Abstract:
There is provided a manually operable afterloader ( 100 ) for use during radiation therapy treatment of a patient. The afterloader ( 100 ) includes a sourcewire reel ( 112 ) having a circumferential groove, dual sized or stepped ( 188 ), for receipt of a non-radioactive portion of a sourcewire ( 130 ) and a shield capsule ( 154 ) having a passageway therethrough for receipt of a radioactive portion of a source wire ( 130 ). A cranking mechanism ( 163 ) is provided to rotate the sourcewire reel ( 112 ) and drive the radioactive sourcewire ( 130 ) out of the shield capsule ( 154 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application Serial No. 60/059,602, filed Sep. 23, 1997, entitled, “Afterloader Apparatus”. 
    
    
     BACKGROUND 
     1. Technical Field 
     The technical field relates generally to remote afterloading devices used to position radioactive treatment sourcewires within catheters inserted into patients to treat cancer or for use in conjunction with an angioplasty procedure, and, more particularly, to a manually operated afterloader. 
     2. Description of the Related Art 
     Radiation is used to treat cancer and other diseases of the body. Brachytherapy, is a general term for the radiation treatment of cancer at close distances inside the body. During brachytherapy, a radioactive source or sources are positioned in the area needing treatment. Angioplasty is a general term for opening a constriction in a blood vessel or artery. Radiation treatment has been found to be useful in preventing reclosure or restenosis of the constriction. Depending on the type of therapy, the radioactive sources are placed permanently inside the body during surgery, or transport tubes (treatment catheters) are placed in the body which are later temporarily loaded with radioactive sources via wires. This temporary afterloading of radioactive material involves a machine called an “afterloader” that will load and unload the radioactive material into and from the transport tubes. 
     Afterloaders are devices generally used accurately advance and retract a flexible drive member containing a radioactive source over a specified distance for a specified time period. An afterloader generally consists of a flexible simulation drive member, a flexible drive member containing a radioactive element or sourcewire, computer controllers and motorized drive mechanisms to operate both types of flexible members, a shielding safe for the radioactive element, an internal timer, and, in brachytherapy, an exit port attached to a rotating wheel that allows multiple transport tubes (previously placed into the patient) to be hooked up to the device at the same time. The afterloader usually sends out the simulation member to check the patency of the transport tube without subjecting the patient to undue radiation exposure, and then sends out the radioactive element. After the treatment is performed in the first transport tube, the afterloader retracts the source into the shielding safe inside the afterloader, a wheel turns and aligns a slot containing the second transport tube to an exit port. The afterloader then repeats its function sending and retracting the simulation member and radioactive member through this second tube. The procedure is repeated until the function is carried out through all the specified transport tubes. Since the afterloaders use a fixed, short length radioactive source, the afterloaders must multi-step this source many times inside each transport tube to cover the diseased area. 
     The current remote afterloaders on the market, initially designed for use in brachytherapy, are particularly complicated. 
     Limiting factors of prior art treatment afterloaders are the physical size and amount of equipment necessary to operate a remote afterloader. In many treatment facilities, there is not enough room for this amount and size of equipment. 
     When used with a sourcewire to treat a stenosis or constriction of an artery, an afterloader need not be so complex as to support multiple transport tubes or computer controlled indexing features. 
     Thus, there exists a need for a simple, compact, portable, self-contained afterloader for use in conjunction with, or after, an angioplasty procedure to provide radiation treatment of a vessel in order to prevent restenosis, i.e., reclosure. 
     SUMMARY 
     A manually operable afterloader is provided for use with a radioactive sourcewire having a relatively short radioactive portion and a relatively long nonradioactive portion. The afterloader generally includes a base plate having a sourcewire reel rotatably mounted thereon. The sourcewire reel includes a circumferential groove which is configured to receive the nonradioactive portion of the sourcewire. A shield capsule or safe is also mounted to the base plate and includes a passageway therethrough for receipt of the radioactive portion of the sourcewire. Preferably, the pathway through the shield capsule is nonlinear so as to prevent inadvertent escape of radiation from the capsule. 
     A guide tube is provided between the sourcewire reel and the pathway of the shield capsule. Adjustment structure or an adjustment clamp is provided about the guide tube to properly align one end of the guide tube with tangent of the sourcewire reel so as to receive the sourcewire from the reel. 
