Abstract:
A waveguide for a radio frequency door like that used in a medical imaging room allows intravenous lines and electrical conduits to be inserted through the door frame without being disconnected from the patient. The waveguide includes a door frame section, and a removable, telescoping or pivoting movable member that cooperates with the door frame section to retain the conduits. The movable member is positioned away from the door frame section during insertion and removal of the conduits from the door frame section, and is positioned adjacent the door frame section when the conduits are being retained. The dimensions and materials of the waveguide are selected to achieve attenuation of electromagnetic interference.

Description:
RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application No. 61/138,799 filed on Dec. 18, 2008, which is incorporated by reference herein. 
    
    
     BACKGROUND 
     The present invention relates to waveguides, and more particularly it relates to waveguides for radio frequency doors and frames. 
     Medical facilities, laboratories, and other facilities may have specially constructed rooms that are used for conducting procedures or operating equipment that is sensitive to environmental radio frequency interference. These rooms can be used for magnetic resonance imaging or other applications where environmental radio frequencies could impede performance of the equipment. Generally, these specially constructed rooms are designed to prevent or attenuate environmental radio frequency interference from entering or leaving the room. Environmental radio frequency interference can come from any number of sources, such as television and radio signals, power equipment, monitors, fluorescent lights, computers, other medical equipment, and the like. 
     Part of the specialized construction for these rooms includes special doors and door frames that are designed to prevent or attenuate environmental frequencies from entering or leaving these rooms. Typically, these types of doors and door frames do not contain any apertures or penetrations that could allow electromagnetic radiation to leak into or out of the room and are provided with a gasket positioned between the door and the door frame such that a seal is formed that prevents or attenuates radio frequency transmission from passing between the door and the door frame. 
     In some situations, the radio frequency door may need to be closed when a patient is inside the room. For example, the patient may require certain test procedures (e.g., magnetic resonance imaging). When the patient is ill, the patient may be connected to medical equipment, intravenous (IV) lines, or other conduits. At times, the medical equipment and supporting stations (e.g., carts, IV stands, etc.) remain outside the room during the procedure. Thus, the patient may need to be disconnected from the medical equipment, IV lines, and other conduits before the radio frequency door may be closed. This is undesirable in most cases because, for example, the medical equipment may be performing life sustaining functions or the IV lines may be providing medication to the patient. 
     SUMMARY 
     One construction of the invention provides a waveguide for an MRI (Magnetic Resonance Imaging) scan room. The waveguide includes a door frame section and a movable member configured to be disposed in a first position in which the movable member cooperates with the door frame section to retain the conduit. The movable member is also configured to be disposed in a second position sufficiently spaced from the door frame section so that the conduit may be at least one of placed adjacent to the door frame section and removed from the waveguide. 
     The movable member be pivotable attached to the door frame section, so that it is swung away from the door frame section when the conduit is being inserted or removed from the waveguide, but is positioned in a slot in the door frame section when the conduits are retained in one or more recesses in the waveguide. Alternatively, the movable member may be attached by one or more telescoping members configured to retract into or extend from the door frame section. The movable member may also be a movable block connected to the door frame section by a tether. The block is moved away from the door frame section before the insertion or removal of the conduit, and is place adjacent the door frame section to retain the conduit during a medical imaging procedure. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a frame and a radio frequency (RF) door illustrating possible locations of a waveguide according to the present invention. 
         FIG. 2  is a perspective view of a waveguide according to the present invention that includes a door frame section and a movable member positioned adjacent the door frame section. 
         FIG. 3  is a perspective view of the waveguide of  FIG. 2 , with the movable member spaced from the door frame section. 
         FIG. 4  is a perspective view of a second construction of a waveguide according to the present invention that includes a telescoping member, with the movable member spaced from the door frame section. 
         FIG. 5  is a perspective view of a third construction of a waveguide according to the present invention that includes two telescoping members, with the movable member spaced from the door frame section. 
