Patent Publication Number: US-2006004243-A1

Title: Radioactive pellet injection apparatus

Description:
This invention relates essentially to an apparatus for injecting minute, spherical radioactive pellets into a diseased part of a patient for the purpose of treating cancer.  
     BACKGROUND OF THE INVENTION  
      There is an attempt to treat liver cancer, in which a plurality of radioactive minute pellets are injected into a liver artery. The injected radioactive pellets are held in capillaries in the cancer tissue, where they function to cut off nutrition to the cancer tissue and destroy the cancer tissue with the radiation. Radioactive pellets for use in this treatment have a diameter of from about 20 microns to about 30 microns so that they can stay at a location in thick blood vessels upstream the diseased part, and neither can harm sound tissues around the diseased part, nor move to other organs via veins to give side effects to such organs. It is desired that the radioactive pellets should be chemically stable for a long time and not exhibit toxicity. Also, it is desired that the pellets should radiate only a beta ray and have a short half-life period, so that they cannot affect sound tissues. Radioactive pellets which can meet the requirements is of vitreous or ceramic material containing, for example, 90Y (yttrium) having a half-life period of 64 hours or 32P (phosphorus) having a half-life period of 14.3 days. Such spherical minute radioactive pellets may be prepared in the following manner, for example. A required amount of minute spherical pellets of vitreous or ceramic material with yttrium or phosphorus mixed therewith is precisely measured and encapsulated. Then, the capsule is radiated with radiation of neutrons in a nuclear reactor to provide the pellets with radioactivity. The thus prepared minute, spherical radioactive pellets are brought to a medical treatment site, where they are injected into a body of a patient.  
      In  FIG. 1 , an apparatus conventionally used for radioactive pellet injection is shown. Radioactive pellets  1  are placed in a phial or medicine bottle  2 , which, in turn, is placed in a container  3  made of acryl. The acrylic container  3  is then placed in a container made of lead. The acrylic container  3  is provided with a stopper  7  also made of acryl. The acrylic stopper  7  includes a guide  6  with hypodermic needle guide through-holes  5   a  and  5   b  formed therein. A pump unit  8  includes a cylinder  9 , a piston  10  and a driver  11  for moving the piston  10 . The cylinder  9  is connected to a hypodermic needle  16  via a tube  13 , a three-way cock  14 , and a tube  15 . The needle  16  is inserted into the phial  2 .  
      The three-way cock  14  is also connected via a tube  19  to a container  19 , which contains a carrier fluid  18  for carrying radioactive pellets. Another hypodermic needle  20  is inserted into the phial  2  and is connected via a tube  21  to another three-way cock  22 , which, in turn, is connected to a catheter  23  and a tube  25  connected to a discharge bottle  24 . The discharge bottle  24  is also placed in a lead container  26 . Dosimeters indicating a dose are disposed behind the phial  2  and at the proximal end of the catheter  23 , respectively.  
      The amount of residual air in the system including the tubes  13 ,  15  and  21 , the three-way cocks  14  and  22 , the phial  2  is very large relative to the amount of radioactive pellets to be injected one time, which is from about 50 mg to about 100 mg. Accordingly, prior to the injection, the residual air must be withdrawn. For that purpose, the tubes  13  and  17  are made to communicate with each other via the three-way cock  14  so that the carrier fluid  18  can be sucked into the cylinder  9 . After that, the three-way cock  14  is operated to make the tubes  13  and  15  communicate with each other, and, at the same time, the three-way cock  22  is operated to make the tubes  21  and  25  communicate with each other so that the carrier fluid  18  within the cylinder  9  can be discharged into the bottle  24 . This procedure is repeated until the absence of air within the tubes  13 ,  15  and  21  is confirmed, and, only after that, the tube  21  is changed over to the catheter  23  by means of the three-way cock  22 , and the injection is started.  
