Magnetic resonance imaging at several RF frequencies
A magnetic resonance imaging system comprises a receiver system to acquire magnetic resonance signals. A control system controls the receiver system to reform an acquisition sequence to acquire the magnetic resonance signals in several acquisition segments. Respective groups of acquisition segments involve acquisition of magnetic resonance signals in different RF-receiver frequency bands. In the respective groups of acquisition segments, magnetic resonance signals are acquired from different nuclei having different gyromagnetic ratios. According to the invention, reconstruction of different types of information carried by the respective nuclei is made possible. For example, imaging of the anatomy of a patient to be examined is performed on the basis of proton magnetic resonance imaging. Imaging of a targeted contrast agent is achieved on the basis of 19 F magnetic resonance imaging. Localisation of a invasive device, such as a catheter, is also performed on the basis of e.g. 19 F magnetic resonance imaging.
1. A magnetic resonance imaging system comprising:
a receiver system to acquire magnetic resonance signals;
a reconstruction unit to reconstruct a magnetic resonance image from the acquired magnetic resonance signals; and
a control system to control the receiver system to
perform an acquisition sequence to acquire the magnetic resonance signals in several acquisition segments,
wherein respective groups of acquisition segments involve acquisition of magnetic resonance signals in different RF-receiver frequency bands,
the control system is arranged to perform oversampling in the signal acquisition in lower RF-receiver frequency bands, and
the reconstruction unit is arranged to account for the oversampling.
2. The magnetic resonance imaging system as claimed in claim 1 , wherein the acquisition sequence includes alternating or interleaved acquisition segments of different groups of acquisition segments.
3. The magnetic resonance imaging system as claimed in claim 1 , wherein
the acquisition sequence includes simultaneous acquisition segments of different groups of acquisition segments,
the different RF-receiver frequency bands of these different groups of acquisition segments relating to different types of nuclei having different gyromagnetic ratios.
4. The magnetic resonance imaging system as claimed in claim 1 , further comprising
an RF-excitation system,
the control system being further arranged to control the RF-excitation system, and
wherein
the acquisition sequence includes RF-excitations from several excitation groups,
respective excitation groups involve RF-excitations in different RF excitation frequency bands.
5. The magnetic resonance imaging system as claimed in claim 1 , wherein at least one of the acquisition segments includes successive RF-excitations at pre-determined flip angles at alternating sign.
6. The magnetic resonance imaging system as claimed in claim 1 , including
a gradient system to apply encoding magnetic gradient fields and
a correction module to correct for differences between the field-of-view at respective RF-receiver frequency bands.
7. The magnetic resonance imaging system as claimed in claim 4 , wherein the control system is arranged to control the RF-excitation system to perform RF-excitation during acquisition of magnetic resonance echo signals at different RF-excitation frequency bands and RF-receiver frequency bands, respectively.
8. The magnetic resonance imaging system as claimed in claim 1 , further including a display system to display magnetic resonance image reconstructed by the reconstruction unit,
the reconstruction unit being arranged to reconstruct respective magnetic resonance images from magnetic resonance signals from respective acquired groups of segments, and
the display system being arranged to successively display the respective magnetic resonance image at a frame rate of at least a threshold frame rate.
9. The magnetic resonance imaging system as claimed in claim 8 , wherein the reconstruction unit is arranged to reconstruct a merged magnetic resonance image from magnetic resonance signals from several acquired groups of segments or from respective magnetic resonance images from magnetic resonance signals from respective acquired groups of segments.
10. The magnetic resonance imaging system as claimed in claim 8 , wherein the display system is arranged to display image information from respective RF-receiver frequency bands is different ways, including in different colors.
11. A magnetic resonance imaging method comprising the acts of:
performing an acquisition sequence to acquire magnetic resonance signals in several acquisition segments, wherein respective groups of acquisition segments involve acquisition of magnetic resonance signals in different RF-receiver frequency bands, and wherein the performing act includes oversampling the magnetic resonance signals in lower RF-receiver frequency bands; and
accounting for the oversampling act.
12. A computer readable medium embodying a computer program, the computer program when executed by a processor is configured to perform an acquisition sequence to acquire magnetic resonance signals in several acquisition segments respective groups of acquisition segments involve acquisition of magnetic resonance signals in different RF-receiver frequency bands, including oversampling the magnetic resonance signals in lower RF-receiver frequency bands; and to account for the oversampling.