a computed tomography apparatus , in the remaining description defined as ct apparatus ( fig1 ). the ct apparatus 1 has a patient supporting table 2 which is slidable along a support 3 having means therein for moving said table 2 at least partly through a scanner opening 4 in the apparatus 1 by means of motors inside the support 3 providing incremental movement modes of said table 2 on which a patient 5 to be examined is placed . the ct apparatus has inside in a manner known per se and not to be described further a rotary scanner moving along a circular formed slit 6 as indicated on fig1 . the apparatus for assisting percutaneous computed tomography - guided surgical activity inside the body of a human , such as the patient 5 , is generally indicated by reference numeral 7 . in a non - limited embodiment of the invention the apparatus 7 consists of a base member 8 , upright members 9 and 9 ′, which are preferably telescopically mounted and mutually lockable by means of a locking handle 10 . further , the apparatus 7 has a transverse member 11 extending from a top region of the upright member 9 ′. the apparatus 7 has a unit 12 moveable along the transverse member 11 and lockable in position there along . the unit 12 has laser beam generator device 13 including a power supply means 14 ( fig1 ) for the device 13 . said power supply means 14 has suitably an on / off switch 15 . the laser beam generator device 13 has suitably a power inlet terminal 16 show in fig1 - 11 . based on calculations to be explained further , transverse insertion angle and craniocaudal insertion angle can be calculated . using , e . g ., turning knob 17 , the transversal insertion angle to be described by a laser beam 13 ′ can be set . similarly , the craniocaudal insertion angle can be set for the beam 13 ′ by means of an adjustment knob 18 ( fig9 ). the turning of the knob 17 is a movement which is transferred through a gear box 17 ′ to a two - dimensional turning device 19 having an outer ring and inner ring which are moveable relative to each other . thus , viewing fig1 turning of knob 17 means that the laser device 13 will be moveable in the direction of the long side of the drawing sheet . movement of the adjustment knob 18 via a first gear box 18 ′ and a second gear box 18 ″ will yield that the ring 21 will move relative to ring 20 in order to be able to move the laser device 13 parallel to the short side of the drawing sheet . the gear box 17 ′ and suitably also the gear box 18 ″ may have angle indicators in order that an operator of the inventive apparatus may know when the set angles have been reached . the laser beam generating device 13 receives power from the power supply 14 via connecting wires 22 . a display for indication of e . g . the craniocaudal insertion angle has been schematically indicated on fig1 by reference numeral 23 . the angle indicator has also been shown as an example on fig6 . similarly , as shown on fig6 an angle indicator for the transversal insertion angle has been indicated by reference numeral 24 . as indicated on fig8 a calculator device 25 could form an integral part of the apparatus and e . g . be locatable on an end part of the transverse member 11 , as indicated on fig6 by reference numeral 11 ′. based on x and y values obtained from tomography image co - ordinate values , it will be possible to calculate the transversal insertion angle and craniocaudal insertion angle and have those angle values shown on displays 25 ′ and 25 ″. as shown on fig6 and 7 , the unit 12 is moveable along the transverse member 11 and can be locked in any position therealong by means of locking members 26 releasable by pushing knobs 27 . in a particular embodiment , it is considered possible to move the unit 12 over a transition region 28 between the transverse member 11 and the upright member 9 ′. suitably , a radome 29 is located below the exit of laser beam generator device 13 , said radome 29 ( fig5 ) being of a material and thickness causing little or negligible refraction of the laser beam 13 when it passes through the radome material . suitably , the exit of the laser beam generator device 13 is close to the inner surface of the radome . the radome is primarily for protecting the laser beam generator device 13 against damage caused by accidental impacts . a more simplified version of the apparatus , according to the invention , forming a prototype of the apparatus is shown in more detail on fig2 . the apparatus has a transverse top beam 11 which is connectable to an upright member 9 , 9 ′. the transverse member 11 has suitably a pair of slide rails 30 , 31 with slide shoes 32 , 33 , 34 , 35 attached to a common plate member 36 . the plate 36 is attached to a unit 37 via a hinge connection 38 and a craniocaudal angle adjustment of connection 39 . the unit 38 consists of a laser beam generator device 40 , suitably of the