Abstract:
A device and method for retaining a position of a treatment applicator include a perineal retainer body configured to receive the applicator and form a positive stop with a perineum of a body of a patient, and a locking bracket configured to secure the perineal retainer body to the applicator. The locking bracket is movable between first and second positions with respect to the perineal retainer body, is configured to exert a clamping force to clamp the applicator, includes an actuator configured to move the locking bracket between the first and second positions, and is vertically accessible for securing and adjusting the applicator with respect to the perineal retainer body. The method includes securing a perineal retainer body to the applicator by a locking bracket, and attaching the perineal retainer body to a body of a patient.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application No. 61/479,839, filed on Apr. 27, 2011, which is expressly incorporated herein in its entirety by reference thereto. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a brachytherapy device and to a method for cervical brachytherapy treatment using a brachytherapy device. Radioactive therapeutics may be delivered to a region of the cervix, e.g., to provide for treatment of cervical cancerous tissue. 
       BACKGROUND INFORMATION 
       [0003]    Brachytherapy is a form of cancer treatment in which radiation sources are placed inside a patient&#39;s body, e.g., to irradiate a tumor. In brachytherapy, a physician typically implants several radioactive seeds in or around a tumor, thereby providing a higher radiation dose to the tumor than would be possible with external beam radiation therapy. Careful placement of the radioactive seeds is critical to allow for localized and precise irradiation of the tumor. 
         [0004]    Cervix applicators using radiation in the treatment of cervical cancer have been in existence since the discovery of Radium in the early 19th century. Historically, Radium sources (sealed sources) were placed in ovoids attached to tubes and thereafter inserted “manually” into vaginal or intrauterine cavities for the treatment of cancer. The insertion of the applicator was associated with significant radiation exposure to the physicians handling the apparatus. 
         [0005]    Henschke et al. at Memorial Hospital in New York are believed to have introduced the “Afterloading Technique” in 1960, in which applicators are inserted first and the radioactive materials thereafter. Other isotopes, such as cesium-137 and iridium-192 sources have slowly replaced Radium. Cervix applicators have been developed in many different versions, and one widely accepted today is the Fletcher-Suit-Delclos (FSD) applicator. This applicator consists of two lateral ovoids and one central tandem. The ovoids can be spread laterally and fixed in place. The tandem is floating, and packing is required. Applicators in use today are considered “manual afterloading applicators.” 
         [0006]    In the early 1980s, High-Dose-Rate (HDR) Remote Afterloading is believed to have been introduced in the United States. These units provided greater protection from radiation exposure to staff and personnel. Applicators were inserted “cold” in specially shielded rooms, and the radioactive sources were inserted “remotely” from control consoles located outside the treatment room. The HDR break-through featured sealed sources much smaller in size than radium or cesium sources and opened new treatment possibilities and with it new opportunities in applicator designs. 
         [0007]    A potential difficulty that remains with cervical brachytherapy applicators is that a GYN applicator inserted into the uterus or the vaginal cavity may have a tendency to dislocate, e.g., by internal muscular pressure which could result in serious consequences and misadministrations during high-dose-rate (HDR) irradiation. 
         [0008]    Thus, it is desirable to provide a method to retain the position of the brachytherapy applicator during irradiation. 
         [0009]    Further it is desirable to provide a device for retaining the position of the applicator that is ergonomic, easy to operate, effective, and easily cleaned and sanitized. 
       SUMMARY 
       [0010]    In accordance with example embodiments of the present invention, a method to retain the position of an applicator during irradiation is accomplished by attaching a perineal bar or retainer body to the applicator, wherein the perineal bar is then held in place via straps looped through, e.g., four access holes and around the patient&#39;s torso. Example embodiments also include a vertically accessible locking and adjustment mechanism for locking and/or adjusting the position of the applicator with respect to the perineal bar or retainer body. 
         [0011]    A vertically accessible locking/adjusting mechanism is advantageous in comparison to side-locking mechanisms. For example, heavy patients with heavy thighs may be problematic when trying to manipulate screws or knobs laterally. The thighs may get in the way and obstruct access to the locking screws. Thus the vertical locking mechanism provides desirable benefits with regard to accessibility and ergonomics. 
