OCTA Vessel Image Compositing for Uniform Retinal Angiography
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Solution Overview
Problem
Existing image filters used for blood vessel enhancement in OCTA images, such as the multiscale Frangi filter, often result in irregular brightness in thick blood vessels, dropout of thin blood vessels, and noise resembling blood vessels in avascular regions like the foveal avascular zone (FAZ).
Innovation Solution
An ophthalmic apparatus and method that includes an image acquisition unit, a projection processor, a blood vessel enhancement processor, a denoising processor, and an image compositing processor, which apply various techniques like multiscale Frangi filters, denoising processes, and image compositing methods to enhance and combine images, addressing issues of brightness irregularity, thin vessel dropout, and noise in avascular regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multiscale Frangi filter is applied to enhance blood vessels, then thick blood vessel enhancement is improved, but brightness irregularity occurs in thick blood vessels and thin blood vessel visibility is reduced
Solution Approach 1:
A denoising process is introduced as an intermediary step between the Frangi filter enhancement and the final image output. This denoising processor acts as a mediator that removes the unwanted noise and brightness irregularities generated by the Frangi filter while preserving the enhanced blood vessel structures, thus resolving the contradiction between enhancement quality and brightness uniformity
Solution Approach 2:
The patent applies the Frangi filter to generate an enhanced image, then creates a separate denoised version of the original image, and finally composites these multiple versions together. This copying approach allows the system to leverage the strengths of each processing path while compensating for their individual weaknesses, achieving both enhancement and uniformity
2Measurement precision
If a multiscale Frangi filter is applied to enhance blood vessels, then blood vessel visibility is improved, but noise resembling blood vessels appears in avascular regions
Solution Approach 1:
The patent converts the harmful noise generated by the Frangi filter into a beneficial signal through the denoising process. The denoising processor specifically targets and removes noise in avascular regions while preserving genuine blood vessel signals, effectively transforming the filter's harmful side effect into an opportunity for improved image quality
Solution Approach 2:
The system uses the denoised image as feedback to guide the final compositing process. By comparing the enhanced image with the denoised version, the system can identify and suppress noise artifacts in avascular regions while maintaining genuine blood vessel visibility, creating a self-correcting enhancement process
3Measurement precision
If a multiscale Frangi filter is applied to enhance blood vessels, then image detail is improved, but image complexity and processing time increase
Solution Approach 1:
The patent segments the image processing into distinct functional modules: the Frangi filter enhancement processor, the denoising processor, and the compositing processor. Each module performs a specific function with optimized complexity, allowing the system to achieve high image detail while managing overall processing complexity through modular architecture
Solution Approach 2:
The denoising process is performed in advance on the original image to create a clean baseline, before the Frangi filter enhancement is applied and before the final compositing. This preliminary action prevents noise from being amplified during enhancement, reducing the need for complex post-processing and simplifying the overall system
Data Source
AI summary
An ophthalmic apparatus of an embodiment example includes an image acquisition unit, image projection processor, blood vessel enhancement processor, denoising processor, and image compositing processor. The image acquisition unit acquires an optical coherence tomography angiography image of a fundus of a subject's eye. The image projection processor applies a projection process to the optical coherence tomography angiography image to generate a projection image. The blood vessel enhancement processor applies a blood vessel enhancing filter that is configured to enhance a blood vessel image to the projection image to generate a blood vessel enhanced image. The denoising processor applies a denoising process to the projection image to generate a denoised image. The image compositing processor applies an image compositing process to the projection image, the blood vessel enhanced image, and the denoised image to generate a composite image.