         FIG. 6  is a perspective view of a fourth construction of a waveguide according to the present invention that includes a sliding mechanism, with the movable member positioned adjacent the door frame section. 
         FIG. 7  is a perspective view of the waveguide of  FIG. 6 , with the movable member positioned partially within a cavity in the door frame section. 
         FIG. 8  is a perspective view of the waveguide of  FIG. 6 , with the movable member spaced from the door frame section and positioned substantially within the cavity in the door frame section. 
         FIG. 9  is a perspective view of a fifth construction of a waveguide according to the present invention that includes a door frame section formed integrally as one piece with the frame and a movable member formed integrally as one piece with the door. 
         FIG. 10  is a perspective view of the waveguide of  FIG. 9 , with the movable member spaced from the door frame section. 
         FIG. 11  is a perspective view of a sixth construction of a waveguide according to the present invention that includes a sliding mechanism similar to the sliding mechanism of  FIGS. 6-8 , with the movable member positioned adjacent the door frame section. 
         FIG. 12  is a perspective view of the waveguide of  FIG. 11 , with the movable member positioned partially within a cavity in the door frame section. 
         FIG. 13  is a perspective view of the waveguide of  FIG. 11 , with the movable member spaced from the door frame section and positioned substantially within the cavity in the door frame section. 
         FIG. 14  is a perspective view of a seventh construction of a waveguide according to the present invention similar to the waveguide of  FIGS. 2 and 3 , with the insert and movable member spaced from the door frame section. 
         FIG. 15  is a perspective view of the waveguide of  FIG. 14 , with the insert and movable member spaced from the door frame section. 
         FIG. 16  is a perspective view of the waveguide of  FIG. 14 , with the insert and movable member positioned adjacent the door frame section. 
         FIG. 17  is a perspective view of an eighth construction of a waveguide for a right hand door, having two pivotable movable members positioned adjacent the door frame section. 
         FIG. 18  is a perspective view of the waveguide of  FIG. 17 , depicting one of the pivotable movable members spaced from the door frame section. 
         FIG. 19  is an exploded view of the waveguide of  FIG. 17 . 
         FIG. 20  is a perspective view of a waveguide similar to  FIG. 18 , but for a left hand door. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       FIG. 1  illustrates possible locations in a radio frequency (RF) door  20  and frame  24  for a waveguide  28 ,  32 ,  36 ,  40 ,  44 ,  112 ,  120  ( FIGS. 2-10 ) according to the present invention. The RF door  20  and frame  24  are constructed of materials that minimize the passage or transmission of radio waves through the door  20  and the frame  24 . For example, the RF door  20  and frame  24  may be constructed from a metal alloy, aluminum or other non-ferrous materials, steel or other ferrous materials, and the like. 
     The door  20  is connected to the frame  24  by one or more hinges (not shown). Accordingly, the door  20  can be moved through a variety of positions with respect to the frame  24  to selectively allow passage through the door frame  24 . For example, the door  20  can be positioned in a variety open positions with respect to the door frame  24 , where varying levels of electromagnetic interference can pass between the door  20  and the frame  24 . The door  20  also has a closed position where the passage of electromagnetic interference of 0-150 MHz between the door  20  and the door frame  24  is substantially prevented or highly attenuated. In other constructions, frequencies in the range of 0-750 MHz may be substantially prevented or highly attenuated. Of course, the range may be extended to include higher frequencies to reflect advances in MRI technology. 
     The frame  24  is positioned to surround four sides of the door  20  when the door  20  is in the closed position and includes a threshold  26  of the door  20 . The frame  24  further includes a strike plate (not shown) that directly opposes a latch (not shown) and door handle  48  when the RF door  20  is in the closed position. The strike plate may be part of a door closing mechanism. An example of a door closing mechanism including a retractable latch and strike plate that may be used in combination with the present invention is described in U.S. Pat. No. 7,448,165, issued Nov. 11, 2008, which is incorporated herein by reference. 
