the present invention will now be described more fully with reference to the accompanying drawings , in which exemplary embodiments of the invention are shown . fig1 is a side view of a phantom device 21 which is applied to a linear accelerator 11 and having an internal organ simulating phantom 23 according to an embodiment of the present invention . referring to fig1 , the phantom device 21 is placed on a horizontal bed 19 . the bed 19 , which forms a set with the linear accelerator 11 , is a horizontal table on which a patient lies down . the linear accelerator 11 includes a body 13 and a gantry 15 rotating relative to the body 13 . a high voltage generator or a microwave generator is installed in the body 13 , and an accelerating tube for accelerating electrons , a magnetic field generator , and a radiation emitting unit 17 are installed in the gantry 15 . radiation output from the radiation emitting unit 17 is emitted to a tumor of the patient lying on the bed 19 . the phantom device 21 having the phantom 23 , which is placed on the bed 19 and located below the radiation emitting unit 17 , receives radiation emitted from the radiation emitting unit 17 . the radiation output from the radiation emitting unit 17 is emitted to the phantom 23 of the phantom device 21 to detect the dose of the emitted radiation . in particular , while the radiation is emitted from the radiation emitting unit 17 , the phantom 23 is moved back and forth , left and right , and up and down by first through third motors which will be explained later . the phantom 23 is designed to resemble the movement pattern of a target body part of the patient . consequently , the dose and distribution of radiation to be emitted to the target body part , i . e ., the tumor , of the patient can be determined in advance by measuring the dose of radiation emitted to a simulant 23 e inside the phantom 23 that is moved in all directions . in order to measure the dose of radiation , a dose detector should be first located in the phantom 23 . a thermoluminescent dosimeter or a metal oxide semiconductor field effect transistor ( mosfet ) dosimeter or film may be used as the dose detector . fig2 is a side view illustrating the entire structure of the phantom device 21 having the phantom 23 of fig1 , according to an embodiment of the present invention . referring to fig2 , the phantom device 21 includes a base plate 27 placed on a flat die , e . g ., the bed 19 ( see fig1 ), and having a horizontal support surface , a z - direction driving unit 91 installed over the base plate 27 and providing a z - direction force , a y - direction driving unit 93 installed over the z - direction driving unit 91 and reciprocating in a y direction ( see fig5 ), an x - direction driving unit 95 installed over the y - direction driving unit 93 and reciprocating in an x direction , and the phantom 23 mounted on the x - direction driving unit 95 . a controller 25 is disposed on the base plate 27 to control the movement pattern of the phantom 23 . the x -, y -, and z - direction driving units 95 , 93 , and 91 three - dimensionally move the phantom 23 relative to the radiation emitting unit 17 , such that the phantom 23 can be moved in the same movement pattern as that of the target body part of the patient . the z - direction driving unit 91 includes a first motor 31 fixed to a side of the base plate 27 , a worm shaft 33 axially rotated by the first motor 31 and having a worm 33 a ( see fig3 ) formed on an outer circumferential surface thereof , a cylindrical worm wheel 35 disposed on a side of the worm shaft 33 and having a plurality of gear grooves 35 c formed on an outer circumferential surface thereof and a female screw 35 d ( see fig3 ) formed on an inner circumferential surface thereof , a driven screw 41 extending upward and engaging with the female screw 35 d of the worm wheel 35 , a lifting plate 43 fixed to an upper end of the driven screw 41 and kept parallel to the base plate 27 , and a lift guide member 73 disposed between the base plate 27 and the lifting plate 43 . the lift guide member 73 guides the lifting movement of the lifting plate 43 and prevents the lifting plate 43 from being rotated . the lift guide member 73 includes cylindrical vertical guiders 39 fixed to the base plate 27 and having open upper ends , and guide rods 43 a mounted on a bottom surface of the lifting plate 43 and partially inserted into the vertical guiders 39 to guide the lifting movement of the lifting plate 43 . a bearing 37 rotatably supports the worm