      When air is being withdrawn, the carrier fluid  18  must flow through the phial  2 , and, therefore, it is inevitable that part of the radioactive pellets  1  is discharged together with the carrier fluid  18 . In some cases, a larger amount of the pellets  1  may be undesirably discharged. Also, turbulence of the carrier fluid  18  may occur in the three-way cock  22 , which could cause radioactive pellets to adhere to the inner wall of the cock  22 , increasing the loss of radioactive pellets. It also involves troublesome cleaning of the cock  22  after the injection. Further, extreme care must be given to the radioactive pellets kept in the discharge bottle  24 .  
      When minute, spherical radioactive pellets are being injected into a diseased part of a patient, fluoroscopy is employed, while adjusting the posture of the patient and the tilt of the phial  2 . If the catheter is too short, it could be pulled out during the adjustment.  
      On the other hand, if the catheter is too long, the radioactive pellets may adhere to the inner surface of the catheter, causing loss of radioactive pellets. Another disadvantage of the above-described apparatus is difficulty of precision control of the flow rate of the radioactive pellets from the phial  2  to the catheter  23 .  
      Therefore an object of the present invention is to realize a radioactive pellet injection apparatus in which air can be discharged easily and in which the flow rate and amount of minute, spherical radioactive pellets to be injected can be precisely controlled.  
     SUMMARY OF THE INVENTION  
      According to the present invention, a cylindrically-shaped capsule of transparent polymeric material is used, which contains minute, spherical radioactive pellets therein. The capsule has stoppers at its opposed ends, each having a hypodermic needle guide through-hole in its center portion. A carrier fluid carrying radioactive pellets to a diseased part of a patient is introduced into the capsule through a hypodermic needle having its distal end inserted into the capsule through the needle guide through-hole at one end thereof. The carrier fluid and the radioactive pellets which are discharged from the capsule through a hypodermic needle inserted into the capsule through the needle guide through-hole at the other end of the capsule are supplied to a catheter, which has its distal end inserted into a diseased part of a patient. In order to prevent radiation from affecting surroundings, the capsule is placed in a protective container made of transparent polymeric material. A first end of the protective container is closed with a stopper having a carrier fluid supply tube connecting portion, to which a carrier fluid supply tube is connected, and a second end is closed with a stopper having a catheter connecting portion, which the catheter is connected to. Each of the two connecting portions of the protective container holds a hypodermic needle to be inserted into the capsule.  
      The protective container is supported by a rotary driving unit of which a tilt angle can be changed by being rotated about a horizontal axis in response to a control signal. The rotary driving unit supports, in addition to the protective container, a radiation detector facing the catheter connecting section. A pump unit for pumping the carrier fluid for supply to a tube connected to the first end of the protective container, a control circuit which supplies the control signal to the rotary driving unit, and a circuit for detecting the dose based on the detection by the radiation detector, are disposed within a console, which is installed beside a treatment bed on which the patient is to be lain. A supporting arrangement for supporting the rotary driving unit includes a coupling unit, which enables detachable attachment of the supporting arrangement to either the bed or the console.  
      The capsule and the protective container for the capsule are made of a transparent material so that it can be visually determined how and how much air and radioactive pellets remain in the capsule and the protective container. In view of processability and radiation shielding ability, an acryl resin is a suitable material for the protective container. Physiological salt solution or contrast medium is suitable for use as the carrier fluid.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a front view of a prior art radioactive pellet injection apparatus.  
       FIG. 2  is a front view of a radioactive pellet injection apparatus according to an embodiment of the present invention.  
       FIG. 3  is a cross-sectional view of a radioactive pellet capsule in a protective container enclosing the capsule. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT  
      Referring to  FIG. 2 , a radioactive pellets injection apparatus according to an embodiment of the present invention includes a treatment console  30  having casters  31  attached thereto. On top of the console  30 , a control panel  32  is disposed, which includes therein a pump unit  32   a , a control circuit  32   b  and a detector circuit  32   c . A rear wall  33  stands upward behind the control panel  32 , and a display  34  is disposed on top of the rear wall  33 .  
