Free breathing motion corrected pixel-wise MRI myocardial T1 parameter mapping
Inventors
Spottiswoode, Bruce S. • Kellman, Peter
Assignees
Siemens Healthineers AG • US Department of Health and Human Services
Publication Number
US-10264994-B2
Publication Date
2019-04-23
Expiration Date
2036-05-16
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Abstract
A method for performing free breathing pixel-wise myocardial T1 parameter mapping includes performing a free-breathing scan of a cardiac region at a plurality of varying saturation recovery times to acquire a k-space dataset; generating an image dataset based on the k-space dataset; and performing a respiratory motion correction process on the image dataset. The respiratory motion correction process comprises selecting a target image from the image dataset, co-registering each image in the image dataset to the target image to determine a spatial alignment measurement for each image, and identifying a subset of the image dataset comprising images with the spatial alignment measurement above a predetermined value. Following the respiratory motion correction process, a pixel-wise fitting is performed on the image dataset to estimate T1 relaxation time values for the cardiac region. Then, a pixel-map of the cardiac region is produced depicting the T1 relaxation time values.
Core Innovation
The invention provides methods, systems, and apparatuses related to performing myocardial T1 parameter mapping during magnetic resonance imaging using a free-breathing scan. It includes performing a free-breathing scan of a cardiac region at multiple varying saturation recovery times to acquire a k-space dataset, generating an image dataset based on this k-space dataset, and performing a respiratory motion correction process on the image dataset. This process comprises selecting a target image, co-registering each image to the target image to determine spatial alignment, and identifying a subset of spatially aligned images for further processing.
Following respiratory motion correction, a pixel-wise fitting is performed on the co-registered image dataset to estimate T1 relaxation time values for the cardiac region, leading to the production of a pixel-map depicting these T1 values. The method also contemplates modifying gradients to enhance phase differences between flowing blood and stationary myocardium to improve image co-registration, and optionally includes insertion of T2 preparation pulses to estimate T2 relaxation times alongside T1 mapping, producing a second pixel-map depicting T2 values.
The background problem addressed is the inefficiency and challenges of existing myocardial T1 parameter mapping techniques during free breathing. Traditional inversion-prepared techniques require long recovery times and are inefficient for free breathing scans. While navigator gating enables free breathing scans, workflows can be complex, and the available interleaved acquisitions are limited in some cardiac views. Saturation recovery based T1 mapping offers more efficient imaging for free breathing. The invention overcomes limitations by using saturation recovery T1 sampling strategies combined with respiratory motion correction without the need for navigators, allowing improved workflow, signal-to-noise, measurement precision, and feasibility for multi-slice free breathing acquisitions.
Claims Coverage
The patent includes three independent claims covering a method, an article of manufacture, and a system for free breathing pixel-wise myocardial T1 parameter mapping. The main inventive features involve respiratory motion correction, free-breathing saturation recovery scanning, and pixel-wise fitting estimation of myocardial T1 relaxation times.
Respiratory motion correction for free-breathing image datasets
Performing respiratory motion correction by selecting a target image from a free-breathing acquired image dataset, co-registering each image to the target to determine spatial alignment, and identifying a subset of images meeting a predetermined spatial alignment threshold for subsequent processing.
Free-breathing scan using saturation recovery with varying saturation times
Acquiring a k-space dataset via free-breathing scans of a cardiac region at a plurality of varying saturation recovery times using a saturation pulse and readout sequence repeated over multiple heartbeats.
Pixel-wise fitting to estimate T1 relaxation time values
Performing pixel-wise fitting on the respiratory motion corrected image dataset to estimate myocardial T1 relaxation time values and producing a corresponding pixel-map depicting these values.
Use of redundant datasets for motion robustness
Acquiring redundant datasets for each saturation recovery time to ensure sufficient data for reliable motion correction and co-registration during free breathing.
Enhancement of phase contrast to improve co-registration
Modifying gradients associated with the readout to enhance phase differences between flowing blood and stationary myocardium, generating a phase map, and using this along with magnitude images to improve image co-registration.
Extension to combined T1 and T2 mapping with variable T2 preparation pulses
Introducing T2 preparation pulses of variable durations between saturation pulse and readout to enable estimation of both T1 and T2 relaxation times through extended pixel-wise fitting and producing a second pixel-map depicting T2 values.
The independent claims collectively cover a free-breathing myocardial imaging method, related system, and computer-readable medium that use saturation recovery imaging, respiratory motion correction by co-registration to a target image, and pixel-wise fitting to map myocardial T1 relaxation times, with optional enhancements such as phase-based co-registration and combined T1/T2 mapping through variable T2 preparation pulses.
Stated Advantages
Motion correction during free breathing offers a simpler workflow than navigated scans.
The invention provides an elegant framework for improving signal-to-noise ratio and measurement precision.
Saturation recovery imaging enables more efficient free breathing scans compared to inversion-prepared techniques requiring long delays.
Phase information and T2 preparation pulses can improve motion correction and contrast between blood and myocardium.
Documented Applications
Quantitative myocardial T1 parameter mapping during magnetic resonance imaging for clinical assessment of conditions such as edema, protein deposition, lipid or iron deposition, fibrotic scar, and diffuse fibrosis.
Combined free breathing myocardial T1 and T2 mapping for assessing acute ischemia, myocarditis, heart transplant rejection, and for estimating blood saturation and hematocrit.
Producing pixel-wise parameter maps that can be used for quantitative evaluation of cardiac tissue characteristics from free breathing MRI scans without requiring breath-hold or navigator gating.
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