     The manually operable afterloader further includes a cranking mechanism which is operably engagable with the sourcewire reel. The cranking mechanism generally includes a crank wheel having a crank handle attached thereto. The crank wheel is connected to a drive shaft which in turn is connected to one side of a slip clutch. The sourcewire reel is mounted on a second shaft which is connected to the opposed side of the slip clutch. Thus, rotation of the crank wheel by a manipulation of the crank handle rotates the respective drive shafts through the clutch to drive the sourcewire on and off the sourcewire reel. Preferably, the slip clutch is designed to slip at a pressure of approximately two pounds to limit the driving or retraction forces provided to the sourcewire. 
     Further, as a safety mechanism, crank handle is pivotally mounted to the crank wheel such that when the crank handle is in a retracted position, it engages a mechanical or frictional safety thereby preventing inadvertent rotation of the crank wheel and thus the sourcewire reel. Further, a releasable braking mechanism may be provided to limit rotation of the sourcewire reel to an initial predetermined amount and, upon release of the braking mechanism, allow further rotation of the sourcewire reel. 
     The sourcewire reel includes a circumferential groove for receipt of the nonradioactive sourcewire and further includes a larger width or diameter groove above the sourcewire groove for receipt of a flexible cable or belt. The flexible belt is provided to restrain the sourcewire within the groove as the reel is rotated so that the sourcewire does not flex or pop out of the groove as it encounters resistive forces going to a treatment catheter. A takeup assembly is provided to control movement of the flexible cable and provide predetermined rates of tension on the cable so as to restrain the sourcewire within its respective groove. Preferably, the takeup assembly includes a first pulley fixedly mounted to the base and adjacent the sourcewire and a floating pulley floatingly mounted and biased by spring tension. An adjustment mechanism is provided to adjust the tension the flexible pulley provides about the belt relative to the fixed pulley. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various embodiments of the presently disclosed afterloader apparatus are described herein with reference to the drawing figures wherein: 
     FIG. 1 is a side view of an afterloader apparatus constructed in accordance with a first embodiment of the present disclosure; 
     FIG. 2 is a top view of the afterloader apparatus embodiment of FIG. 1; 
     FIG. 3 is a side view of the sourcewire reel of the afterloader apparatus; 
     FIG. 4 is a top view of the sourcewire reel of FIG. 3; 
     FIG. 5 is a side view of the sourcewire reel illustrating the side opposite to that illustrated in FIG. 3; 
     FIG. 6 is a cross-sectional view taken along section line  6 — 6  of FIG. 5; 
     FIG. 7 is a cross-sectional view taken along section line  7 — 7  of FIG. 5; 
     FIG. 8 is an enlarged top view of the sourcewire reel; 
     FIG. 9 is a cross-sectional view of the sourcewire reel of FIG. 8 as rotated 90 degrees; 
     FIG. 10 is an enlarged view of the indicated area of detail shown in FIG. 9, which shows the threaded groove configuration; 
     FIG. 11 is an alternative embodiment of the threaded groove configuration of FIG. 10; 
     FIG. 12 is a partial cross-sectional view of an alternative embodiment for retaining the sourcewire on the sourcewire reel; 
     FIG. 13 is a partial cross-sectional view illustrating the payout passageway of the sourcewire from the sourcewire reel according to the alternative embodiment of FIG. 12; 
     FIG. 14 is perspective view of an alternative afterloader apparatus embodiment constructed substantially in accordance with the present disclosure; 
     FIG. 15 is a side perspective view of the afterloader apparatus embodiment of FIG. 14; 
     FIG. 16 is a side perspective view from the side opposite that illustrated in FIG. 15; and 
     FIG. 17 is an enlarged perspective view of the shield capsule of the afterloader apparatus. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now in detail to the drawing figures in which like reference numerals identify similar or identical elements, a first embodiment of the afterloader apparatus of the present disclosure is illustrated in FIGS. 1-11, and is designated generally by the reference numeral  100 . Briefly, the general function of afterloader  100  is to deliver a sourcewire having a radioactive source contained near a distal end to a treatment site within a vessel of a patient to prevent the restenosis of the vessel after an angioplasty procedure. Afterloader  100  drives the sourcewire through a treatment catheter which is attached to afterloader  100  and extends to the treatment site within the vessel. The frame components of afterloader  100  are made of tool grade aluminum or steel. The materials utilized for the various other components of afterloader  100  will be identified as appropriate. 
