Abstract:
A device and method for marking a treatment isocenter on a patient&#39;s body. One embodiment includes a base including alignment indicia, a marker disposed over the base and positioned relative to the indicia for marking the isocenter on the patient&#39;s body and an actuator for actuating the marker and causing a mark indicating the isocenter to be made on the patient&#39;s body. The actuator can include a button and a spring coupled to the marker. Compressing the actuator causes the marker to travel through an ink well prior to piercing the patient&#39;s skin.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional application no. 61/463,986 filed Feb. 25, 2011, entitled IMPROVED ISOMARK TATTOOING DEVICE EMBODIMENTS, the disclosure of which is hereby incorporated by reference in its entirety for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a marking device. More particularly, the present invention relates to a device and a method for marking a treatment isocenter on a patient&#39;s body. 
       BACKGROUND 
       [0003]    Before receiving radiation therapy treatment, a computed axial tomography simulation (CAT scan or CT scan) is typically performed. A CT scan is used to help the radiation oncologist map the target treatment area on a patient&#39;s body. Dosimetrists and physicists plan the treatment from the CT images. The CT scan is performed with the patient in a comfortable, yet stable position for the area being treated. With the patient in the desired treatment position, a CT scan is performed. Using the images from the scan, an oncologist determines a treatment isocenter. When the oncologist determines the isocenter, a computer generates the coordinates for a laser projecting system. The lasers project beams onto the patient, indicating the three points of the coordinates. The center at which the three points intersect in the body defines the isocenter. 
         [0004]    External marks are then placed on the patient&#39;s skin and used to align the patient for treatment. These external marks will indicate where the isocenter or center of treatment is within the patient&#39;s body. When the patient is aligned to these marks, prior to treatment, the isocenter will fall directly under the central axis of the radiation beam. Lining a patient up to these marks ensures that they are in the same position for treatment as they were at the time of simulation. The marks are then tattooed. These tattoos will be used during the course of treatment to reproduce how the patient was positioned during the CT scan. 
         [0005]    There remains a need for improved devices and methods for marking isocenters on a patient&#39;s body. 
       SUMMARY 
       [0006]    The present invention pertains to improved devices and methods for marking isocenters on a patient&#39;s body. An embodiment of the present invention may be found in an isocenter marker that includes a body, a biasing member, a plunger, a releasable lock and a lock actuator. The body includes a base and alignment indicia on the base. A handle on the base is configured for manipulating the body without interfering with laser illumination of the alignment indicia. The base includes a plunger support and an ink well receiving structure. The plunger includes a needle and a needle mount. The needle mount permits motion with respect to the plunger support between a retracted position at which the needle will be free from engagement with an ink well in the ink well receiving structure and a marking position at which the needle extends through an ink well in the ink well receiving structure. The biasing member biases the needle mount from the retracted position toward the marking position. The releasable lock is cooperable with the body to releasably hold the needle mount in the retracted position. 
         [0007]    An embodiment of the present invention may be found in an isocenter marker alignment member. The isocenter marker alignment member includes alignment indicia structure, a handle on the alignment indicia structure, an ink well support on the alignment indicia structure and a needle actuator guide on the alignment indicia structure, the guide adapted to releasably position a needle actuator with respect to the alignment indicia structure and ink well support. 
         [0008]    An embodiment of the present invention may be found in an isocenter needle actuator that includes a housing having a marking end and being configured to replaceably receive a needle having a tip and to support the needle for motion. The isocenter needle actuator includes a plunger in the housing for engaging the needle, the plunger movable between a cocked position at which the needle tip is located within the housing and a marking position at which the needle tip extends beyond the marking end of the housing. A first biasing member is included for driving the plunger from the cocked position to the marking position, as is a cocking actuator to move the plunger to the cocked position, a trigger for releasably retaining the plunger in the cocked position and a second biasing member for biasing the plunger to a retracted position between the cocked position and the marking position at which the needle tip is within the housing. 
         [0009]    An embodiment of the present invention may be found in an isocenter marker that includes a base configured to removably receive ink wells, alignment indicia on the base, a handle on the base, a marking needle on the base and a needle actuator for causing the needle to move from a retracted position to a marking position. 
         [0010]    An embodiment of the present invention may be found in an isocenter alignment marker that includes a base, an ink reservoir in the base, a porous needle guide sleeve in the ink reservoir and alignment indicia on the base. 
         [0011]    While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective illustration of an isocenter marker alignment member and needle actuator configured for use therewith, according to an exemplary embodiment of the present invention. 
