MRI SAR Control via Dynamic RF Parameter Adjustment
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Solution Overview
Problem
MRI apparatuses face challenges in controlling Specific Absorption Ratio (SAR) and Specific Absorbed Energy (SAE) during monitoring and interventional imaging, leading to potential interruptions in medical procedures due to excessive body temperature increases, especially when using contrast media or performing long examinations.
Innovation Solution
An MRI apparatus equipped with an imaging unit, SAR acquisition unit, and prediction unit that continuously monitors actual SAR values and adjusts imaging conditions to prevent exceeding safety limits by changing parameters such as RF signal energy, allowing for safe continuation of imaging sessions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If imaging is carried out continuously to monitor contrast medium delivery or perform interventional procedures, then diagnostic capability and treatment verification are improved, but SAR and SAE values increase causing imaging to be stopped halfway due to safety limits
Solution Approach 1:
The patent applies dynamics by making the imaging conditions adjustable and adaptable during the examination. The system dynamically changes imaging parameters (such as RF signal energy, scan timing, and sequence selection) based on real-time SAR/SAE calculations and prediction, allowing continuous imaging to proceed safely without fixed static parameters
Solution Approach 2:
The patent implements parameter changes by automatically modifying imaging conditions including RF signal energy levels, repetition time (TR), echo time (TE), and flip angles. These parameter adjustments are made in response to calculated SAR/SAE values to maintain imaging continuity while staying within safety limits
Solution Approach 3:
The system employs feedback mechanisms by continuously calculating actual SAR values from measured RF signal energy and predicting future SAE values. This feedback loop enables real-time adjustment of imaging parameters to prevent exceeding safety thresholds while maintaining continuous imaging capability
2Manufacturing precision
If RF signal energy is increased to improve image quality and contrast, then diagnostic image quality is improved, but SAR and SAE values exceed safety standards
Solution Approach 1:
The patent applies parameter changes by automatically adjusting RF signal energy, repetition time (TR), echo time (TE), and flip angles based on calculated SAR/SAE values. This allows the system to optimize image quality parameters while preventing excessive energy absorption that would violate safety standards
Solution Approach 2:
The system applies partial action by using sufficient but not excessive RF signal energy. Instead of always using maximum energy for optimal image quality, the system uses just enough energy to achieve diagnostic quality while staying within SAR/SAE safety limits, avoiding unnecessary energy exposure
3Reliability
If imaging parameters are adjusted to reduce SAR and SAE values, then safety compliance is improved, but image quality and diagnostic capability deteriorate
Solution Approach 1:
The patent implements parameter changes that simultaneously address safety and image quality. By adjusting multiple parameters including repetition time (TR), echo time (TE), flip angles, and RF signal energy in combination, the system maintains diagnostic image quality while ensuring SAR/SAE compliance, rather than simply reducing all parameters
4Measurement precision
If monitoring imaging is performed to verify contrast medium arrival, then diagnostic accuracy is improved, but examination time extends and SAR/SAE limits are reached
Solution Approach 1:
The patent applies dynamics by adaptively adjusting monitoring imaging frequency and parameters based on real-time SAR/SAE calculations. The system dynamically determines when monitoring imaging is necessary versus when it can be reduced or skipped, optimizing the balance between verification accuracy and examination efficiency
Solution Approach 2:
The system applies partial action by performing monitoring imaging at optimized intervals rather than continuously. This provides sufficient verification of contrast medium delivery while minimizing unnecessary RF exposure and examination time, avoiding excessive monitoring that would reach SAR/SAE limits
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 continuous monitoring and adjustment of imaging conditions to prevent SAR and SAE from exceeding safety standards, thereby allowing uninterrupted imaging during contrast medium examinations and interventional procedures, reducing the risk of procedure interruptions due to temperature increases.
Implementation Method 1
excites nuclear spins of a patient placed in a static magnetic field with a radio frequency (RF) signal at Larmor frequency
Implementation Method 2
generates an image by reconstructing a magnetic resonance signal generated from the patient as a result of the excitation
Implementation Method 3
a specific absorption ratio (SAR) has been defined as energy absorbed per unit mass of the patient
Implementation Method 4
an upper limit of long MR examination specific absorbed energy has been prescribed... a sum total of SAR per examination, i.e., a cumulative value or integration value of SAR per examination
Data Source
AI summary
Magnetic resonance imaging (MRI) is configured to carry out sequential imaging, to acquire an actual SAR measurement value at a predetermined timing during the sequential imaging, and to update a subsequent predicted SAE value each time the actual SAR measurement value is acquired.