same type as denoted by reference numeral 13 in connection with the disclosure of the embodiment shown on fig1 - 11 . further , said unit 37 has suitably a level 41 for indicating a craniocaudal insertion angle equal to 0 degrees as also indicated by an angle indicator 42 . a transversal insertion angle indicator 43 is also located on unit 37 and is provided with a fixation knob 44 . when the proper transversal insertion angle and craniocaudal insertion angle have been calculated , the laser beam 40 ′ will point at the correct insertion point 5 ′ on the body of the patient 5 . the needle - type surgical instrument to be inserted into the body of the patient 5 is denoted by reference numeral 45 on fig2 . the instrument 45 is to be hand - held by a surgeon . at a distal end 46 of the instrument , there is located an aiming point or face 46 ′, suitably , but not necessarily , made of a light reflective material . thus , keeping in mind that the laser beam 40 ′ is directed to point with correct transversal insertion angle and craniocaudal angle at the insertion point 5 ′, inserting the instrument at the insertion point 5 ′ and ensuring that the aiming point or face 46 ′ is always hit by the laser beam 40 ′, will ensure that the instrument is moved correctly into the body of the patient 5 . although the laser beam 40 ′ may create only a light spot on the distal end 46 of the instrument , the laser beam could be of a cross - hair type , thus more readily defining a centre point on said distal end 46 . in a manner known per se the needle portion 47 of the instrument 5 has a length scale , e . g . in metric units such as centimetres , to be able to observe the correct insertion depth of needle portion 47 . thus , by knowing the correct transversal insertion angle and the craniocaudal insertion angle , as well as the insertion depth , a safe insertion of the needle portion 47 of the instrument 45 into the body of the patient 5 can be made . the instrument is suitable for withdrawal of body tissue or body liquid sample , withdrawal of excess body fluid , insertion or injection . in a preferred application of the present invention , the instrument is suitable for taking a body tissue or body liquid sample , e . g . known as aspiration cytology , percutaneous fine needle biopsy or surgical micro biopsy . a most important advantage of the present invention over the prior art is the feature of the apparatus being in physical non - contact with the instrument to be inserted into the patient &# 39 ; s body . this is clearly seen from fig1 . in turn , this means that the apparatus , according to the invention does not require any disinfection cleaning operation after a biopsy has been performed , contrary to the prior art apparatus for assisting percutaneous computed tomography - guided surgical activity related to insertion of a needle - type surgical instrument into a human or animal body . a further advantage over the prior art is that the operator may use both hands while introducing the needle , i . e . the operator does not have to support the instrument with one hand . calculation of transversal insertion angle and craniocaudal insertion angle and the combination thereof to obtain the correct direction of insertion is now to be further described with reference to fig1 - 17 . the insertion point is generally denoted by i , and the target , e . g . a malignant tumour is denoted by t . in the simple example as illustrated by fig1 and 14 , the insertion of the instrument 45 and its needle portion 47 is determined to be made in a single tomography image plane with co - ordinates for the target and the insertion point denoted by co - ordinates x1 , y1 and x2 , y2 , respectively . the angle can be calculated on a separate calculating device based on the co - ordinate values or simply be read off from the tomography image viewing screen which suitably has cursor means to connect said co - ordinates on the screen and thereby determine the angle of the cursor relative to the vertical . in the particular case where it is difficult to let the needle portion 47 of the instrument 45 move in a single tomography image slice plane , simply due to internal organs having risk of being punctured by the needle or be damaged or cause internal bleeding or other damages , it is more than often required to have the target in a first tomography image slice plane tp ( xt , yt , zt ) and the insertion point in a parallel tomography image slice plane ip , such as schematically shown on fig1 as well as on fig1 a , 15 b and 15 c . again , the target is given the co - ordinates x1 , y1 , z1 , z being the direction of the movement of the table 2 . the insertion point is denoted by the co - ordinates x3 , y3 , z3 . thus , the purpose of understanding the calculation below and with reference to fig1 , a = y3 − y1 , b = z3 − z1 , and c = x3 − x1 . thus , with reference