Metal resistant MR imaging

A method of magnetic resonance (MR) imaging of at least a portion of a body placed within an examination volume of a MR device, the method comprising:

• with a host computer, controlling a gradient magnetic field coil and at least two RF coils to subject the portion of the body to a first imaging sequence of RF pulses and switched magnetic field gradients and acquire first MR signals via the at least two RF coils, the at least two RF coils having different spatial sensitivity profiles within the examination volume,
• with the host computer, deriving the spatial sensitivity profiles of the at least two RF coils from the acquired first MR signals,
• with the host computer controlling a gradient magnetic field coil and at least two RF coils to subject the portion of the body to a second imaging sequence of RF pulses and switched magnetic field gradients, wherein second MR signals are acquired by parallel acquisition via the at least two RF coils with sub-sampling of k-space,
• with a reconstruction processor, reconstructing a MR image of at least the portion of the body from the acquired second MR signals and from the spatial sensitivity profiles of the at least two RF coils,
• determining a presence of a metal implant in the body portion, wherein the first imaging sequence is selected to be:
• a gradient echo sequence, if no metal implants are determined to be present in the portion of the body, and
• a spin echo sequence or a stimulated echo sequence, if metal implants are determined to be present in the portion of the body.

A magnetic resonance (MR) device comprising:

• at least one main magnet coil configured to generate a steady magnetic field within an examination volume
• a plurality of gradient coils configured to generate switched magnetic field gradients in different spatial directions within the examination volume;
• a plurality of RF coils including at least one RF coil configured to transmit RF pulses into the examination volume and at least two RF coils having different spatial sensitivity profiles within the examination volume configured to receive MR signals from at least a portion of a body of a patient positioned in the examination volume;
• a control processor configured to:
• determine whether a metal implant is disposed in the portion of the body,
• select a first imaging sequence and parameters of the first imaging sequence from a plurality of imaging sequences and parameters in response to determining whether a metal implant is present in the portion of the body,
• control the gradient and RF coils to subject the portion of the body to the selected first imaging sequence of RF pulses and switched magnetic field gradients to repeatedly induce first MR signals in the portion of the body,
• control the at least two RF coils having different spatial sensitivity profiles within the examination volume to acquire the first MR signals,
• derive the spatial sensitivity profiles of the at least two RF coils from the acquired first MR signals,
• control the gradient and RF coils to subject the portion of the body to a second imaging sequence of RF pulses and switched magnetic field gradients to induce second MR signals in the portion of the body,
• control the at least two RF coils to acquire the second MR signals by parallel signal acquisition with sub-sampling of k-space;
• a reconstruction processor configured to reconstruct a MR image from the acquired second MR signals and from the spatial sensitivity profiles of the at least two RF coils;
• and
• a monitor configured to display the reconstructed MR image.

A non-transitory computer readable medium carrying computer software which when run on one or more processors of a magnetic resonance (MR) device, controls the MR device to:

• determine whether or not a metal implant is in a portion of a body,
• select a first imaging sequence from a plurality of imaging sequences based on determining whether or not the metal implant is in the portion of the body,
• generate the selected first imaging sequence of RF pulses and switched magnetic field gradients to generate first MR signals, wherein the first MR signals are acquired via at least two RF coils having different spatial sensitivity profiles within the examination volume,
• derive the spatial sensitivity profiles of the at least two RF coils from the acquired first MR signals,
• generate a second imaging sequence of RF pulses and switched magnetic field gradients to generate the second MR signals, wherein the second MR signals are acquired by parallel signal acquisition via the at least two RF coils with sub-sampling of k-space,
• reconstruct a MR image from the acquired second MR signals and from the spatial sensitivity profiles of the at least two RF coils, and
• control a monitor to display the reconstructed MR image.