and surrounding tissues.
Use of modern ultrasonic scanners with high-frequency sensors with frequency 7-17 MHz helps to get an image of nerve trunks and tumors quickly without any invasion. During the scanning process it is necessary to estimate an anatomic integrity of the nerve trunk, its structure, clearness of the contours of the tumor, nerve and condition of surrounding tissues [4,12].
An ultrasonic image of nerve trunk tumor is typically anechoic mass with not always homogeneous echogenicity. Taking into account the features of tumor anatomy and its location inside of the nerve trunk, the tumor will have round or oval shape with even contours and clear borders. Sometimes it is possible to see spindle shape with distribution of the along the nerve trunk. Use of color duplex mapping mode helps to identify the presence of own tumor vessels and to determine relative positions of the affected nerve with adjacent main vessels. If echoscopy results show unclear borders of the tumor, an invasive relative position to surrounding tissues and vessels, we can say that it is malignant tumor [4,12].
Except for simplicity of use, cheapness and availability the ultrasonic method of diagnostics has one more very important advantage - an opportunity of its use during the operation. So, in case of rather small dimensions of the tumor and rather poor differentiation along the nerve we can carry out contact ultrasonic examination. As a result, the surgeon can identify the borders of the tumor along the nerve more precisely. We have used the intraoperation ultrasonic navigation method many times.
Disadvantages of the method are: visualization of not affected nerve trunks is complicated, i.e. it is hard to identify the nerve in the muscular tissues of the healthy extremity. For its more precise visualization it is necessary to use sensors with higher frequency of radiation. However, proceeding from the physics of the method, the higher is the radiation frequency, the lower is the penetrating ability of the ultrasonic beam into the tissues.
Thus, the high-quality image can be obtained only for superficial objects or for quite large objects.