Disruption of splenic circulation using microbubble-enhanced ultrasound and prothrombin: a preliminary study

Promoting the effect of microbubble-enhanced ultrasound on hyperthermia in rabbit liver

PURPOSE

The heat-sink effect is one reason for the insufficient temperature increase in hyperthermia (HT) treatment for cancer. Microbubbles (MBs) nucleate inertial cavitation under therapeutic ultrasound (TUS) exposure, which form microbubble-enhanced ultrasound (MEUS), which results in blocking blood perfusion in the targeted liver tissues. This study aimed to determine if synergistic effects exist during HT in the liver when combined with MEUS.

METHODS

Forty rabbits with surgically exposed livers were randomly divided into TUS + MB + HT, MB + HT, normal saline + HT, and MB + sham groups (n = 10 in each group). Liver perfusion was evaluated using contrast-enhanced ultrasound. The temperatures of the liver tissues were monitored using thermocouples. Pathological changes were determined by hematoxylin and eosin (H&E) staining. Serum hepatic transaminases were evaluated.

RESULTS

MEUS pretreatment almost completely blocked the perfusion of targeted areas. The TUS + MB + HT and MB + HT groups showed significantly higher temperatures in treated areas than those in the other groups. However, the TUS + MB + HT group exhibited a more stable and regular increase in temperatures in the fitting curves compared with the MB + HT group. H&E staining revealed swelling hepatocytes, hemorrhage, and thrombosis in the portal area in the TUS + MB + HT group.

CONCLUSION

MEUS reduced the blood perfusion in the targeted liver tissues, and, therefore, overcame the heat-sink effect during the HT procedure in rabbits. MEUS pretreatment might have the potential to enhance the therapeutic effect of HT.

Low-frequency ultrasound-mediated microvessel disruption combined with docetaxel to treat prostate carcinoma xenografts in nude mice: A novel type of chemoembolization

The aim of the present study was to investigate whether low-frequency ultrasound (US)-mediated microvessel disruption combined with docetaxel (DTX) can be used as a novel type of chemoembolization. Mice were assigned to four groups: i) The USMB group, treated with low-frequency US combined with microbubbles (USMB); ii) the DTX group, treated with DTX; iii) the USMB + DTX group, treated with combined therapy; and iv) the control group, which was untreated. Immediately after the first treatment, the average peak intensity (API) on contrast-enhanced US was calculated, and tumors were excised for hematoxylin and eosin (HE) staining. At 2 weeks post-treatment, the tumor volumes and wet weights were calculated, and tumors were excised for immunohistochemistry to calculate apoptotic index (AI), proliferative index (PI) and microvessel density (MVD) values. Immediately after the first treatment, in the DTX and control groups, the tumors demonstrated abundant perfusion enhancement, while in the USMB + DTX and USMB groups, blood perfusion of the tumors was interrupted. Compared with that of the control group, the API was significantly lower in the USMB + DTX USMB groups (all P<0.001). HE staining showed that tumor microvasculature was disrupted into flaky hematomas and severely dilated microvessels in the USMB + DTX and USMB groups. In the DTX and control groups, there was no distinct evidence of the disruption and dilation of blood microvessels. At the end of the treatment, the mean tumor inhibition ratio was 73.33, 46.67 and 33.33% for the USMB + DTX, DTX and USMB groups, respectively. The USMB + DTX group had the highest AI, and the lowest PI and MVD compared with the other groups, although the difference between the USMB + DTX and DTX groups with regard to PI and MVD was not significant (USMB + DTX vs. DTX group, P=0.345 and P=0.059, respectively). In conclusion, as a novel type of chemoembolization, USMB combined with DTX is more effective than USMB or DTX alone in inhibiting tumor growth via the enhancement of apoptosis, and the suppression of proliferation and angiogenesis.

