Magnetic resonance fingerprinting thermometry
Inventors
Keenan, Kathryn • Poorman, Megan • Boyacioglu, Rasim • Griswold, Mark A.
Assignees
Case Western Reserve University • University of Colorado Boulder • United States Department of Commerce
Publication Number
US-11519987-B2
Publication Date
2022-12-06
Expiration Date
2041-04-05
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Abstract
A method for temperature quantification using magnetic resonance fingerprinting (MRF) includes acquiring MRF data from a region of interest in a subject using an MRF pulse sequence with smoothly varying RF phase for MR resonant frequencies that is played out continuously. For each of a plurality of time intervals during acquisition of the MRF data the method further includes comparing a set of the MRF data associated with the time interval to an MRF dictionary to determine at least one quantitative parameter of the acquired MRF data, determining a temperature change based on the at least one quantitative parameter and generating a quantitative map of the temperature change in the region of interest. The region of interest can include aqueous and adipose tissue.
Core Innovation
The invention provides a method and system for quantitative mapping of temperature changes in aqueous and adipose tissues using magnetic resonance fingerprinting (MRF). The approach involves acquiring MRF data from a region of interest in a subject with an MRF pulse sequence that applies smoothly varying RF phase for MR resonant frequencies continuously during acquisition. At multiple time intervals within the acquisition, the collected MRF data is compared to an MRF dictionary, enabling determination of quantitative parameters such as T1, T2, and resonant frequency, which are then converted to measures of temperature change, producing quantitative temperature maps of the region.
The method can also generate a thermal signal MRF dictionary dynamically at each time interval by using baseline and prior temperature data, allowing direct matching of acquired data to predict temperature changes with improved temporal resolution. The MRF pulse sequence may be optimized, for example using a quadratic RF phase modulation (MRFqRF), to allow faster temperature quantification and monitoring, providing temperature mapping in both water- and fat-based tissues simultaneously without requiring sequence interleaving or reconstruction modification.
The background problem addressed is the difficulty of accurately and rapidly measuring temperature changes in both aqueous and adipose tissues during thermal therapies. Conventional proton resonant frequency shift (PRFS) techniques effectively map temperature changes in aqueous tissues but are unreliable in adipose tissues due to lack of free water protons. Relaxation-based methods like T1 or T2 mapping used for adipose tissue temperature measurement require calibration and have limited temporal resolution. Combining PRFS with relaxation methods slows acquisition and compromises mapping quality. Conventional MRF can map multiple tissue properties but requires long acquisition times and has not been used dynamically for temperature monitoring. Thus, there is a need for a method that provides quantitative temperature mapping in both aqueous and adipose tissues with high temporal resolution using MRF.
Claims Coverage
The patent includes two independent claims covering a method and a magnetic resonance imaging (MRI) system for temperature quantification using magnetic resonance fingerprinting (MRF). There are six main inventive features identified from these claims.
Temperature quantification method using MRF with smoothly varying RF phase
A method whereby MRF data is acquired from a region of interest using an MRF pulse sequence with smoothly varying RF phase for MR resonant frequencies played out continuously. During multiple temperature measurement time intervals within acquisition, a thermal signal MRF dictionary is generated, MRF data for each interval is compared to this dictionary to determine temperature changes, and quantitative temperature maps are generated.
Dynamic thermal signal MRF dictionary generation based on previous temperature changes
Generating the thermal signal MRF dictionary for a given temperature measurement time interval using information related to determined temperature changes from a prior time interval, enabling dynamic updating of the dictionary during acquisition.
Baseline quantitative parameter determination via MRF dictionary comparison
Determining baseline quantitative parameters during a baseline measurement time interval by comparing acquired MRF data to an MRF dictionary, which serves as input for subsequent thermal signal MRF dictionary generation.
Use of MRF with quadratic RF phase (MRFqRF) pulse sequence
Employing an MRF pulse sequence with quadratic RF phase modulation to provide the smoothly varying RF phase, facilitating sensitive and fast temperature quantification.
MRI system configured to perform temperature quantification using MRF
An MRI system equipped with magnet, gradient, and RF systems and a computer system programmed to acquire MRF data with smoothly varying RF phase, generate thermal signal MRF dictionaries dynamically, compare MRF data to these dictionaries, determine temperature changes, and generate quantitative temperature maps.
Temperature changes associated with tissue heating or cooling
The temperature changes determined by the method or system correspond to heating or cooling of tissue in the region of interest, enabling real-time monitoring in thermal therapies.
Overall, the claims cover a method and system for continuous and dynamic temperature quantification in tissues using magnetic resonance fingerprinting with smoothly varying RF phase, dynamic thermal dictionary generation based on prior measurements, and implementation via an MRI system utilizing an MRFqRF pulse sequence to generate temperature maps for thermal therapy guidance.
Stated Advantages
Provides multi-contrast temperature mapping of both aqueous and adipose tissues simultaneously using magnetic resonance fingerprinting.
Enables faster temporal resolution and continuous temperature monitoring by reducing the number of time points per acquisition and employing pulse sequences with smoothly varying RF phase.
No need for interleaving sequences or modifying reconstruction for relaxation mapping, simplifying acquisition and preserving temporal resolution.
Allows generation and dynamic updating of thermal signal MRF dictionaries during acquisition, improving temperature estimation accuracy over time.
Can be used in low signal-to-noise ratio (SNR) scenarios, enhancing applicability in clinical settings.
Supports real-time or near-real-time temperature monitoring during thermal surgical procedures or therapies, enabling treatment modification or cessation based on temperature thresholds.
Documented Applications
Monitoring temperature changes in aqueous and adipose tissues during thermal surgical procedures.
Guidance of thermal therapies including heating or cooling of tissues in a subject.
Temperature quantification and continuous monitoring during laser ablation or other thermal treatments.
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