MR imaging with spiral acquisition

A method of magnetic resonance (MR) imaging of an object positioned in an examination volume of an MR device, the method comprising:

• subjecting the object to an imaging sequence comprising at least one RF excitation pulse and modulated magnetic field gradients,
• acquiring MR signals by sampling k-space along multiple planar spiral k-space trajectories in k-space traversed with a constant radial k-space speed, wherein
• a current spiral trajectory is traversed inward from a predetermined start k-space position such that a radial k-space sampling density is at least a current threshold value until a current end k-space position at which the radial k-space sampling density increases to a current ceiling value, and
• a next spiral trajectory is traversed inward from a next start k-space position after the current end k-space position such that the radial k-space sampling density is at least a next threshold value until a next end k-space position at which the radial k-space sampling density reaches a next ceiling value and wherein the multiple planar spiral k-space trajectories are offset in-plane from an origin of k-space so as to each start at a different origin for enhancing the sampling density in a periphery of the k-space.

A magnetic resonance (MR) device including at least one main magnet coil for generating a uniform, static magnetic field within an examination volume, a number of gradient coils for generating switched magnetic field gradients in different spatial directions within the examination volume, at least one RF coil for generating RF pulses within the examination volume and/or for receiving MR signals from an object positioned in the examination volume, a control unit for controlling a temporal succession of RF pulses and switched magnetic field gradients, and a reconstruction unit for reconstructing a MR image from the received MR signals, wherein the MR device is arranged to perform either

• subjecting the object to an imaging sequence comprising at least one RF excitation pulse and modulated magnetic field gradients,
• acquiring MR signals by sampling k-space along multiple planar spiral k-space trajectories in k-space traversed with a constant radial k-space speed, wherein
• a current spiral trajectory is traversed outward from a predetermined current initial k-space position until a current final k-space position such that at the current final k-space position a radial k-space sampling density decreases below a predetermined current threshold value, and
• a next spiral trajectory is traversed outward from a next initial k-space position until a next final k-space position such that the radial k-space sampling density decreases below a predetermined next threshold value at the next final k-space position and wherein the multiple planar spiral k-space trajectories are offset in-plane from an origin of k-space so as to each start at a different origin for enhancing the sampling density in a periphery of the k-space, or,
• subjecting the object to an imaging sequence comprising at least one RF excitation pulse and modulated magnetic field gradients,
• acquiring MR signals by sampling k-space along the multiple planar spiral k-space trajectories in k-space traversed with a constant radial k-space speed, wherein
• a current spiral trajectory is traversed inward from a predetermined start k-space position such that a radial k-space sampling density is at least a current threshold value until a current end k-space position at which the radial k-space sampling density increases to a current ceiling value, and
• a next spiral trajectory is traversed inward from a next start k-space position after the current end k-space position such that the radial k-space sampling density is at least a next threshold value until a next end k-space position at which the radial k-space sampling density reaches a next ceiling value and wherein the multiple planar spiral k-space trajectories are offset in-plane from an origin of k-space so as to each start at a different origin for enhancing the sampling density in a periphery of the k-space.

A non-transitory computer-readable medium storing a computer program to be run on a magnetic resonance (MR) device, which computer program comprises instructions to:

• subjecting an object to an imaging sequence comprising at least one RF excitation pulse and modulated magnetic field gradients,
• acquiring MR signals by sampling k-space along multiple planar spiral k-space trajectories in k-space traversed with a constant radial k-space speed, wherein
• a current spiral trajectory is traversed outward from a predetermined current initial k-space position until a current final k-space position such that at the current final k-space position the radial k-space sampling density decreases below a predetermined current threshold value, and
• a next spiral trajectory is traversed outward from a next initial k-space position until a next final k-space position such that the radial k-space sampling density decreases below a predetermined next threshold value at the next final k-space position and wherein the multiple planar spiral k-space trajectories are offset in-plane from an origin of k-space so as to each start at a different origin for enhancing the sampling density in a periphery of the k-space, or,
• subjecting the object to an imaging sequence comprising at least one RF excitation pulse and modulated magnetic field gradients,
• acquiring MR signals by sampling k-space along multiple planar spiral k-space trajectories in k-space traversed with a constant radial k-space speed, wherein
• a current spiral trajectory is traversed inward from a predetermined start k-space position such that the radial k-space sampling density is at least a current threshold value until a current end k-space position at which the radial k-space sampling density increases to a current ceiling value, and
• a next spiral trajectory is traversed inward from a next start k-space position after the current end k-space position such that the radial k-space sampling density is at least a next threshold value until a next end k-space position at which the radial k-space sampling density reaches a next ceiling value and wherein the multiple planar spiral k-space trajectories are offset in-plane from an origin of k-space so as to each start at a different origin for enhancing the sampling density in a periphery of the k-space.