     Referring initially to FIGS. 1 and 2, afterloader  100  includes a frame base plate  110  having a sourcewire reel  112  rotatably disposed thereabove by a shaft  114  which is supported by a roller bearing  116  mounted in vertical support frame  118 . Additional bearings which support a drive shaft for rotatable motion will be described further herein. 
     A guide tube clamp  122  is secured to a vertically oriented mounting plate  124  which in turn is secured to base plate  110 . A guide tube  126  is aligned with a tangent of sourcewire reel  112  and defines the path along which a sourcewire  130  is payed out from sourcewire reel  112 . Guide tube clamp  122  is adjustable to align an end of guide tube  126  with sourcewire  130  retained on sourcewire reel  112 . The components of guide tube clamp  122  are thereafter tightened to fix the alignment of guide tube  126  relative to the sourcewire path. 
     A cable or flexible belt  128  is provided to securely retain a flexible sourcewire  130  on sourcewire reel  112 . In order to payout sourcewire  130  from sourcewire reel  112 , a tangent opening  132  is provided by a take-up assembly  134  which serves to divert flexible belt  128  from sourcewire reel  112  temporarily to allow a gap to be formed at tangent opening  132  thus permitting sourcewire  130  to exit sourcewire reel  112  tangentially and enter guide tube  126  which, as noted above, is adjusted to have an opening aligned with the tangent coming off of tangent opening  132 . 
     An adjustable take-up assembly  134  is provided to guide and tension flexible belt  128 . Takeup assembly  134  includes a fixed pulley  136  rotatably secured to mounting plate  124  and a floating pulley  138  which is rotatably mounted by way of a yoke  140  through a bracket  144 . A first end of flexible belt  128  is secured to sourcewire reel  112  with a clamp (described below). Belt  128  is wound over sourcewire  130 , and is deflected away from sourcewire  130  and onto fixed pulley  136 , around floater pulley  138  and back to a second clamp on sourcewire reel  112 . Takeup assembly  134  also includes a threaded adjusting rod  146  and nut  148 . Threaded adjusting rod  146  is connected to yoke  140 . A compression spring  142  is disposed between nut  148  and bracket  144  to spring bias threaded rod  146  and hold it and floating pulley  13  tension thereby tensioning flexible belt  128 . The tension of flexible belt  128  can be adjusted by advancing or retracting nut  148  on thread rod  146  to achieve the desired tension. 
     A releasable brake mechanism or stop release lever  150  is pivotally mounted to a bracket  152  which is secured to mounting plate  124 . Stop release lever  150  is preferably spring biased toward an engaged orientation with sourcewire reel  112 . The stop release lever  150  limits rotation of sourcewire reel  112  to a predetermined initial amount so that sourcewire  130  can initially only advance a predetermined distance. The predetermined distance is preferably chosen to allow a distal end of sourcewire  130  to advance to within about 3-5 cm of the distal end of a blind lumen in an associated treatment catheter. This prevents sourcewire  130  from hitting or piercing the distal end of the blind lumen and allows, when the braking mechanism is released, fine tuning of the position of the radioactive source, on the distal end of the sourcewire, within the treatment zone of the catheter. This may be accomplished with the aid of fluoroscopy. Stop release lever  150 , is pivoted to a disengage position disconnecting it from sourcewire reel  112  to allow a further limited amount of advancement of sourcewire  130 . 
     A shield capsule  154  is securely disposed above frame base plate  110  by proximal vertical support  156  and distal vertical support  158 . Shield capsule  154  is preferably formed of a material which prevents the escape of radiation from a radioactive source. To accomplish the prevention of escape of the radiation, which can only travel in smear or line of sight direction, from a !active source contained at the distal end of sourcewire  130 , shield capsule  154  defines a pathway  160  which is non-linear. In particular, pathway  160  includes linear segments  160   a,    160   b  and  160   c  which are in communication to form a continuous non-linear pathway  160  through shield capsule  154 . When the radioactive source is positioned at the mid-point of shield capsule  154 , radiation is prevented from escaping out the open ends of pathway  160  due to the non-linear configuration of pathway  160  preventing the emission of radiation therefrom which, as noted above, travels in a line of sight capacity only. While interconnected linear segments are disclosed to form pathway  160 , it is contemplated that other non-linear configurations, such as, for example, curvilinear, may be used as long as the pathway allows unimpeded travel of sourcewire  130  therethrough. At the outlet of pathway  160  a connector member such as Luer connector  162  is provided in order to connect guide tube  126  with a treatment catheter (not shown). Preferably connector  162  is a proprietary type connector configured to mate only with a correspondingly configured connector on a treatment catheter or extension tube. 
