Handheld Laser Perfusion Imaging Spherical Wavefront Motion Artifacts
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Solution Overview
Problem
Laser-based perfusion imaging techniques, such as LSCI and LDPI, are sensitive to small movements during measurement, leading to motion artifacts and errors in perfusion assessment, making it challenging to distinguish between blood flow-induced blurring and motion artifacts.
Innovation Solution
A handheld laser-based perfusion imaging apparatus is designed with a light source configured to project a coherent light beam with a spherical wavefront or a planar wavefront, positioned to reduce sensitivity to rotational and translational movements, using optical components like single mode optical fibers, focusing lenses, and pinhole apertures to create a wavefront that is convex or parallel to the measurement field, and optionally incorporating a gimbal mount for further stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a handheld laser-based perfusion imaging apparatus is used, then ease of operation is improved, but sensitivity to motion artifacts worsens
Solution Approach 1:
The patent applies spherical wavefront illumination by positioning the light source at the center of a sphere that encompasses the measurement field. This curved wavefront geometry makes the perfusion measurement insensitive to rotational movements of the handheld apparatus, as rotations around the sphere center do not change the optical path lengths. The spherical illumination pattern ensures that motion artifacts are minimized while maintaining ease of handheld operation.
2Measurement precision
If movement correction processing is applied, then measurement precision is improved, but device complexity worsens
Solution Approach 1:
The patent extracts the motion correction function from the processing domain and implements it in the optical domain through spherical wavefront illumination. Instead of using complex algorithms to correct motion artifacts after acquisition, the system prevents motion artifacts from occurring in the first place by designing the optical geometry such that rotational movements do not affect the measurement. This eliminates the need for complex movement correction processing.
3Reliability
If spherical wavefront illumination is used, then sensitivity to rotational motion is reduced, but manufacturing precision requirements worsen
Solution Approach 1:
The patent changes the illumination parameter from a conventional planar or focused wavefront to a spherical wavefront. This parameter change fundamentally alters the system's sensitivity characteristics, making it insensitive to rotational movements. The spherical wavefront is achieved by positioning the light source at the center of the measurement sphere, which can be accomplished with relatively loose tolerances because the insensitivity to rotation provides a large margin for error in positioning.
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
The apparatus is less sensitive to small motion artifacts, maintaining measurement accuracy even during handheld operation by reducing the impact of rotational and translational movements, thereby improving the reliability of perfusion imaging.
Implementation Method 1
The light source is configured for projecting a beam of coherent light onto a measurement field
Implementation Method 2
the beam of coherent light comprises a spherical wavefront, wherein the wavefront is convex towards the measurement field
Implementation Method 3
The tissue of a subject is illuminated with coherent light and the backscattered light forms a so-called speckle pattern on the imaging sensor array
Implementation Method 4
Due to the interaction of light with moving red blood cells within the tissue, the speckle patterns become time dependent
Implementation Method 5
the one or more optical components are configured to position a center of the spherical wavefront at or near a pivot point of said handheld laser-based perfusion imaging apparatus
Data Source
AI summary
Disclosed is a handheld laser-based perfusion imaging apparatus having a light source and an imaging device which are arranged in a fixed orientation to each other in the apparatus. The light source is configured for projecting a beam of coherent light onto a measurement field at a predetermined distance spaced apart from the apparatus. The imaging device is configured for recording speckle intensity maps of the measurement field and/or images of Doppler shifted light of the measurement field. The light source is configured to provide a substantially spherical wavefront or a substantial planar wavefront, at least at the measurement field. Preferably, the apparatus with the light source that provides a substantial planar wavefront, including a gimbal mount. Also disclosed is a method for measuring a perfusion in a tissue using the handheld laser-based perfusion imaging apparatus as described above.