Magnetic Resonance Tomography Metallic Object Localization
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Solution Overview
Problem
Magnetic resonance tomography units face challenges in real-time monitoring due to complex image acquisition and slow image sequences, as well as interference from metallic instruments that generate no signal but hinder acquisition, especially in the vicinity of compact metallic objects used during interventions.
Innovation Solution
A method utilizing a magnetic resonance tomography unit that employs radiofrequency pulses, magnetic field gradients, and balanced steady-state free precession sequences to excite nuclear spins and suppress background noise, allowing for precise localization of compact metallic objects by generating high-contrast signals and reconstructing artifacts to determine the object's position without detailed knowledge of susceptibility differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional magnetic resonance tomography is used for real-time monitoring, then image acquisition is performed, but the image sequence is slow and complex
Solution Approach 1:
The patent segments the image acquisition process by focusing only on local regions of interest around metallic objects rather than acquiring full volumetric images. This is achieved through localized excitation pulses and targeted sampling in k-space, reducing the overall data acquisition burden while maintaining monitoring capability.
Solution Approach 2:
The system performs preliminary localization of metallic objects using susceptibility-based signal characteristics before detailed imaging. The white marker gradient technique pre-identifies object positions, allowing subsequent focused acquisition only in relevant regions, thus speeding up real-time monitoring.
2Adaptability or versatility
If metallic instruments are present in the examination region, then they can be used during intervention, but they generate artifacts and hinder signal acquisition
Solution Approach 1:
The patent converts the harmful susceptibility-induced signal variations into beneficial localization information. Metallic objects create characteristic signal patterns and phase shifts that are normally considered artifacts, but the system exploits these same patterns to precisely locate and track the metallic objects through susceptibility-based detection methods.
Solution Approach 2:
The system introduces a white marker gradient as an intermediary mechanism to separate metallic object signals from surrounding tissue signals. This gradient creates a reference framework that allows differentiation between artifact signals from metal and genuine tissue signals, enabling simultaneous presence of metallic instruments and clear imaging.
3Measurement precision
If local receiving antennae are arranged directly on the examination object, then signal-to-noise ratio improves, but positioning and application complexity increases
Solution Approach 1:
The patent replaces the mechanical approach of physically positioning local coils on the patient with a field-based solution using white marker gradients. Instead of mechanically placing antennae to achieve spatial selectivity, the system uses gradient field manipulation to achieve localized signal detection, eliminating the complexity of antenna positioning while maintaining high signal-to-noise ratio in regions of interest.
Data Source
AI summary
A magnetic resonance tomography unit for localizing metallic objects and an operating method are provided. In one act of the method, an excitation pulse is used to excite nuclear spins in a region surrounding a compact metallic object. Magnetic resonance data is acquired with samplings along a plurality of trajectories, where the samplings take place using a bSSFP sequence, and the nuclear spins are dephased by a gradient. A position of a geometric focal point of the compact metallic object is ascertained based on a position of a visual focal point of acquired artifacts.