     Referring to FIG. 2, to facilitate payout of sourcewire  130  from sourcewire reel  124 , a cranking mechanism  163  is provided which includes a crank wheel  164  securely mounted to a drive shaft  166  which in turn is operatively connected to a clutch  168 . Drive shaft  166  is rotatably mounted with respect to base plate  110 . Clutch  168  may be any suitable slip clutch type, for example, a Berg model no. JCO-4 is one suitable clutch which acts as a slip clutch in one direction. An opposite side of clutch  168  is connected to sourcewire reel  124  by way of shaft  114 . Clutch  168  is preferably rated to slip at approximately two pounds of force to limit the drive and retraction forces provided to sourcewire  130 . This is desirable to prevent sourcewire  130  from advancing through the walls of a treatment catheter and to prevent retraction of sourcewire  130  if stuck within the treatment catheter. Preferably, a two-way clutch may be utilized to provide the user with a positive indication at the extreme limits of travel for sourcewire  130 . Drive shaft  166  is supported by bearings  167  in support frame  120 . 
     A crank handle  170  is preferably pivotally attached to crank wheel  164  by a pivot pin  171  and is movable between a retracted position, as shown in FIG. 2, wherein crank handle  170  in a recess  172  formed in crank wheel  164  and a operative position wherein crank handle  170  is rotated 90 degrees outwardly from its retracted position. A curved camming surface  174  is provided on crank handle  170  to interact with a stop member  176  which is preferably spring loaded to be biased in a retracted orientation such that when crank handle  170  is in the operative position, stop member  176  is biased away from housing wall  177 . Stop member  176  is biased against housing wall  177  by the outer surface of crank handle  170  when crank handle  170  is in the retracted position as illustrated in FIG.  2 . In this manner, stop member  176  frictionally engages housing wall  177  to prevent inadvertent operation of crank wheel  164 . Preferably top member  176  is formed from a material having a high coefficient of friction. 
     Referring now to FIGS. 3-10, specific details of a preferred embodiment of sourcewire reel  112  will now be addressed in greater detail. Sourcewire reel  112  includes a cylindrical hub  178  which surrounds a mounting bore  180 . Mounting bore  180  is configured and dimensioned to securely receive shaft  114 . Preferably, bore  180  is provided with gear teeth  182  which mesh with complimentary gear teeth formed on shaft  114  to ensure that no slippage occurs between sourcewire reel  112  and shaft  114 . A pair of stop members  184  and  186  are provided on the outer surfaces of sourcewire reel  112 . Stop members  184  and  186  prevent sourcewire reel  112  from being rotated so far that sourcewire  130  detaches from sourcewire reel  112 . Stop member  184  limits the amount of rotation of sourcewire reel  112  in a first direction, and thus the distance sourcewire  130  travels in a first direction. Stop member  186  similarly limits the amount of rotation of sourcewire reel  112  in a second direction and thus limits the distance sourcewire  130  travels in a second direction. Finally, as shown in FIG. 4, a threaded groove  188  is formed around the outer perimeter of sourcewire reel  112 . Threaded groove  188  receives both the sourcewire  130  and flexible belt  128 . 
     Referring now to FIG. 5, in order to retain a first or proximal most ends of the sourcewire  130  and flexible belt  128 , a pair of clamps  190  and  192  may be provided on sourcewire reel  112 . The operation of clamps  190  and  192  will be explained with reference to FIGS. 5-7 which show the details of clamp  190 . Clamp  192  operates in the same manner. As shown in FIG. 6, sourcewire reel  112  is provided with a bore  194  formed to extend from terminus  196  of threaded groove  188  to a recess  198  formed in the surface of sourcewire reel  112  a radial distance inwardly from the outer edge of the sourcewire reel. In this manner, the sourcewire  130  or flexible belt  128  as appropriate, is fed through bore  194  into recess  198 . Thereafter, clamp  190  is threadably secured into recess  198  to secure a respective end of sourcewire  130  or belt  128  within recess  198 . As shown in FIG. 7, recess  198  is preferably formed as a stepped recess having an upper shelf portion  198   a  and a lower shelf portion  198   b.  A threaded bore  200  is provided in communication with lower shelf portion  198   b.  Clamp  190  is preferably configured and dimensioned to the same configuration of recess  198  with slightly smaller dimensions in order to fit therein. Clamp  190  is secured in recess  198  by a threaded screw (not shown). 
