Immobilisation and stabilisation device used for radiation therapy

1. PRESENTER : DR.MOUMITA PAUL
1st Year PGT
MODERATOR : DR.P.P.MEDHI
REGISTRAR,DEPARTMENT OF
RADIATION ONCOLOGY
BBCI

2.  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. Main :
 To limit movement of the patient
 To reduce the probability of positioning errors
 Primary goal in treatment using radiation
therapy :
---to deliver curative dose of radiation to the
target
---minimising the dose to surrounding normal
tissue as far as possible.

4. Incidental benefits:
 Reduction in daily set up time
 Reduction in patient’s fear and worry
 No need for the patient to be awake,alert and
co-operative.
 Conversion into a rigid body

5.  Immobilisation techniques primarily address
the issue of reducing intratreatment motion
and improving reproducibility of patient
position from day to day.
 ……1.Target volume margins
2.Radiobiological rationale behind
immobilisation.
3.Use of 3D treatment planning and
programs and new treatment modalities.

7. Slope of dose response curve of
many tumours is sufficiently
large,i.e.little change in dose
will significantly reduce
tumour control probability.
 y= % change in control/%
change in dose
y50~ 1.3 to 2
 Strong corelation between
local recurrence and
inadequate coverage of
defined target volume within
high dose region.

8.  The development of new immobilisation
methods and materials has made it possible
to immobilise almost any area of body of a
co-operative patient to 3mm, allowing use of
margins of no more than 5mm, except when
target motion within the patient is an
issue.Special techniques for head and neck
targets can yield positional accuracies of 1-2
mm or even less for invasive immobilisation.

9.  1.Target volume to be treated
 2.Structures to be spared
 3.Treatment portal arrangement
 4.General condition and comfort of patient

10.  Ease of use
 Ease of constructing the device
 Patient comfort : Fully supported in a comfortable
and relaxed position
 Device should conform to the patient’s external
surface contours
 The device should optimally position the patient so
as to minimise the normal tissue complications
 It should not obstruct the path for beam
 Device should be usable on simulator,CT/MRI and
other treatment planning imaging systems
 Surface dose should not be altered
 Adequate space for reference marks
 Rigid and hold its shape over time
 Re-usability

11. Early Days :
 Plastic head cups(doggy dish)
 Standardised neck rolls
 Masking tapes
 Not to move during treatment
 Hold the breath

12.  Skin marks
 Plaster of Paris cast
 Bite blocks
 Vacuum molded plastic masks
 Polyurethane foam molds

13.  Laser
 Base plate
 Indexer
 Head supports :timos
 Acrylic mould/ Cobex cast
 Thermoplastic mould
 Vacuum mould
 Gill Thompson frame

14.  Used for aligning the
patient for
immobilisation.
 Range 1.5 to 5 m
 Line width < 0.5 mm
at 3m
 Line length >43 cm at
3m

15.  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 plate then can
be positioned over the
pins of the two pin
indexing bar.

16.  The plate onto which
the head
immobilisation systems
are secured is usually
referred to as a base
plate.
 It’s material should be
strong, yet it should
minimally attenuate
the radiation beam.
 Most base plates are
acrylic and recently
carbon fibre base
plates are hugely
developed.

17.  Provide means to facilitate intertreatment set up
reproducibilty.
 Head cups,Head and Neck supports,Foam rubber
wedges which are carefully indexed by
size,shape,elevation above the treatment couch.

18.  Head and Neck supports—
Clear – plastic
Opaque – foam rubber or polyurethane foam
 Indexed supports provide Head and Neck height or
slant info for set up duplication.

19.  1960s – Complete body
support or helmets were
cast from POP.
 Advantages : Easily
available,relatively
inexpensive,modified
with ease.
 Disadvantage :
Immobilisation not very
good, not reused,get
damaged with use very
soon
 Mostly used in children
for—
CSI for Medulloblastoma
CNS Leukemia

20.  1970s
 A transparent form fitting plastic
shellfabricated using a special vacuum
forming device – Vacu-former.
 PVC sheets electrically heated to soften the
plastic and then formed over a plaster model
of the patient by creating a vacuum between
them.
 Quite stable.

21.  Made from perspex sheets
 It forms hard nonmalleable material when mixed
and allowed to set.
 Materials required :
 POP bandage and powder
 Perspex sheet
 Vaseline
 Base plate
 Head rest

23. Advantages: Disadvantages:
 Effective fixation.
 Close conformity
between body surface
and mould.
 Portals can be marked.
 Windows may be cut.
 Wax bolus can be applied.
 Can be used for CT/MRI
without causing any
distortion of image.
 Difficult and
cumbersome to
make.
 Relatively
delicate,with
use/rough handling it
may get fractured.
 Expensive.
 Cannot be reused.

24. 1.Thermoplastics
2.Vacuum Bag
3.Polyurethane foam casts

25.  Low temperature
orthopedic plastics.
 Polycaprolactone/PV
C/Cellulose acetate.
 Softens at 60 degree
centigrade(working
temp.)
 Melts at 150 degree
centigrade(melting
point)
 Solid sheets or a flat
plastic mesh of
different thicknesses.

26.  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 body
contours,and in a few minutes the mask hardens.

