MRI B0 Modulation for Interference Reduction
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Solution Overview
Problem
Magnetic resonance tomographs require complex shielding to reduce emissions and interference, which is costly and inefficient, as they need to manage high-frequency excitations and weak signal receptions effectively.
Innovation Solution
A magnetic resonance tomograph with a magnet device that rapidly changes the homogeneous magnetic field strength between two predetermined values, allowing for separate frequency ranges for excitation and reception, thereby reducing the need for extensive shielding by shifting the Larmor frequency into less interfered bands and using modulation to spread the signal, facilitating active interference suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complex shielded cabins are installed around the magnetic resonance tomograph, then emissions and interference are reduced, but device complexity and cost increase
Solution Approach 1:
The patent changes the frequency parameter of the magnetic resonance signals by dynamically adjusting the magnetic field strength B0. This frequency shifting moves the signals away from common interference bands, reducing the need for extensive shielding without requiring complex structural modifications
Solution Approach 2:
The patent converts the potential harm of frequency interference into a benefit by using the same magnetic field modulation to both encode spatial information and shift frequencies. The interference that would normally require shielding is instead used as a mechanism to differentiate signal frequencies, turning a harmful factor into a useful encoding tool
2Power
If high-frequency pulses are generated for excitation, then nuclear spins are excited effectively, but electromagnetic emissions increase requiring shielding
Solution Approach 1:
The patent employs periodic modulation of the magnetic field strength during the excitation and signal reception phases. By periodically varying B0, the system generates time-dependent frequency shifts that encode spatial information while reducing continuous high-frequency emissions, allowing effective excitation with reduced electromagnetic pollution
3Object-affected harmful factors
If frequency shifting is used to reduce interference, then shielding requirements are reduced, but magnetic field control complexity increases
Solution Approach 1:
The patent makes the magnetic field control system multi-functional by using the same B0 modulation to achieve both frequency shifting for interference reduction and spatial encoding for imaging. This universal approach eliminates the need for separate control mechanisms, reducing overall system complexity despite the advanced control requirements
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 minimizes shielding requirements, enhances signal-to-noise ratio, and reduces electromagnetic interference, allowing for effective imaging without costly shielded cabins by optimizing magnetic field control and signal processing.
Implementation Method 1
a magnet device (10) with a magnet controller (60) for changing a homogeneous magnetic field B0 in a measurement volume
Implementation Method 2
align nuclear spins of the examination object with a strong external magnetic field and excite them to precess around this alignment by means of an alternating magnetic field
Implementation Method 3
The measurement volume is the volume in which the Larmor frequency L1 of the nuclear spins to be recorded in the first homogeneous magnetic field B01 matches the frequency of an excitation pulse
Implementation Method 4
The precession or return of the spins from this excited state to a lower-energy state in turn generates an alternating magnetic field in response, which is received by antennas
Implementation Method 5
a magnet controller (60) for changing a homogeneous magnetic field B0 in a measurement volume with a magnetic field strength that can be changed between a first predetermined value and a second predetermined value in a short predetermined time
Data Source
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AI summary
The invention relates to a magnetic resonance imaging (MRI) scanner and a method for operating the MRI scanner. The MRI scanner has a magnetic unit designed to change a homogeneous magnetic field B0 in a measurement volume within a short, predetermined time, with a magnetic field strength that can be varied between a first predetermined value when nuclear spins are excited and a second predetermined value when magnetic resonance signals are received.