         [0012]    In accordance with example embodiments of the present invention, the vertical locking screw when tightened, lifts a tapered fork (resembling a tuning fork) and simultaneously squeezes a polymeric component together which then clamp onto, e.g., two parallel tubes of the applicator, which may correspond to, e.g., a tandem and a ring tube. 
         [0013]    The locking screw may be rotatable about an axis that is at least one of (a) substantially coplanar with the longitudinal axes of the two parallel tubes, (b) substantially parallel to the plane containing the longitudinal axes of the two parallel tubes, and/or (c) substantially perpendicular to the longitudinal axes of the two parallel tubes. 
         [0014]    In accordance with example embodiments of the present invention, a device for retaining a brachytherapy applicator includes a perineal retainer body configured to receive and clamp the applicator, the retainer body being configured to form a positive stop with the perineum of a patient when the applicator is clamped by the retainer body and inserted into the patient, a locking bracket movable between a first position and a second position with respect to the retainer body, the locking bracket configured to exert a clamping force to clamp the applicator when the locking bracket moves from the first position to the second position, and an actuator configured to move the locking bracket between the first position and the second position. 
         [0015]    The movement of the locking bracket between the first and second positions may be along a line that substantially falls in a plane containing the anteroposterior axis and the dorsoventral axis of the patient when the clamped applicator is inserted into the patient. 
         [0016]    The actuator may be manually accessible in a direction substantially falling along the plane containing the anteroposterior axis and the dorsoventral axis of the patient when the clamped applicator is inserted into the patient. 
         [0017]    The actuator may be a lead screw forming a threaded connection with the locking bracket. 
         [0018]    The locking bracket may have a camming surface configured to slide across a respective camming surface of the retainer body as the locking bracket is moved from the first position to the second position. 
         [0019]    The device may be configured to clamp two parallel tubes of the applicator, which may correspond to, e.g., a tandem and a ring tube. 
         [0020]    The locking bracket may be configured to move with respect to the retainer body along an axis that is at least one of (a) substantially coplanar with the longitudinal axes of the two parallel tubes, (b) substantially parallel to the plane containing the longitudinal axes of the two parallel tubes, and/or (c) substantially perpendicular to the longitudinal axes of the two parallel tubes. 
         [0021]    Example embodiments of the present invention are described in more detail below with reference to the appended Figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIGS. 1 and 2  are perspective views of a perineal retainer attached to a CT compatible HDR ring and tandem applicator. 
           [0023]      FIG. 3  shows the perineal retainer of  FIG. 1  in an open state. 
           [0024]      FIG. 4  shows the perineal retainer of  FIG. 1  with the locking bracket and locking screw removed from the retainer body. 
           [0025]      FIGS. 5 and 6  show the perineal retainer of  FIG. 1  in open and closed states, respectively. 
           [0026]      FIG. 7  shows a lock screw tool configured to convert the perineal retainer of  FIG. 1  between the open state and the closed state. 
           [0027]      FIGS. 8 and 9  sequentially illustrate the assembly of the perineal retainer of  FIG. 1 . 
           [0028]      FIGS. 10 and 11  sequentially illustrate the attachment and securement of the perineal retainer of  FIG. 1  to the HDR ring and tandem applicator of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIGS. 1 and 2  are perspective views of an assembly  5  of a perineal retainer  100  attached to a CT compatible high dosage radiation (HDR) ring and tandem applicator  200  according to an example embodiment of the present invention. Although a specific applicator  200  is described in connection with the illustrated embodiment, it should be understood that any suitable applicator may be provided. For example, any applicator described in U.S. Pat. No. 7,666,130, which is hereby incorporated by reference in its entirety, may be provided for the applicator  200 . 
         [0030]    It noted that  FIG. 2  shows the assembly  5  supported on a support cone for purposes of illustration. However, the cone does not form part of the assembly  5 . 
         [0031]    The perineal retainer  100 , which is described in greater detail below, is provided as an accessory to an HDR ring and tandem applicator  200 , such as the Mick CT Compatible HDR Ring and Tandem Applicator (e.g., the 32 mm set) commercially available from Mick Radio-Nuclear Instruments, Inc. of Mt. Vernon, N.Y. The general purpose of the perineal retainer is to retain the ring and tandem applicator in the patient to the required depth and to avoid applicator slippage in the patient. It is generally intended for use where high dose rate (HDR) radiation is an accepted clinical practice in the treatment of the cervix and the urethra. 