           [0013]      FIG. 2  is a partially exploded perspective view of the needle actuator of  FIG. 1 , according to an exemplary embodiment of the present invention. 
           [0014]      FIG. 3  is a partially exploded perspective view of the needle actuator of  FIG. 1 , according to an exemplary embodiment of the present invention. 
           [0015]      FIG. 4  is a perspective view of a press version needle actuator, according to an exemplary embodiment of the present invention. 
           [0016]      FIG. 5  is a cross-sectional view of the press version needle actuator of  FIG. 4 , according to an exemplary embodiment of the present invention. 
           [0017]      FIG. 6  is a perspective view of an isocenter marker, according to an exemplary embodiment of the present invention. 
           [0018]      FIG. 7  is an exploded perspective view of the isocenter marker of  FIG. 6 , according to an exemplary embodiment of the present invention. 
           [0019]      FIG. 8  is a cross-sectional view of the isocenter marker of  FIG. 6 , according to an exemplary embodiment of the present invention. 
           [0020]      FIG. 9  is a perspective view of an isocenter marker, according to an exemplary embodiment of the present invention. 
           [0021]      FIG. 10  is an exploded perspective view of the isocenter marker of  FIG. 9 , according to an exemplary embodiment of the present invention. 
           [0022]      FIG. 11  is a cross-sectional view of the isocenter marker of  FIG. 9 , according to an exemplary embodiment of the present invention. 
           [0023]      FIG. 12  is a perspective view of an isocenter marker, according to an exemplary embodiment of the present invention. 
           [0024]      FIG. 13  is a cross-sectional view of the isocenter marker of  FIG. 12 , according to an exemplary embodiment of the present invention. 
           [0025]      FIG. 14  is a perspective view of an unassembled disposable cartridge usable with the isocenter marker of  FIG. 12 , according to an exemplary embodiment of the present invention. 
           [0026]      FIG. 15  is a perspective view of the disposable cartridge of  FIG. 14 , shown assembled, according to an exemplary embodiment of the present invention. 
           [0027]      FIG. 16  is a perspective view of an isocenter marker, according to an exemplary embodiment of the present invention. 
           [0028]      FIG. 17  is a cross-sectional view of the isocenter marker of  FIG. 16 , according to an exemplary embodiment of the present invention. 
           [0029]      FIG. 18  is a perspective view of a servo-operated isocenter marker alignment member, according to an exemplary embodiment of the present invention. 
           [0030]      FIG. 19  is a perspective view of an internal portion of the servo-operated isocenter marker alignment member of  FIG. 18 , according to an exemplary embodiment of the present invention. 
           [0031]      FIG. 20  is a perspective view of an internal portion of the servo-operated isocenter marker alignment member of  FIG. 18 , according to an exemplary embodiment of the present invention. 
           [0032]      FIG. 21  is a schematic view of an ink disk, according to an exemplary embodiment of the present invention. 
           [0033]      FIG. 22  is a top view of the ink disk of  FIG. 21 , according to an exemplary embodiment of the present invention. 
           [0034]      FIG. 23  is a schematic view of a needle assembly, according to an exemplary embodiment of the present invention. 
           [0035]      FIG. 24  is a schematic view of a needle assembly including a safety guard, showing the safety guard in an extended position according to an exemplary embodiment of the present invention. 
           [0036]      FIG. 25  is a schematic view of the needle assembly and safety guard of  FIG. 24 , showing the safety guard in a retracted position according to an exemplary embodiment of the present invention. 
           [0037]      FIG. 26  is a schematic view of a pushbutton needle assembly, according to an exemplary embodiment of the present invention. 
           [0038]      FIG. 27  is a schematic view of the pushbutton needle assembly of  FIG. 26 , in combination with an ink well, according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]      FIG. 1  is a perspective illustration of an isocenter marker alignment member  10  and a needle actuator  12  configured for use with the isocenter marker alignment member  10 . It will be appreciated that in some embodiments, the isocenter marker alignment member  10  may be aligned at a desired location on a patient&#39;s body and can then be releasably secured to the patient&#39;s skin at the desired location. The needle actuator  10  may subsequently be used to tattoo the patient at the location indicated by the isocenter marker alignment member  10 . 
