MRI Patient Position Detection Using Out-of-Band RF Pulses
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Solution Overview
Problem
Existing magnetic resonance imaging (MRI) systems lack precise patient positioning information, leading to conservative safety measures that limit transmit power due to uncertainty about the patient's distance from the magnet bore, potentially causing overheating and burns.
Innovation Solution
A method using RF transmit pulses outside the examination frequency band to ascertain the patient's position, generating response signals that are analyzed to determine the patient's location relative to the magnet bore, allowing for more accurate monitoring and adjustment of safety protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conservative safety measures are used due to lack of patient position information, then patient safety is protected, but transmit power is limited causing reduced imaging quality and longer examination times
Solution Approach 1:
The patent replaces mechanical positioning systems with electromagnetic field-based position detection. By using RF transmit pulses at frequencies outside the examination band and analyzing the resulting signals, the system determines patient position without mechanical sensors or markers, enabling dynamic safety adjustments while maintaining examination efficiency
Solution Approach 2:
The system continuously monitors patient position through RF signal analysis and provides feedback to adjust transmit power in real-time. This closed-loop control allows the system to adapt to actual patient positioning, optimizing both safety and examination efficiency by avoiding unnecessary power limitations
2Temperature
If transmit power is limited due to uncertainty about patient distance from magnet bore, then overheating is prevented, but imaging quality deteriorates and examination time increases
Solution Approach 1:
The system performs preliminary position determination using RF pulses before the actual imaging sequence. By pre-ascertaining patient position and calculating safety distances, the system can optimize transmit power parameters for the subsequent examination, reducing overall examination time while maintaining temperature control
Solution Approach 2:
The patent implements dynamic transmit power adjustment based on real-time patient position information. Instead of using fixed conservative power limits, the system continuously adapts power levels according to actual patient positioning, optimizing both heating control and examination efficiency
3Measurement precision
If RF transmit pulses are used at examination frequency band for positioning, then position information can be obtained, but imaging signals are interfered with and SAR increases
Solution Approach 1:
The patent segments the RF frequency spectrum into different bands: examination frequency band for imaging and position determination band for positioning. By using distinct frequency bands, the system obtains accurate position information without interfering with imaging signals or excessively increasing SAR, as the positioning pulses are transmitted separately and analyzed independently
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 safer MRI operations by dynamically adjusting transmit power based on actual patient positioning, reducing the risk of overheating and enabling more effective magnetic resonance protocols.
Implementation Method 1
The at least one transmit antenna of the magnetic resonance apparatus generates an RF transmit pulse with a frequency band that is outside of an examination frequency band of the magnetic resonance apparatus
Implementation Method 2
The generated RF fields cause heating of the tissue of the patient, which is described by a specific absorption rate (SAR)
Implementation Method 3
The magnet unit includes a main magnet for generating a main magnetic field
Implementation Method 4
a gradient coil unit for generating a gradient magnetic field in an examination region of the magnetic resonance apparatus
Implementation Method 5
A subsequent relaxation generates imaging and/or spectroscopic magnetic resonance signals that are received by one or more receive antenna(s) of the magnetic resonance apparatus
Data Source
AI summary
Systems and methods for ascertaining an item of position information about a position of a patient positioned in a magnetic resonance apparatus are provided. The magnetic resonance apparatus includes at least one transmit antenna, wherein each of the at least one transmit antennas is provided to generate RF transmit pulses for generating magnetic resonance signals in the body of the patient. Furthermore, the magnetic resonance apparatus includes at least one receive antenna that is configured to receive a response signal of the RF transmit pulse, for example a magnetic resonance signal triggered by the RF transmit pulse. An RF transmit pulse is generated with the at least one transmit antenna of the magnetic resonance apparatus, which pulse includes a frequency band which is outside of an examination frequency band of the magnetic resonance apparatus. The item of position information is ascertained using the response signal of the RF transmit pulse.