System and method for phase contrast imaging with improved efficiency
A system and method is provided for magnetic resonance angiography (MRA) that includes performing a pulse sequence using the MRI system, the pulse sequence including a phase-based flow encoding to collect a time-series of image data from the portion of the vasculature of the subject and identifying at least a portion of the time series of image data corresponding to a period of reduced flow through the portion of the vasculature. The portion of the time series of image data is subtracted from the time series of image data to create a time series of images of the portion of the vasculature having background tissue surrounding the portion of the vasculature substantially suppressed.
1. A method of acquiring a magnetic resonance angiography (MRA) image of a portion of a vasculature of a subject using a magnetic resonance imaging (MRI) system, the method comprising:
performing a pulse sequence using the MRI system, the pulse sequence including a phase-based flow encoding to collect a time-series of image data from the portion of the vasculature of the subject;
monitoring, during the performing of the pulse sequence, a cardiac cycle of the subject and synchronizing the collection of the time-series of image data from the portion of the vasculature of the subject to the cardiac cycle of the subject;
identifying at least a portion of the time series of image data within the cardiac cycle and corresponding to a period of reduced flow through the portion of the vasculature; and
subtracting the portion of the time series of image data within the cardiac cycle from the time series of image data to create a time series of images of the portion of the vasculature having background tissue surrounding the portion of the vasculature substantially suppressed.
2. The method of claim 1 wherein identifying at least a portion of the time series of image data includes selecting at least one image frame to create a subtraction image.
3. The method of claim 2 wherein subtracting includes subtracting the subtraction image from each image frame reconstructed from the time series of image data.
4. The method of claim 2 wherein identifying at least a portion of the time series of image data includes selecting multiple image frames and averaging the multiple image frames to create a subtraction image.
5. The method of claim 4 wherein subtracting includes subtracting the subtraction image from each image frame reconstructed from the time series of image data.
6. The method of claim 1 wherein identifying includes selecting at least one image frame from a time series of images reconstructed from the time series of image data corresponding to reduced flow from through the portion of the vasculature.
7. The method of claim 1 wherein subtracting includes iteratively processing each image frame reconstructed from the time series of image data with respect to the identified at least a portion of the time series of image data.
8. The method of claim 1 wherein a minority of image frames is acquired using a flow-rephased gradient waveform.
9. A magnetic resonance imaging (MRI) system comprising:
a magnet system configured to generate a polarizing magnetic field about at least a portion of a subject arranged in the MRI system;
a plurality of gradient coils configured to apply a gradient field to the polarizing magnetic field;
a radio frequency (RF) system configured to apply an excitation field to the subject and acquire MR image data therefrom;
a computer system programmed to:
perform a pulse sequence using the MRI system, the pulse sequence including a phase-based flow encoding to collect a time-series of image data from the portion of the vasculature of the subject;
monitor, during the performing of the pulse sequence, a cardiac cycle of the subject and synchronize the collection of the time-series of image data from the portion of the vasculature of the subject to the cardiac cycle of the subject;
identify at least a portion of the time series of image data within the cardiac cycle and corresponding to a period of reduced flow through the portion of the vasculature; and
subtract the portion of the time series of image data within the cardiac cycle from the time series of image data to create a time series of images of the portion of the vasculature having background tissue surrounding the portion of the vasculature substantially suppressed.