to fig7 the following calculations can be made . tan   ∠   tv =  c   d  ∠   tv = tan - 1   c   d  ∠   c   c _ :  tan   ∠   c   c =  a   b  ∠   c   c = tan - 1   a   b  insertion depths ={ square root over ( c 2 + l + d 2 + l )} thus , by turning the proper adjustment means for transversal insertion angle and craniocaudal angle to obtain the composite direction of insertion , as well as the insertion depth , a safe insertion procedure is obtained . naturally , it will be important to carefully check in a step - by - step fashion , how the insertion proceeds by taking repeated sets of tomography image slices . on fig1 there is shown in a simplified block diagram form a micro processor 48 and at the outputs therefrom displays 49 and 50 for showing the computed craniocaudal insertion angle and the transversal insertion angle , respectively , as well as a display 51 for showing the insertion depth . the microprocessor 48 calculates the appropriate insertion angle values and insertion depth value based on the co - ordinates of the proposed insertion point 5 ′, denoted by co - ordinates ix , iy , iz , and the co - ordinates of the target t , denoted by co - ordinates tx , ty , tz . in order to make sure that the transverse member or arm 11 ; 57 ; 60 is located exactly at right angle to the craniocaudal direction , the apparatus is provided with an auxiliary laser beam generator device 63 providing a light plane 64 parallel to said craniocaudal direction . as shown on fig2 the plane 64 will hit and lie along the bed 2 , thus indicating that the arm 11 is transversely of the craniocaudal direction . the microprocessor 48 , its displays 49 , 50 , 51 and the laser generator devices 13 and 63 are powered from a power supply 52 . as an alternative to battery operation 52 , the apparatus may be powered from the mains 61 via an ac to dc converter 62 , said dc convertor e . g . delivering 12v dc or 24v dc . although , the supporting device may be of a type located on a floor , with reference to fig1 , an alternative is to slidably attach the apparatus supporting device to a bed or table base member 53 which supports the computed tomography ( ct ) machine patient supporting movable table or bed 2 . said supporting device may have a telescopic vertical adjustment means 10 . the laser beam generator device 13 is movable along said transverse member or arm 11 as described before . in the further alternative , with reference to fig1 , an apparatus supporting device 54 is suspended from a ceiling 55 above said patient supporting movable table or bed 2 . the supporting device 54 may have means , e . g . telescopic vertical adjustment means 56 for adjusting the level of a transverse member or arm 57 above the human or animal body 5 . the laser beam generator device is movable along said transverse member or arm 57 . in a still further alternative and with reference to fig1 , an apparatus supporting device 58 is suspended from a top region on the ct apparatus 1 . the supporting device 58 may have means , e . g . telescopic vertical adjustment means 59 for adjusting the level of a transverse member or arm 60 , above the human or animal body 5 . the laser beam generator device 13 is movable along said transverse member or arm 60 . in order to more fully appreciate the importance of the present invention , reference is now directed to attached fig2 a , 21 b , fig2 and fig2 a , 23 b , 23 c , 23 d and 23 e . in fig2 a and 21 b are shown a first medical case showing a tumour having a liquid part 70 and a solid tissue part 71 . as seen , the tumour is associated with the right lung 72 of the patient . for reference the spine is denoted by reference numeral 73 and the aorta by reference numeral 74 . further , the heart is denoted by reference numeral 75 . in order to perform a biopsy , the needle part of the biopsy instrument , as denoted by reference numeral 76 is to be inserted into the solid tissue of the tumour . as noted from fig2 b the distance required for insertion and the angle of insertion is denoted by the cursor 77 . the ct slice image and evaluation thereof indicates that the insertion angle is to be 90 degrees and the insertion depth to be 3 . 