Ring Artifact Detection in CT Imaging via Polar Coordinate Mapping

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Solution Overview

Problem

Medical imaging devices, such as CT scanners, often produce images with concentric ring artifacts that degrade image quality, necessitating automatic detection and correction methods to improve image clarity.

Innovation Solution

A method and system for determining ring artifacts in images by mapping pixels to a polar coordinate image, identifying a protection region, smoothing the image, generating a residual image, and locating ring artifacts based on the residual image, utilizing techniques like interpolation, boundary extraction, and gradient analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If automatic ring artifact detection is implemented, then image quality improvement is achieved, but processing complexity increases

Engineering Contradiction:

Improveimage qualityVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The image processing is divided into distinct stages: coordinate transformation to polar coordinates, protection region identification, smoothing operation, residual image generation, and ring artifact detection. Each stage handles a specific aspect of the problem, making the overall complex process manageable and systematic

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A protection region is introduced as an intermediary element that prevents smoothing operations from affecting important image features. This intermediary structure allows the algorithm to distinguish between regions requiring smoothing and regions that should be preserved, reducing false detections

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If polar coordinate transformation is applied, then ring artifact detection accuracy is improved, but computational load increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidcomputational load

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The image is pre-transformed to polar coordinates before detection operations. This preliminary transformation reorganizes the data structure so that concentric ring artifacts appear as linear features in the transformed space, making them easier to detect and analyze in subsequent steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The detection problem is shifted from spatial domain to a transformed coordinate domain. By changing the coordinate system from Cartesian to polar, the algorithm exploits the geometric properties of ring artifacts to convert a complex 2D pattern recognition problem into a more tractable analysis in the transformed space

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If smoothing operations are performed on the entire image, then noise reduction is achieved, but important features are lost

Engineering Contradiction:

Improvenoise reductionVSAvoidfeature loss

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

Different regions of the image receive different treatments. The protection region identification step determines which areas should be preserved from smoothing, allowing the algorithm to apply noise reduction selectively only to non-critical regions while maintaining important features in protected areas

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of applying smoothing to the entire image, the algorithm performs partial smoothing only on regions outside the protection zones. This partial action approach reduces noise where safe while avoiding over-smoothing that would degrade important image features

Inventive Principle:

Principle #16Partial or excessive action

4Measurement precision

If residual image generation is used, then ring artifact localization is improved, but processing time increases

Engineering Contradiction:

Improvelocalization accuracyVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The residual image extraction step isolates the ring artifact components by subtracting the smoothed image from the original. This extraction separates the artifact signal from the rest of the image content, enabling focused detection and localization without processing the entire image at full complexity

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS11544821B2Systems and methods for determining ring artifact

Publication Date: 2023.01.03 SHANGHAI UNITED IMAGING HEALTHCARE

AI summary

The embodiments of the present disclosure disclose methods and systems for determining a ring artifact. The method for determining the ring artifact may include: obtaining an original image; mapping a plurality of pixels in the original image to a polar coordinate image; determining a protection region in the polar coordinate image; obtaining a smooth image by smoothing at least one region in the polar coordinate image other than the protection region; generating a residual image based on the polar coordinate image and the smooth image; determining a location of the ring artifact in the original image based on the residual image. In the present disclosure, the original image may be mapped to a trapezoidal region or a triangular region in the polar coordinate image, and the gradient angle image may be used for image processing, which may reduce the influence of noise. An accurate location of the ring artifact may be determined, and information for imaging device detection and air correction may be provided.