wheel 35 . the z - direction driving unit 91 will be explained later with reference to fig3 and 4 . a first plate 45 is disposed on the lifting plate 43 . the first plate 45 has a horizontal surface large enough to support the y - direction driving unit 93 . if the lifting plate 43 is large enough to support the y - direction driving unit 93 , the first plate 43 may be omitted . the y - direction driving unit 93 includes a second motor 49 installed on the first plate 45 , a lead screw 51 ( see fig5 ) axially rotated by the second motor 49 , and a driven block 53 fixed to the second plate 57 by engaging with the lead screw 51 , and linearly moved in a y direction by the axial rotation of the lead screw 51 to reciprocate the second plate 57 in the y direction . a plurality of bearings 47 fixed to the first plate 45 are disposed under the second plate 57 and guide the movement of the second plate 57 relative to the first plate 45 . a plurality of bearings 58 are also disposed on the second plate 57 to horizontally support a phantom fixing plate 61 and guide the phantom fixing plate 61 in an x direction . the y - direction driving unit 93 will be explained again with reference to fig5 . the x - direction driving unit 95 includes a third motor 63 fixed to the second plate 57 , and the phantom fixing plate 61 is reciprocated in an x direction by the third motor 63 . the x - direction driving unit 95 has a construction as shown in fig6 and will be explained later with reference to fig6 . the phantom 23 is disposed on the phantom fixing plate 61 , and fixing means for firmly fixing the phantom 23 to a top surface of the phantom fixing plate 61 is provided . the fixing means includes two support walls 29 facing each other with the phantom 23 therebetween , and a phantom fixing unit 30 passing through one of the two support walls 29 and pressing the phantom 23 in an “ f ” direction . the phantom 23 installed on the phantom fixing plate 61 is formed by stacking a plurality of acrylic slabs , and includes the simulant 23 e therein . the simulant 23 e can simulate an internal organ , such as lung , liver , heart , or stomach , of the human body , which moves according to respiration . fig3 and 4 are an exploded perspective view and a side view , respectively , illustrating the z - direction driving unit 91 of the phantom device 21 of fig2 . according to embodiments of the present invention . referring to fig3 and 4 , the first motor 31 is disposed on a side of a top surface of the base plate 27 , and the worm shaft 33 is connected to the shaft of the first motor 31 . the worm shaft 33 is horizontally supported by a plurality of shaft supports 34 and is axially rotated by the torque of the first motor 31 . the worm shaft 33 is made of synthetic resin or engineering plastic . the worm 33 a formed on the worm shaft 33 has helical gear teeth formed thereon such that the helical gear teeth engage with the gear grooves 35 c formed on the outer circumferential surface of the worm wheel 35 . the bearing 37 is disposed beside the worm 33 a . the bearing 37 is a thrust bearing that rotatably supports the worm wheel 35 . the bearing 37 and the worm wheel 35 should be concentric . the worm wheel 35 disposed on the bearing 37 has a sidewall 35 a and a bottom 35 b , and has a cylindrical shape open at an upper end thereof . the bottom 35 b is fixed to the bearing 37 to be horizontally supported . the sidewall 35 a with a predetermined thickness has the gear grooves 35 c and the female screw 35 d respectively formed on the outer and inner circumferential surfaces thereof . the gear grooves 35 c engage with the worm 33 a , and when the worm shaft 33 is axially rotated in an “ a ” direction , are rotated in a “ b ” direction to move up and down the driven screw 41 . the driven screw 41 meshes with the worm wheel 35 . the driven screw 41 includes a male screw 41 a partially engaging with the female screw 35 d and a fixing part 41 b having a predetermined thickness and integrally formed with an upper end of the male screw 41 a . the fixing part 41 b is coupled to the square lifting plate 43 . the lifting plate 43 , which is an acrylic plate having a predetermined thickness , horizontally and fixedly supports the driven screw 41 and moves up and down the first plate 45 according to the movement of the driven screw 41 . three vertical guiders 39 are installed around the worm wheel 35 . the vertical guiders 39 are vertical pipe - shaped members into which the vertical guide rods 43 a are inserted to guide the