To improve the cavitation-to-tissue ratio (CTR) of cavitation imaging during the treatment with high-intensity focused ultrasound (HIFU), we proposed a pulse inversion based broadband subharmonic cavitation imaging method (PIBSHI). Due to the fact that the subharmonic signal is a unique nonlinear vibration characteristic of cavitation bubbles, we extracted the broadband subharmonic signal to get a high-CTR cavitation imaging. The simulation showed that the subharmonic signal produced by cavitating bubbles with different sizes varied, and the signal was stronger than other subharmonics when the bubbles' resonant frequency was close to 1/2 subharmonic frequency. Further experiment results demonstrated that compared with the conventional B-mode images, broadband subharmonic cavitation imaging (BSHI) has improved the CTR by 5.7 dB, and the CTR was further improved by 3.4 dB when combined with pulse inversion (PI) technology. Moreover, when the bandwidth was set to 100%~140% of the 1/2 subharmonic frequency in PIBSHI, the CTR was the highest and the imaging showed the optimal quality. The study may have reference value for the development of precise cavitation imaging during HIFU treatment, and contribute to improve the safety of HIFU treatment.
High-Intensity Focused Ultrasound Ablation ; Ultrasonography

The FPGA-based phased-signal generator described in this paper meets the requirement of massive output channels and high resolution of HIFU. After experimental measurements, this phased-signal generator can output 256 channels of phase signals and each channel has a phase resolution of 2nS. The phased-signal generator also has many other advantages such as simple implementation method and high reliability.
Equipment Design ; High-Intensity Focused Ultrasound Ablation ; instrumentation

We present a case of retained placenta accreta treated by high-intensity focused ultrasound (HIFU) ablation followed by hysteroscopic resection. The patient was diagnosed as submucosal myoma based on ultrasonography in local clinic. Pathologic examination of several pieces of tumor mass from the hysteroscopic procedure revealed necrotic chorionic villi with calcification. HIFU was performed using an ultrasound-guided HIFU tumor therapeutic system. The ultrasound machine had been used for real-time monitoring of the HIFU procedure. After HIFU treatment, no additional vaginal bleeding or complications were observed. A hysteroscopic resection was performed to remove ablated placental tissue 7 days later. No abnormal vaginal bleeding or discharge was seen after the procedure. The patient was stable postoperatively. We proposed HIFU and applied additional hysteroscopic resection for a safe and effective method for treating retained placenta accreta to prevent complications from the remaining placental tissue and to improve fertility options.
Chorionic Villi ; Fertility ; High-Intensity Focused Ultrasound Ablation ; Humans ; Methods ; Myoma ; Placenta, Retained* ; Ultrasonography* ; Uterine Hemorrhage

We present a case of retained placenta accreta treated by high-intensity focused ultrasound (HIFU) ablation followed by hysteroscopic resection. The patient was diagnosed as submucosal myoma based on ultrasonography in local clinic. Pathologic examination of several pieces of tumor mass from the hysteroscopic procedure revealed necrotic chorionic villi with calcification. HIFU was performed using an ultrasound-guided HIFU tumor therapeutic system. The ultrasound machine had been used for real-time monitoring of the HIFU procedure. After HIFU treatment, no additional vaginal bleeding or complications were observed. A hysteroscopic resection was performed to remove ablated placental tissue 7 days later. No abnormal vaginal bleeding or discharge was seen after the procedure. The patient was stable postoperatively. We proposed HIFU and applied additional hysteroscopic resection for a safe and effective method for treating retained placenta accreta to prevent complications from the remaining placental tissue and to improve fertility options.
Chorionic Villi ; Fertility ; High-Intensity Focused Ultrasound Ablation ; Humans ; Methods ; Myoma ; Placenta, Retained* ; Ultrasonography* ; Uterine Hemorrhage

This paper introduces HIFU system software based on a phased-array HIFU device. Combined with the database and computer graphics technology, this HIFU system software can be used to develop the therapy planning semi-automatically, implement the pilot project efficiently and accelerate the clinical studies.
Computer Graphics ; High-Intensity Focused Ultrasound Ablation ; methods ; Software ; Software Design

OBJECTIVETo investigate the accuracy of ultrasound monitoring during pulsed high intensity focused ultrasound (PHIFU) treatment and improve the sensitivity of ultrasound monitoring of tissue necrosis caused by PHIFU treatment.