      A coupler, e.g. a hinge  36 , is detachably carried by a bracket  35  on the upper side surface of the console  30 . The hinge  36  includes a rotating section  36   a  rotatably about a vertical center axis  37   a  as indicated by an arrowed arc  37 . An arm  39  is rotatably mounted to the rotating section  36   a  by means of a spindle  40 , which horizontally extends perpendicular to the axis  37   a  so that the arm  39  can move about the axis  37   a  and also about the spindle  40  as indicated by an arrowed arc  38 . The arm  39  is carried by the rotating section  36   a  in such a manner that, when it is rotated to a desired position about the axis  37   a  and the spindle  40 , it can be held in that position. One end of a universal joint assembly  42  is mounted to the distal end of the arm  39  by means of a spindle  41  so that it can rotate about the spindle  41  in either direction as indicated by an arrowed arc  43 . The manner of mounting the universal joint assembly  42  to the spindle  41  is such that, when the universal joint assembly  42  is rotated to a desired position about the spindle  41 , it can be held in that position. The universal joint assembly  42  has a spindle  42   a  extending perpendicular to the spindle  41  and a spindle  42   b  extending in parallel with the spindle  41 .  
      The other end of the universal joint assembly  42  is connected via a spindle  44  to a rotary driving unit  46 . The rotary driving unit  46  has driving means (not shown) disposed in it and is rotatable about the spindle  44  in either direction as indicated by an arrowed arc  45 . A carriage table  47  is mounted to the rotary driving unit  46 . The carriage  47  carries a cylindrical, radiation-shielding protective container  48  and a radiation detector  49 , which will be described in detail later. A catheter connecting portion  50  is disposed at one end of the protective container  48 , to which the radiation detector  49  faces. A tube  51  extends from the other end of the protective container and is connected to the pump unit  32   a  within the control panel  32 . The rotary driving unit  46  and the radiation detector  49  are connected, via a cable  52 , to the control circuit  32   b  and the detector circuit  32   c , respectively, within the console  30 . The rotary driving unit  46  is arranged to rotate about the spindle  44  in response to a control signal applied thereto from the control circuit  32   b.    
      The rotary driving unit  46  is rotatable also about the spindle  42   a  of the universal joint assembly  42  and is mounted to the spindle  42   a  in such a manner that, when it is rotated about the spindle  42   a  to a desired position, it can be held in that position. Further, the rotary driver  46  is rotatable also about the spindle  42   b  of the universal joint assembly  42  and is mounted to the spindle  42   b  in such a manner that, when it is rotated about the spindle  42   b  to a desired position, it can be held in that position. Accordingly, the rotary driving unit  46  can be rotated about the spindles  42   a  and  42   b  of the universal joint assembly  42  to a position in which the spindle  44  of the rotary driving unit  46  is horizontal, and can be held in that position. The rotary driving unit  46  in that position can be further rotated about the spindle  44  so that the tilt angles the protective container  48  and the radiation detector  49  with respect to a horizontal plane can be changed. The arm  39 , the universal joint assembly  42 , the rotary driving unit  46  and the carrying table  47  form together a supporting arrangement.  
      As shown in  FIG. 3 , the protective container  48  is formed of a cylindrical member  53  enclosing a capsule  60 , and stoppers  54  and  55  screwed into the opposed ends of the cylindrical member  53 . The cylindrical member  53  and the stoppers  54  and  55  are formed of a transparent polymeric material, e.g. an acrylic resin, and their walls are thick. The stopper  54  has a tube connecting section  56  to which the tube  51  connected to the pump unit  30   a  is connected. A hypodermic needle  57  extending into the interior of the cylindrical member  53  is attached to the tube connecting section  56 . The stopper  55  has a catheter connecting section  50  extending outward of the cylindrical member  53 . A hypodermic needle  59  extending into the interior of the cylindrical member  53  is attached to the catheter connecting section  50 .  