lifting movement of the lifting plate 43 and prevent the lifting plate 43 from being rotated . the guide rods 43 a are annular rods fixed to the bottom surface of the lifting plate 43 and vertically and downwardly extending from the bottom surface of the lifting plate 43 , and correspond to the vertical guiders 39 in a one - to - one manner . the guide rods 43 a partially inserted into the vertical guiders 39 as shown in fig2 are vertically driven simultaneously with the movement of the lifting plate 43 to prevent the lifting plate 43 from being shaken or rotated . the first plate 45 is closely fixed to the top of the lifting plate 43 . the first plate 45 , which is a square acrylic plate having a predetermined thickness , has a horizontal surface on which the plurality of bearings 47 are disposed . the y - direction driving unit 93 is disposed on the first plate 45 . fig5 is a perspective view for explaining the mechanism of driving the second plate 57 by means of the y - direction driving unit 93 of fig2 , according to an embodiment of the present invention . referring to fig5 , the y - direction driving unit 93 is disposed on a side of a top surface of the first plate 45 . the y - direction driving unit 93 horizontally moves the second plate 57 in a y direction . the y - direction driving unit 93 includes the second motor 49 fixed to a side on a top surface of the first plate 45 , the lead screw 51 horizontally extending to be connected to the shaft of the second motor 49 and having both ends supported by supporters 54 , and the driven block 53 allowing the lead screw 51 to pass therethrough and reciprocated in a longitudinal direction of the lead screw 51 by the axial rotation of the lead screw 51 . the driven block 53 is fixed to a protrusion 57 a of the second plate 57 . the protrusion 57 a is fixed to an end of the second plate 57 , and extends toward the lead screw 51 to be coupled to the driven block 53 to transmit the movement force of the driven block 53 to the second plate 57 . the bearings 47 fixed to the top surface of the first plate 45 are inserted into bearing grooves 57 b having predetermined widths and depths . the bearings 47 whose upper ends are inserted into the bearing grooves 57 b support horizontally the second plate 57 such that the second plate 57 can be smoothly moved in the y direction . the plurality of bearings 58 mounted on the second plate 57 support the phantom fixing plate 61 horizontally ( see fig6 ), and guide the phantom fixing plate 61 in an x direction . a metal piece 56 is disposed on a front end of the protrusion 57 a , and two sensors 55 are disposed on both sides under the metal piece 56 . the sensors 55 are spaced by a predetermined distance from each other , and sense the movement distance of the metal piece 56 . each of the sensors 55 generates a signal when the metal piece 56 passes through the sensor 55 . accordingly , when the metal piece 56 moved along the driven block 53 reaches one of the sensors 25 , the sensor 55 generates a signal to the controller 25 to indicate that the metal piece 56 has reached the sensor 55 . next , the controller 25 reversibly rotates the second motor 49 to move the driven block 53 in the opposite direction . the sensing mechanism is well known . the sensors 55 of the y - direction driving unit 93 determine the maximum y - direction reciprocating distance of the second plate 57 . accordingly , the maximum y - direction stroke of the second plate 57 can be increased by increasing the distance between the sensors 55 . in practice , however , the metal piece 56 is reciprocated between the sensors 55 without reaching the sensors 55 . the stroke of the metal piece 56 , that is , the stroke of the driven block 53 , is controlled by the controller 25 . fig6 is a detailed perspective view for explaining the mechanism of driving the phantom fixing plate 61 by means of the x - direction driving unit 95 , according to an embodiment of the present invention . the x - direction driving unit 95 horizontally moves the phantom fixing plate 61 in an x direction . referring to fig6 , the x - direction driving unit 95 includes the third motor 63 disposed on a side of a top surface of the second plate 57 , a lead screw 69 axially rotated by the torque of the third motor 63 , and a driven block 71 allowing the lead screw 69 to pass therethrough and be reciprocated by the axial rotation of the lead screw 69 . the driven block 71 is coupled to a c - shaped projection 61 b fixed to an end of the phantom fixing plate 61 . the