System and method for phase contrast imaging with improved efficiency
Inventors
Edelman, Robert R • Glielmi, Christopher • Koktzoglou, Ioannis • Offerman, Erik J
Assignees
Siemens Healthineers AG • NorthShore University HealthSystem • National Institutes of Health NIH • US Department of Health and Human Services
Publication Number
US-8838204-B2
Publication Date
2014-09-16
Expiration Date
2032-12-18
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Abstract
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.
Core Innovation
The invention provides a system and method for magnetic resonance angiography (MRA) that employs a phase-based flow encoding pulse sequence to collect a time-series of image data from vasculature. A portion of this time series corresponding to a period of reduced flow is identified and subtracted from the entire time series to generate images with the background tissue substantially suppressed around the vasculature.
The problem addressed arises from conventional phase contrast (PC) MRA techniques which require acquiring two separate data sets—one flow-encoded and one flow-compensated—to perform image subtraction for visualization of blood flow. This necessity doubles the scan time and causes artifacts due to differences in gradient waveforms and consequent eddy currents, leading to spatial and temporal background phase shifts that complicate image quality and velocity measurement accuracy.
The invention overcomes these drawbacks by eliminating the requirement for two separate acquisitions. Instead, it uses a single pulse sequence synchronized to the cardiac cycle to acquire a continuous time series and then identifies frames corresponding to reduced flow for subtraction. This approach improves imaging efficiency by halving acquisition time, reduces artifacts from background phase shifts, shortens echo times to lessen susceptibility effects, and enhances temporal resolution and accuracy in flow velocity determination without complex phase correction algorithms.
Claims Coverage
The patent includes two independent claims that cover the method and system aspects of the invention. The main inventive features center on the pulse sequence for phase-based flow encoding synchronized to the cardiac cycle and subtraction techniques to suppress background tissue in vascular imaging.
Method for MRA image acquisition with phase-based flow encoding and cardiac synchronization
The method performs a pulse sequence with phase-based flow encoding to collect a time-series of vasculature image data, monitors the subject's cardiac cycle during acquisition, synchronizes data collection to the cardiac cycle, identifies portions of the data corresponding to reduced flow, and subtracts these reduced-flow portions from the entire time series to suppress background tissue in the resulting images.
MRI system programmed for synchronized phase-based flow encoding and background suppression
The MRI system comprises a magnet system, gradient coils, an RF system, and a computer system programmed to perform the pulse sequence with phase-based flow encoding synchronized to the cardiac cycle. The system identifies portions of the time series corresponding to reduced flow and subtracts these portions from the time series to produce images with substantially suppressed background tissue around the vasculature.
Together, these inventive features enable acquisition of MRA images using a single synchronized pulse sequence with phase-based flow encoding and background subtraction, improving image quality, efficiency, and accuracy without the need for separate reference scans or complex corrections.
Stated Advantages
Improves temporal resolution by a factor of two compared to conventional phase contrast MRI.
Reduces the minimum echo time, which helps suppress phase shifts due to magnetic susceptibility effects.
Ensures gradient-induced eddy currents are substantially equivalent across frames, minimizing background phase shifts and reducing the need for complex correction algorithms.
Increases imaging efficiency by eliminating the requirement to acquire two separate data sets.
Documented Applications
Non-contrast-enhanced magnetic resonance angiography (MRA) imaging of human vasculature with suppressed background tissue.
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