Optimization of low-frequency low-intensity ultrasound-mediated microvessel disruption on prostate cancer xenografts in nude mice using an orthogonal experimental design

The present study aimed to provide a complete exploration of the effect of sound intensity, frequency, duty cycle, microbubble volume and irradiation time on low-frequency low-intensity ultrasound (US)-mediated microvessel disruption, and to identify an optimal combination of the five factors that maximize the blockage effect. An orthogonal experimental design approach was used. Enhanced US imaging and acoustic quantification were performed to assess tumor blood perfusion. In the confirmatory test, in addition to acoustic quantification, the specimens of the tumor were stained with hematoxylin and eosin and observed using light microscopy. The results revealed that sound intensity, frequency, duty cycle, microbubble volume and irradiation time had a significant effect on the average peak intensity (API). The extent of the impact of the variables on the API was in the following order: Sound intensity; frequency; duty cycle; microbubble volume; and irradiation time. The optimum conditions were found to be as follows: Sound intensity, 1.00 W/cm²; frequency, 20 Hz; duty cycle, 40%; microbubble volume, 0.20 ml; and irradiation time, 3 min. In the confirmatory test, the API was 19.97±2.66 immediately subsequent to treatment, and histological examination revealed signs of tumor blood vessel injury in the optimum parameter combination group. In conclusion, the Taguchi L₁₈ (3)⁶ orthogonal array design was successfully applied for determining the optimal parameter combination of API following treatment. Under the optimum orthogonal design condition, a minimum API of 19.97±2.66 subsequent to low-frequency and low-intensity mediated blood perfusion blockage was obtained.

High-intensity focused ultrasound ablation: an effective and safe treatment for secondary hypersplenism

OBJECTIVE

Hypersplenism is a common disease. The conventional treatment is splenectomy and partial splenic embolization; however, both of them have high complication rates and technical defects. Therefore, safer and more effective techniques should be considered for the treatment of hypersplenism. High-intensity focused ultrasound (HIFU) may provide an effective and safe way for treatment of hypersplenism. Therefore, we conducted this study to assess the safety and efficacy of HIFU in treatment of secondary hypersplenism.

METHODS

A total of 28 patients who suffered from secondary hypersplenism were treated with HIFU ablation. All patients who underwent HIFU were closely followed-up over a year. MRI scan was performed, and the spleens were observed. Blood counts and liver function tests were also carried out.

RESULTS

In the follow-up process, the levels of white blood cells and platelets in the blood after HIFU were significantly higher than those before HIFU, liver function also improved after HIFU treatment. In addition, the symptoms were ameliorated significantly or even disappeared. The MRI showed that the ablation area had turned into a non-perfused volume, and after 12 months of HIFU ablation, the ablated area shrank evidently; the sunken spleen formed a lobulated shape and the splenic volume decreased.

CONCLUSION

HIFU ablation is a safe, effective and non-invasive approach for secondary hypersplenism.

ADVANCES IN KNOWLEDGE

For the first time we used HIFU ablation to treat secondary hypersplenism. It not only expands indications of HIFU but also provides better choice for the treatment of secondary hypersplenism.

Hemostatic effects of microbubble-enhanced low-intensity ultrasound in a liver avulsion injury model

OBJECTIVES

Microbubble-enhanced therapeutic ultrasound (MEUS) can block the blood flow in the organs. The aim of this study was to evaluate the hemostatic effect of microbubble-enhanced pulsed, low-intensity ultrasound in a New Zealand White rabbit model of avulsion trauma of the liver. The therapeutic ultrasound (TUS) transducer was operated with the frequency of 1.2 MHz and an acoustic pressure of 3.4 MPa. Microbubble-(MB) enhanced ultrasound (MEUS) (n = 6) was delivered to the distal part of the liver where the avulsion was created. Livers were treated by TUS only (n = 4) or MB only (n = 4) which served as controls. Bleeding rates were measured and contrast enhanced ultrasound (CEUS) was performed to assess the hemostatic effect, and liver hemoperfusion before and after treatment. Generally, bleeding rates decreased more than 10-fold after the treatment with MEUS compared with those of the control group (P<0.05). CEUS showed significant declines in perfusion. The peak intensity value and the area under the curve also decreased after insonation compared with those of the control group (P<0.05). Histological examination showed cloudy and swollen hepatocytes, dilated hepatic sinusoids, perisinusoidal spaces with erythrocyte accumulation in small blood vessels, obvious hemorrhage around portal areas and scattered necrosis in liver tissues within the insonation area of MEUS Group. In addition, necrosis was found in liver tissue 48 h after insonation. We conclude that MEUS might provide an effective hemostatic therapy for serious organ trauma such as liver avulsion injury.