     As shown in  FIG. 1 , the waveguide  28 ,  32 ,  36 ,  40 ,  44 ,  112 ,  120  ( FIGS. 2-10 ) may be positioned anywhere along the door frame  24 . In preferred constructions, the waveguide  28 ,  32 ,  36 ,  40 ,  44 ,  112  is positioned anywhere along the strike side of the door frame  24 . The waveguide  28 ,  32 ,  36 ,  40 ,  44 ,  112 ,  120  allows at least one conduit  52  (see  FIG. 5 ) to pass through at least one of the door  20  and the frame  24  while still attenuating or substantially preventing the passage of electromagnetic radiation of 0-150 MHz into or out of the room. The conduit  52  may be an intravenous (IV) line, tube, cable, etc. and may be attached to a patient. The conduit  52  should be composed of non-conductive materials. The waveguide  28 ,  32 ,  36 ,  40 ,  44 ,  112 ,  120  may be positioned along the strike side of the door frame  24  in a position that is easily accessible to medical personnel and does not cause undo stress on the conduit  52  when positioned in the waveguide  28 ,  36 ,  40 ,  44 . For example, the waveguide  28 ,  36 ,  40 ,  44 ,  112 ,  120  may be located slightly below the strike plate such that is it approximately at the waist level of a normal person. In other constructions, the waveguide  28 ,  32 ,  36 ,  40 ,  44 ,  112 ,  120  may be positioned along the threshold  26  of the door frame  24  or a different side of the door frame  24 . 
     As illustrated in  FIGS. 2 and 3 , one construction of the waveguide  28  includes a door frame section  56  and a movable member  60 . The door frame section  56  may be formed as a separate piece from the door frame  24 . The door frame section  56  includes a slot  64  (see  FIG. 3 ) into which an insert  66  may be permanently attached by welding, adhesive, fasteners, etc. Alternatively, insert  66  could be eliminated so that recesses  68 ,  72  are formed in the frame  24 . The door frame section  56  includes first and second semi-cylindrically shaped recesses  68  and  72 . The first and second recesses  68 ,  72  each have a length L 1  that is approximately equal to the thickness of the door frame section  56 . The first recess  68  has a maximum depth D 1 , and the second recess  72  has a maximum depth D 2 . In other constructions, the door frame section  56  may contain no recesses or a different number of recesses. If the door frame section  56  does not have a recess, then movable member  60  should have a recess. Of course, in other constructions, the recesses may be shaped or oriented differently. 
     In  FIG. 2 , the movable member  60  is positioned within the slot  64  in the door frame section  56  such that it is positioned adjacent to insert  66 . In  FIG. 3 , the movable member  60  is spaced from the door frame section  56 . The movable member  60  is shaped such that the contour of the door frame section  56  is substantially the same when the movable member  60  is positioned adjacent the door frame section  56  as the adjacent surfaces of the door frame. 
     The movable member  60  includes third and fourth semi-cylindrically shaped recesses  76  and  80 . The third and fourth recesses  76 ,  80  each have a length L 2  that is approximately equal to the length of the movable member. The third recess  76  has a maximum depth D 3 , and the fourth recess  80  has a maximum depth D 4 . In other constructions, the movable member  60  may contain no recesses or may contain a different number of recesses. If the movable member  60  does not have a recess, then door frame section  56  should have a recess. Of course, in other constructions, the recesses may be shaped or oriented differently. 
     A tether  84  contains two ends. One end is attached to the door frame section  56  and the other end is attached to the movable member  60 . When the movable member  60  is spaced from the door frame section  56 , as shown in  FIG. 3 , the tether  84  will prevent the movable member  60  from being lost or misplaced. The tether  84  is attached near the lower portions of the door frame section  56  and the movable member  60  so it does not interfere with the waveguide  28  when a user positions a conduit  52  therein. 