         [0040]    The isocenter marker alignment member  10  includes a base  14  and a handle  16 . In some embodiments, the handle  16  is an integral extension of the base  14  while in other embodiments the handle  16  may be separately formed and subsequently attached to the base  14 . In some embodiments, the handle  16  is sized and configured to permit a user to easily grasp the handle  16  while not interfering with any projected laser beams used for alignment. The base  14  includes alignment indicia  18  that may be utilized for aligning the isocenter marker alignment member  10  with the aforementioned laser beams. In some embodiments, the alignment indicia  18  may include one or more of raised surface features or grooves extending into the base  14 . In some embodiments, the alignment indicia may be white or otherwise permit easy viewing of the incident laser beams. 
         [0041]    While not illustrated, the base  14  may include an adhesive portion on an underside (in the illustrated orientation) of the base  14  for releasably securing the isocenter marker alignment member  10  to a patient&#39;s skin. The adhesive portion, if present, may be covered by a removable release layer  23  that protects the adhesive portion until ready for use. In some embodiments, the base  14  is configured to guide the needle actuator  12 . In the illustrated embodiment, the base  14  includes a needle actuator guide  20  that forms a raised, wall shaped to engage and guide the needle actuator  12 . In some embodiments, an ink well support  22  is located at or near a center part of the needle actuator guide  20 . The needle actuator guide  20  may be configured or adapted to releasably position the needle actuator  12  with respect to the alignment indicia  18  and the ink well support  22 . While not illustrated, in some instances an ink well may be removably disposed within the ink well support  22 . 
         [0042]    In some embodiments, the needle actuator  12  is configured to accommodate disposable needles, thereby reducing the per patient cost. In some embodiments, the user may instead desire to treat the entire needle actuator  12  as being disposable, depending on economics and their preferences. The needle actuator  12  includes a main barrel  25  and a needle section  24  that is threadedly or otherwise removably attached to the main barrel  25 . A tapered portion  26  that is configured to interact with the needle actuator guide  20  extends distally from the needle section  24 . The main barrel  25 , needle section  24  and tapered portion  26  may, in combination, be considered as forming a housing  28 . An actuator cocking handle  30  extends proximally from the main barrel  25 . 
         [0043]      FIGS. 2 and 3  are partially exploded perspective views of the needle actuator  12 , illustrating that the main barrel  25  includes a first semi-cylindrical portion  32  and a second semi-cylindrical portion  34 . The distal end  36  of the main barrel  25  is configured to accommodate a needle  38 , as seen in  FIG. 3 . In some embodiments, as illustrated, the needle  38  includes a cylindrical needle  40  that is overmolded within a polymer portion  42 . The needle  38  includes a distal end  44 . The needle  38  is movable between a retracted position in which the distal end  44  of the needle  38  remains within the tapered portion  26  and a marking position in which the distal end  44  of the needle  38  extends distally from the tapered portion  26 . 
         [0044]    In some embodiments, the main barrel  25  is configured to accommodate a biasing mechanism that biases the needle  38  to its marking position. In some embodiments, the main barrel  25  is configured to accommodate a biasing mechanism that biases the needle  38  to its retracted position. As illustrated, a spring  46  and a spring  48  are disposed within the main barrel  25 . A latch  50  interacts with a shaft  52 . Once assembled with a needle  38  disposed within the needle section  24 , the needle  38  is disposed in its retracted position. In some embodiments, the actuator handle  30  may be pulled backwards to cock against the spring  46 , when the latch  50  latches onto the actuator handle  30 . Pressing the latch  50  releases and causes the needle  38  to move distally relative to the tapered portion  26  such that the needle  38  extends distally of the tapered portion  26  a distance sufficient to permit the needle  38  to reach and penetrate at least partially into the patient&#39;s skin. If an ink well is disposed within the ink well support structure  22 , the needle  38  will carry ink under the patient&#39;s skin, thereby tattooing the patient. The spring  48  returns the needle  38  to a position inside the main barrel  25 . 
         [0045]      FIGS. 4 and 5  illustrate an embodiment of a needle actuator  50  that may be used with an isocenter marker alignment member. The needle actuator  50  includes a housing  52 , a tapered distal end  54  and an actuator  56 . As can be seen in  FIG. 5 , the needle actuator  50  includes a needle  58  and an actuation shaft  60  that extends from the needle  58  to the actuator  56 . The needle  58  is secured to the actuation shaft  60 . In some embodiments, a proximal end of the actuation shaft  60  forms the actuator  56 . A spring  62  is disposed within the needle actuator  50  and is configured to bias the actuation shaft  60 , and hence the needle  58 , into a retracted position. To use, the actuator  56  may be depressed to move the actuation shaft  60  against the spring  62 , thereby extending the needle  58  distally out of the tapered distal end  54 . In some embodiments, a safety plug  64  may include a raised portion  66  that is configured to interact with an aperture  68  that is formed within the tapered distal end  54  to hold the safety plug  64  in place until removal is desired. 
