Immobilization devices


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A presentation regarding the Immobilization devices used in positioning the patient during radiotherapy treatment for cancer.

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  • Was mentioned earlier. Should it be repeated here again?
  • Immobilization devices

    1. 1. Dr. Nikhil S.
    2. 2. Definition  Any device that helps to establish and maintain the patient in a fixed, well defined position from treatment to treatment over a course of radiotherapy or prevent the patient from moving during a single treatment session.
    3. 3. Objectives Main:  to limit the patient movement  to reduce the probability of positioning errors Incidental benefits:  Redn in daily set up time  Redn in pt s fear and worry  No need for pt to be awake, alert & co-op  Conversion into a rigid body
    4. 4. Desirable characteristics  Ease of use  Ease of constructing the device  Patient Comfort: Fully supported in a comfortable and relaxed position  Tactile reminder to the pt of how it feels  All movements be constrained  Device conforms to the pt’s external surface contours(H&N)  The device be appropriate to the particular patient(e.g. obese) and anatomy(e.g. abdomen) under trtmt.
    5. 5.  The device should optimally position the patient so as to minimize the normal tissue complications  It should not obstruct the path for beam  Device be usable on simulator, CT/MRI and other trtmt planning imaging systems  Surface dose should not be altered.  Adequate space for reference marks.  Rigid & holds its shape over time
    6. 6.  Cost considerations:  Of materials and device itself  Staff time 4 construction of device  Staff time 4 each patient set up  Necessary supplies  Re-usability  Storage space
    7. 7. History of Immobilization methods. Early Days:  Plastic head cups(doggy dish)  Standardized neck rolls  Masking tapes  Not to move during T/ t  Hold the breath
    8. 8. 1960 -1970s  Skin marks  Plaster of Paris cast  Bite blocks  Vacuum molded plastic masks  Polyurethane foam molds
    9. 9. Early 1980s and onwards:  Laser  Base plate  Indexer  Head supports: timos  Acrylic mould/ Cobex cast  Thermoplastic mould  Vacuum mould  Gill Thompson frame
    10. 10. In detail about...  Adhesive tapes  Velcro tapes  Generic body supports- indexed and non- indexed  POP casts  Vacuum molded plastic masks  Acrylic mould/ cobex casts  Polyurethane foam casts  Vacuum bags  Thermoplastic masks
    11. 11. Adhesive tapes:  with paper, cloth, masking tapes  To discourage movt. Eg. Tape across pt s forehead attached to couch side rails
    12. 12. Straps with velcro backing  Strips of adhesive velcro tapes with hook facing outwards can be permanently fixed to the side rails.  Padded and re usable  Helps to keep hand at side and feet together  No pain
    13. 13. GENERIC BODY SUPPORTS  Foam rubber wedges  Other foam rubber supports  One-size-fits-all plastic head cups/ doggie bowls  Neck rolls  Knee and lumbar supports  Thigh and heel stirrups  Prone face holders with cut outs for nose and mouth  Do not offer guidance for inter treatment set up reproducibility  But gives added comfort and stability
    14. 14. Foam wedges- used for patient comfort.
    15. 15. Indexed supports  Simple improvement of generic body supports  provide means to facilitate inter trtmt set up reproducibility.  Head cups, H&N supports, Foam rubber wedges which are carefully indexed by size, shape, elevation above the trtmt couch.
    16. 16.  Head & Neck supports- Clear- plastic Opaque- foam rubber or polyurethane foam  Indexed supports provide Head & Neck height or slant info for setup duplication  To support the head during trtmt of 1. lungs 2. Scln 3. oesophagus 4. any trtmt which necessitates securing Head&Neck.
    17. 17. Body Cast techniques  1960s- Complete body supports or helmets were cast from POP.  Labor intensive and time consuming  Immobilization helmet required initially creation of a model of patient’s head.  POP casts lose shape over time & become flexible  Mostly used in children for -- craniospinal irradiation for medulloblastoma -- CNS leukemia.
