STIR-UTE MRI Sequence for Cryoablation Temperature Delineation
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Solution Overview
Problem
Conventional MRI techniques for cryoablation procedures fail to accurately differentiate between tissue at lethal and non-lethal temperatures, leading to imprecise visualization and potential under or over-treatment of target tissues during cryoablation procedures.
Innovation Solution
The implementation of a short tau inversion recovery ultrashort echo time (STIR-UTE) MRI sequence, which selectively visualizes regions between -40°C and -8°C by utilizing specific inversion times based on the T1 relaxation time of frozen tissue, allowing for precise delineation of the lethal temperature zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional MRI sequences with echo times greater than 500 msec are used, then all tissues below 0°C are displayed as dark, but the entire visualized dark region may not be at sufficient lethal temperature and may overestimate the actual ablated zone
Solution Approach 1:
The patent changes the echo time parameter from conventional values (>500 msec) to ultrashort echo time (UTE) values. This parameter change enables the MRI sequence to capture signal from frozen tissue before complete signal loss occurs, allowing differentiation between lethal and non-lethal temperatures within the frozen region.
Solution Approach 2:
The patent employs dynamic adjustment of inversion time (TI) values in the STIR-UTE sequence to selectively nullify signals from specific temperature ranges. By varying TI dynamically, the system can highlight different temperature zones within the ice ball, enabling precise visualization of the lethal temperature region.
2Measurement precision
If MR thermometry using ultrashort echo time MRI sequences is used to estimate temperature based on T2*, then temperature differentiation is possible, but multiple images at different TEs are required and signal changes are so minute that it is hard to differentiate the signal decay
Solution Approach 1:
The patent extracts and utilizes the T1 relaxation time property of frozen tissue specifically, rather than relying on T2* measurements that require multiple echo times. By focusing on T1-based STIR inversion recovery, the method simplifies the imaging approach while maintaining temperature differentiation capability.
Solution Approach 2:
The patent changes the fundamental relaxation time parameter measured from T2* (in conventional UTE) to T1 (in STIR-UTE). This parameter change simplifies the imaging sequence by requiring only a single echo time while maintaining the ability to differentiate temperatures through inversion time variations.
3Measurement precision
If calculations of T2* based on multiple images at different TEs are performed, then temperature estimation is possible, but the calculations are difficult to perform when imaging in regions susceptible to physiological motion
Solution Approach 1:
The patent performs preliminary nulling of the frozen tissue signal using STIR inversion recovery before acquiring the UTE image. This preliminary action simplifies the subsequent image analysis by eliminating the need for complex T2* calculations and making the technique more robust to physiological motion.
4Illumination intensity
If conventional MRI T1 or T2 weighted sequences are used, then the entire ice ball is shown as signal void, but the physician cannot depend on the visualized size and volume of the ice ball to determine correct tumor coverage and adequate treatment margins
Solution Approach 1:
The patent applies local quality enhancement by making specific temperature regions within the ice ball hyperintense while keeping other regions dark. The STIR-UTE sequence selectively highlights the lethal temperature zone (between -40°C and -8°C) through appropriate inversion time selection, providing localized temperature information within the frozen tissue.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate visualization and measurement of the ablated tissue volume during cryoablation, ensuring adequate tumor coverage and minimizing damage to healthy tissue by providing real-time feedback on the extent of cell death.
Implementation Method 1
short tau inversion recovery ultrashort echo time (STIR-UTE) MRI sequence, which selectively visualizes regions between -40°C and -8°C by utilizing specific inversion times based on the T1 relaxation time of frozen tissue
Implementation Method 2
short tau inversion recovery ultrashort echo time (STIR-UTE) MRI sequence
Implementation Method 3
Magnetic resonance imaging (MRI) is an attractive tool for monitoring cryoablation procedures
Implementation Method 4
conventional MRI spin-lattice relaxation time (T1-) or spin-spin relaxation time (T2-) weighted sequences
Implementation Method 5
conventional MRI spin-lattice relaxation time (T1-) or spin-spin relaxation time (T2-) weighted sequences
Data Source
AI summary
The present disclosure is directed to systems and methods for generating images using short tau inversion recovery, ultrashort echo time (STIR-UTE) MRI sequences. The STIR-UTE MRI sequences can be used to generate images that can differentiate between regions that are at temperatures that are either lethal or non-lethal to cell life. Thus, these sequences can be beneficial for implementations such as in monitoring cryoablation procedures.