Swept Focus ARFI Scanning for Uniform Tissue Characterization
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Solution Overview
Problem
Acoustic radiation force impulse (ARFI) imaging faces limitations due to the non-uniform response of focused ultrasound beams, which restricts the range of tissue characteristics measurement and introduces transducer heating and scanning delays, especially when measuring over a range of depths and laterally.
Innovation Solution
The implementation of swept focus in ARFI scanning, where a time-varying focal position is achieved by altering the phase profile across the ultrasound transducer array, allowing for a broader extent of focused ultrasound and reducing the need for repetitive pulses, thereby extending the depth and lateral range of tissue characterization while minimizing transducer heating and scanning time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate ARFI pulses are transmitted at different depths with a fixed focus, then tissue characteristics can be measured at multiple depths, but the scanning time increases and transducer heating occurs due to repeated pulses
Solution Approach 1:
The patent applies dynamic focusing by continuously varying the focal position of the ultrasound beam along the axial direction during a single ARFI pulse transmission. This dynamic adjustment of focus allows the beam to maintain optimal concentration across multiple depths without requiring separate pulses for each depth, thereby reducing scan time while preserving measurement capability.
Solution Approach 2:
The patent implements continuous focal sweeping during the ARFI pulse transmission, creating an uninterrupted sequence of focal points that continuously probe different tissue depths. This continuous action replaces the discrete, repeated pulsing approach, maintaining measurement effectiveness while reducing the total number of pulses and associated heating issues.
2Power
If a focused ARFI beam is transmitted at a single focal point, then the beam intensity is maximized at the focus, but the lateral and depth extent of useful measurements is limited
Solution Approach 1:
The patent dynamically sweeps the focal position along the axial direction during pulse transmission, creating a continuous sequence of focal points that extends the effective depth range. This dynamic approach maintains high beam intensity at each moment while collectively covering a broader depth interval, overcoming the limitation of fixed single-point focusing.
Solution Approach 2:
The patent extends the measurement capability from a single focal point to a focal line by introducing temporal variation in the focal position. This transforms the measurement volume from a point-like region to an extended region along the axial dimension, effectively increasing the usable depth range while maintaining beam intensity through continuous refocusing.
3Area of stationary object
If ARFI pulses are repeated to measure displacement at different laterally spaced locations, then lateral coverage is improved, but transducer heating increases and scanning efficiency decreases
Solution Approach 1:
The patent combines multiple measurement objectives into a single ARFI pulse transmission by implementing focal sweeping that simultaneously addresses multiple lateral positions and depth levels. This merging of functions reduces the total number of repetitive pulses required, thereby decreasing cumulative acoustic output and transducer heating while maintaining comprehensive lateral and depth coverage.
Solution Approach 2:
The patent makes the ARFI pulse multi-functional by enabling it to perform measurements at multiple lateral locations and depth levels through dynamic focal adjustment. This universal approach allows a single pulse to accomplish what previously required multiple separate pulses, improving scanning efficiency and reducing thermal load on the transducer.
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 enables more uniform tissue characterization over a greater range of depths and laterally, reducing the number of focal zones needed, thus decreasing scan time and acoustic output, while maintaining effective tissue displacement measurement and minimizing temperature rise.
Implementation Method 1
transmitting a transmit beam with a time varying focal position as an acoustic radiation force impulse
Implementation Method 2
altering a phase profile across an array of transducers over a time period
Implementation Method 3
generating continuous transmit waveforms over the time period with the altering phase profile, and transmitting a beam of acoustic energy... the beam having a line focus in response to the altering phase profile
Data Source
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AI summary
Acoustic radiation force impulse (ARFI) scanning (30) uses a swept focus in transmit. Using a changing delay or phase profile (32) across the array during the generation of the ARFI pulse, a time varying focus is provided for the ARFI beam. This time varying focus may be used to extend the focus in depth, azimuth, and/or elevation. Less repetition may be needed to measure tissue characteristics from displacements due to the multi or continuous change in foci within a given ARFI transmit beam.