The Relationship of Cavitation to the Negative Acoustic Pressure Amplitude in Ultrasonic Therapy

The relationship between the cavitation and acoustic peak negative pressure in the high-intensity focused ultrasound （HIFU） field is analyzed in water and tissue phantom. The peak negative pressure at the focus is determined by a hybrid approach combining the measurement with the simulation. The spheroidal beam equation is utilized to describe the nonlinear acoustic propagation. The waveform at the focus is measured by a fiber optic probe hydrophone in water. The relationship between the source pressure amplitude and the excitation voltage is determined by fitting the measured ratio of the second harmonic to the fundamental component at the focus, based on the model simulation. Then the focal negative pressure is calculated for arbitrary voltage excita- tion in water and tissue phantom. A portable B-mode ultrasound scanner is applied to monitor HIFU-indueed cavitation in real time, and a passive cavitation detection （PCD） system is used to acquire the bubble scattering signals in the HIFU focal volume for the cavitation quantification. The results show that： （1） unstable cavitation starts to appear in degassed water when the peak negative pressure of HIFU signals reaches 13.5 MPa; and （2） the cavitation activity can be detected in tissue phantom by B-mode images and in the PCD system with HIFU peak negative pressures of 9.0 MPa and 7.8 MPa, respectively, which suggests that real-time B-mode images could be used to monitor the cavitation activity in two dimensions, while PCD systems are more sensitive to detect scattering and emission signals from cavitation bubbles.

Experimental Study on the Effect of High-intensity Focused Ultrasound (HIFU) Using Sonablate-500 in the Ablation of Canine Prostate

To investigate the safety, feasibility and effectiveness of transrectal high-intensity focused ultrasound （HIFU） in the ablation of canine prostate, 20 dogs were divided randomly into 5 groups. Sixteen canine prostates were treated with the third-generation transrectal HIFU device （Sonablate-500^TM）. Transrectal ultrasound images of the prostate and prostatic urethra were observed preoperatively and postoperatively. Serial study was performed 30 min, 30 days, 60 days and 180 days after the therapy. The rectum, periprostatic tissues, and prostate were excised en bloc and the tissues were fixed for gross and histological analysis. Our results showed that the average maximal diameter of prostatic urethra was 0.59-0.11 cm before the operation and 2.57±0.98 cm 60 days after the operation. The volume of prostate was 6.5±3.12 cm^3 before the treatment while the volume was 4.13±0.23 cm^3 60 days after the treatment and the differences were statistically significant （P〈0.05）. Histologically, there was a clear demarcation between the necrotic area of the treated tissues and the unaffected surrounding tissues. All the necrotic tissues in the targeted zone broke off and the prostatic urethra became cavitary 60 days later. The more frequent complications were urinary retention and frequency and hematuria. No rectal injury occurred during the treatment. It is concluded that the third-generation transrectal HIFU is capable of destroying prostatic tissue, substantially increasing the width of the prostatic urethra without causing injury to the adjacent tissues. The risk of postoperative complications associated with HIFU was low. HIFU may become a safe, effective and minimally invasive alternative for the treatment of prostatic diseases.

Efficacy of therapeutic ultrasound vs sham ultrasound on pain and physical function in people with knee osteoarthritis: A meta-analysis of randomized controlled trials

AIM: To determine the efficacy of therapeutic ultrasound vs sham for improving pain and physical function immediately post-intervention in people with knee osteoarthritis(OA). METHODS: We hand searched meta-analyses on the topic published in 2010 and updated the search in three electronic databases(MEDLINE, EMBASE, CINAHL) January 1, 2009 to September 5, 2013 to identify relevant studies. The inclusion criteria were human randomized controlled trials published in the English language in which active therapeutic ultrasound was compared tosham ultrasound, data for people with knee OA were reported separately, participants were blinded to treatment allocation and outcomes assessed before and after treatment included pain, self-reported physical function and performance-based physical function. Two reviewers independently screened titles and abstracts retrieved in the search to identify trials suitable for full text review. Data extraction and risk of bias assessment of the identified trials were completed independently by two reviewers. Pooled analyses were conducted using inverse-variance random effects models.RESULTS: We screened 1013 titles and abstracts. Meta-analysis of pain outcomes from 5 small trials(281 participants/OA knees) showed that, compared to sham ultrasound, therapeutic ultrasound improves pain [standardized mean difference(SMD)(95%CI) =-0.39(-0.70--0.08); P = 0.01] but not physical function [self-reported in 3 trials(130 participants/OA knees): SMD(95%CI) =-0.21(-0.55-0.14), P = 0.24; walking performance in 4 trials(130 participants/OA knees): SMD(95%CI) =-0.11(-0.59-0.37), P = 0.65). For the walking performance outcome, the dispersion of the estimated effects exceeded that expected due to sampling error(χ2 = 8.37, P = 0.04, I 2 = 64%). Subgroup analyses of three trials that administered high dose ultrasound improved the consistency(I2 = 28%) but the treatment effect remained insignificant.CONCLUSION: Meta-analyzed double-blind placebocontrolled randomized trials provide low-strength evidence that therapeutic ultrasound decreases knee OA pain and very low-strength evidence that it does not improve physical function.

The Effect of Deep Friction Massage versus Stretching of Wrist Extensor Muscles in the Treatment of Patients with Tennis Elbow

Overuse injuries of the elbow and forearm are very common in athletes. This study was conducted to evaluate the effect of muscle stretching and deep friction massage with using wrist joint support during management of tennis elbow. This study included forty patients with tennis elbow divided into two equal groups: the first group with a mean age 38.1 ± 0.294 followed a physical therapy program in form of deep friction massage on the proximal attachment of wrist extensor muscles, the second group with a mean age 37.6 ± 0.253, submitted to stretching exercises of wrist extensors. Both of groups submitted to ultrasonic therapy with wrist splint during treatment period, three sessions per week for six weeks. Outcome measures were universal goniometer, visual analogue scale, and squeezing sphygmomanometer. The results showed that there was a significant improvement in ROM of wrist flexion and wrist extension, and handgrip in second group and it was more than in the first group while no significant difference in pain. This study showed that stretching exercise is more beneficial in the management of patients with tennis elbow.