RF Pulse Interpolation Circuitry for MRI Slew Rate Control
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in generating RF pulses with high baseband frequencies, leading to increased slew rates that overload RF amplifiers and result in transient phenomena, potentially damaging the amplifier or causing system failures.
Innovation Solution
The implementation of RF pulse generating circuitry that interpolates digital data to reduce the slew rate of RF pulses, using a slew rate limiter and interpolating circuitry to generate a second data string with reduced variation between adjacent data points, thereby reducing the load on RF amplifiers and stabilizing the output waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If digital data is generated at predetermined time intervals for high baseband frequency pulses, then the pulse generation capability is improved, but the slew rate increases causing RF amplifier overload
Solution Approach 1:
The patent applies preliminary action by performing interpolation processing on the digital data string before generating the RF pulse. The interpolation circuitry processes the envelope data in advance to reduce the variation amount between adjacent data points, thereby reducing the slew rate before the data reaches the RF amplifier. This preliminary processing prevents the harmful high slew rate from reaching the amplifier while still enabling high baseband frequency pulse generation.
2Object-generated harmful factors
If the variation amount of digital data is reduced through interpolation, then the slew rate decreases reducing RF amplifier load, but the data processing complexity increases
Solution Approach 1:
The patent introduces an interpolation circuitry as an intermediary component between the digital data generation and RF amplifier stages. This intermediary performs the necessary interpolation processing to reduce the variation amount in the data string. By dedicating a specific interpolation circuitry for this function, the complexity is localized and managed separately, allowing the rest of the system to operate without being burdened by the processing complexity.
3Reliability
If interpolation processing is applied to reduce slew rate, then RF amplifier stability is improved, but the pulse width increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the interpolation factor and processing parameters to achieve the desired reduction in variation amount without excessive pulse widthening. By adjusting the interpolation parameters, the system optimizes the balance between slew rate reduction and pulse width maintenance, ensuring that the pulse remains sufficiently short for UTE applications while still protecting the RF amplifier.
Data Source
AI summary
A magnetic resonance imaging apparatus according to an embodiment includes first generating circuitry and second generating circuitry. The first generating circuitry interpolates a first data string of digital data including envelope information of a radio frequency (RF) pulse to be output, thereby generating a second data string in which a variation amount of digital data adjacent to each other in the first data string is smaller than an upper limit value. The second generating circuitry generates a signal of the RF pulse by combining the second data string generated by the first generating circuitry and information relating to a carrier wave of the RF pulse, and outputs the signal to an RF amplifier.