27. Advantages: Disadvantages:
 Can be used practically
for all body parts.
 Relatively easy to make.
 Portals can be marked on
surface with ease.
 Treatment windows can
be cut.
 Wax bolus can be fixed to
surface.
 Can be used with CT/MRI
scan.
 Expensive(Rs1500-
3500).
 Windows cut cannot
be reused.
 When old becomes
brittle and too soft
when activated.
 Material ages in
direct relation to
circumstances.

28.  Consists of a shell (envelope) of tough urethane
plastic material which is partially filled with pre
expanded polystyrene micro spheres.
 Semi deflated cushion moulded around the
patient’s gross body contours.
 When air is removed from the cushion by vacuum
pump,microspheres are pulled together tightly
within the cushion and becomes rigid.

30. Advantages Disadvantages
 Easy to use.
 Reasonably good
immobilisation.
 Requires little time to
prepare.
 Comfortable for patient.
 Can be reused.
 Contour and shape
may change with
handling and use.
 Expensive.

31.  2 component chemical systems
 Patient placed in the treatment positionon top of a
plastic bag.
 The bag rests within a specialised 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 customised device is
ready for use.

32. Used in combination with other patient
support systems for
•Ca breast
•Ca prostate
•Lower extrimities
•Lung
•Pituitary gland
•Head and Neck region

33. Advantages Disadvantages
 Rigid
 Stable
 Radiolucent
 Comfortable
 Do not prevent patient
movement and rotation
when used by
themselves.
 Cannot conform
completely to changes
in body contour as
other methods.

35.  Alternative method for immobilisation of head and neck
patients
 For those who cannot tolerate thermoplastic mould due to
claustrophobia/anxiety.
 A dental mold is formed to the patient’s maxillary
teeth,and a vacuum creates suction to the hard palate.
 The dental mold is attached to the carbon fibre frame
which is fixed to the table’s indexing system frame.

36.  All immobilisation devices in some sense are
positional devices.
 Positioning devices are ancillary devices which
maintain the patient in a non standard
treatment position.

37.  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 extrimities,a large
belly,or a pendulous breast.
 Proximity of the target (PTV) to the surrounding
radiosensitive structures.

38.  Neck rolls
 Foam wedges
 Head holders
 Arm board
 Knee saddle
 Thigh stirrups
•Hand grip
•Over head arm
positioner
•Shoulder retractor
PATIENT ELEVATION
SYSTEM
•Breast board
•Prone breast platform
support
•Thermoplastic
brassiere,breast ring
•Belly board

39.  Used to maneuver body parts out of the way
of the beam or into a better position.

40.  Designed to position the extrimities 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. Overhead arm positioner T bar hand grip

42.  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.

43. 1.Tilt board
 Severe obesity
 Lung disease
 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.

45.  Used in the treatment of breast cancer with
parallel opposed tangential fields.

46.  Made up of rigid plastic
 The back support includes a head holder
 It is cut away to prevent interference with the
tangential field for steep beam angles

47.  Rigid trough like supporting device mounted
on top of the treatment couch.
 Involved breast hangs under window in the
bottom of the trough.
 Provides improved separation between the
target and the normal tissues.
 Lateral tangential films are used for
treatment.
 Reduces pulmonary,cardiac,skin
complications.

49.  Treatment of women with large,flaccid or
pendulous breasts.
 Prevents severe skin reactions resulting from
skin overlap in the inframammary fold.

50.  Thick mattress for
supporting the patient
prone with a window
cut out for the
patient’s belly.
 Provide more comfort
and stability in prone
position(obese
patient).
 Reduces the amount of
intestine in the lateral
radiation fields.

51.  Head fixation devices :
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.

52.  Consist of a rod in
each external
auditory canal and
a clip moulded to
the bridge of the
nose.

53.  For IMRT of head
and 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.

55.  Integrates a compact robotically positioned
linac with image guided stereotactic
localisation.
Basic components:
 Robotic linac
 Image guided hardware:
 -- a pair of orthogonal X ray sources
 -- imaging panel

57.  Implantation of fiducial markers in or around
the tumours
 Patient stabilisation
 Body length vacuum bag
 CT and PET images
 Thin cuts 1.25 mm HR DRR(Digitally
reconstructed radiography)
 DRR compared to images acquired by
orthogonal X ray sources.

58.  ExacTrac, a fast and
highly accurate X ray
system, provides
detailed target
visualisation and non-
coplaner positioning
and monitoring for
stereotactic cranial
radiosurgey
treatments.

59.  The ExacTrac frameless radiosurgery system
ensures highly accurate delivery of single or
multi-fraction treatment with a patient-
friendly mask that facilitates a streamlined
workflow.
 Reproducible conformity with a precise non-
invasive stereotactic mask system.
 Compatible with multiple couch tops.
 Allows for time saving and patient-friendly
treatment without comprising accuracy.

60.  The Brainlab Non-Invasive Mask System uses
a U-shaped frame,two vertical posts, a three
piece thermoplastic mask,and an optimal
bite block attachment for noninvasive cranial
immoilisation.

61.  The Brainlab noninvasive mask system uses
three pieces of thermoplastic material
custom molded to the patient’s head and
attached to vertical posts on either side of
the patient’s head.
 These posts are then attached to a U-
shapped frame which is attached to the
treatment couch,thus providing
immobilisation of head.

62.  Immobilisation and positioning is an
indispensable part of radiotherapy treatment.
 With better on board imaging and better
target localisation systems and softwares
(IGRT) the need for rigid immobilisation is
gradually decreasing.