      The capsule  60  includes a main body  62  having a cavity  61  in which minute, spherical radioactive pellets are enclosed, and stoppers  63  and  64  screwed into the opposite ends of the main body  62 . The main body  62  and the stoppers  63  and  64  are formed of a transparent polymeric resin, e.g. an acrylic resin. The stoppers  63  and  64  have needle guide through-holes  65  and  66 , respectively. Rubber packing members  67  and  68  are interposed between the cavity  61  and the needle guide through-holes  65  and  66 , respectively.  
      Thus, when the stoppers  54  and  55  are screwed into the opposite ends of the protective container  48  with the capsule  60  placed therein, the needles  57  and  59  extends into the cavity  61  of the capsule  60  through the needle guide through-holes  65  and  66 , respectively, whereby a path is formed to extend from the tube connecting section  56 , through the needle  57 , the cavity  61  and the needle  59  to the catheter connecting section  50 .  
      For providing medical treatment with radioactive pellets, a dummy capsule (not shown) with only the carrier fluid contained in the protective container  48 , but without radioactive pellets, is loaded. Then, the pump unit  32   a  is operated, with the catheter connecting section  50  opened, to thereby push out the air in the system from the pump unit  32   a  to the catheter connecting section  50  completely through the catheter connecting section  50 , while monitoring the capsule  60 . At the same time, the catheter  69  is inserted into a diseased part of a patient to be treated, while looking at the catheter  69  through, for example, a fluoroscope.  
      After the air within the tube  51  is completely discharged, a normal capsule  60  having its cavity  61  filled with radioactive pellets and carrier fluid is substituted for the dummy capsule in the protective container  48 . With this apparatus, since the system from which air has to be removed includes only the pump unit  32   a  and the path extending from the pump unit  32   a  to the hypodermic needle  57  inserted into the capsule  60  and does not include radioactive pellets, operation to remove air is easy.  
      Thereafter, the hinge  36  with the arm  39  mounted thereto is detached from the bracket  35  on the console  30 , and, then, attached to a bracket (not shown) mounted on a side of the medical treatment bed on which the patient is lying. Then, the proximal end of the catheter  69  having its distal end inserted into the diseased part of the patient is connected to the catheter connecting section  50  of the protective container  48 .  
      After that, the protective container  48  is brought to a position near to the patient by rotating the arm  39  about the rotating section  36   a  and the spindle  40  and rotating the universal joint assembly  42  about the spindle  41 . Then, the rotary driving unit  46  is rotated about the spindle  42   a  and/or the spindle  42   b  of the universal joint assembly  42  to adjust the position of the rotary driving unit  46  so that the spindle  44  of the rotary driving unit  46  assumes a horizontal position. Then, the pump unit  32   a  is activated to inject the radioactive pellets in the carrier fluid in the capsule  60  into the diseased part through the catheter  69 . Since the capsule  60  containing radioactive pellets is fixed indirectly to the treatment bed during the injection, the catheter is prevented from falling out from the diseased part of the patient if the bed moves or tilts. Furthermore, since the distance between the capsule  60  and the diseased part is short, with no components except the catheter  69  intervening, loss of radioactive pellets in the injection path can be minimized.  
      The amount of radioactive pellets injected can be observed from outside the protective container  48 . In addition, the detector circuit  32   c  processes an output signal from the radiation detector  49  and causes the amount injected and the injection rate to be displayed on the display  34 . The rate of injection can be adjusted by adjusting the rate at which the carrier fluid is pumped by the pump unit  32   a . The tilting of the protective container  48  can be adjusted by rotating the rotary driving unit  46  about the spindle  44  in response to a control signal provided by the control circuit  32   b , whereby the injection rate can be adjusted. In other words, it is possible to control the injection rate to be constant, which also can be displayed on the display  34 .  
      It is desirable that the dummy capsule be made of colored material so that it can be readily discerned from a normal capsule containing radioactive pellets. Preferably, the injection apparatus with a dummy capsule placed in a protective container should be sent to a treatment site, together with a normal capsule filled with radioactive pellets and carrier fluid attached separately.