METHODSBovine liver ex vivo was dot-exposed with HIFU at the therapeutic doses of 2000 J (group A) and 1440 J (group B). The two groups were further divided into groups A1 (power 100 W, duty cycle 100%, irradiate 20 s) A2 (power 100 W, duty cycle 50%, irradiate 40 s), A3 (power 100 W, duty cycle 40%, irradiate 50 s), B1 (power 120 W, duty cycle 100%, irradiate 12 s), B2 (power 100 W, duty cycle 50%, irradiate 24 s), and B3 (power 100 W, duty cycle 40%, irradiate 30 s). The gray scale changes in the ultrasonic images after the exposures were observed, and the correlation function of the image was calculated before and after the exposure. The accuracy of evaluations based on the correlation function and gray-scale changes was compared.

RESULTSThe correct rate of gray scale-based evaluation of tissue necrosis caused by PHIFU was only 51%, while that by correlation function-based evaluation reached 85%.

CONCLUSIONMonitoring of tissue necrosis caused by PHIFU treatment can not rely solely on evaluation of gray-scale change of the ultrasound images, and the correlation function-based evaluation can be more accurate and sensitive for that purpose.

Numerical simulation is one of the most significant methods to predict the temperature distribution in high-intensity focused ultrasound (HIFU) therapy. In this study, the adopted numerical simulation was used based on a transcranial ultrasound therapy model taking a human skull as a reference. The approximation of the Westervelt formula and the Pennes bio-heat conduction equation were applied to the simulation of the transcranial temperature distribution. According to the temperature distribution and the Time Reversal theory, the position of the treatable focal region was corrected and the hot spot existing in the skull was eliminated. Furthermore, the influence of the exposure time, input power and the distance between transducer and skull on the temperature distribution was analyzed. The results showed that the position of the focal region could be corrected and the hot spot was eliminated using the Time Reversal theory without affecting the focus. The focal region above 60 degrees C could be formed at the superficial tis sue located from the skull of 20 mm using the hot spot elimination method and the volume of the focal region increases with the exposure time and the input power in a nonlinear form. When the same volume of the focal region was obtained, the more power was inputted, the less the exposure time was needed. Moreover, the volume of the focal region was influenced by the distance between the transducer and the skull.
Computer Simulation ; High-Intensity Focused Ultrasound Ablation ; Hot Temperature ; Humans ; Neoplasms ; therapy ; Skull

High intensity focused ultrasound (HIFU) is a very complex transient process and can cause tissue coagulation necrosis. The cavitation and boiling behaviour of bubbles in the focal region play very important roles throughout an injury process. This paper reviews the research done by domestic and foreign scholars on behaviours of bubbles in HIFU irradiation process and summarizes in the focal region bubble cavitation and boiling generation, related detective means and relationships with hyperecho, temperature rise of the focus and injury shape.
Biophysical Phenomena ; High-Intensity Focused Ultrasound Ablation ; methods ; Humans ; Thermal Conductivity ; Thermodynamics

Animals ; Heart Diseases ; surgery ; High-Intensity Focused Ultrasound Ablation ; instrumentation ; methods ; Humans

OBJECTIVETo compare the effect of low-dose focused ultrasound pre-irradiation and microbubbles for enhancing the ablation effect of high intensity focused ultrasound (HIFU) on VXhepatic tumor in rabbits.

METHODSFifty-five rabbits bearing VXhepatic tumor were randomly divided into low-dose pre-irradiation + HIFU ablation group, microbubbles+HIFU ablation group, and HIFU ablation group for corresponding treatments. The pathological changes in the tumors after low-dose irradiation, time for HIFU ablation, tumor volume with coagulative necrosis, energy efficiency factor (EEF), pathological changes in the ablated tumor, and sound channel of HIFU ablation were observed.

RESULTSTumor cell edema, vacuolar changes in the cytoplasm and tumor interstitial vascular congestion were observed 24 h after low-dose pre-irradiation. The ablation time were significantly shorter, coagulative necrosis volume was larger, and EEF was lower in low-dose irradiation + HIFU ablation group and microbubbles+HIFU ablation group than in simple HIFU ablation group (P<0.05), but the differences between the former two groups were not significant. The effectiveness and stability of the synergistic effect of low-dose pre-irradiation were inferior to microbubbles, but the former ensured a better safety of the sound channel.

CONCLUSIONLow-dose irradiation has comparable synergistic effect in HIFU with microbubbles with such advantages as non-invasiveness, high concentration and good safety, and can be a potentially new method to enhance the efficiency of HIFU.