         [0046]      FIG. 6  is a perspective view of an isocenter marker  70 . In some embodiments, the isocenter marker  70  includes a base  72  and a handle  74  that extends from the base  72 . The base  72  includes alignment indicia  76 . In some embodiments, the handle  74  may be integrally molded with the base  72 . A plunger assembly  78  extends upwardly from the base  72 . It will be appreciated that in some embodiments, the plunger assembly  78  is sized and configured such that incident laser beams having an elevation angle of greater than about  45  degrees are not impeded or blocked by the plunger assembly  78 . 
         [0047]    In some embodiments, the plunger assembly  78  may be removably secured to the base  72  such that an ink well or other ink source may be replaced or otherwise disposed within the base  72 . The plunger assembly  78  includes a plunger support  80  and an actuator  82 . In some embodiments, the base  72  and the plunger assembly  78 , in combination, include a tab and slot securement feature  84  that permits the plunger assembly  78  to be attached to the base  72  by positioning the plunger assembly  78  proximate the base  72  and rotating the plunger assembly  78  relative to the base  72  to secure the plunger assembly  78  in position. 
         [0048]      FIG. 7  is an exploded view of the isocenter marker  70  while  FIG. 8  is a cross-sectional view thereof, illustrating additional features of the isocenter marker  70 . The isocenter marker  70  includes a plunger assembly  90  that includes a needle  92  extending downwardly (in the illustrated embodiment) from the actuator  82 . A biasing mechanism such as a spring  94  is disposed between the plunger assembly  90  and the base  72 . In some embodiments, the plunger assembly  90  includes an annular raised portion  104  that is sized to hold the actuator  82  within the plunger support  80 . In some embodiments, as illustrated, the base  72  includes a raised portion  96  that anchors the spring  94 . An ink source  98  may be secured underneath the base  72  using adhesively attached foil or other thin penetrable membrane material with a bubble ink reservoir contained between its layers. In some embodiments, the tab and slot securement feature  84  can be seen as including several tabs  100  that extend outwardly from the plunger support  80  and several corresponding slots  102  that are formed within the base  72  proximate the raised portion  96 . In some embodiments, the tab and slot securement feature may be replaced by ultrasonic welding, adhesive, snap engagement features, or other means of assembling plunger support  80  to base  72 . 
         [0049]    In use, the spring  94  biases the needle  92  into a retracted position. The isocenter marker  70  may be positioned in a desired position on a patient without anchoring the isocenter marker  70 . Once aligned using incident laser beams and the alignment indicia  76 , a tattoo may be formed by depressing the actuator  82 , thereby driving the needle  92  through an ink source and into the patient&#39;s skin. Once the actuator  82  is released, the spring  94  returns the needle  92  to its retracted position. The isocenter marker  70  may then be moved to another position on the patient, and the procedure may be repeated as desired to form additional alignment tattoos either with the same ink source  98  or upon replacement of ink source  98 . 
         [0050]      FIG. 9  is a perspective view of an isocenter marker  110 . In some embodiments, the isocenter marker  110  includes a base  112  and a handle  114  that extends from the base  112 . In some embodiments, the handle  114  is configured to enable the user to keep their hand far enough away from the base  112  to limit or prevent laser shadows. The base  112  includes alignment indicia  116 . In some embodiments, the alignment indicia  116  form or otherwise include tapered grooves  118  formed within the base  112 . In some embodiments, the handle  114  may be integrally molded with the base  112 . A plunger assembly  120  extends upwardly from the base  112 . The plunger assembly  120  includes a plunger support  122 , an actuator  124  and a release actuator  126 . In some embodiments, the actuator  124  and the release actuator  126  are integrally molded. In some embodiments, as will be described with respect to  FIGS. 10 and 11 , the actuator  124  may not be deployed unless the user also engages the safety mechanism  126 . 
         [0051]      FIG. 10  is an exploded perspective view of the isocenter marker  110  while  FIG. 11  is a cross-sectional view thereof, illustrating additional features of the isocenter marker  110 . The plunger support  122  includes a first groove  128  that is configured to accommodate a biasing mechanism  130  that is affixed or otherwise secured to the actuator  124  as well as a second groove  132  that is configured to accommodate an alignment tab  134 . The actuator  124  includes a central structure  136  to which the alignment tab  134  is affixed or otherwise secured. A needle  138  extends downward (in the illustrated embodiment) from the central structure  136 . 
