Segmented Slip Ring for MRI-Guided Radiotherapy
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Solution Overview
Problem
Combining radiotherapy and MRI technologies is challenging due to the interference of high-power radiotherapy sources with the MRI magnetic fields, leading to degraded image quality from stray magnetic fields created by the power delivery via slip rings.
Innovation Solution
A radiotherapeutic apparatus with a slip ring that includes non-conductive sections or breaks to prevent a continuous circumferential current path, allowing power to be routed through one side or the other, and a control mechanism to suppress imaging during transient disturbances, ensuring continuous power delivery to the radiotherapy source while minimizing magnetic field interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If power is delivered to the rotating radiotherapy source via a continuous slip ring, then the source can rotate continuously, but stray magnetic fields are created that interfere with MRI fields and degrade image quality
Solution Approach 1:
The slip ring is segmented into non-conductive sections that break the continuous circumferential current path. This segmentation prevents the formation of stray magnetic fields while still allowing power to be delivered to the rotating radiotherapy source through the conductive sections.
Solution Approach 2:
Different sections of the slip ring have different electrical properties - conductive sections for power delivery and non-conductive sections for preventing stray magnetic fields. This local differentiation of properties allows the slip ring to simultaneously enable rotation and prevent magnetic interference.
2Object-affected harmful factors
If non-conductive sections are added to the slip ring to prevent stray magnetic fields, then MRI image quality is maintained, but the complexity of the power delivery system increases
Solution Approach 1:
The slip ring is divided into distinct conductive and non-conductive sections along its circumference. This segmentation is implemented as a straightforward structural modification that prevents stray magnetic fields without requiring complex additional components or control systems.
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 solution allows for effective power delivery to rotating radiotherapy sources without disrupting the MRI magnetic fields, maintaining image quality and enabling precise radiation therapy planning and execution.
Implementation Method 1
this is aligned with the main and gradient magnetic fields as well as with the magnetic fields emitted by the RF transmitter antennae and the magnetic fields associated with the magnetic resonance signals. This has the ability to create stray magnetic fields that interfere with the MRI field(s)
Implementation Method 2
a static magnetic field is generated by way of a main magnet, usually provided with electrically superconducting main magnet coils, and is used to align nuclear spins
Implementation Method 3
usually provided with electrically superconducting main magnet coils
Implementation Method 4
radiofrequency (RF) pulses are generated by RF transmitter antennae (coils) to cause perturbations to the local magnetic field, notably to tip the aligned nuclear spins
Implementation Method 5
Magnetic resonance signals are acquired by RF receiver coils
Implementation Method 6
gradient coils are provided to generate temporary gradient magnetic field pulses for spatial encoding of the magnetic resonance signals
Data Source
AI summary
We provide a radiotherapeutic apparatus comprising a patient support, magnetic coils disposed around the patient support for creating a magnetic field therewithin, a radiation source producing a beam of radiation directed toward the patient support and mounted on a rotatable support thereby to rotate the radiation source around the patient support, a slip ring for conveying electrical power to the radiation source and located around the patient support, including at least one electrical interruption therein. This creates a slip ring in which there is no continuous circumferential path, and one in which the current is therefore forced to take a route via one side or the other.