Radiotherapy Apparatus MV kV Imaging Synchronization
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Solution Overview
Problem
The independent operation of megavoltage (MV) and kilovoltage (kV) imaging systems in radiotherapy apparatus leads to significant artefacts in kV images due to scatter from MV pulses, resulting in poor image quality and contrast.
Innovation Solution
A control unit synchronizes the operation of therapeutic and diagnostic radiation sources and their associated detectors, allowing the therapeutic source to emit radiation while the diagnostic source is inactive, and vice versa, ensuring that images are read and any accumulated scatter data is cleared, thereby eliminating artefacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MV and kV imaging systems operate independently and simultaneously, then both imaging functions are available, but significant artefacts appear in kV images due to scatter from MV pulses
Solution Approach 1:
The patent applies periodic action by alternating between MV and kV imaging modes in time. The system operates in discrete cycles where the MV source emits radiation followed by a pause, then the kV source emits radiation followed by a pause, repeating this sequence. This temporal separation ensures that scatter from one source does not contaminate the other detector, eliminating artefacts while maintaining both imaging capabilities.
2Area of stationary object
If the aperture size of radiation beams is increased, then more tissue can be imaged, but scatter from the other beam affects the detector
Solution Approach 1:
By using periodic alternating operation between MV and kV modes, the system can employ larger beam apertures during each mode's active period without concern for scatter from the other mode. The temporal separation ensures that when one beam is active with large aperture, the other beam is inactive, so its scatter cannot affect the detector.
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 approach improves the quality of images by eliminating artefacts and allows for increased aperture size of radiation beams without compromising image quality, enabling cleaner kV images and enhanced CT datasets.
Implementation Method 1
a source of therapeutic radiation adapted to irradiate a spatial volume, and an associated detector located on an opposite side of the spatial volume relative to the therapeutic source, to capture an image of the radiation as attenuated by objects in the spatial volume
Implementation Method 2
a source of diagnostic radiation, having an energy less than that of the therapeutic radiation, adapted to irradiate the same spatial volume from a different direction, and an associated detector located on an opposite side of the spatial volume relative to the diagnostic source, to capture an image of the radiation as attenuated by objects in the spatial volume
Implementation Method 3
the kV images contain significant artefacts arising from the MV pulse; some of the scatter from the MV pulse exits the patient at about 90° and impinges on the kV detector
Data Source
AI summary
In radiotherapy apparatus comprising an imager for the MV beam and a separate kV imaging system, it is common for there to be significant artifacts in the kV image arising from the MV pulse. We disclose such a radiotherapy apparatus which is adapted to (i) cause the therapeutic source to emit radiation while keeping the diagnostic source inactive, (ii) read an image from the detector associated with the therapeutic source, (iii) cause the diagnostic source to emit radiation and while keeping the therapeutic source inactive, (iv) read an image from the detector associated with the diagnostic source, and (v) repeat as necessary. The control unit is preferably adapted to, at steps (ii) and (iv), read an image from both of the detectors, or to clear the “inactive” detector. The detectors are ideally flat-panel detectors, capturing a two-dimensional image.