         [0032]    The perineal retainer  100  may be reusable in its entirety and may be properly cleaned and sterilized prior to every use. For example, the perineal retainer  100  may be autoclaved repeatedly without any substantial alteration and/or damage to the physical structure and mechanical properties of perineal retainer  100 . It should be understood, however, that retainer may be, in whole or in part, disposable. 
         [0033]    The perineal retainer  100  includes a body (or “Butterfly”)  110  that may be affixed to the patient&#39;s body by any appropriate mechanism, e.g., suturing, strapping, and/or any other preferred methods or mechanism. Such securement of the perineal retainer  100  may be advantageous to prevent slippage of the applicator  200 , which is supported by the perineal retainer  100 , with respect to the patient&#39;s body from the predetermined applicator position. When affixed, the perineal retainer  100  according to the example embodiment contacts the perineum of the patient to basically form a positive stop to prevent over-insertion of the applicator  200  beyond its predetermined position in the patient&#39;s body. Similarly, the securement of the perineal retainer  100  to the patient&#39;s body (e.g., via straps, etc.) prevents unintended retraction of the applicator  200  from its predetermined position in the patient&#39;s body. That is, the securement holds the perineal retainer  100  against the patient&#39;s body. 
         [0034]    To facilitate strapping of the perineal retainer  100  to the patient&#39;s body, the perineal retainer body  110  includes strapping attachment provisions in the form of four apertures  115  configured to receive respective end loops of one or more strap members configured to, e.g., extend around the patient&#39;s body. 
         [0035]    The HDR ring and tandem applicator  200 , which is supported by the perineal retainer  100 , includes ring  205 , ring support tube  210 , central tandem  215 , and universal connector  220 . The ring applicator  200  is designed for insertion into a cervix, generally after the cervix has been dilated through the use of an appropriate pharmaceutical. After ring applicator  200  has been inserted into the cervix, radiation is provided, e.g., from iridium-192, at ring  205 . 
         [0036]    The universal connector  220  (a coupling device) connects ring support tube  210  and central tandem  215 . The distal end of ring support tube  210  is connected to ring  205  to support ring  205  in a predetermined location relative to ring support tube  210 . Universal connector  220  includes lock nut  221  so that the relative positioning of the ring  205  and tandem  215  may be provided and secured. Central tandem locator  216  is formed as a part of central tandem  215  and connects to universal connector  220 . Central tandem locator  216  positions central tandem  215  such that central tandem end section  217  is central (or concentric) to ring  205 . Central tandem  215  may be, for example, rigidly attached to universal connector  220  such that central tandem  215  does not “float.” A radiation dose is deliverable, e.g., via an HDR after loader, to a cervical wall by the HDR ring  205 . 
         [0037]    Support brackets  235  and  240  are provided to maintain the relative positioning between the central tandem end section  217  and HDR ring  205  by forming rigid supports between the ring support tube  210  and the central tandem  215 . 
         [0038]    Interface connector  212  and tandem interface connector  218  provide for connecting applicator  200  to, e.g., an HDR afterloader. Interface connector  212  and tandem interface connector  218  may be compatible with all HDR afterloaders. The connectors  212 ,  218  may be identical, or each connector  212 ,  218  may be different so that the connectors  212 ,  218  are connectable only to a corresponding connector of the afterloader, e.g., to avoid misconnections to the afterloader. 
         [0039]    Although ring  205  is provided as a single monolithic portion, the ring  205  may be provided as any number of split portions. For example, adjustable split ring tubes, such as provided in U.S. Pat. No. 7,666,130, which is incorporated herein its entirety by reference thereto, may be provided. Further, the portion  205  may form different shapes than a ring. 
         [0040]    The applicator  200  also includes a rectal retractor  230 . Rectal retractor  230  is attached to the remainder of the applicator  200  through universal connector  220 . Rectal retractor  230  is inserted vaginally. Rectal retractor  230  may be adjusted to exert a force on a rectum and may be locked in place. The adjustment may be made via handle portion  231  of retractor shaft  232  of the retractor  230 . The shaft  232  is also supported by the universal connector  220 . 
