Zero-crossing tracking technique for noninvasive ultrasonic temperature estimation.
OBJECTIVE
The purpose of this study was to investigate the feasibility of a zero-crossing tracking (ZCT) technique for temperature estimation using ultrasound images.


METHODS
The backscattered ultrasound radio frequency (RF) echo from a heated region experiences time shifts, which have been identified as causing a gross effect on sound speed changes and thermal expansion. The ZCT technique tracks the shifts in the zero-crossing instants between preheated and postheated A-lines to estimate the echo shifts caused by local temperature changes. Compared to the conventional cross-correlation (CCR) technique, ZCT does not require intensive computational loadings for correlation operations; hence, the computational efficiency could be improved. Phantom experiments were performed to compare the results of temperature estimation by using the ZCT and CCR techniques.


RESULTS
The imaging probe was a commercial linear array, and a high-intensity focused ultrasound transducer was used as a heating source. The acquired RF echo data were processed using the ZCT and CCR techniques. The estimation results of both techniques were similar. However, the ZCT technique yielded up to 7-fold better computational efficiency than the CCR technique.


CONCLUSIONS
The ZCT technique has the ability to monitor temperature changes with superior processing speed. This method could be an alternative signal-processing technique for ultrasonic temperature estimation.
Ju
Kuen-Cheng
KC
Department of Biomedical Engineering, I-Shou University, Kaohsiung, Taiwan. kcju@isu.edu.tw
Liu
Hao-Li
HL
D005240:Feasibility Studies; D006358:Hot Temperature; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted; D013696:Temperature; D014159:Transducers; D014464:Ultrasonic Therapy / Q000295:instrumentation / Q000379:methods*