the present invention will be further explained below in detail with reference to the preferred embodiments and accompanying drawings . as shown in fig3 , fig4 and fig5 , the ultrasonic therapeutic system guided by an imaging device consists of an imaging device for imaging the target and an ultrasonic therapeutic device . said ultrasonic therapeutic device comprises an ultrasonic therapeutic applicator 5 that includes an ultrasonic transducer , a box 3 , and a moving unit that is connected to the ultrasonic therapeutic applicator 5 and controls its movement , i . e . mechanical arm 1 . the ultrasonic therapeutic applicator 5 is placed in the box 3 that is full of couplant liquid . the mechanical arm 1 that drives ultrasonic therapeutic applicator 5 to move , extends through the wall of the box and is connected to the ultrasonic therapeutic applicator 5 . the compensating units are arranged on the box 3 and make the level of couplant liquid in the box 3 unchanged when the mechanical arm 7 drives the ultrasonic therapeutic applicator 5 to move . said compensating units are the first compensating unit 2 and the second compensating unit 6 , which are arranged symmetrically at opposing sides of the box 3 and incorporate with the box 3 . the two symmetrical compensating units have the same shape and size . the mechanical arm 1 extends horizontally through the two symmetrical compensating units ; the ultrasonic therapeutic applicator 5 on the mechanical arm 1 is located between the two compensating units . the two compensating units are sealed and fixed with the mechanical arm 1 at one end and are sealed and fixed with the box 3 at the other end . the compensating units adopt flexible telescopic sleeves , which are made from flexible material . at the connection points of two flexible telescopic sleeves , the mechanical arm 1 has a suitable shape corresponding to the connection ends of flexible telescopic sleeves . two flexible telescopic sleeves have certain capability of repeated deformation when driven by the mechanical arm 1 . for example , when the mechanical arm 1 moves in x - direction , two flexible telescopic sleeves correspondingly elongate or shorten the same length in x - direction ; when the mechanical arm 1 moves in y - direction and z - direction , two flexible telescopic sleeves deform correspondingly . during treatment , the mechanical arm 1 drives the ultrasonic therapeutic applicator 5 to move and accordingly its focal point moves . the ultrasonic waves transmitted from the ultrasonic therapeutic applicator 5 go through the couplant liquid 4 and then are focused at the target ( not illustrated in figures .). the focal point of the ultrasonic therapeutic applicator 5 can move in x , y , z - directions to meet the requirements for the three - dimensional entity of the target to be treated . the compensating units move when the mechanical arm 1 moves and can deform in x , y , z - directions . when the focal point of the ultrasonic transducer is required to move in x - direction , the mechanical arm 1 drives the ultrasonic therapeutic applicator 5 to move in x - direction . as shown in fig4 , when the mechanical arm 1 moves δx toward + x - direction , it drives the ultrasonic therapeutic applicator 5 to move δx and meanwhile the first compensating unit 2 shortens δx and the second compensating unit 6 elongates δx . the volume change in the first compensating unit 2 is δv 1 and the volume change in the second compensating unit 6 is δv 2 . a certain structural shape for the first compensating unit 2 and the second compensating unit 6 can be selected so that the formula δv 1 + δv 2 = 0 becomes possible . therefore , when the ultrasonic therapeutic applicator 5 moves in x - direction , the sum of volumes of the box 3 and the two compensating units is not changed and accordingly the level of couplant liquid in the box keeps unchanged before and after the mechanical arm moves . when the focal point of the ultrasonic transducer is required to move in y - direction , the mechanical arm 1 drives the ultrasonic therapeutic applicator 5 to move in y - direction . as shown in fig5 , when the mechanical arm 1 moves δy toward + y - direction , it drives the ultrasonic therapeutic applicator 5 to move δy and meanwhile the first compensating unit 2 and the second compensating unit 6 move δy in y - direction . the volume change in the first compensating unit 2 is δv 1 and the volume change in the second compensating unit 6 is δv 2 . a certain structural shape for the first compensating unit 2 and the second compensating unit 6 can be selected so that the formula δv 1 + δv 2 = 0 becomes possible . therefore , when the ultrasonic therapeutic applicator 5 moves in y - direction , the sum of volumes of the box 3 and the two compensating units is not changed and accordingly the level of couplant liquid in the box keeps unchanged before and after the mechanical arm moves . when the focal point of the ultrasonic transducer is required to move in z - direction , the conditions of movement can be analyzed with reference to the movement in y - direction and it will not be repeated here . in the following two embodiments , only the shape changes of the compensating units are described and other structures are the same as mentioned above . here the mri apparatus is selected as the imaging device and the ultrasonic transducer in the ultrasonic therapeutic applicator 5 adopts an ultrasonic transducer with a fixed focal length . as shown in fig6 a and fig6 b , in this embodiment , both the first compensating unit 2 and the second compensating unit 6 adopt