modern immobilization devices

1. IMMOBILIZATION IN RADIOTHERAPY
Resmi.K.Bharathan
Radiation Physicist
Malabar Cancer Centre

2. Immobilization Device
Any device that helps to maintain the patient in a fixed position
➢Prevent the patient movement from treatment to
treatment over a course of radiotherapy

3. WHY IT IS IMPORTANT??
• To position target accurately.
• To minimise the dose to surrounding normal tissue as far as possible.
• Reduces the time in daily patient setup .
• Makes the patient feel more secure and less apprehensive.
• Especially in CNS tumours (small fields, critical adjacent structures).
• Reduces the reliance on patient cooperation and alertness.

4. PROPERTIES OF AN IMMOBILISATION DEVICE
• Lightweight
• Strong and durable
• Minimally affect the megavoltage treatment beam
• Do not cause CT imaging artifacts
•no high Z materials
•Maintains its integrity throughout treatment course
•Easy to use •Inexpensive

5. PREREQUISITES OF IMMOBILISATION
• Fully supported in a comfortable and relaxed position
• Device conforms to patients body contour.
• Should be sturdy and maintain shape over time.
• See the target Volume to be treated and structures to be spared.
• Treatment portal arrangement.
• General condition of patient.

6. HEAD,NECK AND BRAIN IMMOBILIZATION
• Initial construction and selection of proper immobilization for head and neck cancer is one of the most
important parts of ensuring proper treatment of the patient.
• In the past, patients for head & neck cancers were taped to the table across their forehead.
A bite block was occasionally used in order to tilt the neck in a reproducible manner.
• Current methods for head & neck and brain tumors include a variety of masks, molds and frame
systems. In some instances, shoulder straps are used to pull the shoulders out of the treatment field for
the neck.

7. Contd..
• The most common immobilization
device used to treat head&neck
cancers is an aquaplast.
• This device is made from a
rigid plastic that becomes pliable
when placed in warm water.
• When it is wet ,it is placed
over the patients body and
conforms to the contour of the
treatment area.

8. Contd…..
• Advantages: Aquaplast provide great reproducibility in daily
treatments,lightweight and easy to use.
• Additionally modifications can be made to the mask if the patient
experiences swelling or weight loss during the treatment.
• Disadvantages: windows cut cannot be reused.
• when old becomes brittle and too soft when activated

9. 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 developed

10. Indexing Bar
• indexing bar is designed for reproducible
positioning and stable fixation of base plates on the
treatment couch.
• 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.

11. Head Rest
The basic immobilization device used in radiotherapy is
the head rest, shaped to fit snugly under the patient’s
head and neck area, allowing the patient to lie
comfortably on the treatment couch.
Head and neck supports are made of molded
polyurethane foam. They come in six different heights
and contours to attain the desired head angulation
and/or neck position.

12. Bite Block
• To treat the patient with the mouth open
OR
• To move the tongue away from the target
volume during treatment
• Ensuring that the tongue remains depressed

13. Shoulder retractor
• In patients with short neck or in patients where
opp lateral fields are used to treat the neck, the
shoulders need to be retracted caudally to avoid
entrance and exit doses.
• An elastic strap ,equipped with handles and
attached to each side of the treatment couch,
can be used for the patient to pull on.

14. THORAX AND BREAST IMMOBILIZATION
• There are two common immobilization
systems used when treating tumors in
chestcavity.
• 1)VACLOK : these are custom, beanbag
type pillows that are placed around the
patients upper body.
• The air is then vacuumed out of the bag
for a custom fit and sealed in order to retain
its shape.
• vacloks are radio translucent., almost
air equivalent. they are washable
and reusable.

15. BREAST BOARD:
It is used specifically for the treatment
of breast cancer.
• It has several adjustable features to
allow for the manipulation of patients arms,
wrists, head and shoulders.
• Breast boards are generally constructed
of carbonfiber, allowing the device to be
lightweight and durable.

16. Contd..
• Carbon fiber boards have lower attenuation levels, which permit
maximum beam penetration.
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.

17. Wing Board
Wing board is used to help position
patient’s arms overhead during the
treatment of breast, lung and thorax.

18. PELVIC IMMOBILIZATION
• There are two different crucial aspects in the immobilization of pelvic region.
• 1)to properly maintain patients outer contour during treatment with respect to
isocentre.
• 2)other is related to variation of internal structures during daily treatments.
• Immobilization systems such as vacloks, belly boards, and the hip-fix(using
aquaplast) system are commonly used during treatments of pelvic region

19. Belly board
• Belly boards are used when the patient is treated
prone.
• Belly boards allow the small bowel to drop below the
lateral field to avoid severe side effects of irradiation.
• Use of the belly board significantly decreases the
average volume of small bowel that would otherwise
be within the lateral field during standard box
technique treatment.

20. All in One(AIO) Board
The AIO Solution facilitates and refines treatments. With one base plate and
different sets of cushions and thermoplastic masks, all parts of the body are
positioned and immobilized in a comfortable, exact and reproducible way.