Radiotherapy Detector Control Circuitry for Artefact Reduction
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Solution Overview
Problem
Portal images derived from megavoltage (MV) radiation in radiotherapy suffer from artefacts due to ionization of the transistor array and read-out electronics, leading to low-quality images with poor contrast, and the low duty cycle of the MV source is necessary to prevent thermal overload but results in inefficient treatment times.
Innovation Solution
Implementing control circuitry that resets the interpreter after a therapeutic pulse and groups pulses into 'flurries' to enable multiple pixels simultaneously, allowing for increased pulse rates and reducing artefacts by managing thermal load through optimized timing schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the MV source operates in a pulsed manner at a low duty cycle to prevent thermal overload, then thermal management is improved, but treatment time increases and clinical efficiency decreases
Solution Approach 1:
The control circuitry resets the interpreter circuitry before each MV pulse arrives, preparing the system in advance to prevent artefact formation. This preliminary action allows the system to handle higher pulse rates without accumulating thermal damage or artefacts, thereby reducing total treatment time while maintaining thermal safety
Solution Approach 2:
The system uses periodic pulsing of the MV source with optimized duty cycles, combining short high-intensity pulses with reset periods. This periodic operation allows thermal management while maintaining acceptable treatment speeds by efficiently utilizing the active pulse periods
2Measurement precision
If the interpreter is reset after each MV pulse to remove artefacts, then image quality is improved, but the complexity of the control circuitry increases
Solution Approach 1:
The interpreter is reset in advance before each MV pulse rather than continuously or after detection of artefacts. This preliminary resetting action simplifies the control logic by using a predetermined timing scheme based on the pulsed nature of the MV source, avoiding the need for complex artefact detection and correction algorithms
Solution Approach 2:
The control circuitry uses feedback from the pulsed MV source timing to trigger interpreter resets at optimal moments. This feedback-based timing ensures artefact-free images while maintaining simple circuitry that only needs to respond to the known pulsed operation pattern of the therapeutic radiation source
3Productivity
If multiple pixels are enabled simultaneously to increase treatment speed, then productivity is improved, but the risk of thermal overload and artefact formation increases
Solution Approach 1:
The control circuitry enables multiple pixels to be ready simultaneously but only activates signal collection during the brief intervals between MV pulses. This preliminary preparation allows the system to process data from multiple pixels without increasing thermal load, as the actual data collection occurs during cool-down periods when thermal accumulation is minimal
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 enhances image quality by reducing artefacts and increasing clinical efficiency by allowing higher pulse rates, thereby improving treatment speed and reducing thermal overload risks.
Implementation Method 1
An upper layer 12 consists of a scintillator under the application x-rays 14. The light 16 thus produced impinges on an array 18 of photodiodes
Implementation Method 2
The light impinges on the photodiode in the array and creates an electronic signal
Implementation Method 3
When a MV pulse arrives, it will not only cause scintillation in the scintillator, but will also impinge on the transistor array and the read-out electronics and ionise the material of which they are formed. This will therefore create a further electronic signal
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
Flat panel images obtained during concurrent radiotherapy typically suffer from artefacts that relate to the pulses of MV energy. For a radiotherapeutic apparatus comprising a pulsed source of therapeutic radiation, a detector comprising control circuitry, an array of pixel elements, each having a signal output and an 'enable' input and being arranged to release a signal via the signal output upon being triggered by the enable input, and an interpreter arranged to receive the signal outputs of the pixel elements, the interpreter having a reset control, there are advantages in the control circuitry being adapted to reset the interpreter after a pulse of therapeutic radiation, prior to enabling at least one pixel of the array. Alternatively, the control circuitry can prompt a plurality of pulses by the pulsed source and then enable a plurality of pixels of the array. In effect, the therapeutic pulses are grouped into a short flurry of pulses. It is therefore preferred that the plurality of pixels comprises substantially all the pixels of the array.