truncated - cone - shaped flexible telescopic sleeves . the area of the upper surface of truncated - cone ( small end “ a ”) is s 1 and the area of the lower surface of truncated - cone ( big end “ b ”) is s 2 . the length of the truncated - cone is t when the ultrasonic therapeutic applicator 5 is in static status . the small end “ a ” is fixed with and connected to the mechanical arm 1 and the big end “ b ” is fixed with and connected to the box 3 . under the control of the mechanical arm 1 , when the focal point of the ultrasonic therapeutic applicator 5 moves in x - direction ( as shown in fig4 ), as shown in fig7 a and fig7 b , v = volume of telescopic sleeve , from geometry we know . when the ultrasonic therapeutic applicator 5 moves towards x - direction , s 1 is not changed during movement because the small end “ a ” of the truncated - cone - shaped compensating unit is fixed with the mechanical arm 1 and meanwhile s 2 is also not changed because the big end “ b ” of the truncated - cone - shaped compensating unit is fixed with the box 3 . fig7 a shows the shape changes of the first compensating unit 2 as below : fig7 b shows the shape changes of the second compensating unit 6 as below : therefore , when moving in x - direction , the total volume change of the two compensating units is zero and the level of couplant liquid keeps stable . when the focal point of the ultrasonic therapeutic device in fig3 moves towards y - direction , under the control of the mechanical arm 1 , the focal point of the ultrasonic therapeutic applicator 5 moves towards y - direction ( as shown in fig5 ). the volume change of the first compensating unit 2 is shown in fig8 a : the volume change of the second compensation unit 6 is shown in fig8 b : therefore , when moving in y - direction , the total volume change of the two compensation units is zero and the level of couplant liquid keeps stable . the conditions of movement when the ultrasonic therapeutic device moves towards z - direction are the same as when moving towards y - direction and it will not be repeated here . from this , it can be seen that in this embodiment , the level of couplant liquid can keep stable surely when the ultrasonic therapeutic applicator 5 moves in x , y and z - directions and when the mechanical arm 1 drives the focal point of the ultrasonic therapeutic applicator to move . as shown in fig9 a and fig9 b , in this embodiment , the first compensating unit 2 and the second compensating unit 6 are prismoid - shaped flexible telescopic sleeves . the length and width of its upper surface is b 1 and a 1 , and its area is s 1 . the length and width of its lower surface is b 2 and a 2 , and its area is s 2 . the height of the prismoid is t . the other structures are the same as those in embodiment 1 . when the ultrasonic therapeutic applicator 5 in fig4 moves towards x - direction , as shown in fig1 a , the height of the first compensating unit 2 is changed from t to t − δt , but s 1 and s 2 are not changed during movement . the volume change of the first compensating unit 2 after movement is as below : as shown in fig1 b , the height of the second compensating unit 6 is changed from t to t + δt , but s 1 and s 2 are not changed during movement . the volume change of the second compensating unit 6 after movement is as below : therefore , when moving in x - direction , the total volume change of the two compensating units is zero and the level of couplant liquid keeps stable . when the focal point of the ultrasonic therapeutic applicator 5 in fig5 moves towards y - direction , the volume change of the first compensating unit 2 is shown in fig1 a : the volume change of the second compensating unit 6 is shown in fig1 b : therefore , when moving in y - direction , the total volume change of the two compensating units is zero and the level of couplant liquid keeps stable . from this , we can conclude that the sum of volumes of the two compensating units before and after movement keeps unchanged and the level of couplant liquid will keep the original level . the conditions of movement when the ultrasonic therapeutic device moving towards z - direction are the same as when moving towards y - direction and it will not be repeated here . from the embodiment 1 and embodiment 2 , it can be seen that two flexible telescopic sleeves arranged symmetrically at opposing sides of the box 3 and sealed and fixed with the mechanical arm 1 are provided here , so that the level of couplant liquid can keep stable surely when the mechanical arm 1 moves in x , y and z - directions , and accordingly the interference to mri can be minimized to the utmost and the diagnostic accuracy of mri apparatus is improved .
an ultrasonic therapeutic device and an ultrasonic therapeutic system including the ultrasonic therapeutic device and guided by an imaging device are provided . the ultrasonic therapeutic device includes an ultrasonic therapeutic applicator that comprises an ultrasonic transducer , a box which contains the ultrasonic therapeutic applicator and the couplant liquid , a moving unit which extends through the wall of the box and connects the ultrasonic therapeutic applicator , and compensating units which set on opposing sides of and incorporate with the box and holds the level of the liquid when the moving unit drives the ultrasonic therapeutic applicator to move . stabilization of the liquid level in the box consequently decreases the interference to imaging results of an imaging device due to the level changing of the couplant liquid and improves the diagnostic accuracy of the imaging device .