MRI Scan Sequence Adjustment Under Low SAR Limits
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Solution Overview
Problem
Magnetic resonance imaging systems face challenges in minimizing scanning time while adhering to low Specific Absorption Rate (SAR) limits, particularly when imaging vulnerable subjects like infants or pregnant women, leading to increased scanning time due to prolonged waiting periods for thermal energy dissipation.
Innovation Solution
Adjusting the scan sequence by modifying the amplitude and width of radio-frequency and gradient pulses based on an adjustment factor, calculated to minimize scanning time and repetition time while maintaining compliance with SAR limits, using a method that determines an optimal adjustment factor to balance pulse characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the radio-frequency excitation pulse power is increased to reduce scanning time, then productivity is improved, but the specific absorption rate (SAR) increases causing safety issues
Solution Approach 1:
The patent implements dynamic adjustment of radio-frequency pulse parameters by introducing an adjustment factor that modifies the amplitude and duration of RF pulses based on real-time SAR calculations. This allows the system to optimize scanning speed while maintaining SAR within safe limits through continuous parameter adaptation rather than using fixed pulse settings
Solution Approach 2:
The patent changes the parameters of radio-frequency pulses by applying an adjustment factor that modifies both the amplitude and duration of pulses. This parameter transformation allows the system to reduce SAR impact while maintaining imaging quality, resolving the contradiction between scanning speed and safety constraints
2Productivity
If the repetition time is reduced to minimize scanning time, then productivity is improved, but the SAR limit is exceeded causing thermal energy accumulation
Solution Approach 1:
The patent performs preliminary calculation of the adjustment factor before executing the pulse sequence by estimating the SAR contribution of each pulse and determining optimal parameter adjustments in advance. This preliminary action allows the system to plan the entire scan sequence to comply with SAR limits while minimizing total scanning time
Solution Approach 2:
The patent implements a feedback mechanism where the adjustment factor is calculated based on the actual SAR measurements and pulse sequence characteristics, then used to modify subsequent pulse parameters. This closed-loop control ensures SAR compliance is maintained throughout the scan while optimizing scanning efficiency
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
The adjusted scan sequence minimizes scanning time and repetition time in low SAR modes without exceeding safety limits, ensuring efficient and safe imaging with maintained image quality.
Implementation Method 1
The transmit/receive coil generates a radio-frequency excitation signal to excite a scan subject to generate a magnetic resonance signal
Implementation Method 2
a large part of the power of the radio-frequency excitation pulse is absorbed by the scan subject and converted into thermal energy
Data Source
AI summary
Embodiments of the present application provide a magnetic resonance scanning and imaging method, and a magnetic resonance imaging system. The method includes: determining a pulse to be adjusted in a scan sequence, the pulse to be adjusted including a first radio-frequency pulse and a first gradient pulse applied along with the first radio-frequency pulse; determining an adjustment factor based on the first gradient pulse and a minimum repetition time related to a specific absorption rate of radio-frequency energy; adjusting the scan sequence based on the adjustment factor; and, using the adjusted scan sequence, performing a diagnostic scan on a site to be examined, to obtain a magnetic resonance image.