3D Fluence Modulation CT Scatter Shield
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Solution Overview
Problem
Conventional CT systems face issues with non-uniform x-ray distribution due to anatomical variations, leading to overexposure in peripheral regions, increased scattered radiation, and limited dynamic range, which affects image quality and radiation dose distribution.
Innovation Solution
The implementation of a Fluence Gate (FG) and Scatter Shield (SS) apparatus, comprising rotating drums with x-ray attenuating sheets, dynamically modulates the x-ray fluence and shields scattered photons to ensure primary photons reach the detector, synchronized to maintain a line-of-sight during image acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a uniform x-ray beam is used for imaging, then the beam coverage is simple and consistent, but the radiation dose becomes highly non-uniform with overexposure in peripheral regions and underexposure in central regions
Solution Approach 1:
The patent applies local quality by varying the x-ray beam fluence across different spatial regions to match the anatomical structure. Bowtie filters and fluence modulation systems create non-uniform beam intensity distributions where central regions receive lower fluence and peripheral regions receive higher fluence, optimizing dose distribution according to the specific attenuation characteristics of different anatomical zones
Solution Approach 2:
The patent changes the fluence parameter of the x-ray beam from uniform to non-uniform distribution. By adjusting the beam intensity profile using modulators and filters, the system transforms the homogeneous beam into a spatially varying fluence pattern that compensates for anatomical variations, thereby achieving more uniform dose distribution
2Reliability
If high x-ray fluence is applied to peripheral regions to ensure adequate exposure, then detector saturation is avoided, but unnecessary radiation dose is introduced to these regions
Solution Approach 1:
The patent applies local quality by delivering different fluence levels to different anatomical regions. Peripheral regions receive higher fluence to prevent detector saturation and ensure adequate signal, while central regions receive lower fluence to minimize unnecessary radiation dose, matching the beam intensity to the local attenuation requirements
3Quantity of substance
If scatter radiation is present in the detector, then more photons are detected, but the contrast resolution of the reconstructed image deteriorates
Solution Approach 1:
The patent extracts scattered photons from the detected signal using scatter rejection techniques. Anti-scatter grids and collimators are positioned to selectively block scattered radiation paths while allowing primary photons to reach the detector, thereby removing the harmful scattered component from the detected signal
Solution Approach 2:
The patent introduces intermediary devices such as anti-scatter grids and collimators between the patient and detector. These intermediaries selectively transmit primary photons while blocking scattered photons, acting as mediators that separate useful signal from harmful interference
4Manufacturing precision
If the detector dynamic range is increased to handle varying fluence, then both overexposed and underexposed regions are captured, but the device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-modulating the x-ray beam fluence before it reaches the patient and detector. By adjusting the beam intensity distribution in advance using modulators and filters, the system ensures that the detector receives a more uniform signal distribution, reducing the required dynamic range
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 reduces radiation dose inhomogeneity, minimizes scattered radiation, and optimizes image quality by ensuring uniform fluence and reducing the dynamic range requirements of the detector, resulting in improved contrast resolution and reduced patient exposure.
Implementation Method 1
a robotic fluence gate system affixed to the gantry between the x-ray source and the x-ray detector and comprising a rotational platform configured to rotate on a second axis of rotation and a plurality of fluence modulation sheets forming a fluence gate window, the fluence gate system configured to modulate a fluence of the beam of x-ray photons
Implementation Method 2
a robotic scatter shield system affixed to the gantry between the x-ray source and the x-ray detector and comprising a rotational platform configured to rotate on a third axis of rotation and a plurality of scatter shield sheets forming a scatter shield window, the scatter shield system configured to shield scattered x-ray photons from the x-ray detector
Implementation Method 3
synchronize a speed and a phase of rotation of the gantry, the fluence gate system, and the scatter shield system to maintain a line-of-sight from the x-ray source to the x-ray detector during capture of each projection of the target
Data Source
Figure 1A~1D
Figure 2A~2C
Figure 3A~3E
AI summary
Described are apparatus and methods of operation for three dimensional fluence modulation and scatter shielding for dedicated computed tomography (CT). Through the disclosed invention, the number of incident photons on the field of view (FOV) of the imaging system becomes proportional to the path length of the photon through the anatomy of interest. The apparatus is comprises a patient specific x-ray fluence modulation unit and a scatter shield unit. The fluence modulation unit reduces radiation dose differences across the anatomical part and the dynamic range requirements for the x-ray detector. The scatter shield unit is intended for preventing the scattered beams from reaching the x-ray detector. The internal structures of each unit are composed of elements with adjustable positions dependent on the specific shape of the object in the field-of-view (FOV). Method of operation are also provided.