    18. 18. Vacuum moulded plastic masks or bubble packs…  1970s- “bubble pack”.  A transparent form-fitting plastic shell fabricated using a special vacuum forming device - Vacu-Former.  polyvinyl chloride sheet electrically heated to soften the plastic and then formed over a plaster model of the patient by creating a vacuum between them.  quite stable  labor intensive.
    19. 19. Acrylic Mould / Cobex cast  Made from perspex sheets  It forms hard nonmalleable material when mixed and allowed to set.  Materials required :  POP bandage & powder  Perspex sheet  Vaseline  base plate  head rest
    20. 20.  Advantages :  Effective fixation  Close conformity between body surface  and mould.  Portals can be marked.  Windows may be cut.  Can be used for CT/MRI without causing  any distortion of image.  Disadvantages:  Difficult and cumbersome to make .  Relatively delicate, with use / rough  handling it may get fractured.  expensive.  Cannot be reused.
    21. 21. Newer body casts techniques  1. polyurethane foam casts  2. vacuum bags  3. thermoplastics
    22. 22. Polyurethane foam casts (alpha cradle)  2 component chemical systems  Patient placed in the treatment position on top of a plastic bag.  The bag rests within a specialized form constructed of solid Styrofoam blocks.  When two chemicals are combined in the bag, they begin to expand into a polyurethane foam.  As the foam rises, technician maneuvers it around the patient .  Support given to anatomic structures that do not lie flat on the treatment couch.  Once the foam hardens, the customized device is ready for use.
    23. 23. used in combination with other patient support systems for  ca breast  ca prostate  lower extremities  lung  pituitary gland  head and neck region  Hodgkin's disease.
    24. 24. ADVANTAGES  rigid  stable  radiolucent.  comfortable DISADVANTAGES  do not prevent patient movement and rotation when used by themselves.  cannot conform completely to changes in body contour as other methods.
    25. 25. Vacuum bags  Radiolucent plastic cushions filled with tiny polystyrene ball.  Semi-deflated cushion moulded around the patient's gross body contours.  Using vacuum pump air is pumped out and the balls come together to form a firm solid support.  The cushion becomes an entirely rigid and comfortable mold of the patient's body.
    26. 26. advantages disadvantages  shape maintained through out  REUSABLE  comfortable and secure  for support of -- 1. head 2. upper thorax 3.the pelvis 4. breast. .  conforms well to gross surface changes  less well to the finer details.  strict immobilization possible in combination with other devices only
    27. 27. Thermoplastics  Low-temperature orthopedic plastics.  Polycaprolactone  Softens at 60 C (working temp)  Melts at 150 C (melting pt)  solid sheets or a flat plastic mesh of diff thicknesses.
    28. 28.  precut thermoplastic mesh  softened by soaking in warm water for a few minutes.  Then mask stretched around the topside of a patient who is already in the treatment position  soft thermoplastic moulded to the patient's facial contours, and in a few minutes the mask hardens.
    29. 29.  no strength or cushioning properties  wont support the patient's weight.  easy to use.  allow treatments with few skin marks.  Reference lines drawn on the plastic sheet.  some loss of skin sparing through the material.
    30. 30.  Other materials used are:  different hardening tapes such as  1. fiberglass tape  2. light-cast tape (a thermoplastic that hardens under ultraviolet light).
    31. 31. Laser  Used for aligning the patient for immobilisation
    32. 32. Base Plate • The plate onto which the head immobilization systems are secured is usually referred to as a base plate. • Its material should be strong ,yet it should minimally attenuate the radiation beam. • Most base plates are acrylic and recently carbon fiber base plates are hugely devolped
    33. 33. Indexer • The indexing bar can be placed at the desired indexing indents of the couch and it can be locked down by rotating the levers. • The base plates then can be positioned over the pins of the two pin indexing bar.
    34. 34. Positioning devices  All immobilization devices in some sense are positioning devices.  positioning devices are ancillary devices which maintain the patient in a nonstandard treatment position.