         [0041]    In order to support the applicator  200  in its fixed position relative to the patient&#39;s cervix, the perineal retainer  100  includes a slot  120  formed between two adjacent wings  125  of the perineal retainer body  110 . The slot  120  includes a clamping region  121  configured to receive and clamp ring support tube  210  and central tandem  215 , thereby securing the applicator  200  in its predetermined position when the perineal retainer  100  is secured to the patient&#39;s body. 
         [0042]    The slot  120  also includes an enlarged region  122  below the clamping region, which extends to the open lower end of the slot  120 . The enlarged region  122  of the slot  120  is configured to (a) allow ease of passage of the ring support tube  210  and the central tandem  215  during assembly, since the enlarged portion  122  is dimensioned to allow clearance and/or reduced friction in comparison to the clamping portion  121  when the perineal retainer  100  is in an open (or unclamped) state, and (b) allow movement of the rectal retractor shaft  232  along the slot even when the perineal retainer  100  is in a closed (or clamped) state, thereby allowing the operator to manipulate the rectal retractor  230  relative to the ring  205  and tandem  215  when the applicator  200  and perineal retainer  100  are secured in the predetermined position relative to the patient. 
         [0043]    In order to secure the ring support tube  210  and the central tandem  215  relative to the perineal retainer body  110 , the perineal retainer  100  is adjusted from the open state to the closed state. In the illustrated example, the mechanism for doing so involves an interface between the perineal retainer body  110 , locking bracket  140 , and locking screw  180 . 
         [0044]    Referring, e.g., to  FIGS. 3 and 4 , the locking bracket  140  is rigid and generally shaped as an inverted (or upside-down) U-shaped member having a camming channel  145  formed between two opposed camming projections  150 , which form a raised portion of the perineal retainer body  110 . When the perineal retainer  100  is assembled, the camming channel  145  receives projections  130 , each of which extends transversely from the downward extension of a respective wing  125 . Thus, the projections  130  extend outwardly from wings  125  in a direction generally aligned with the direction of insertion of the applicator  200  into the patient. 
         [0045]    The locking screw  180  includes a head portion  185  connected to a shaft having a threaded locking bracket engagement portion  190  and a perineal retainer body engagement portion  195 . When the perineal retainer  100  is assembled, the external threads of the locking bracket engagement portion  190  engage corresponding internal threads of a bore of the locking bracket  140  through which the shaft  187  extends. Further, the perineal retainer body engagement portion  195 , which has an enlarged diameter in comparison to the reduced diameter portion  198 , is received and axially constrained, but allowed to rotate, by a pair of opposed slots or grooves  138  in respective projections  130 . Further, in the assembled state of the perineal retainer  100 , the locking bracket  140  is slidable with respect to the perineal retainer body  110  generally along the axis of the locking screw  180 . To secure the locking bracket  140  while allowing slidability, the locking bracket  140  includes two opposed guide elements, each in the form of a pair of mounting pins  155 , which may be provided, e.g., by pressing the pins  155  into corresponding bores in the camming projections  150 . 
         [0046]    Since the locking bracket  140  is prevented from rotating about the axis of the locking screw  180 , rotation of the locking screw  180  about its axis with respect to the perineal retainer body  110  also results in a corresponding rotation of the locking screw  180  about its axis with respect to the locking bracket  140 . Thus, rotation of the locking screw causes a linear translation of the locking screw  180  and the locking bracket  140  with respect to each other due to the threaded engagement between the threaded portion  190  of the shaft  187  of the locking screw  180  and the internal threads of the corresponding bore in the perineal retainer body  110 . Further, since the enlarged perineal retainer body engagement portion  195  is axially constrained in notches or slots  138  of the perineal retainer body  110 , the relative translation between the locking bracket  140  and the locking screw  180  results in a corresponding translation between locking bracket  140  and the perineal retainer body  110 . 
         [0047]    Thus, in the assembled state of the perineal retainer  100 , rotation of the locking screw  180  in a first rotational direction, e.g., clockwise, causes translation of the locking bracket  140  in a first direction  141 , and rotation of the locking screw in a second, opposite rotational direction, e.g., counter-clockwise, causes translation of the locking bracket  140  in a second direction  142  opposite the first direction  141 . 