90 cm . with such short insertion depth and a well defined insertion angle , the biopsy is fairly straight forward to perform , even with prior art biopsy techniques . however , a more complicated and true case , medical case number two , is shown on fig2 . this particular case , using the prior art free - hand technique and aiming the biopsy instrument using eye measures , clearly indicates the severe risks which are imposed on patient during biopsy sample taking . in this particular case an attempt has been made to hit with the biopsy instrument needle 80 a tumour 81 located in the left lung 82 . as a complication in the biopsy operation , the operator has managed to puncture the lung which has therefore partly collapsed . the image shown on fig2 does not represent the first insertion of the biopsy needle 80 . a repeated insertion is represented by fig2 and , as shown , the needle has unintentionally passed very close to the aorta 83 , with a very narrow margin . if the aorta had been punctured , a serious bleeding could have occurred . for reference , the spine has been indicated by reference numeral 84 and the heart by reference numeral 85 . the medical case of fig2 clearly indicates that insertion angle of the biopsy instrument as well as insertion depth in many cases is highly critical . it will be appreciated that using the method and apparatus of the present invention could all together have avoided the dangerous situation shown with reference to fig2 . a third medical case , represented by fig2 a - 23 e is now to be described very briefly , the biopsy using the technique according to the present invention . in order to more fully understand the ct slice images , reference 90 denotes a rib . the left kidney is denoted by reference 91 . aorta is denoted by reference 92 . interior vena cava is denoted by reference 93 . the liver is denoted by reference 94 . the medical situation is that the patient has a collection of liquid in the pancreas , as denoted by reference numeral 95 . situation of post - pancreatitis is denoted by reference numeral 96 . further , pseudo - cysts are denoted by reference numeral 97 . as shown on the images of fig2 it was a prime object to remove the large collection of liquid within the pancreas and in particular in the pseudo - cysts , as shown on fig2 d . it will be appreciated that not only is the insertion depth calculation critical , but the insertion angles are highly critical , in particular with such a long biopsy needle or cannula to be used . notably and as clearly shown on fig2 d and 23 e , the needle or cannula , as indicated by reference numeral 98 is extremely long , almost the cross sectional width of the human body at the location of the ct slice image . without the aid of the present method and apparatus , a puncture procedure as shown would take very long time and involve high risks of not hitting the target properly . thus , with further reference to fig2 the ct slice images clearly indicate a very complicated puncture of a series of liquid collections in the pancreas where a very long needle 98 has been inserted from the left side of the abdomen transversally towards the right . in the particular case shown , the patient was lying on the right side . on fig2 b the needle has been inserted at a correct angle and a control ct slice has been made to check that the needle is on a right path . the fact that the complete needle is shown indicates that the insertion has been made exactly in the transversal plane being the same as the ct slice image plane . fig2 d indicates the needle 98 being moved further in , and the path of the needle is still a correct one . a further advancement of the needle to the liquid collection to the far right of the patient , ( next to the liver 94 ) is shown on fig2 e . after the needle 98 hit the target shown on fig2 e , a thin wire was inserted through the needle to be a pilot wire for a thin tube to be inserted into the human body over the steel wire . the tube ( not shown ) was for draining the liquid in the pancreas .
a method and an apparatus for assisting percutaneous computed tomography - guided surgical activity inside a human or animal body , such as withdrawal of body tissue or body liquid sample , withdrawal of excess body liquid , insertion or injection , said method for determining insertion depth , transversal insertion angle and craniocaudal insertion angle for a needle - type surgical instrument to be inserted into the human or animal body from an insertion entry point on a skin surface of said body to a target inside said body . from a first tomography image coordinate values of said entry point are determined , and from said first or a second tomography image coordinate values of said target point are determined . based on said coordinate values values of said insertion depth , transversal insertion angle and craniocaudal insertion angle are calculated . said calculated values are applied to an instrument insertion guiding apparatus positioned adjacent said body in no physical contact therewith , said apparatus having a laser which provides a laser beam , manipulating adjustment means on said apparatus to let the laser beam assume the values of transversal insertion angle and craniocaudal insertion angle and to let the laser beam point at the entry point . the instrument with a needle pointed end thereof is located at said entry point and a longitudinal axis of the instrument is aligned with said laser beam , the aligning being made by letting a distal end face of said instrument be pointed at by said laser beam .