Detection of tissue coagulation by decorrelation of ultrasonic echo signals in cavitation-enhanced high-intensity focused ultrasound treatment

Abstract

BackgroundA noninvasive technique to monitor thermal lesion formation is necessary to ensure the accuracy and safety of high-intensity focused ultrasound (HIFU) treatment. The purpose of this study is to ultrasonically detect the tissue change due to thermal coagulation in the HIFU treatment enhanced by cavitation microbubbles.MethodsAn ultrasound imaging probe transmitted plane waves at a center frequency of 4.5 MHz. Ultrasonic radio-frequency (RF) echo signals during HIFU exposure at a frequency of 1.2 MHz were acquired. Cross-correlation coefficients were calculated between in-phase and quadrature (IQ) data of two B-mode images with an interval time of 50 and 500 ms for the estimation of the region of cavitation and coagulation, respectively. Pathological examination of the coagulated tissue was also performed to compare with the corresponding ultrasonically detected coagulation region.ResultsThe distribution of minimum hold cross-correlation coefficient between two sets of IQ data with 50-ms intervals was compared with a pulse inversion (PI) image. The regions with low cross-correlation coefficients approximately corresponded to those with high brightness in the PI image. The regions with low cross-correlation coefficients in 500-ms intervals showed a good agreement with those with significant change in histology.ConclusionsThe results show that the regions of coagulation and cavitation could be ultrasonically detected as those with low cross-correlation coefficients between RF frames with certain intervals. This method will contribute to improve the safety and accuracy of the HIFU treatment enhanced by cavitation microbubbles.

Selective detection of cavitation bubbles by triplet pulse sequence in high-intensity focused ultrasound treatment

“…12,13) Since the lifetime of cavitation bubbles is on the order of 1 ms and up to the order of 10 ms even under sustained oscillation for maintaining the presence of bubbles, [14][15][16] the guidance by high-speed ultrasonic imaging achieving a frame rate of more than 1 kfps using unfocused transmission is promising. [17][18][19][20] Microbubbles such as cavitation bubbles are known to oscillate nonlinearly, and harmonic imaging is widely used for their detection. [21][22][23] A pulse inversion (PI) method, 24) in which two opposite-phase ultrasound pulses are transmitted and the received echo signals are summed, can maintain the spatial resolution because a band limiting filter is not required to cancel the fundamental component and enhance the second-harmonic component.…”

Transluminal Approach with Bubble-Seeded Histotripsy for Cancer Treatment with Ultrasonic Mechanical Effects

“…However, it is possible to monitor and control the effects of both the thermal effects and mechanical effects during BSH by using an in-site monitoring method as described earlier in this report. Instead, it might be very useful to have both effects in one therapeutic setting as far as it is controllable because both thermal and mechanical effects have their own advantages and disadvantages, and we can use both effects under the various conditions suited to each effect by changing the pulse exposure parameters (Yoshizawa et al 2016); however, further study on this is needed.…”

Enhancement of High-Intensity Focused Ultrasound Heating by Short-Pulse Generated Cavitation

“…Good agreement between the ultrasonic cavitation image and coagulation area indicates possibility to accurately estimate coagulation area in real time from ultrasound images, though a coagulation detection method such as decorrelation imaging [72] is also required to determine the appropriate acoustic dose. Cavitation bubbles can not only accelerate ultrasonic heating but make mechanical tissue treatment such as histotripsy possible.…”