         [0048]      FIGS. 3 and 5  show the perineal retainer  100  in its open state, with the locking bracket  140  in its lowermost position relative to the perineal retainer body  110 . Thus, relative to the locking bracket  140 , the locking screw  180  is in its uppermost position. 
         [0049]      FIG. 6  shows the perineal retainer  100  in its closed state, with the locking bracket  140  in its uppermost position relative to the to the perineal retainer body  110 . Thus, relative to the locking bracket  140 , the locking screw  180  is in its lowermost position. 
         [0050]    Accordingly, when the locking screw  180  is rotated about its axis in the first rotational direction, the perineal retainer  100  may be transitioned from its open state to its closed state. Likewise, when the locking screw  180  is rotated about its axis in the second rotational direction, the perineal retainer  100  may be transitioned from its closed state to its open state. 
         [0051]    Movement of the locking bracket  140  in the first direction  141  causes camming surfaces  152  of the locking bracket  140  to translate in the first direction  141  with respect to the respective camming surfaces  132  of the projections  130  of the perineal retainer body  110 . The camming surfaces  152  of locking bracket  140  are in contact with the camming surfaces  132  of the perineal retainer body  110  during the translation of the locking bracket  140  relative to the perineal retainer body  110 . Further, the camming channel  145  is tapered such that the trailing portions of the camming surfaces  152  are closer together than the leading portions of the camming surfaces  152  during movement of the locking bracket  140  in the first direction. Thus, movement of the locking bracket  140  in the first direction from the open position to the closed position causes the camming surfaces  132  of the of the perineal retainer body  110  to be pressed inwardly toward each other as the camming surfaces  152  slide therealong. In this regard, the camming surfaces  152  act as cams, and camming surfaces  132  act as cam followers in response to movement of the camming surfaces  152 . 
         [0052]    This inwardly directed force, in directions  126 ,  127 , causes the clamping portion  121  of the slot  120  of the perineal retainer body  110  to narrow as the locking bracket is translated in the first direction with respect to the perineal retainer body  110 . Thus, when the perineal retainer is in the open state, the ring support tube  210  and the central tandem  215  are relatively easily slidable into their predetermined positions in the clamping portion  121  of the slot  120 . Once the ring support tube  210  and the central tandem  215  are in their predetermined positions, the locking screw  180  may be rotated in the first rotational direction to cause the clamping portion  121  to narrow and constrict to apply a laterally directed clamping pressure on the ring support tube  210  and the central tandem  215 , thereby locking or securing the ring support tube  210  and the central tandem  215  in their predetermined positions relative to the perineal retainer  100 . 
         [0053]    Similarly, rotation of the locking screw in the second rotational direction allows the clamping portion  121  of the slot  120  to expand, thereby removing the clamping force in order to release the ring support tube  210  and the central tandem  215  from their locked or secured position. As indicated above, the camming channel  145  is tapered. Thus, when the locking bracket  140  is moved in the second direction  142  from its closed position to its open position, the trailing portions of the camming surfaces  152  are further apart than the leading portions of the camming surfaces  152 . Thus, movement of the locking bracket  140  in the second direction  142  from the open position to the closed position allows the camming surfaces  132  of the perineal retainer body  110  to expand outwardly away from each other as the camming surfaces  152  slide therealong. Contact between the camming surfaces  132  and  152  may be maintained during this expansion of the clamping portion  121  due to e.g., internal spring force in the wings  125  and/or outward force exerted by the ring support tube  210  and/or central tandem  215 . 
         [0054]    Because the areas of contact between the camming surfaces  132  and the camming surfaces  152  expands along the entire length of the clamping portion  121 , an even clamping pressure and force distribution is provided along the length of the clamping portion  121  of slot  120 . Thus, it is ensured that both the ring support tube  210  and the central tandem  215  are securely clamped in their predetermined positions. 
         [0055]    Further facilitating the evenness of the clamping pressure and force distribution along the length of the clamping portion  121  is that the wings  125  are able to move in a parallel manner (or without substantial rotation) in the region of the clamping region  121  during the contraction of the clamping portion. To facilitate this feature, the slot  120  of perineal retainer  100  extends into an enlarged cutout  123  configured to increase the flexibility of the wings  125  by reducing the material structure in the upper portion of the perineal retainer body  110  above the wings  125 . 
