MRI Detector Unit Layout With Nested Shim and RF Screen
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Solution Overview
Problem
The challenge in magnetic resonance devices is to achieve a compact and efficient design that maintains magnetic field homogeneity while maximizing the patient receiving area, which is often compromised by the thickness of the detector unit components.
Innovation Solution
A detector unit design featuring concentrically arranged radio frequency antenna and gradient coil units with oblong shim units positioned to minimize radial space, integrated with a thin RF screen and fixing units, allowing for a compact and efficient arrangement of shim units outside the gradient coil unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the detector unit components (gradient coil unit, shim units, RF screen) are arranged with conventional spacing and thickness, then the magnetic field homogeneity is maintained, but the radial extent increases reducing the patient receiving area
Solution Approach 1:
The shim units are integrated within the gradient coil unit structure, with shim boxes positioned in recesses of the gradient coil unit. The RF screen is arranged between the gradient coil unit and the shim units, creating a nested configuration where multiple components occupy overlapping spatial envelopes, thereby minimizing the overall radial extent while maintaining functional separation
Solution Approach 2:
The shim units are arranged in the radial direction between the gradient coil unit and the RF screen, utilizing the radial dimension to optimize spacing. The gradient coil unit has recesses that accommodate shim boxes, creating localized raised areas on the inner surface, which allows precise positioning in the radial dimension to minimize overall thickness
2Area of stationary object
If the shim units are positioned closer to minimize radial space, then the patient receiving area is maximized, but eddy currents may increase affecting image quality
Solution Approach 1:
The RF screen is positioned between the gradient coil unit and the shim units, serving as an intermediary component. This screen acts as a barrier that blocks eddy currents generated in the shim units from affecting the gradient coil unit, and vice versa, allowing the components to be positioned closer together without compromising image quality
Solution Approach 2:
The detector unit is segmented into distinct functional components (gradient coil unit, shim units, RF screen) that are electrically isolated from each other. The RF screen creates electrical separation between the gradient coil unit and shim units, preventing eddy current interference while allowing compact radial arrangement
3Area of stationary object
If the detector unit radial extent is minimized for compact design, then patient access is improved, but the arrangement complexity of components increases
Solution Approach 1:
The shim units are merged with the gradient coil unit structure by integrating shim boxes into recesses of the gradient coil unit. This merging eliminates the need for separate mounting structures and simplifies the overall assembly, reducing arrangement complexity while maintaining compact radial dimensions
Solution Approach 2:
The gradient coil unit serves multiple functions: it generates gradient magnetic fields and simultaneously provides structural support and positioning for the shim units through its recesses. The RF screen serves both as an electromagnetic shield and as a structural element that defines the radial arrangement of components, reducing the need for additional support structures
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 design enhances magnetic field homogeneity, reduces eddy currents, and increases patient comfort by minimizing the detector unit's radial extent, thereby optimizing image quality and patient access.
Implementation Method 1
The shim unit typically comprises at least one shim box, at least one shim box receptacle and at least one shim plate... Depending on the inhomogeneity of the main magnetic field, in particular due to the environment, shim plates are arranged within the shim box... Thanks to their susceptibility, to increase the homogeneity of the main magnetic field
Implementation Method 2
The detector unit comprises an RF screen, which is arranged at least in part between the radio frequency antenna unit and the gradient coil unit
Implementation Method 3
In addition, gradient pulses are emitted with the aid of a gradient coil unit
Implementation Method 4
by means of suitable antenna facilities, high frequency radio frequency pulses, i.e. RF pulses, are sent out, which leads to the nuclear spins of specific atoms excited resonantly
Implementation Method 5
the body of an object to be examined, in particular of a patient, is usually subjected with the aid of a main magnet to a relatively high main magnetic field
Data Source
AI summary
The disclosure relates to a detector unit comprising a radio frequency antenna unit and a gradient coil unit surrounding the radio frequency antenna unit concentrically, each embodied as hollow cylinders surrounding a cylinder axis in the longitudinal direction. The detector unit comprises at least four shim units, which are embodied as oblong shapes and are each arranged in parallel to the cylinder axis at various positions in the circumferential direction on a first inner surface, with said first inner surface corresponding to the side of the gradient coil unit facing towards the cylinder axis, and forming raised areas in the direction of the cylinder axis. The detector unit comprises a fixing unit embodied for fixing the at least four shim units to the gradient coil unit, and an RF screen, which is arranged at least partly between the radio frequency antenna unit and the gradient coil unit.