional cardiac imaging at 7T, MAGMA 2018
4Steensma, Comparing Signal-to-Noise Ratio for Prostate Imaging at 7T and 3T, jMRI 2019.
5Krikken et al., Homogeneous B1+ for bilateral breast imaging at 7T using a five dipole transmit array merged with a high density receive loop array, NMR in Biomed 2018.
6Haghnejiad, S.A., Flexible dipoles for multitransmit headneck MRI at 7T, eSMRMb 2016
Birdcage coils
Birdcages for low and high field MRI can be delivered. Like dipole arrays, birdcages can be combined with high density receive array for high sensitivity and fast parallel imaging. Depending on frequency and imaging target a best fitting solution can be chosen.
For example, an integrated 1H/23Na transmit coil for combined imaging of anatomy and sodium metabolism. Transmit coil were integrated with multi-channel receive coil for accelerated 1H and or 23Na imaging. Current solution focuses on imaging of the knee1, but can be used for imaging of other extremities. Prototype can also be upscaled to a headcoil model.
1Brinkhof et al., Uncompromised MRI of knee cartilage while incorporating sensitive sodium MRI, Proc. ISMRM 2019
Phantoms
MR compatible phantoms from tissue mimicking materials such as ethylene glycol or polyvinylpyrrolidone are used as a filler. Gel-phantoms combining a PVP solution with Agar can be constructed for MRI based safety validation of RF coils in MR thermometry. Fluid filled phantoms with ethyleneglycol or saline-solution can be used for system calibrations. Multiple phantom geometries, such as a pelvic mimicking or a head mimicking shape can be produced. Phantoms can be integrated with cavities for placement of thermal probes or an endo-coil.
Interface boxes
Interface box to extend the transmit/receive capabilities of the MRI systems. Robust mechanical design allows for placement in the magnetic field without the use of additional fixation methods. The current prototype combines two 16 channel transmit/receive switch boxes for in a 32 channel parallel transmit/receive setup. Additional interface boxes can be implemented for receive only purposes and for different operating frequencies.
MRI system upgrades
High performance upgrades to extend the possibilities of the MRI system. Previous work integrates a 32 channel RF amplifier as an add-on to a 7T system for extended multi-transmit capabilities and improved image quality1. Other possibilities exist in integrating multi-nuclear amplifiers in the MRI system, or in integrating multi-transmit possibilities in the system using vector modulators.
References
1Steensma et al., Approaching the ultimate intrinsic coil performance for 7T body imaging with high-density parallel transmit/receive arrays, Proc. ISMRM 2019
