Designing 2D and 3D Adiabatic Pulses

Multi-Dimensional Adiabatic Pulse Design Using a Sub-Pulse Approach

A new method designs and implements spatially selective, multidimensional adiabatic radio frequency (RF) pulses for use in magnetic resonance imaging (MRI). Spatially selective inversion is achieved adiabatically in both two- and three-dimensional (2D and 3D) regions of interest. The multidimensional adiabatic pulses are designed by dividing a parent adiabatic pulse into 2D selective sub-pulse elements. Selective excitation is achieved by the sub-pulses while the phases and amplitudes of the sequence of sub-pulses are prescribed according to an adiabatic full passage (the parent adiabatic pulse). The approach can be extended to 3D by applying blips along the remaining direction between sub-pulses.

Complete Spatiotemporal Properties

Previous methods for designing a 2D adiabatic pulse use 1D amplitude-modulated sub-pulses to define a slice in one spatial direction and frequency- and amplitude-modulation of these consecutive sub-pulses to define a slice in a second spatial direction. By using 2D sub-pulses, this new approach enables 3D selection in space. By exploiting the spatiotemporal properties of this 3D excitation, it is possible to perform 3D spatiotemporally-encoded MRI (rather than exciting the entire object simultaneously). Furthermore, it offers the flexibility to choose the desired modulation method in either direction and/or to choose the desired shape of the selective excitation (square, cylinder, etc. Other advantages include significant acceleration in STEREO (scan-time), better image fidelity, compensation for B0 inhomogeneities in 1D, and volumetric slab selection for SWIFT.

BENEFITS AND FEATURES:

• Spatially selective, multidimensional adiabatic radio frequency (RF) pulses
• 2D and 3D adiabatic pulse design
• Complete spatiotemporal properties
• Uses a sub-pulse approach
• Significant acceleration in STEREO (scan-time)
• Image fidelity – better k-space trajectory to reduce saturation in center of k-space
• Can compensate for B0 inhomogeneities in 1D
• Provides volumetric slab selection for SWIFT (faster, higher resolution)
• Software implemented on MRI scanner
• Potentially disruptive (low-cost) technology

APPLICATIONS:

• May enable anatomy specific (breast, brain) scanners
• Could expand customer base beyond hospitals and imaging centers
• Selectively exciting a desired shape adiabatically can be used in applications such as navigator, in which the pulse can be tailored to a target organ to track anatomic motion.
• Can be used to selectively excite a volume of interest (e.g., the heart) to permit high resolution imaging in the volume in reduced time (i.e., since the field-of-view is reduced by volume selection, the number of k-space samples required to achieve a given resolution is reduced).

Phase of Development - Pilot scale demonstration