MRI-Guided Radiotherapy MLC Alignment
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Solution Overview
Problem
Conventional radiotherapy systems integrated with MRI imaging face challenges in delivering high-quality imaging and treatment while minimizing exposure to healthy tissue, particularly due to the narrow bore of MRI systems which restricts the adjustment of the patient position and requires specialized collimators that are not ideally suited for QA and in-vivo dosimetry.
Innovation Solution
A radiotherapy system incorporating a multi-leaf collimator (MLC) and a radiation detector with detector elements aligned to the MLC leaves, positioned outside the MRI coils, allowing for accurate radiation delivery and quality assurance, and enabling real-time imaging and motion tracking of the patient during treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MRI coils are placed around the patient for imaging, then real-time imaging quality is improved, but therapeutic radiation is blocked from reaching the patient
Solution Approach 1:
The MRI system is segmented into separate imaging and treatment zones. The imaging apparatus with MRI coils is positioned to image the patient while the radiation source and collimator are positioned separately to deliver treatment through the imaging zone without being blocked by the coils.
Solution Approach 2:
The imaging apparatus acts as an intermediary that allows radiation to pass through its imaging zone while providing real-time imaging. The system is designed so that radiation can traverse the imaging zone between the source and patient, and the MRI coils are positioned to image through this path without blocking the radiation beam.
2Object-affected harmful factors
If the radiation beam is directed from multiple directions to minimize healthy tissue exposure, then the therapeutic dose to the tumor is improved, but the treatment time and system complexity increase
Solution Approach 1:
The imaging apparatus and radiation therapy apparatus are merged into a single integrated system sharing a common support structure and control system. This allows multiple radiation beams to be delivered from different directions while maintaining real-time imaging capability without requiring separate independent systems.
Solution Approach 2:
The imaging apparatus serves multiple functions: it provides real-time imaging for treatment guidance, allows radiation to pass through its imaging zone, and works in conjunction with the collimator system to enable multi-directional beam delivery. The integrated system performs both imaging and treatment functions simultaneously.
3Measurement precision
If the patient remains still during therapy to minimize damage to surrounding tissue, then radiation targeting precision is improved, but the ability to treat moving targets is reduced
Solution Approach 1:
The imaging apparatus provides real-time imaging feedback during radiation delivery, allowing the system to detect patient motion and adjust the radiation beam position accordingly. The control system uses this feedback to track moving targets and maintain accurate targeting precision even when the patient moves.
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
The system achieves high-quality dose distributions and accurate radiation targeting, minimizing exposure to healthy tissue while providing effective quality assurance and in-vivo dosimetry, even with the constraints of the MRI system's geometry.
Implementation Method 1
a source of radiation mounted on a chassis, the chassis being rotatable about the central axis and the source being adapted to emit a beam of radiation through the gap
Implementation Method 2
a multi-leaf collimator comprising a plurality of elongate leaves movable between at least a withdrawn position in which the leaf lies outside the beam, and an extended position in which the leaf projects across the beam
Implementation Method 3
a radiation detector mounted to the chassis opposite the source, the radiation detector having a plurality of detector elements aligned with the elongate leaves when projected onto an isocentric plane
Implementation Method 4
an imaging apparatus, comprising a first magnetic coil and a second magnetic coil, the first and second magnetic coils having a common central axis parallel to the translation axis
Data Source
AI summary
A radiotherapy system comprises a patient support, moveable along a translation axis, an imaging apparatus, comprising a first magnetic coil and a second magnetic coil, the first and second magnetic coils having a common central axis parallel to the translation axis, and being displaced from one another along the central axis to form a gap therebetween, the imaging apparatus being configured to obtain an image of a patient on the patient support, a source of radiation mounted on a chassis, the chassis being rotatable about the central axis and the source being adapted to emit a beam of radiation through the gap along a beam axis that intersects with the central axis, a multi-leaf collimator comprising a plurality of elongate leaves movable between at least a withdrawn position in which the leaf lies outside the beam, and an extended position in which the leaf projects across the beam, and a radiation detector mounted to the chassis opposite the source, the radiation detector having a plurality of detector elements aligned with the elongate leaves when projected onto an isocentric plane.