Faint Fluorescence Imaging for Surgery With Contrast Enhancement
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Solution Overview
Problem
Current fluorescence-guided surgery methods are ineffective for utilizing faint fluorescence sources such as autofluorescence of the parathyroid gland or fluorescent probes due to their weak signals being overwhelmed by excitation light and ambient light, leading to undetectable imaging.
Innovation Solution
A method involving excitation light emission, simultaneous or alternate capture of fluorescence and white light images, inverse gamma correction, noise suppression, normalization, and creation of composite images with enhanced contrast and a defined region of interest to highlight faint fluorescence sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescence excitation light is shone on fluorescent dye infused tissue to detect fluorescence light, then fluorescence light can be detected using a wavelength filter, but the fluorescence signal is overwhelmed by reflected excitation light which is orders of magnitude more intense
Solution Approach 1:
The imaging system is segmented into multiple spectral channels: one for fluorescence detection and another for reflected light detection. This allows separate processing and combination of signals, enabling the weak fluorescence signal to be extracted from the overwhelming reflected excitation light background.
Solution Approach 2:
A reference channel acts as an intermediary to measure the reflected excitation light intensity, which then serves as a basis for generating a mask to suppress the reflected light in the fluorescence image. This intermediary measurement enables effective separation of the fluorescence signal from the dominant reflected light.
2Measurement precision
If autofluorescence imaging is performed in the near infrared spectrum around 785 nm excitation wavelength, then parathyroid gland autofluorescence can be detected, but the weak autofluorescence signal is outshone by excitation light and ambient light
Solution Approach 1:
The system dynamically adjusts the excitation light intensity based on real-time feedback from the reference channel. By modulating the excitation light power, the system optimizes the fluorescence signal while minimizing the overwhelming ambient and reflected light interference, enabling detection of weak autofluorescence signals.
Solution Approach 2:
The system changes the spectral parameters by detecting both at the fluorescence emission wavelength and at a reference wavelength. This parameter change approach allows differentiation between the autofluorescence signal and the broadband ambient light, enabling selective enhancement of the weak autofluorescence.
3Measurement precision
If image processing is performed to increase contrast between fluorescence light and background, then faint fluorescence sources become visible, but processing time and computational complexity increase
Solution Approach 1:
The system performs preliminary actions by capturing a reference image of the reflected light before fluorescence imaging and pre-processing it to generate a suppression mask. This preliminary processing reduces the computational burden during real-time fluorescence imaging, enabling fast contrast enhancement without excessive processing time.
Solution Approach 2:
The system extracts only the essential components needed for contrast enhancement: the reference light image and the fluorescence image. By taking out and processing only these critical elements rather than the entire image data set, the system achieves effective contrast improvement with minimal processing time.
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
Enhances visibility of faint fluorescence signals by increasing contrast and masking background noise, allowing for effective visualization of faint fluorescence sources in surgical environments.
Implementation Method 1
Fluorescence excitation light is shone on the dye infused tissue, causing the fluorescent dye to emit fluorescence emission light
Implementation Method 2
The parathyroid gland includes naturally occurring fluorescent molecules that emit fluorescence light in the near infrared spectrum when excited by excitation light of suitable wavelengths
Implementation Method 3
Capturing one or more fluorescence images of the operation area at a wavelength range of fluorescence light emitted by the faint fluorescence source
Implementation Method 4
This slight shift in wavelength is exploited by using a wavelength filter configured to let light with the wavelength of the fluorescence light pass to shield off reflected excitation light from entering a camera
Data Source
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AI summary
The present disclosure relates to a method and a system (1) for visualization of faint fluorescence in surgery, in particular open surgery, as well as to a software program. The method comprises the following steps: - Emitting excitation light (12) from an excitation light source (6) onto an operation area (10) containing a faint fluorescence source (16), in particular parathyroid tissue exhibiting autofluorescence and/or fluorescent probes exhibiting fluorescence at similar intensity as the autofluorescence, as well as white light from a white light source, - Capturing one or more fluorescence images of the operation area (10) at a wavelength range of fluorescence light emitted by the faint fluorescence source (16) as well as one or more white light images, - Performing image processing on the one or more fluorescence images and creating one or more false colour fluorescence images from the one or more fluorescence images, wherein a contrast between the fluorescence light emitted by the faint fluorescence source and background is increased, and - Creating one or more composite images (50) by overlaying the one or more false colour fluorescence images over the one or more white light images.