     The first recess  68  and the third recess  76  are formed in the door frame section  56  and the movable member  60 , respectively, such that they oppose each other and form a first conduit retainer  88  when the movable member  60  is positioned adjacent the door frame section  56 . Similarly, the second recess  72  and fourth recess  80  oppose each other and form a second conduit retainer  92  when the movable member  60  is positioned adjacent the door frame section  56 . In other constructions, the waveguide  28  may contain a different number of conduit retainers or may contain differently shaped conduit retainers. For example, a semi-cylindrically shaped recess may be present in the movable member  60  but not in the door frame section  56 . When the movable member  60  is positioned adjacent the door frame section  56 , the recess will cooperate with the door frame section  56  to form a semi-cylindrical conduit retainer rather than a cylindrical conduit retainer as described above. If opposing recesses contain rectangular recesses, a rectangular conduit retainer may be formed when the movable member  60  is positioned adjacent the door frame section  56 . 
     The first and second conduit retainers  88 ,  92  shown in  FIGS. 2 and 3  are substantially cylindrical and have lengths L 1 , L 2  that are equal to the lengths L 1 , L 2  of the door frame section  56  and the movable member  60 . The first conduit retainer  88  has a maximum depth D 1  that is equal to the maximum depths D 1 , D 3  of the first recess  68  and the third recess  76 , and the second conduit retainer  92  has a maximum depth D 2  that is equal to the maximum depths D 2 , D 4  of the second recess  72  and the fourth recess  80 . The depths D 1 , D 2  are sized to accommodate at least one conduit  52  therein. The lengths L 1 , L 2  of the first and second conduit retainers  88 ,  92  are each at least four times greater than the depths D 1 , D 2  such that radio frequency emissions between 0-150 MHz are substantially attenuated and prevented from passing into or out of the room. The length of a hollow tube (e.g., conduit retainer) should be at least three times greater than the diameter to attenuate radio frequency emissions between 0-150 MHz (see Brewer, Ron, “Shielding: A Look at Waveguide Penetrations,”  EE Evaluation Engineering , January 2001). 
     Of course, waveguides are not limited to the attenuation of frequencies in a specific range. Equations 1-3 (see Brewer) may be used to calculate the attenuation per unit length A UL  in decibels per inch (dB/in.) for a given frequency F. Equation 2 is used to calculate the cut-off frequency F CO  if the cross-sectional shape of the waveguide is rectangular with width W in inches, and Equation 3 is used to calculate the cut-off frequency F CO  if the cross-sectional shape of the waveguide is circular with diameter D in inches. Of course equations may also be derived for calculating the cut-off frequency of other shapes of waveguides. 
     
       
         
           
             
               
                 
                   
                     
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     It is preferable for the length of the conduit retainer to be at least four times greater than the maximum depth because the 4:1 ratio will provide over 120 dB attenuation for frequencies up to approximately 9 GHz (see Brewer). In this way, a hole can be introduced in an RF shield without substantially comprising its ability to shield RF transmissions. In some constructions, the depths D 1 , D 2  are equal to 0.75 inches and the lengths L 1 , L 2  are equal to 4.5 inches. 
       FIG. 4  illustrates a second construction of a waveguide  32  in accordance with the present invention. The waveguide  32  is similar to the waveguide  28  of  FIGS. 2 and 3  except the waveguide  32  contains a telescoping member  96  instead of a tether  84 . The telescoping member  96  may be coupled to the door frame section  56  and the movable member  60  in any reasonable manner (e.g., fasteners, adhesive, welding, etc.). The telescoping member  96  is positioned such that it does not interfere with the first and second conduit retainers  68 ,  88 . The telescoping member  96  is configured to alternately retract into and extend from the door frame section  56  to position the movable member  60  adjacent to or spaced from the door frame section  56 . The telescoping member  96  is positioned near the lower edge of the waveguide  32  such that the conduits  52  ( FIG. 5 ) may be positioned in the recesses  68 ,  72 ,  76 ,  80  from the top. In other constructions, the telescoping member  96  may be positioned at different heights or at different positions along the length of the waveguide  32 . 
