Method and system for T1 mapping for tissue characterized by short-T2 relaxation in MRI
Inventors
Sommer, Stefan • HILBERT, Tom • Nanz, Daniel
Assignees
Balgrist Campus Ag • Siemens Healthineers AG
Publication Number
US-12339339-B2
Publication Date
2025-06-24
Expiration Date
2043-04-11
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Abstract
An MRI method and system for mapping T1 relaxation times of a biological object with a part having a short-T2 relaxation time. The MRI system first performs one or several magnetization preparation radio frequency pulse sequences, with successive RF pulse sequences being separated by a repetition time interval TR. The MRI system acquires an MRI signal generated by the part of said biological object during each repetition time interval TR in response to a plurality of 3D readout blocks generated by the MRI system and applied to the part of the biological object. For each readout block, an MRI signal is acquired by the MRI system at a different recovery time. Each readout block is sensitive to short-T2 signal. An image of the part is reconstructed from each MRI signal and T1 values are mapped for the part from at least two of said reconstructed images.
Core Innovation
The invention provides a magnetic resonance imaging (MRI) method and system designed to map T1 relaxation times of biological tissue characterized by short-T2 relaxation times, typically less than 1 ms. This method employs one or multiple magnetization preparation radio frequency (RF) pulse sequences separated by a repetition time interval TR. During each TR interval, the MRI system acquires MRI signals from the biological object's part using multiple 3D readout blocks, each acquired at a distinct recovery time and configured to be sensitive to short-T2 signals.
From each acquired MRI signal corresponding to a readout block, an image of the tissue is reconstructed. T1 values are then mapped from at least two of these reconstructed images, allowing for quantitative imaging of short-T2 tissues. The approach overcomes limitations in traditional MRI sequences which fail to capture short-T2 signals due to their rapid decay and echo formation delays.
The method allows the readout blocks to be temporally separated or to form a continuous readout excitation pulse sequence with overlapping or contiguous acquisition windows. It optionally supports multi-echo acquisitions within each readout block to provide additional dimensions of signal information (such as T2* and phase), enabling improved separation of short-T2 and long-T2 tissue contributions and enhancing T1 mapping accuracy. The system is suitable for clinical use and addresses problems such as B1-inhomogeneity sensitivity and long scan times found in prior techniques.
Claims Coverage
The claims include a single independent claim defining a novel MRI method and additional dependent claims specifying features that further refine the method and system capabilities.
MRI method for T1 mapping with multiple short-T2 sensitive 3D readout blocks
Performing one or more magnetization preparation RF pulse sequences separated by repetition time TR; acquiring MRI signals during each TR using multiple 3D readout blocks each sensitive to short-T2 signals and acquired at different recovery times; reconstructing images from these signals and mapping T1 values from two or more reconstructed images.
Temporal separation of readout blocks
Separating each short-T2 sensitive 3D readout block and its corresponding acquired MRI signal by a positive time interval from the next readout block and its signal, ensuring distinct acquisition periods.
Continuous readout excitation pulse sequence
Forming the multiple readout blocks into a continuous readout excitation pulse sequence executed by the MRI system where MRI signals are acquired at different recovery times allowing the creation of images at multiple different recovery times.
Multi-echo acquisition within readout blocks
Each readout block comprises a train of RF excitation pulses with predefined flip angles, each followed by multiple gradient echoes, adding an additional dimension to MRI signals enabling separation of signal components and improved mapping.
Use of specific 3D readout sequences sensitive to short-T2
The readout blocks comprise one or more RF excitations using ultra-short echo time (UTE), zero echo time (ZTE), or single-point imaging (SPI) sequences optimized for capturing short-T2 signals.
Magnetization preparation employing inversion or saturation recovery sequences
The magnetization preparation RF pulse sequence used in the method is an inversion or saturation recovery pulse sequence to prepare magnetization prior to readout.
Combining reconstructed images for short-T2 tissue information extraction
Combining two or more reconstructed images to extract quantitative information about biological tissue characterized by short-T2 relaxation times.
Direct fitting of analytical models to reconstructed images
Extracting T1 and T2* relaxation information directly from two or more reconstructed images by fitting an analytical model to the imaging data.
MRI system configured to execute the method
An MRI system apparatus configured for performing the above magnetic resonance imaging method steps for mapping T1 relaxation times in biological objects with short-T2 characteristics.
The claims collectively define a novel MRI method and system featuring multiple short-T2 sensitive 3D readout blocks acquired at different recovery times following magnetization preparation sequences, enabling accurate quantitative T1 mapping in tissues with short-T2 relaxation, employing advanced readout and acquisition strategies including continuous sequences and multi-echo approaches.
Stated Advantages
Enables T1 mapping of biological tissues characterized by short-T2 relaxation times suitable for clinical applications.
Provides a method sensitive to short-T2 signals allowing quantitative imaging where traditional MRI sequences fail due to rapid signal decay.
Reduces sensitivity to B1-inhomogeneity effects improving measurement accuracy and reproducibility.
Allows simultaneous or combined mapping of T1, T2*, proton density, phase, magnetic field (B0), and susceptibility (QSM) information.
Supports accelerated data acquisition through continuous readout blocks and multi-echo acquisitions to shorten scan times.
Documented Applications
Quantitative T1 mapping of tissues and biological objects exhibiting short-T2 relaxation times (e.g., cortical and trabecular bone, tendon, ligament, myelin, lung).
Clinical imaging for measuring physical tissue properties less affected by scanner or acquisition parameters.
Longitudinal monitoring of disease progression or therapy response through reproducible T1 measurements.
Cross-institutional comparison of quantitative tissue parameters enabling database creation and enhanced diagnostic evaluation based on T1 mapping.
Combined T1, T2*, and magnetic susceptibility mapping using multi-echo and multi-recovery time acquisitions.
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