Photoacoustic Tomography Sensitivity Correction
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Solution Overview
Problem
Photoacoustic tomography apparatuses face challenges in achieving uniform spatial sensitivity distribution, leading to deteriorated quantitativity of information due to limited acoustic wave detection ranges, especially when examining large objects like human breasts, where acoustic waves cannot be measured in all directions.
Innovation Solution
A display data obtaining apparatus that includes a light source, acoustic wave probe, and signal processing unit, which calculates and corrects spatial sensitivity distribution data to reduce fluctuations in sensitivity, allowing for improved quantitativity of information even in limited measurement conditions by dividing voxel data by spatial sensitivity coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic wave detection is performed in all directions (360°) around the subject, then measurement precision and spatial sensitivity uniformity are improved, but device complexity and measurement difficulty increase significantly
Solution Approach 1:
The patent pre-calculates and stores spatial sensitivity distribution data for each voxel position in the measurement region before actual imaging. This preliminary computation creates a correction map that accounts for geometric attenuation and detector positioning, allowing the system to compensate for limited detection angles without requiring 360° acoustic wave detection during actual measurement
Solution Approach 2:
The patent introduces spatial sensitivity distribution data as an intermediary correction factor between the raw acoustic wave detection data and the final reconstructed image. This intermediary data set, pre-computed based on the specific detector geometry and positioning, mediates the transformation of limited-angle detection data into quantitatively accurate images by compensating for position-dependent sensitivity variations
2Device complexity
If the acoustic wave measurement region is limited (cannot detect in all directions), then device complexity is reduced, but information completeness and measurement precision deteriorate
Solution Approach 1:
The patent applies local quality correction by computing and applying spatially varying sensitivity factors for each voxel position. Instead of using a uniform detection approach, the system tailors the sensitivity correction to each local region's geometric relationship with the detectors, compensating for information loss in limited measurement configurations through position-specific correction
Solution Approach 2:
The system pre-calculates the spatial sensitivity distribution for each voxel based on the limited detection geometry before actual imaging. This preliminary action creates a correction map that anticipates and compensates for information loss, allowing complete quantitative reconstruction even when acoustic waves cannot be detected in all directions during measurement
3Measurement precision
If spatial sensitivity distribution correction is applied, then quantitativity of obtained information is improved, but signal processing complexity increases
Solution Approach 1:
The spatial sensitivity correction factors are pre-computed and stored in a lookup table before actual imaging. This preliminary calculation of sensitivity distributions for all possible voxel positions transforms a potentially complex runtime correction problem into a simple data retrieval and multiplication operation during image reconstruction, maintaining high quantitativity while minimizing processing complexity
Solution Approach 2:
The patent creates a computational model (copy) of the spatial sensitivity distribution that mirrors the physical detector geometry and positioning. This virtual model allows the system to simulate and correct for sensitivity variations without requiring complex real-time calculations, replacing intricate signal processing with efficient lookup and application of pre-computed correction factors
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 effectively reduces spatial sensitivity fluctuations, enhancing the quantitativity of display information by correcting for spatial sensitivity variations, thereby improving the accuracy of optical characteristic distribution data in photoacoustic tomography.
Implementation Method 1
light emitted from a light source such as a laser... light beams having various wavelengths... optical energy absorption factor
Implementation Method 2
acoustic wave detector (also called a probe or transducer)... detect an acoustic wave (typically ultrasound) generated from a living tissue
Implementation Method 3
photoacoustic tomography (PAT)... an elastic wave, which is generated when the examined region having absorbed the energy of the irradiated light is momentarily expanded, is received as a detected signal
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3C
AI summary
Provided is a display data obtaining apparatus capable of, in photoacoustic tomography, reducing a fluctuation in sensitivity which depends on location for image reconstruction even in a limited measurement condition in which a photoacoustic wave generated in the entire subject cannot be obtained in a sufficient range. The display data obtaining apparatus includes: an acoustic wave detecting unit for detecting an acoustic wave generated from a subject irradiated with pulsed light to obtain a signal; a first data deriving unit for deriving first data exhibiting an optical characteristic distribution of the subject based on the obtained signal obtained by the acoustic wave detecting unit; a memory for storing spatial sensitivity distribution data specific to the display data obtaining apparatus; and a second data deriving unit for deriving second data exhibiting the optical characteristic distribution of the subject using the first data and the spatial sensitivity distribution data.