    35. 35. Need for positioning devices  set up the patient in a special position designed to improve the therapeutic ratio and patient's comfort.  optimal beam access is limited by external anatomic features such as the extremities, a large belly, or a pendulous breast.  proximity of the target (PTV) to the surrounding radiosensitive structures.
    36. 36. List of positioning devices  Neck rolls  Foam wedges  Head holders  Timos  Arm board  Knee saddle  Thigh stirrups  Hand Grip  Over head arm positioner  Shoulder retractor  PATIENT ELEVATION SYSTEMS  Breast board  Prone breast platform support  Thermoplastic brassiere, breast ring  Belly board
    37. 37. Neck Roll, Foam wedge, Head holder and Timo  used to maneuver body parts out of the way of the beam or into a better position
    38. 38.  maxillary antrum tumors- - patient's head positioned with chin hyper extended to include the superior extent of the maxillary antrum in the anterior field without including the eye.
    39. 39.  pituitary or small brain tumors -- head positioned with neck in extreme flexion .  anterior beam can avoid the dose-limiting structures such as the optic chiasm, the retina, and much of the brain tissue
    40. 40. Arm board, knee saddle, and thigh stirrups  Designed to position the extremities in a comfortable and reproducible manner.  Used for soft tissue sarcomas in the arms or legs.  Necessary to remove the uninvolved arm or leg from the path of the radiation beam.
    41. 41. Upper limb positioning  Arm best treated with 90 degree extension & treatment couch rotated 90 degrees.  Axis of the arm aligned with the axis of gantry rotation for planning & delivering precise isocentric treatment
    42. 42. overhead arm positioner  Used to position the extremities if interfering with treatment of some other region.  Positioned above the head or at the sides with either:  1)couch rail mounted or tilt board mounted hand grips and arm supports .  2) or an overhead arm positioner hand grip device. (e.g., the butterfly or the T- bar)
    43. 43. T bar hand grip T-bar hand grip mounted on a horizontal plastic board.  Used in combination with head and neck support device.  adjustable hand grip positions available.  Maintains the patient in a reproducible arms-up position.  Used for treating various lesions in the thorax and abdomen.
    44. 44. Shoulder retractors  Patient nudged into a position with arms and shoulders down.  Footboard attached to hand grips through nylon ropes with adjustable tension.  Reproducible.  very useful for treating head and neck cancers with lateral fields.
    45. 45. lower limb positioning  Position the uninvolved leg sufficiently outside the radiation field.  Knee saddles or stirrups mounted on the couch rail used with a customized solid foam or vacuum bag support.
    46. 46. Patient elevation systems 1. tilt board  severe obesity  lung disease  Built-in hand grips or arm supports that provide comfortable and reproducible arms-up support.  Used for treating lung cancer through lateral fields without the interference of arms or shoulders. severe sloping chest by positioning the patient so that the antero-posterior vertical beam impinges orthogonally .
    47. 47. breast board  Used in the treatment of breast cancer with parallel opposed tangential fields.  Advntg:  Provides arm support to bring the arm above the shoulders and out of the way of the lateral field.  Allows the patient to be positioned with the chest wall horizontal avoiding angulation of the collimator.  Takes advantage of gravity to pull the large breast down into a better treatment position.
    48. 48. Modern breast board  Rigid plastic.  wide range of indexed tilt angles .  The back support includes a head holder.  It is cut away to prevent interference with the tangential field for steep beam angles.  Also contains an arm support system.
    49. 49. Wing board  It comfortably supports the patients arms during trtmt of breast, lung and thorax.
    50. 50. thermoplastic brassiere or breast ring  Treatment of women with large, flaccid, or pendulous breasts.  Prevents severe skin reactions resulting from the skin overlap in the infra-mammary fold.
    51. 51. Prone breast platform support  patient lies prone  rigid trough-like supporting device mounted on top of the treatment couch.  Involved breast hangs under its own weight through a window in the bottom of the trough. .  provides improved separation between the target and the normal tissues.  Lateral tangential beams are used for treatment.  Reduces pulmonary ,cardiac, skin complications .