         [0052]    The second groove  132  has a bottom surface  140  that is configured to interact with a lower surface  142  of the release actuator  126 . It will be appreciated, particularly with respect to  FIG. 11 , that the bottom surface  140  of the second groove  132  prevents further downward movement of the actuator  124 . However, by pressing the release actuator  126  inwardly, the lower surface  142  of the release actuator  126  moves inwardly and is no longer blocked by the bottom surface  140  of the second groove  132 . Instead, the release actuator  126  includes a channel  144  that accommodates the plunger support  122  and permits limited downward travel of the actuator  124 . As a result, the needle  138  is permitted to extend downwardly a distance that accommodates a desired depth of penetration into the patient&#39;s skin. 
         [0053]    The isocenter marker  110  includes a label  150  that may be affixed to a lower surface of the base  112 . The label  150  includes an ink reservoir  152  such that when the needle  138  moves downward, the needle  138  penetrates the ink reservoir  152  and carries a small amount of ink into the patient&#39;s skin to create a tattoo. In some embodiments, the label  150  includes areas of increased or decreased surface reflectivity  154  that align with the alignment indicia  116  formed in the base  112 , particularly in instances when the alignment indicia  116  include apertures extending through the base  112 , such that increased contrast with base  112  improves visibility of laser alignment precision. 
         [0054]      FIG. 12  is a perspective view of an isocenter marker  160 . In some embodiments, the isocenter marker  160  includes a disposable cartridge  162  that can be placed into an actuator assembly  164 . As can be seen in  FIGS. 14 and 15 , the disposable cartridge  162  includes the components that need to be changed for each patient, i.e., a needle  166  and an ink reservoir  168 . The disposable cartridge  162  may be molded as a unitary structure  170  including a needle arm  171 , a needle  166  may be attached and the unitary structure  170  may be folded along living hinges to form the assembled disposable cartridge  162 . An adhesive label that bears the ink reservoir  168  may be applied to the disposable cartridge  162  to properly locate the ink reservoir  168  as well as to hold together the folded unitary structure  170 . Although not illustrated, the base  170  may include alignment indicia as discussed herein with respect to other embodiments. 
         [0055]    The actuator assembly  164  includes a cocking mechanism  174 . The cocking mechanism  174  includes a handle  176 , a shaft-shaped hammer  178  bearing a spring  180 , a cocking handle  172 , and a latch mechanism  182 . In use, once a disposable cartridge  162  has been disposed within the isocenter marker  160 , cocking the handle  172  pulls back the hammer  178 , compressing the spring  180 . Releasing the latch mechanism  182  causes, by virtue of the spring force of the spring  180 , the hammer  178  to move forward striking a rear portion of the needle arm  171 , causing the needle arm  171  to swing down. As a result, the needle  166  penetrates the ink reservoir  168 . After use, the disposable cartridge  162  may be disposed and the actuator assembly  164  may be used again for another patient. 
         [0056]      FIG. 16  is a perspective view of an isocenter marker  190  while  FIG. 17  is a cross-sectional view thereof. The isocenter marker  190  includes a handle assembly  192  and a base  194 . The handle assembly  192  is configured to accommodate a disposable cartridge  196  that includes a needle  198  and an ink reservoir  200 . In some embodiments, the base  194  is configured to electronically detect the alignment lasers, and thus may include one or more sensors  202  disposed within alignment indicia  204 . An on/off switch  206  may be used to turn the electronics (not illustrated) on and off, and several indicator lights  208  inform the user whether alignment has been achieved. In some embodiments, the indicator lights  208  may be colored LEDs. 
         [0057]    The handle assembly  192  includes an actuator button  210 . A shaft  212  is held in a rearward position against the force of a biasing spring  214 . When the actuator button  210  is released, the shaft  212  moves towards the disposable cartridge  196 . The shaft  212  pushes on an actuator bar  216  that moves along an incline on a needle spring arm  218 , thereby causing the needle spring arm  218  to move downwardly (in the illustrated orientation), pushing needle  198  to penetrate the ink reservoir  200  and tattoo the patient. After full actuation, the actuator bar  216  becomes trapped beyond the automatically retracting needle spring arm  218  and needle  198 , making the disposable cartridge save against an accidental second needle exposure. After use, the disposable cartridge  196  may be removed and the isocenter marker  190  is ready for use with another patient. 