lead screw 69 is parallel to the shaft of the third motor 63 and has both ends horizontally supported by supporters 72 . in order to transmit the torque of the third motor 63 to the lead screw 69 , a driving pulley 65 is mounted on the shaft of the third motor 63 , a driven pulley 66 is mounted on an end of the lead screw 69 , and the driving pulley 65 and the driven pulley 66 are connected to each other via a belt 67 . accordingly , the torque of the third motor 63 can be transmitted to the lead screw 69 via the belt 67 . the driven block 71 is reciprocated in a longitudinal direction of the lead screw 69 by the axial rotation of the lead screw 69 , and reciprocates the phantom fixing plate 61 in an x direction by means of the projection 61 b fixed to the bottom thereof . the phantom fixing plate 61 horizontally supported by the bearings 58 disposed on the second plate 57 is reciprocated within a predetermined range . a plurality of bearing grooves 61 a into which upper ends of the bearings 58 are inserted are disposed on the phantom fixing plate 61 such that the phantom fixing plate 61 can be linearly moved . the bearing grooves 61 a having predetermined widths and depths are parallel to one another . in order to limit the maximum movement distance of the phantom fixing plate 61 , a metal piece 56 is disposed on an end of the projection 61 b and a pair of sensors 55 are installed under the metal piece 56 . the operating principles of the metal piece 56 and the sensors 55 are the same as described with reference to fig5 . fig7 is a perspective view illustrating the phantom fixing plate 61 and the support walls 29 of the phantom device of fig2 , according to an embodiment of the present invention . referring to fig7 , the pair of support walls 29 are disposed at both sides on the top surface of the phantom fixing plate 61 . the support walls 29 face each other to be spaced apart by a predetermined distance , and firmly press the phantom 23 ( see fig2 ) disposed therebetween as shown in fig2 . the support walls 29 and the phantom fixing unit 30 are made of acryl . the number and structure of the support walls 29 are not limited to the present embodiment . the phantom fixing unit 30 is disposed on one of the support walls 29 . a female screw hole 29 a into which a pressing screw 30 a of the phantom fixing unit 30 is inserted is formed in the support wall 29 . the phantom fixing unit 30 includes the pressing screw 30 a inserted into the female screw hole 29 a , a cylindrical screw connection 30 b into which an end of the pressing screw 30 a is fixedly inserted , and a disk - shaped support plate 30 e integrally formed with the screw connection 30 b . a front end of the pressing screw 30 a inserted into the screw connection 30 b is fixed by a fixing screw 30 d . a female screw hole 30 c into which the fixing screw 30 d is inserted is formed in a sidewall of the screw connection 30 b . fig8 is a side view for explaining the operating principle of the phantom fixing unit 30 of fig7 , according to an embodiment of the present invention . referring to fig8 , the phantom 23 can be pressed in an “ f ” direction by rotating the pressing screw 30 a of the phantom fixing unit 30 mounted on one of the support walls 29 . the phantom 23 mounted on the phantom fixing plate 61 is formed by stacking a plurality of unit slabs 23 a . the structure of the phantom 23 will be explained in detail with reference to fig9 . fig9 is a partially exploded perspective view of the phantom 23 of fig2 , and fig1 is an exploded perspective view illustrating any one of the unit slabs 23 a constituting a phantom body 23 z of the phantom 23 of fig9 , according to embodiments of the present invention . the phantom 23 formed by stacking the plurality of slabs 23 a includes the phantom body 23 z having therein a space that simulates the shape of an internal organ , and the simulant 23 e located in the space inside the phantom body 23 z . each of the slabs 23 a constituting the phantom body 23 z has a predetermined thickness and is made of acryl . section holes 23 g are formed in some slabs 23 a as illustrated in fig1 . the section holes 23 g are through - holes representing outlines of the cross - section of the internal organ . that is , the section holes 23 g represent images of the internal organ tomographed at intervals in a direction from the back to the chest . accordingly , the section holes 23 g have different shapes for different slabs 23 a , and the shape of the internal organ can be embodied by sequentially