Data acquisition acceleration in magnetic resonance angiography applications using magnetization-prepared simultaneous multi-slice acquisition
A method for producing an image representative of the vasculature of a subject using a MRI system includes the acquisition of a signal indicative of a subject' cardiac phase. During each heartbeat of the subject, image slices of a volume covering a region of interest (ROI) within the subject are acquired by applying a volume-selective venous suppression pulse to suppress (a) venous signal for an upper slice in the ROI; (b) venous signal for slices that are upstream for venous flow in the ROI; and (c) background signal from the upstream slices. Next, a slice-selective background suppression pulse is applied to suppress background signal of the upper slice. Following a quiescent time interval, a spectrally selective fat suppression pulse is applied to the entire volume to attenuate signal from background fat signal. Then, a simultaneous multi-slice acquisition of the upper slice and the upstream slices is performed.
1. A method for using magnetic resonance angiography to acquire an image representative of the vasculature of a subject with a magnetic resonance imaging (MRI) system, the method comprising:
acquiring a signal indicative of a cardiac phase of the subject;
during each heartbeat of the subject, acquiring a plurality of image slices of a volume covering a region of interest within the subject using an acquisition process comprising:
applying a volume-selective venous suppression pulse to suppress (a) venous signal for an upper slice in the region of interest; (b) venous signal for one or more upstream slices that are upstream for venous flow in the region of interest; and (c) background signal from the one or more upstream slices for venous flow;
applying a slice-selective background suppression pulse to suppress background signal of the upper slice;
following a quiescent time interval, applying a spectrally selective fat suppression pulse to the entire volume to attenuate signal from background fat signal; and
performing a simultaneous multi-slice acquisition of the upper slice and the one or more upstream slices for venous flow.
2. The method of claim 1 , wherein each acquisition process is performed following a user-selected time delay after the R-wave of each heartbeat.
3. The method of claim 1 , wherein the volume-selective venous suppression pulse comprises a tracking saturation pulse applied downstream to the upper slice and the one or more upstream slices.
4. The method of claim 1 , wherein the slice-selective background suppression pulse applies a 90 degree flip angle to the upper slice.
5. The method of claim 1 , wherein the slice-selective background suppression pulse applies a 180 degree flip angle to the upper slice.
6. The method of claim 1 , wherein the spectrally selective fat suppression pulse is a 90 degree RF pulse which rotates magnetizations in fat tissue of the entire volume into the x-y plane of the subject.
7. The method of claim 1 , wherein the spectrally selective fat suppression pulse is a 180 degree RF pulse which completely inverts longitudinal magnetization of fat in the entire volume and wherein the method further comprises:
waiting a predetermined inversion time prior to performing the simultaneous multi-slice acquisition of the upper slice and the one or more upstream slices, wherein the predetermined inversion time is selected such that longitudinal magnetization of fat in the upper slice and the one or more upstream slices recovers through a zero point when acquiring k-space data during the simultaneous multi-slice acquisition.
8. The method of claim 1 , wherein the simultaneous multi-slice acquisition is performed using a single-shot pulse sequence.
9. The method of claim 8 , wherein the single-shot pulse sequence is a balanced steady-state free precession pulse sequence or spoiled gradient echo pulse sequence.
10. A system for using magnetic resonance angiography to acquire an image representative of the vasculature of a subject, the system comprising:
an electrocardiogram device configured to acquire a signal indicative of a cardiac phase of the subject;
an imaging device comprising a plurality of coils configured to:
during each heartbeat of the subject, apply a preparation pulse sequence to a volume, the preparation pulse sequence comprising:
a volume-selective venous suppression pulse that suppresses (a) venous signal from an upper slice in a region of interest, (b) venous signal from one or more upstream slices that are upstream for venous flow in the region of interest, and (c) background signal from the one or more upstream slices,
a slice-selective background suppression pulse that suppresses background signal of the upper slice,
a spectrally selective fat suppression pulse applied to the volume to attenuate signal from background fat signal, and
following each preparation pulse sequence, perform a simultaneous multi-slice acquisition of the upper slice and the one or more upstream slices to update a k-space dataset covering the region of interest; and
a central control computer unit configured to apply a reconstruction process to the k-space dataset to generate one or more images.