    52. 52. Belly board  Thick mattress for supporting the patient prone with a window cutout for the patient's belly.  provide more comfort and stability in the prone position (obese patient) .  Reduces the amount of intestine in the lateral radiation fields.
    53. 53. Treatment chair.  Not popular.  Made of carbon fiber grids .  Chair can be mounted on the treatment couch.  Contain head and neck supports as well as arm rests.  Patients with troubled breathing and cannot be placed in a recumbent position.  Advantageous for treatment of mediastinal disease.  Reduces the amount of irradiated normal tissue.
    54. 54. Head Fixation Devices  Stereotactic radio surgery(SRS) immobilization requires greater precision and accuracy.  Stereotactic frame bolted to the patient's skull before the target localization procedure and attached until treatment is complete.  Single-fraction technique.  Impractical for fractionated radiotherapy
    55. 55.  1. Gill-Thomas-Cosman system  frame fixed to the head with a dental mold. occipital tray with a cast of the occiput. strap that holds the device tightly to the head.
    56. 56.  2nd device consist of a rod in each external auditory canal and a clip molded to the bridge of the nose
    57. 57. 3. invasive  For IMRT of head& neck  bone screws set into the inner table of the skull.  screws have internal threads and can receive the standoffs which remain in place during the course of therapy.
    58. 58. SRS using thermoplastic shell
    59. 59. Traditional bite block  Dental impression mouthpiece. Rigidly supported by and referenced to a solid base plate placed under the patient's head and fastened to the treatment couch.  The patient's reproducible head position is recorded according to the reference numbers
    60. 60. Modern bite block systems  Has optical tracking systems that verify correct placement of fiducial markers incorporated within the bite block apparatus.  Positions of the fiducial markers relative to the isocenter compared at the time of the acquisition of the planning CT scan.  Graphical user interface suggests shifts in patient position as per the plan.
    61. 61. Site Technique Trtmt to trtmt(mm) alignment Pelvis, abdomen Alpha cradle 3 to 4 Laser Un-immobilized 6 to 8 Laser breast Alpha cradle/ vacuum bags 3 Light field thorax Un-immobilized 4 Laser Head and neck Face mask with neck 2.5 to 4 Laser Mechanical 3 Laser Bite block 4 Laser Intracranial Un-immobilized 3 Laser Face mask with neck 2 to 2.5 Laser Stereotactic non- invasive 1 to 1.5 Mechanical Stereotactic-invasive <1 Mechanical
    62. 62. Head and Neck  proximity of tumor to critical normal tissues.  good immobilization will enable smaller treatment margins and reduce side effects.  Most accurate: Perspex shell  Patient supine with head on a customized head rest and as flat as possible to maintain the spinal cord parallel to the couch top.  Neck chin distance
    63. 63.  Fixed to the couch top in at least five places.  mouth bite  pull the shoulders inferiorly.  anterior and lateral reference marks made on the shell.  selected parts can be cut out to reduce skin dose
    64. 64. Ear  Patient is immobilised lying supine in a custom-made shell.  Neck extended to move the orbit superiorly out of the treated volume.
    65. 65. Nose  The patient is immobilised in a thermoplastic or Perspex shell.  Wax nostril plugs to help produce a more homogeneous dose distribution.
    66. 66. Oral cavity  Patient supine with a straight spine.  Immobilized in a Perspex or thermoplastic shell.  custom-made mouth bite -- pushing the tongue inferiorly when irradiating the hard palate or upper alveolus. -- separate the roof of the mouth from the inferior oral cavity when irradiating the tongue
    67. 67.  Pts may find it difficult to tolerate.  may precipitate swallowing and thus cause movement of critical structures.  distort the anatomy and make volumes on CT more difficult to define.
    68. 68. oropharynx  The patient lies supine with the spine as straight as possible and no mouth bite,  but any dentures should be left in place.  A shell with at least five fixation points is constructed to ensure immobilization
    69. 69. hypopharynx  The treated volume will usually extend inferior to the level of the shoulders which should be as low as possible to facilitate beam entry.  No mouth bite is required.
