Variable Flip-Angle T1 Mapping for Skull Heating in MRgFUS

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Solution Overview

Problem

Current magnetic resonance guided focused ultrasound (MRgFUS) treatments face challenges due to skull heating, which limits treatment efficacy and safety, particularly in non-central brain targets, and requires improved real-time monitoring to prevent unintended injury and optimize treatment duration.

Innovation Solution

The method employs a combination of variable flip-angle T1 mapping and proton resonance frequency shift thermometry using a 3D spiral ultra-short echo time sequence to simultaneously monitor skull and brain heating, allowing for accurate temperature measurement and adjustment during MRgFUS procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If focused ultrasound is applied to non-central brain targets, then treatment versatility is improved, but skull heating increases causing safety issues

Engineering Contradiction:

Improvetreatment versatilityVSAvoidskull heating

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements real-time thermometry monitoring during FUS treatment to continuously measure skull temperature and provide feedback to the control system. This allows dynamic adjustment of ultrasound parameters to prevent excessive skull heating while maintaining treatment efficacy for non-central targets

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs pre-treatment thermal mapping and skull heating assessment to identify high-risk regions before applying focused ultrasound. This preliminary action allows surgeons to plan treatment trajectories that minimize skull heating while reaching non-central targets

Inventive Principle:

Principle #10Preliminary action

2Reliability

If real-time skull thermometry is implemented, then treatment safety is improved, but device complexity increases

Engineering Contradiction:

Improvetreatment safetyVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent integrates thermometry capabilities into the existing MRI system, allowing the MRI scanner to perform both anatomical imaging and temperature monitoring functions. This multi-functionality reduces the need for separate dedicated thermometry devices while maintaining treatment safety

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent uses MRI as an intermediary modality to indirectly measure skull temperature through T1 relaxation time changes and proton resonance frequency shifts. This indirect measurement approach avoids the need for direct temperature sensors in the skull, simplifying the overall system architecture

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If skull cooling intervals are extended, then treatment productivity is improved, but total treatment time increases

Engineering Contradiction:

Improvetreatment productivityVSAvoidtotal treatment time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

Real-time thermometry provides continuous feedback on skull temperature, allowing the system to dynamically determine when cooling intervals should end and the next sonication can begin. This feedback-driven approach optimizes the balance between cooling periods and treatment delivery, maximizing productivity while minimizing total treatment time

Inventive Principle:

Principle #23Feedback

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

This approach enables precise and real-time monitoring of temperature changes in the skull and brain, enhancing treatment safety, reducing waiting times between sonications, and facilitating the development of MRgFUS for less central brain targets by providing a direct, non-invasive method to assess thermal dose and prevent unintended heating.

Implementation Method 1

acquiring, by a variable flip-angle (VFA) T1 mapping sequence, MR data in an area of interest of a subject corresponding to cortical bone of at least part of the skull that is heated by the application of focused ultrasound

Methodology Applied

Scientific EffectT1 mapping thermometry:

Implementation Method 2

calculating a corresponding temperature change by tracking changes in a proton resonance frequency (PRF) during the application of the focused ultrasound

Methodology Applied

Scientific EffectProton resonance frequency shift:

Data Source

PatentUS20240353514A1Systems and methods for magnetic resonance based skull thermometry

Publication Date: 2024.10.24 UNIV OF VIRGINIA

AI summary

Described herein are systems, methods, and computer-readable medium for magnetic resonance (MR) based thermometry. A method for magnetic resonance based thermometry includes: acquiring, by a variable flip-angle T1 mapping sequence, MR data in an area of interest of a subject that is heated by the application of focused ultrasound (FUS) to the brain of the subject, where the MR data includes T1 values over time, and where the acquisition of the MR data includes applying an accelerated three-dimensional ultra-short spiral acquisition sequence with a nonselective excitation pulse; tracking changes in proton resonance frequency and determining, based at least in part on a mathematical relationship established by T1 mapping thermometry, a temperature change in the area of interest over time, and where the temperature change is caused at least in part by a change in the applied FUS.