Multi-frequency therapeutic ultrasound: A review

Focused ultrasound is a noninvasive, radiation-free and real-time therapeutic approach to treat deep-seated targets, which benefits numerous diseases otherwise requiring surgeries. Treatment efficiency is one of the key factors determining therapeutic outcomes, but improving it solely by increasing the total power can be limited by the performance of general ultrasound devices. To address this, multi-frequency therapeutic ultrasound, using additional ultrasound waves of different frequencies on top of the standard single-frequency wave, provides a promising method for treatment efficiency enhancement with limited power. Several applications and numerical works have demonstrated its superiority on treatment enhancement. This paper presents an overview of the mechanisms, implementations, applications and decisive parameters of the multi-frequency therapeutic ultrasound, which could help to pave the way for better understanding and further developing this technology in the future.

Gall bladder wall thickening as non-invasive screening parameter for esophageal varices - a comparative endoscopic - sonographic study

Background

The mortality due to hemorrhage of esophageal varices (EV) is still high. The predominant cause for EV is liver cirrhosis, which has a high prevalence in Western Europe. Therefore, non-invasive screening markers for the presence of EV are of interest. Here, we aim to investigate whether non-inflammatory gall bladder wall thickening (GBWT) may serve as predictor for the presence of EV in comparison and combination with other non-invasive clinical and laboratory parameters.

Methods

One hundred ninety four patients were retrospectively enrolled in the study. Abdominal ultrasound, upper endoscopy and blood tests were evaluated. GBWT, spleen size and the presence of ascites were evaluated by ultrasound. Platelet count and Child-Pugh-score were also recorded. The study population was categorized in two groups: 122 patients without esophageal varices (non EV) compared to 72 patients with EV were analyzed by uni-and multivariate analysis.

Results

In the EV group 46% showed a non-inflammatory GBWT of ≥4 mm, compared to 12% in the non-EV group (p < 0.01). GBWT was significantly higher in EV patients compared to the non-EV group (mean: 4.4 mm vs. 2.8 mm, p < 0.0001), and multivariate analysis confirmed GBWT as independent predictor for EV (p < 0.04). The platelets/GBWT ratio (cut-off > 46.2) had a sensitivity and specificity of 78 and 86%, PPV 76% and NPV of 87%, and ROC analysis calculated the AUC of 0.864 (CI 0.809–0.919).

Conclusions

GBWT occurs significantly more often in patients with EV. However, because of the low sensitivity, combination with other non-invasive parameters such as platelet count is recommended.