Adaptive SAR Control for MRI Patient Safety
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) systems face challenges in accurately estimating and controlling the specific absorption rate (SAR) for patients of varying sizes and positions, leading to potential tissue heating issues, as existing methods rely on worst-case scenarios and do not account for individual patient geometric details and RF power distribution.
Innovation Solution
An adaptive MRI SAR control system that includes an RF transmit coil, an anthropometric unit, and an adaptive SAR unit, which measures transmitted and reflected RF power to determine patient-specific SAR values, adjusting scan parameters based on confirmed patient mass and position to ensure SAR levels remain within safety limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worst-case SAR estimation is used for all patients, then patient safety is ensured, but scanning performance is reduced due to overly conservative SAR limits
Solution Approach 1:
The patent applies local quality by transitioning from uniform worst-case SAR estimation to patient-specific SAR calculation. Each patient's unique anatomical geometry, tissue composition, and positioning are considered to determine localized SAR values, allowing safer patients to undergo scanning at higher RF power levels while maintaining safety for those at higher risk.
Solution Approach 2:
The patent changes the parameter estimation approach from fixed worst-case values to dynamic patient-specific parameters. By measuring actual patient mass, body composition, and positioning, the system adjusts SAR estimation parameters in real-time, enabling optimized scan parameters that adapt to each patient's characteristics rather than applying universal conservative limits.
2Productivity
If patient-specific SAR estimation is implemented, then scanning performance improves, but system complexity increases
Solution Approach 1:
The patent implements self-service by enabling the MRI system to automatically measure patient mass using integrated scales, determine body composition through image analysis, calculate patient-specific SAR values, and adjust scan parameters without requiring manual input from operators. The system serves itself by gathering necessary data and performing complex calculations autonomously.
Solution Approach 2:
The patent replaces manual mechanical measurement methods with automated electronic and computational systems. Instead of manual weighing and measurement, the system uses electronic scales, computer-based image analysis, and automated SAR calculation algorithms to determine patient-specific parameters, reducing operational complexity.
3Illumination intensity
If RF power is increased for larger patients, then image quality improves, but tissue heating risk increases
Solution Approach 1:
The patent implements feedback by using measured patient mass, body composition, and positioning data to continuously adjust RF power levels. The system calculates patient-specific SAR values based on actual patient characteristics and feeds this information back to optimize scan parameters, ensuring RF power is increased only when safe based on real patient data rather than applying fixed conservative 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
This approach provides more accurate and patient-specific SAR estimates, reducing the risk of tissue heating and improving scanning performance by accounting for individual variations in patient size and position, thereby enhancing patient safety and examination efficiency.
Implementation Method 1
at least one radio frequency (RF) transmit coil transmits measured RF power to excite and manipulate magnetic resonance in tissues of a subject
Implementation Method 2
Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) uses radio frequency (RF) pulses of electromagnetic energy to excite resonance in tissues of a subject. A body also absorbs/dissipates some of the energy of the RF pulses as resistive loss, resulting in tissue heating.
Data Source
AI summary
A magnetic resonance system (1) includes at least one radio frequency (RF) transmit coil (6), an RF transmitter (34), an anthropometric unit (28), and an adaptive SAR unit (40). The at least one radio frequency (RF) transmit coil (6) transmits measured RF power to excite and manipulate magnetic resonance in tissues of a subject (57) in an examination region. The RF transmitter (34) controls the amount of transmitted RF power based on a specific absorption rate (SAR) for an imaging sequence. The anthropometric unit (28) determines a mass of a portion of the subject which receives the transmitted RF power based on a determined total mass. The adaptive SAR unit (40) adjusts a selected scan sequence based on the SAR parameters determined from the measured transmitted RF power and a measured reflected power, achieved IB|+I field, the mass of the portion of the subject which receives the transmitted RF power and applicable SAR parameter models stored in a SAR reference unit (46).