Pulsatile motion effects on 3D magnetic resonance angiography: implications for evaluating carotid artery stenoses
Osama Al-Kwifi1, Jae K Kim, Jeff Stainsby
1Medical Imaging Research, Sunnybrook and Women's College Health Science Centre, Toronto, Ontario, Canada. osama@sten.sunnybrook.utoronto.ca
Abstract:
In-plane carotid artery motion during a 3D MR angiography (MRA) scan can significantly degrade the resulting image resolution. This study characterizes the effect of cardiac pulsatility on 3D contrast-enhanced (CE) MRA with elliptical centric acquisitions using a point-spread function (PSF) analysis. Internal carotid artery (ICA) motion was collected from volunteers and patients using both MR and ultrasound (US) scans. After measuring the carotid artery motion displacement, a simulation was performed which calculated the blurring effects for three different protocols: nongated and two different cardiac gating schemes. The motion sensitivity of each protocol was evaluated for different spatial resolutions. The selection of optimal imaging parameters for a given scan time was investigated. The final results showed that cardiac-gated acquisitions only over a limited region of k-space high spatial frequencies are more time-efficient than cardiac gating for the entire k-space, as it allows for higher resolutions to be achieved and for capturing the arterial phase with low spatial frequencies. Selecting the optimal gating parameters depends directly on the motion characteristics of each individual. Our initial clinical experience is presented, and the need for a real-time tool that characterizes motion behavior for each individual as a prescan protocol is discussed.
Insights
Cardiac gating in 3D MRA improves image resolution by addressing carotid artery motion. Optimizing gating strategies for individual patient motion enhances scan efficiency and diagnostic accuracy.
Area of Science:
- Medical Imaging
- Cardiovascular Imaging
- Biomedical Engineering
Background:
- In-plane carotid artery motion during 3D MR angiography (MRA) degrades image resolution.
- Cardiac pulsatility is a primary driver of this motion, impacting diagnostic quality.
Purpose of the Study:
- To characterize the impact of cardiac pulsatility on 3D contrast-enhanced (CE) MRA.
- To evaluate different cardiac gating schemes for optimizing image resolution and scan time.
Main Methods:
- Collected internal carotid artery (ICA) motion data from volunteers and patients using MRI and ultrasound.
- Performed simulations to assess blurring effects of nongated and two cardiac-gated protocols using point-spread function (PSF) analysis.
- Evaluated motion sensitivity across various spatial resolutions and imaging parameters.
Main Results:
- Cardiac-gated acquisitions focusing on specific k-space regions are more time-efficient than full k-space gating.
- Partial k-space gating allows for higher resolutions and better capture of the arterial phase.
- Optimal gating parameters are individualized based on patient-specific motion characteristics.
Conclusions:
- Selective cardiac gating strategies offer improved time efficiency and resolution in 3D MRA.
- Individualized motion characterization is crucial for selecting optimal prescan protocols.
- Development of real-time motion analysis tools is needed for routine clinical application.
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