         [0056]    Although the illustrated example shows the clamping of two structures  210 ,  215 , it should be understood that any number of structures, including a single structure or more than two structures may be clamped in the clamping portion  121 . Further, although the clamping portion  121  is a single continuous portion, it should be understood that the clamping portion  121  may be provided at multiple separate locations along the slot  120 . 
         [0057]    Although the locking bracket  140 , which is made of a strong material, e.g., titanium, is sufficiently rigid to maintain the inward clamping force on the perineal retainer body  110  despite the open U-shaped configuration, it should be understood that other configurations may be provided. For example, the locking bracket  140  may be formed in a non-U-shaped structure or a support member may be provided, e.g., near the open end of the U-shaped structure. 
         [0058]    Referring, e.g., to  FIG. 3 , the range of movement  146  of the locking bracket  140  relative to the perineal retainer body  110  is bounded by a positive stop formed between the upper portion of the camming channel  145  of the locking bracket  140  and the upper portion of the projections  130  of the perineal retainer body  110 . It should be understood, however, that the limits of the movement of the locking bracket  140  relative to the perineal retainer body  110  may be provided by any other suitable mechanism(s). Further, during use, the upper translation limit of the locking bracket  140  may be determined by the positive stop mentioned above and/or frictional resistance due to increased clamping force between the camming surfaces  132 ,  152 . 
         [0059]    Rotation of the locking screw  180  in the first and second rotational directions may be performed using a lock screw tool  300 , illustrated, e.g., in  FIG. 7 . The lock screw tool  300  includes a handle  305  formed of, e.g., an autoclavable material, and a driving shaft  310  formed of, e.g., stainless steel(s), which is also autoclavable. Thus, the lock screw tool  300  is, as an entire unit, autoclavable. The driving shaft  310  extends from the handle to the driving interface or connector  315  that is keyed (e.g., as a hexagonal or other keyed structure) to a driving receptacle  186  in the head portion  185  of the locking screw  180 , which is configured to receive the driving connector  315  in order to allow rotation of the locking screw  180  via rotation of the handle  305  of the lock screw tool  300 . It should be understood, however, that any suitable mechanism for rotating the locking screw  180  may be provided. For example, a ratcheting driving mechanism and/or a manual thumb screw may be provided. 
         [0060]      FIGS. 8 and 9  sequentially illustrate the assembly of the perineal retainer  100 . As illustrated in  FIG. 8 , the locking bracket  140  is mounted onto the perineal retainer body  110  by inserting the mounting pins  155  at the bottom of the locking bracket  140  into grooves  135  of the raised section, corresponding to projections  130 , of the perineal retainer body  110 . This is performed easily by pinching together, e.g., manually, the two wings  125  at the bottom of the perineal retainer body  110 . The user may then ensure that the locking screw  180  is fully “extended” such that the locking screw  180  is in its uppermost position relative to the locking bracket  140  such as when the locking bracket  140  is in its fully open position in the assembled perineal retainer  100 . 
         [0061]    Referring to  FIG. 9 , to complete the assembly, the user ensures that the short threaded section  195 , which is the perineal retainer body engagement portion  195 , of the locking screw  180  is inserted in the oval-shaped notch  138  in the top of the raised section  130 , corresponding to projections  130 , of the perineal retainer body  110 . The user may then again ensure that the locking screw  180  is still “fully” extended, thus ensuring that the assembled perineal retainer  100  is in its open state. 
         [0062]    It is noted that the perineal retainer body engagement section  195  of the locking screw  180  is threaded in order to allow the section  195 , which is enlarged with respect to reduced diameter portion  198  of the shaft  187 , to be passed through the internally threaded bore of the locking bracket  140  by rotating the threaded connection until the section  195  disengages the internal threads of the bore. Further axial extension then allows engagement of the threads of the threaded locking bracket engagement portion  190  to engage the internal threads of the bore. This arrangement may facilitate manufacture of the locking screw, since a continuously threaded shaft may be machined, e.g., on a lathe, to form the reduced diameter portion  198 , to thereby also delineate the portions  190  and  195  adjacent the reduced diameter portion  198 . It should be understood, however, that any suitable manufacturing process may be provided and that the perineal retainer body engagement portion  195  may be provided without threads and/or be of a different diameter than the threaded locking bracket engagement portion  190 . 
