Separated Respiratory Phases for In Vivo Ultrasonic Thermal Strain Imaging

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Ultrasound Technology

Background:

• Thermal strain imaging (TSI) estimates temperature changes using ultrasonic echo shifts, valuable for thermotherapies.
• Physiological motion artifacts significantly challenge in vivo TSI accuracy.
• Existing methods struggle to effectively compensate for respiratory-induced motion.

Purpose of the Study:

• To develop a novel respiration separated thermal strain imaging (RS-TSI) method.
• To mitigate artifacts caused by physiological motion in in vivo TSI.
• To enhance the accuracy and temporal resolution of temperature estimations during thermotherapies.

Main Methods:

• Proposed RS-TSI method analyzes exhalation and inhalation phases independently.
• Utilized normalized cross-correlation (NXcorr) of RF images to determine respiratory frequency.
• Implemented quasi-periodic phase division, NXcorr thresholds for frame selection, and motion compensation.
• Combined phase-specific TSI results via extrapolation and interphase averaging.

Main Results:

• RS-TSI successfully separates TSI analysis into exhalation and inhalation phases.
• Improved motion compensation achieved by setting frame selection ranges based on respiratory frequency.
• RS-TSI ensures frame selection across both respiratory phases, unlike dynamic frame selection (DFS).
• Temporal intervals of RS-TSI output are approximately halved compared to DFS.

Conclusions:

• RS-TSI effectively overcomes physiological motion artifacts in in vivo TSI.
• The method enhances accuracy and temporal resolution for temperature monitoring in thermotherapies.
• RS-TSI represents a significant advancement for ultrasound-based thermal monitoring applications.