     Referring to FIG. 5, a transport clamp  202  is provided to retain the outer end of flexible belt  128  during transport of sourcewire reel  112 . This is necessary to replace the sourcewire on afterloader  100  with a new sourcewire depending upon the level of radioactivity and decay of the sourcewire. Referring to FIGS. 8 and 9, clamp  202  fits within a recess  204  formed in sourcewire reel  112 . Clamp  202  functions in a similar manner as clamps  190  and  192 . For example, a bore  206 FIG. 8 is formed radially inward through sourcewire reel  112  at the beginning of threaded groove  188 . Bore  206  is in communication with recess  204  so that clamp  202  may secure the end of flexible belt  128  therein. 
     Referring to FIG. 10, the wrapping arrangment of flexible belt  128  around sourcewire reel  112  to retain sourcewire  130  within threaded groove  188  will now described in detail. Threaded groove  188  is preferably formed as a compound groove  188  having a lower groove portion  188   a  formed directly radially inwardly of outer groove portion  188   b.  Sourcewire  130  is wrapped onto sourcewire reel  112  within threaded groove portion  188   a  and flexible belt  128  is wrapped around sourcewire reel  112  over sourcewire  130  and is retained in outer groove portion  188   b.  As illustrated in FIG. 10, the diameter of flexible belt  128  is significantly larger than that of sourcewire  130 . In this manner, flexible belt  128 , upon paying out of sourcewire  130  from sourcewire reel  112 , prevents resistant forces, which are created due to negotiation of sourcewire  130  through the catheter and numerous turns through a tortuous passageway to the treatment site, from forcing sourcewire  130  out of threaded groove  188 . 
     Referring to FIG. 11, an alternative embodiment of retaining sourcewire  130  within sourcewire reel  112  is illustrated by threaded groove  288  which includes a arcuate lower portion  288   a  and a squared-off upper portion  288 b. Sourcewire  130  is retained in lower portion  288   a  by flexible belt  228  having a rectangular cross-section. It is within the scope of the present disclosure that numerous different geometries may be utilized for the groove portions as well as flexible belt  228 . 
     Referring to FIGS. 12 and 13, a further alternative embodiment for retaining sourcewire  130  within a threaded groove  388  of a sourcewire reel  312  is illustrated. Soucewire reel  312  is similar to sourcewire r  112  except that the configuration is modified to accommodate a retaining cover  328  which is formed as a cylindrical member having a cylindrical recess  329  formed therein. Retaining member  328  performs a similar function to that of flexible belt  128  above and acts as a cap which is inserted over sourcewire reel  312  to retain sourcewire  130  in threaded groove  388 . 
     Retainer member  328  is configured and dimensioned such that the inner side wall surface  328   a  forms a cylindrical sidewall having a diameter slightly larger than the diameter of the ridges  388   c  of threaded groove  388 . In this manner, upon insertion of retainer  328  over threaded groove  388 , sourcewire  130  is slightly impinged against threaded groove  388  and is thereby prevented from leaving threaded groove  388 . 
     A bore  331  is formed through retainer  328  in tangential relationship with threaded groove  388 . In this manner, sourcewire  130  is permitted to payout or exit threaded groove  388  upon rotation of sourcewire  312  as indicated by the arrow in FIG.  13 . Sourcewire  130  enters into guide tube  326  having an inlet opening in communication with bore  331  so as to receive source wire  130 . 
     Referring now to FIGS. 14-17, an alternative embodiment of an afterloader apparatus is depicted in the digital images shown therein. The afterloader illustrated in FIGS. 14-17 is substantially the same in structure and operation as afterloader  100  described hereinabove. One difference between the afterloader depicted in FIGS. 14-17 and afterloader  100  is shown in  15  wherein the crank handle is fixed in a operable position to permit cranking of the crank wheel at all times. A further difference is that the takeup assembly is oriented vertically rather than horizontally, as is takeup assembly  134  of afterloader  100 . Other minor differences may be provided without affecting the overall functioning and sourcewire retaining structure of the disclosed manually operated afterloader. 
     Although the illustrative embodiments of the present disclosure have been described herein with reference to the accompanying drawings, it is to be understood that the disclosure is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the disclosure. All such changes and modifications are intended to be included within the scope of the present disclosure.