         [0058]      FIG. 18  is a perspective view of an isocenter marker alignment member  250  while  FIGS. 19 and 20  illustrate internal components thereof. In some embodiments, the isocenter marker alignment member  250  is servo-operated, meaning that it electronically detects the incident aligning laser beams and adjust itself accordingly. The isocenter marker alignment member  250  includes an alignment aperture  252  that is secured to orthogonally arranged sliding members  254  and  256 . The isocenter marker alignment member  250  includes motor driven assemblies  258  and  260  that cause motion of the sliding members  254  and  256 , respectively. Alignment slots  262  permit incident laser light to pass through and strike sensors  264 . The sensors  264  are configured to detect the laser light and provide signals to integrated circuit assemblies not shown. Sensor  266  and  268  are mounted at an elevation proud of the 4 sensors  264  such that the angle of incidence of the laser beams may be inferred and the proper parallax adjustment to the position detected by sensors  264  may be included in the positioning calculation, after which the integrated circuit provides movement instructions to the motor driven assemblies  258  and  260  in order to align the device. Once aligned, the alignment aperture  252  is used for positioning any tattoo marker device. 
         [0059]    In some embodiments, as illustrated, the isocenter marker alignment member  250  includes an adhesive layer that permits adhering the device to the patient in the general area of the laser markers to which it will self align by means of the servos. The adhesive layer is visible in  FIGS. 18-20  only where tab  270  of the adhesive layer protrudes from under the device. Release liner tab  272  is visible beneath tab  270 . After device use, the adhesive layer  270  and the release liner  272  are replaced for subsequent uses. 
         [0060]      FIG. 21  is a schematic view of an ink disk  300  while  FIG. 22  is a top view thereof. The ink disk  300  includes an ink reservoir  302  and a porous needle guide sleeve  304 . The guide sleeve  304  is sufficiently porous to permit ink to pass from the ink reservoir  302  into the guide sleeve  304 . In some embodiments, the ink disk  300  may include an adhesive backing  306  that may be used to releasably secure the ink disk  300  to a patient. While not illustrated, in some cases the ink disk  300  may include a release liner that protects the adhesive backing  306  until the ink disk  300  is ready for use. The ink disk  300  includes alignment indicia  308  and in some embodiments may include a handle tab  310 . 
         [0061]      FIG. 23  is a schematic view of a needle assembly  320  that may be used in combination with the ink disk  300 . The needle assembly  320  includes an overmolded polymer member  322  that is configured to permit the user to easily grasp the needle assembly  320 . The needle assembly  320  also includes a needle  324  that is sized and configured to penetrate a patient&#39;s skin to a desired depth. 
         [0062]      FIGS. 24 and 25  are schematic views of a needle assembly  330  that may be used in combination with the ink disk  300 . The needle assembly  330  includes an overmolded polymer member  332  that is configured to permit the user to easily grasp the needle assembly  330 . The needle assembly  330  also includes a needle  334  that is sized and configured to penetrate a patient&#39;s skin to a desired depth. The needle assembly  330  also includes a safety guard  336 . In  FIG. 24 , the safety guard  336  is shown in an extended position in which the needle  334  is at least partially covered to limit or prevent accidental sticks. In  FIG. 25 , the safety guard  336  is shown in a retracted position in which the needle  334  is exposed and is ready for use. In some embodiments, the safety guard  336  may be moved into the retracted position by squeezing an upper portion of the safety guard  336 . In some embodiments, the safety guard  336  is self-biased to remain in the extended position, and only remains in the retracted position while a user applies pressure to the safety guard  336 . 
         [0063]      FIG. 26  is a schematic view of a push button needle assembly  350 . The push button needle assembly  350  includes a housing  352  and a button  354 . A spring  356  extends between the button  354  and a needle  358 . It will be appreciated that depressing the button  354  will compress the spring  356  and cause the needle  358  to move downward (in the illustrated orientation). The push button needle assembly  350  includes a needle guard  360 . In some embodiments, the needle guard  360  includes locking nubs  362  that are configured to releasably engage with the profile of an ink reservoir, as shown in  FIG. 27 . In  FIG. 27 , it can be seen that an ink reservoir  370  includes a side profile that complements the locking nubs  362  and thus help to locate the push button needle assembly  350  relative to the ink reservoir  370 . 
         [0064]    Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.