       FIG. 5  illustrates a third construction of a waveguide  36  in accordance with the present invention. The waveguide is similar to the waveguide of  FIGS. 2-4  except the waveguide  36  includes two telescoping members  100 ,  104 . The telescoping members  100 ,  104  may be coupled to the door frame section  56  and the movable member  60  in any reasonable manner (e.g., fasteners, adhesive, welding, etc.). The first and second telescoping members  100 ,  104  are positioned at a height between first and third recesses  68 ,  76  and the second and fourth recesses  72 ,  80 . The telescoping members  100 ,  104  are spaced along the length of the waveguide  36 . Similar to the telescoping member  96  of  FIG. 4 , the first and second telescoping members  100 ,  104  are configured to alternately retract into and extend from the door frame section  56  to position the movable member  60  adjacent to or spaced from the door frame section  56 . The conduits  52  are placed in the first conduit retainer  68  from the top and in the second conduit retainer  92  from the bottom. In other constructions, the first and second telescoping members  100 ,  104  may be positioned differently with respect to the waveguide  36 . 
       FIGS. 6-8  illustrate a fourth construction of a waveguide  40  in accordance with the present invention. The waveguide  40  is similar to the waveguide of  FIGS. 2-5  except it includes a sliding mechanism that allows the movable member  60  to slide into and out of a cavity  108  formed in the door frame  24 . The sliding mechanism may include a track coupled to the frame  24  and rollers coupled to the movable member  60  such that the rollers roll along the track as the waveguide  40  is moved into and out of the cavity  108 . In use, the user slides the movable member  60  downward into the cavity  108  in the door frame  24  to open the first and second conduit retainers  88 ,  92 . When the first and second recesses  68 ,  72  are unopposed by the third and fourth recesses  76 ,  80 , the first and second conduit retainers  68 ,  92  are open, and the conduits  52  may be positioned in one or both of the first and second recesses  68 ,  72 . The movable member  60  may be slid upward, back to the fully closed position, as shown in  FIG. 6 , to close the conduit retainers  88 ,  92  and retain the conduits  52  therein. 
     In other constructions, the sliding mechanism may operate in a different manner. For example, the movable member  60  may be spaced from the door frame member  56  by sliding the movable member  60  in a direction that is not vertical. For example, the sliding mechanism may include a cam and track that cooperate to allow the movable member to be spaced away from the door frame section  56 . 
       FIGS. 9 and 10  illustrate a fifth construction of a waveguide  44  in accordance with the present invention. The waveguide  44  contains a door frame section  56  that is formed integrally as one piece with the door frame  24 , and a movable member  60  that is formed integrally as one piece with the door  20 . First and second recesses  68 ,  72  are formed in the frame  24 , and third and fourth recesses  76 ,  80  are formed in the door  20 . The recesses  68 ,  72 ,  76 ,  80  are formed such that the first and third recesses  68 ,  76  oppose each other when the door is in a closed position ( FIG. 9 ) to form a first conduit retainer  68 . Similarly, the second and fourth recesses  72 ,  80  oppose each other when the door is in the closed position ( FIG. 9 ) to form a second conduit retainer  92 . Similar to the waveguides of  FIGS. 2-8 , the length L 3  of each of the first and second conduit retainers  88 ,  92  is at least four times greater than the maximum depth D 1 , D 2  of each of the first and second conduit retainers  88 ,  92 . 
     When the door  20  is in an open position ( FIG. 10 ), the first and second recesses  68 ,  72  do not directly oppose the third and fourth recesses  72 ,  80 . Thus, when the door is in the open position, the first and second conduit retainers  88 ,  92  are open and a conduit  52  may be positioned in one of the recesses  68 ,  72 ,  76 ,  80 . Once the conduit  52  is placed in one of the recesses  68 ,  72 ,  76 ,  80 , the door  20  may be closed to retain the conduit  52  in one of the conduit retainers  88 ,  92 . In other constructions, a different number of recesses may be formed in the door  20  or the frame  24 . Of course, the recesses may be differently shaped, sized, or positioned. 
