Inhibition effects of high mechanical index ultrasound contrast on hepatic metastasis of cancer in a rat model.
OBJECTIVE
The liver is the most common organ for tumor metastasis. The development of new methods to depress hepatic metastasis is of great importance in improving survival. The aim of this study was to observe the effects of high-mechanical index ultrasound contrast on hepatic metastasis of colorectal cancer.


METHODS
Hepatic metastasis models were established by injecting human colon carcinoma LoVo cells into the spleens of Sprague-Dawley rats. The rats were divided into a control group, a microbubble plus ultrasound group, a simple ultrasound group, and a simple microbubble group. The ultrasound contrast agent SonoVue (1 mL/kg) was injected via the tail vein, and high-mechanical index ultrasound contrast (frequency, 1.5 MHz; mechanical index, 1.7) was performed on the spleen intermittently for 2 minutes. The animals were sacrificed after 10 days, and the sizes and number of hepatic metastases were measured and compared. Histologic pathology and splenic ultrastructure were observed.


RESULTS
The number and sizes of hepatic metastases patently decreased in rats in the microbubble plus ultrasound group (P < .01). There were no obvious differences among the control group, simple ultrasound group, and simple microbubble group in hepatic metastases (P > .05). Histologic pathology showed that the number of tumor cells in the spleens decreased considerably, and massive necroses, hemorrhages, and thrombi were observed in the tumor and spleen tissues of rats in the microbubble plus ultrasound group. Transmission electron microscopy showed that the mitochondria of tumor cells and endothelial cells were clearly swelled, and there were gaps among endothelial cells and platelets aggregated in capillary vessels.


CONCLUSIONS
This research shows that intermittent high-mechanical index ultrasound contrast may inhibit the hepatic metastasis of cancer in a rat model.
Zhong
Hua
H
Department of Ultrasound, Southwest Hospital, Third Military Medical University, Chongqing 400038, China.
Li
Rui
R
Hao
Ying-xue
YX
Guo
Yan-li
YL
Hua
Xing
X
Zhang
Xiao-hang
XH
Chen
Zhao-hui
ZH
D000818:Animals; D002277:Carcinoma / Q000000981:diagnostic imaging / Q000556:secondary* / Q000628:therapy*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging / Q000628:therapy*; D003287:Contrast Media / Q000627:therapeutic use; D004195:Disease Models, Animal; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary* / Q000628:therapy*; D008297:Male; D010743:Phospholipids / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013459:Sulfur Hexafluoride / Q000627:therapeutic use*; D016896:Treatment Outcome; D014463:Ultrasonography
D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride