X-ray CT Dose Control for Region of Interest Noise
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Solution Overview
Problem
Current X-ray CT techniques are suboptimal for dose optimization as they neglect spectral effects and scattered radiation, leading to inefficient dose distribution and reduced image quality, especially when the region of interest is not at the image center.
Innovation Solution
An image generation device and method that calculates the optimum dose profile based on noise propagation in individual voxels, accounting for scatter and spectral effects, to improve the signal-to-noise ratio specifically for a user-selected region of interest, using noise propagation algorithms and scatter models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dose optimization techniques are used based on measured attenuation in the center of the detector, then the noise in the center of the reconstructed object is optimal, but the contrast-to-noise ratio in the region of interest significantly deteriorates when the region of interest is not at the center
Solution Approach 1:
The patent applies local quality by shifting from global dose optimization (centered on the image center) to local dose optimization tailored to the specific region of interest. The system calculates region-specific dose profiles that account for the actual location and geometry of the region of interest, thereby optimizing image quality locally rather than uniformly across the entire field of view.
Solution Approach 2:
The patent employs preliminary action by using scout views or preliminary scans to identify and characterize the region of interest before the actual diagnostic scan. This preliminary information is then used to pre-calculate the optimal dose profile, allowing the system to prepare region-specific optimization parameters in advance, which are subsequently applied during the main imaging process.
2Object-generated harmful factors
If scatter offset correction techniques are used prior to reconstruction, then scattered radiation is reduced, but the calculation of the optimum dose profile becomes suboptimal because scatter effects and their subtraction impact are not adequately accounted for
Solution Approach 1:
The patent applies feedback by incorporating scatter correction information back into the dose profile calculation process. The system uses measured or estimated scatter values to adjust and refine the dose profile optimization, creating a feedback loop where scatter characterization informs dose optimization, thereby accounting for scatter effects that were previously neglected.
Solution Approach 2:
The patent introduces an intermediary approach by using scatter estimation models or scatter correction algorithms as intermediate steps between raw projection data and final image reconstruction. These intermediaries provide scattered radiation information that is then integrated into the dose optimization calculation, serving as a bridge that connects scatter correction with dose profile optimization.
3Device complexity
If spectral effects such as beam hardening are neglected in dose optimization, then the calculation is simpler, but the accuracy of noise estimation and dose profile optimization deteriorates
Solution Approach 1:
The patent applies parameter changes by incorporating spectral information and beam hardening effects into the dose optimization model. The system adjusts optimization parameters to account for energy-dependent attenuation variations, transforming the calculation from a simple monoenergetic model to a more complex polyenergetic model that reflects actual physical conditions.
Solution Approach 2:
The patent uses preliminary action by pre-calculating or pre-characterizing spectral effects and beam hardening parameters before the main dose optimization process. Lookup tables or pre-computed correction factors for spectral effects are prepared in advance, allowing the optimization algorithm to incorporate these effects without excessive computational burden during the actual optimization step.
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 while reducing the patient dose, homogenizing noise artifacts, and optimizing dose distribution for asymmetric patient geometries by accurately accounting for scattered radiation and spectral effects.
Implementation Method 1
X-ray CT is a technique which determines the internal make-up of an object by passing X-rays through the object and measuring the attenuation of the X-rays passing through the object
Implementation Method 2
Spectral effects originating e.g. from beam hardening and the influence of scattered radiation are neglected
Data Source
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AI summary
The present invention relates to an image generation device for generating an image from measured data, wherein image quality is optimized for a region of interest and to an imaging system comprising this image generation device. The image generation device comprises a noise determination unit for determining a distribution of noise in a projection domain of the region of interest, and a dose control unit (32) for determining a dose profile for a radiation source (2) of said image generation device based on said determined distribution of noise by using a noise propagation algorithm. Thereby, signal-to-noise ratio of a reconstructed volume can be improved and is not sensitively dependent on a selected region of interest.