       FIGS. 11-13  illustrate a sixth construction of a waveguide  112  in accordance with the present invention. The waveguide  112  is similar to the waveguide of  FIGS. 2-8  except the insert  66 A and movable member  60 A are oriented differently within the slot  64 A formed in the door frame section  56 A. The insert  66 A may be permanently attached to door frame section  56 A such that the insert  66 A is positioned below the movable member  60 A and the first and second recesses  68 A,  72 A face upward toward the movable member  60 A. The movable member  60 A is positioned in the slot  64 A above the insert  66 A and is oriented such that the third and fourth recesses  76 A,  80 A face downward toward the first and second recesses  68 A,  72 A, respectively. 
     The waveguide  112  includes a sliding mechanism similar to the sliding mechanism of waveguide  40  that allows the movable member  60 A to slide into and out of a cavity  116  formed in the door frame  24 A. The sliding mechanism may include a track coupled to the frame and rollers coupled to the movable member such that the rollers roll along the track as the movable member  60 A is moved into and out of the cavity. In use, the user slides the movable member  60 A upward into the cavity  116  ( FIGS. 12 and 13 ) to open the first and second conduit retainers  88 A,  92 A ( FIG. 11 ). The conduits  52  may be placed in the first and second recesses  68 A,  72 A, and the movable member  60 A may be slid downward, back to the fully closed position ( FIG. 11 ) to close the conduit retainers  88 A,  92 A and retain the conduits  52  therein. 
       FIGS. 14-16  illustrate a seventh construction of a waveguide  120  in accordance with the present invention. The waveguide  120  is similar to the waveguide  28  of  FIGS. 2 and 3  except the insert  66  is removable from the door frame section  56 . In use, the insert  66  and movable member  60  are removed from the slot  64  and are spaced apart from each other. Conduits  52  may be placed in the first and second recesses  68 ,  72 . The movable member  60  may be positioned adjacent the insert  66  to close the conduit retainers  88 ,  92  and retain the conduits  52  therein ( FIG. 15 ). The user may adjust the position of the conduits  52  within the conduit retainers  88 ,  92  by sliding the insert  66  and movable member  60  together as one unit with respect to the conduits  52  to ensure the conduits  52  are not crimped and may move freely within the conduit retainers  88 ,  92 . The insert  66 , movable member  60 , and conduits  52  may be positioned in the slot  64  of the door frame section  56 , as shown in  FIG. 16 . 
     The waveguide  120  includes optional positioning pins  124 ,  128  ( FIGS. 14 and 15 ) that are received in respective apertures  132 ,  136  in the insert  66  to guide the insert  66  into position in the slot  64 . The insert  66  and movable member  60  include an optional hinge  140  ( FIGS. 15 and 16 ) that allows the movable member  60  to pivot with respect to the insert  66  for opening and closing the conduit retainers  88 ,  92 . In other constructions, the waveguide may have a different positioning device to aid in the alignment and insertion of the insert  66  and movable member  60  into the slot  64  or the waveguide may not include a positioning device. In other constructions, the waveguide may not include a hinge or may include a tether, telescoping member, or the like. In yet other constructions, at least one of the insert  66  and movable member  60  may be connected to the door frame section  56  with a tether, telescoping member, or the like. 
     In other constructions, a waveguide similar to waveguides  28 ,  32 ,  36 ,  40 , or  44  may be located in the RF door  20 . For simplicity, a waveguide similar to waveguide  28  of  FIGS. 2 and 3  will be exemplified. The door frame section would be replaced by a corresponding door section to reflect that it is positioned in the door rather than the frame but is otherwise substantially the same except for its location. The door could contain a door section having a slot similar to the slot  64  of  FIGS. 2 and 3 . A movable member similar to movable member  60  may be received in the slot to be positioned adjacent the door section in a similar manner like the movable member  60  of  FIGS. 2 and 3  is received in the slot  64  to be positioned adjacent the door frame section  56 . The movable member  60  may be spaced from the door section in a similar manner as described for each of the embodiments described above. 