    70. 70. nasopharynx  The chin is elevated to spare the oral cavity and orbit  the spine should be kept as straight as possible if posterior neck nodes are present, to facilitate matching of an electron boost.  A mouth bite may be used to depress the tongue away from the treated volume.
    71. 71. larynx  shoulders are immobilized in the shell as inferiorly as possible  shoulder tips should be inferior to the lower border of the cricoid cartilage  thus permitting lateral radiation beams to treat the larynx without the need to angle them inferiorly.  Grip bars on the side of the couch may help to achieve this.
    72. 72. Salivary glands  neck slightly extended to move the orbits superiorly and reduce the chance of beams exiting through the eye.
    73. 73. sinuses  Patients should be immobilised supine in a Perspex or thermoplastic shell.  If the neck is not irradiated, the shoulders do not need to be immobilised.  If the low neck nodes are to be treated (level III–V) the neck should be extended to allow treatment of most of the neck nodes with an anterior beam, avoiding the oral cavity and pharynx where possible.
    74. 74.  mouth bite  Patients should be asked to look straight ahead to avoid rotating the lens or retina, particularly if the orbital cavity is included in the treated volume.  Wax plugs in the nostrils are used if the tumour extended inferiorly in the nasal cavity to enable a more uniform dose distribution.
    75. 75. orbit  The proximity several critical normal structures  excellent immobilisation is vital.  A custom-made thermoplastic or Perspex shell is created with the patient supine  the chin in a neutral position.
    76. 76. CNS GLIOMAS  The patient lies supine with the head immobilized in an individual Perspex or thermoplastic shell.  More rigorous immobilization with a stereotactic frame and mouth bite is possible.
    77. 77. Medulloblastoma CONVENTIONAL  Pt treated prone with indvdl facial support and a shell down over the shoulders to immobilize head, neck and shoulders. CONFORMAL  Pt treated supine on carbon fiber couch top, neck extended  Vacuum molded bag to support head and shoulders.  Thermoplastic shell covers face and shoulders  Indexed knee rest(spine)  Hips fixed in foam forms  Arm rests
    78. 78. Pituitary tumors Thyroid tumors  Perspex shell or relocatable frame  Neutral position  Perspex shell  Neck extended  Shoulders as low as possible
    79. 79. LUNG  Pt supine with arms above head  Pt holds on to T bar device with their elbows supported laterally  If treatment delivery is prolonged, vacuum bag should be used to reduce movement.
    80. 80. Breast  Patient treated supine  With an immobilization device which secures both arms above the head  Head rest, elbow and arm rests, knee supports and a foot board provides stability  Large pendulous- breast support either with thermoplastic shell or breast cup.  Prone  Reduces mean lung and cardiac dose  More homogenous dose distribution
    81. 81. Esophagus & stomach  Patient treated supine with arms above the head.  Ideally immobilized with a vacuum formed polystyrene bag.  Cervical esophagus tumors- thermoplastic or perspex shell
    82. 82. Pancreas & liver rectum  Patient lies supine in a vacuum molded bag with arms above the head in arm rest  Prone position  Belly board used  Which allows small bowel to be displaced anteriorly
    83. 83. prostate Patient treated Supine Head pad combined with individually adjustable knee and ankle supports used
    84. 84. Urinary bladder  Pt supine  With arms folded across the chest  With ankle supports to stabilize the leg and pelvis
    85. 85. CERVIX  Patient supine with arms on the chest  Knee and lower leg immobilization or alpha cradles to prevent pelvic rotation  Obese- belly board
    86. 86. Anal canal  Treated prone to displace bowels superiorly  Belly board– displaces the bowels anteriorly into the blly-board aperture.
    87. 87. Cyber knife  Integrates a compact robotically positioned linac with image guided stereotactic localization  Basic components:  Robotic linac  Image guidance hardware:  --a pair of orthogonal x ray sources  -- imaging panel
    88. 88.  Implantation of fiducial markers in or around the tumors  Patient stabilization  Body length vacuum bag  CT and PET images  Thin cuts 1.25mm--> HR DRR  DRR compared with images acquired by orthogonal X ray sources.