Bolus Function Initialization for Ultrasound Perfusion Analysis
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Solution Overview
Problem
Existing diagnostic methods using contrast agents in ultrasound imaging struggle to accurately model the second passage of contrast agents, leading to inaccuracies in perfusion parameter calculations due to the simple bolus function's limitations in handling re-circulation, resulting in unreliable perfusion parameter values and algorithm instabilities, especially when the second passage overlaps with the first.
Innovation Solution
A dedicated procedure for initializing fitting parameters is introduced, which involves fitting the echo signal with a combined bolus function consisting of two simple bolus functions for the first and second passages, using a truncated echo signal to estimate parameters for the combined function, thereby improving the accuracy of perfusion parameter calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple bolus function is used to model contrast agent circulation, then the model is simple and easy to implement, but it cannot accurately model the second passage of contrast agent leading to inaccurate perfusion parameter calculations
Solution Approach 1:
The patent segments the contrast agent circulation into distinct passages (first passage, second passage, etc.) and models each passage separately using individual bolus functions. This segmentation allows the model to capture the temporal characteristics of each passage while maintaining mathematical tractability, resolving the contradiction between model simplicity and accuracy in modeling multiple passages.
Solution Approach 2:
The patent performs preliminary action by estimating parameters for each passage based on the truncated echo signal before final perfusion parameter calculation. This preliminary parameter estimation for multiple passages enables accurate modeling of contrast agent re-circulation, thereby improving perfusion parameter accuracy without excessive model complexity.
2Measurement precision
If a combined bolus function modeling multiple passages is used, then perfusion parameter accuracy improves, but algorithm instabilities occur especially when passages overlap
Solution Approach 1:
The patent segments the fitting process into separate optimization steps for each passage. By fitting the first passage, second passage, and subsequent passages independently in sequence rather than simultaneously, the algorithm avoids the instabilities that arise from optimizing all parameters at once, especially when passages overlap temporally.
Solution Approach 2:
The patent performs preliminary fitting of earlier passages before fitting later passages. This sequential preliminary action stabilizes the optimization process by establishing parameter estimates for earlier passages that serve as a foundation for subsequent passage fitting, reducing algorithmic instability even when passages overlap.
3Ease of manufacture
If fitting parameters are not properly initialized, then the fitting process is simpler to implement, but perfusion parameter estimation accuracy deteriorates
Solution Approach 1:
The patent performs preliminary action by estimating initial parameters for each passage based on the truncated echo signal before the final fitting process. This preliminary parameter estimation provides accurate starting points for the optimization algorithm, ensuring convergence to correct perfusion parameters without making the implementation overly complex.
Solution Approach 2:
The patent replaces manual or arbitrary parameter initialization with an automated parameter estimation mechanism based on the truncated echo signal. This substitution of the initialization mechanism with a data-driven approach improves accuracy while maintaining implementation simplicity through algorithmic automation.
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
This approach enhances the accuracy of perfusion parameter estimation by accurately modeling both passages of the contrast agent, reducing algorithm instabilities and providing robust estimates, even in noisy conditions, thereby improving the quality of blood perfusion analysis.
Implementation Method 1
The contrast agent acts as an efficient ultrasound reflector, and it can be easily detected by applying ultrasound waves and measuring echo signals that are returned in response thereto
Data Source
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Figure 2C~2D
AI summary
A solution is proposed for analyzing a body-part (150) perfused with a contrast agent, which has been pre-administered as a bolus to circulate through the body-part with a first passage and possibly with at least one second passage during an analysis interval. A corresponding data-processing method (A1-A14) includes the steps of providing (Al1-A3) at least one input signal indicative of a response to an interrogation signal of a corresponding location of the body-part during the analysis interval, and fitting (A4-A11) each input signal over the analysis interval by an instance of a combined bolus function of time, based on a combination of a first simple bolus function of time modeling the first passage of the contrast agent and at least one second simple bolus function of time each one modeling a corresponding second passage of the contrast agent, being defined by the values of a set of first fitting parameters of the first simple bolus function, a set of second fitting parameters of each second simple bolus function and a delay parameter of each second simple bolus function with respect to the first simple bolus function. In the solution according to an embodiment of the invention, the step of fitting each input signal includes estimating (A4-A5) a peak instant of the input signal when the corresponding response reaches an absolute peak, setting (A6) a truncation interval within the analysis interval according to the peak instant, fitting (A7-A8) a truncated signal defined by the input signal over the truncation interval by an instance of a truncated simple bolus function of time, modeling a single passage of the contrast agent during the truncation interval, being defined by the values of a set of truncated fitting parameters, and initializing (A9) the first fitting parameters, the second fitting parameters of each second simple bolus function and the delay parameter of each second simple bolus function according to the values of the truncated fitting parameters.