     In other constructions, the movable member  60  may be coupled to the door frame section  56  using alternative components. For example, the movable member  60  may be attached to the door frame  24  by a hinge such that the movable member  60  is operable to pivot from a first position, in which the movable member  60  is positioned adjacent the door frame member, to a second position, in which the movable member  60  is spaced from the door frame member. 
       FIGS. 17-20  depict an eighth construction of a waveguide according to the present invention having two pivotable movable members.  FIGS. 17-19  depict the eighth construction for a right hand door, whereas  FIG. 20  depicts the eighth construction for a left hand door. 
     Referring to  FIGS. 17-19 , waveguide  150  includes a door frame  24 B having a door frame section  56 B. Door frame section  56 B includes a block  67 B, a bent or stamped metal support plate  65 B that is received in a slot  64 B of block  67 B, and an insert  66 B that is received in plate  65 B. Insert  66 B has a first recess  68 B and a second recess  72 B which, together with respective first movable member  60 B and second movable member  61 B, form first conduit retainer  88 B and second conduit retainer  92 B respectively (see  FIG. 17 ). As best shown in  FIG. 19 , insert  66 B, plate  65 B, and block  67 B are held together by a plurality of bolts  71 B that are received in apertures  81 B,  73 B and  75 B. 
     First movable member  60 B and second movable member  61 B have respective apertures  77 B and  79 B that receive a pivot pin  69 B ( FIG. 19 ). Pivot pin  69 B is also received in an aperture  90 B of insert  66 B. 
     As best shown in  FIG. 17 , first conduit retainer  88 B is formed by first recess  68 B and first movable member  60 B, when the movable member is disposed adjacent to the door frame section  56 B. Similarly, second conduit retainer  92 B is formed by second recess  72 B and second movable member  61 B when the second movable member is disposed adjacent to door frame section  56 B. The length of each of the first and second conduit retainers  88 B,  92 B is at least four times greater than the maximum depth of each of the first and second conduit retainers, as discussed above in connection with the other constructions, e.g., the fifth construction in  FIGS. 9-10 . Likewise, the materials used in the eighth construction of  FIGS. 17-20  are similar to the materials used in the other constructions discussed above. 
     As shown in  FIG. 18 , conduits  52 B may be placed in or removed from the conduit retainers by pivoting the respective movable member about pivot pin  69 B ( FIG. 19 ) away from door frame section  56 B. In  FIG. 18 , second movable member  61 B has been pivoted away from the door frame, thereby enabling the operator to insert or remove a conduit. Once the conduit is in place, the second movable member can be pivoted back to its position adjacent door frame section  56 B, thereby creating second conduit retainer  92 B. Of course, the operation with respect to first conduit retainer  88 B, first recess  68 B, and first movable member  60 B is similar. 
     Waveguide  152  depicted in  FIG. 20  is substantially similar to waveguide  150  depicted in  FIG. 17-19 , except waveguide  152  is configured for a left hand door. As such, some of the components have been changed or re-oriented to accommodate a left hand door. 
     Referring to  FIG. 20 , door frame  24 C has a door frame section  56 C that includes a block  67 C, and a bent or stamped metal plate  65 C and an insert  66 C that are received in block  67 C. Block  67 C, plate  65 C and insert  66 C are held together by bolts (not shown) in a similar manner as discussed above in connection with  FIG. 19 . 
     First and second pivotable movable members  60 C and  61 C, together with recesses  68 C and  72 C, form respective first conduit retainer  88 C and second conduit retainer  92 C when pivotable members  60 C and  61 C respectively are disposed adjacent to door frame section  56 C. Likewise, pivotable members  60 C and  61 C may be disposed away from the door frame section to enable conduits to be either inserted or removed from the respective conduit retainers. 
     Other components and dimensions of the left hand door version shown in  FIG. 20  are similar to those of the right hand door version depicted and described in connection with  FIGS. 17-19 . 
     Thus, the invention provides, among other things, a waveguide for a radio frequency door. Various features and advantages of the invention are set forth in the following claims.