stacking the slabs 23 a . referring to fig9 , the plurality of slabs 23 a are sequentially stacked to form one phantom 23 . each of the slabs 23 a is rectangular and has through - holes 23 f formed in four corners thereof . the through - holes 23 f permit vertical rods 23 b to pass therethrough . the vertical rods 23 b upwardly pass through the through - holes 23 f of the stack of slabs 23 a and upper ends of the vertical rods 23 b are coupled to nuts 23 c to vertically fasten the slabs 23 a to one another . in particular , a film 81 ( see fig8 ) may be inserted into the stack of slabs 23 a fixed by the nuts 23 c as shown in fig8 by loosening the nuts 23 c and slightly lifting the slabs 23 a . the film 81 is used to detect the dose of radiation passing through the simulant 23 e . simulant pieces 23 d are inserted into the section holes 23 g of the slabs 23 a . the simulant pieces 23 d are automatically stacked when the slabs 23 a are sequentially stacked , so as to form one simulant 23 e . the simulant 23 e is made of a tissue - equivalent material for a simulated subject . for example , a simulant 23 e simulating a lung is made of cork since the density of cork is almost equivalent to that of the lung . the simulant 23 e is made of a proper material according to the kind of a simulated internal organ . the simulant pieces 23 d may be made of acryl similarly to the slabs 23 a , or teflon or paraffin . the simulant pieces 23 d are inserted into the section holes 23 g , the slabs 23 a are stacked , and radiation is emitted to the phantom 23 in a thickness direction of the simulant pieces 23 d . as a result , the energy level of radiation at a target depth can be obtained and radiation treatment planning can be conducted based on the energy level . fig1 and 12 are perspective views illustrating some slabs 23 a of the phantom 23 of fig9 , according to embodiments of the present invention . the slabs 23 illustrated in fig1 and 12 are disposed under the simulant 23 e as illustrated in fig8 . referring to fig1 , a plurality of dosimeter grooves 23 k are formed in a top surface of a slab 23 a , according to an embodiment of the present invention . the dosimeter grooves 23 k are arranged at predetermined intervals and allow thermoluminescent dosimeters 83 to be inserted thereinto . since the slab 23 a on which the thermoluminescent dosimeters 83 are installed is disposed under the simulant 23 e as illustrated in fig8 , the dose of radiation under the simulant 23 e can be obtained . referring to fig1 , a plurality of dosimeter grooves 23 m extend longitudinally in a slab 23 a , according to an embodiment of the present invention . the plurality of dosimeter grooves 23 m are parallel to one another , and allow mosfet dosimeters to be inserted thereinto . accordingly , since the slab 23 a on which the mosfet dosimeters 85 are installed is disposed under the simulant 23 e as illustrated in fig8 , the dose of radiation under the simulant 23 e can be obtained . while the present invention has been particularly shown and described with reference to exemplary embodiments thereof , it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims .
provided is a phantom device having an internal organ simulating phantom . the phantom device comprises : a phantom receiving radiation emitted from a radiation emitting unit and comprising therein a simulant that simulates an internal organ ; a lifting unit installed under the phantom to support the phantom and moving the phantom relative to the radiation emitting unit , the lifting unit comprising : a worm shaft axially rotated by an external torque and having a worm formed on an outer circumferential surface thereof , a cylindrical worm wheel having gear grooves formed on an outer circumferential surface thereof to engage with the worm and a female screw formed on an inner circumferential surface thereof , and rotated by the axial rotation of the worm shaft ; and a driven screw engaging with the female screw of the worm wheel , and moved up and down by the rotation of the worm wheel to move up and down the phantom ; and a horizontal moving unit interlocking with the lifting unit and horizontally moving the phantom . accordingly , since the phantom device can simulate any movement pattern , even the respiratory movement pattern of a patient &# 39 ; s internal organ to accurately determine a desired dose of radiation to be delivered to the body part , high quality assurance of radiation therapy equipment can be achieved and therapeutic effect can be improved .