         [0063]    It is further noted that, while the lower portion the locking bracket  140  is maintained secured by the engagement of mounting pins  155  in grooves  135 , the upper portion is secured in its installed position via the engagement of the reduced diameter portion  198  of the locking screw  180  with the perineal retainer body portion  195 . In particular, the reduced diameter portion  198  is pressed between two opposed grooves (extending in the general direction of the longitudinal axis of the locking screw  180 ) in the perineal retainer body portion  195 , whereby the grooves partially encircle the reduced diameter portion  198  such that the reduced diameter is pushed and snapped into place between the grooves in the manner of a detent. If should be understood, however, than any suitable securement mechanism may be provided. 
         [0064]      FIGS. 10 and 11  sequentially illustrate, respectively, the attachment and securement of the perineal retainer  100  to the HDR ring and tandem applicator  200 . Referring to  FIG. 10 , the user slides the assembled perineal retainer  100  in its open state, as shown, vertically down over the tandem  215  and ring tube  210  as close as possible to the ring and tandem connecting bracket  235 . The user may then ascertain that the perineal retainer  100  is all the way down and seated on top of the ring tube  210 . At this stage, the locking screw  180  may still be extended. 
         [0065]    Referring to  FIG. 11 , to secure the perineal retainer  100  to the applicator  200 , the user inserts the lock screw tool  300  into the socket or driving receptacle  186  of the screw and turn it in the first rotational direction, e.g., clockwise, all the way to a positive stop. At this stage, the perineal retainer  100  is fixed to the applicator  200 . The user may ascertain that the perineal retainer  100  is attached “firmly” and that it cannot be displaced or slide along the applicator tubes  210 ,  215 . 
         [0066]    After securement of the perineal retainer  100  to the applicator  200  in accordance with  FIG. 11 , the perineal retainer  100  may be strapped to the patient such that the assembly  5  causes proper predetermined placement of the ring  205  and end portion  217  of the central tandem  215 . 
         [0067]    Because of, e.g., the curvature of the perineal retainer  100 , an ergonomic and effective locating mechanism is provided. For example, referring to  FIG. 3 , side edges  111  have an ergonomic curved profile that facilitates placement of the perineal retainer body  110  between the patient&#39;s thighs. Further, referring to the side view of  FIG. 2 , the perineal retainer body has a concave shape that more comfortably and easily fits the sloping and curved profile of the patient&#39;s perineum. 
         [0068]    It is noted that the materials of which the components of the perineal retainer  100  are formed facilitate cleaning and sterilization, among other desirable properties. In this regard, the perineal retainer body  110  is a single monolithic piece formed of PPSU (polyphenylsulfone) material, and the locking bracket  140  and the locking screw  180  are each formed, respectively, as a single monolithic piece of titanium. It should be understood however, any one or more, or all, of the three components  110 ,  140 ,  180  may be formed of different material(s) and/or be formed from multiple constituent components. 
         [0069]    Prior to sterilization, the perineal retainer  100  may be thoroughly cleaned. Using an enzymatic detergent (e.g., Terg-A-Zyme®, MicroZyme™, or equivalent), the perineal retainer  100  may be soaked, e.g., for not less than ten (10) minutes. The perineal retainer  100  may then be transferred to an ultrasonic cleaner containing, e.g., clean enzymatic detergent. It may be desirable to not allow the components of the perineal retainer  100  to dry. The cleaner may be run for, e.g., (10) minutes. The perineal retainer  100  may then be rinsed thoroughly, e.g., three times, using sterile water, and the components of the perineal retainer  100  may be allowed to thoroughly dry before packaging for sterilization. 
         [0070]    Sterilization of the perineal retainer  100  may be provided via an autoclave. For example, the perineal retainer  100  may be exposed to the following steam cycle: 
         [0071]    2.1 Temperature: 132° C. (Gravity Displacement). 
         [0072]    2.2 Exposure Dwell: 10 minutes. 
         [0073]    2.3 Drying: 15 minutes. 
         [0074]    Thus, the perineal retainer  100  is easily cleanable and sterilizable. 
         [0075]    Although the present invention has been described with reference to particular examples and exemplary embodiments, it should be understood that the foregoing description is in no manner limiting. Moreover, the features described herein may be used in any combination.