The document discusses various immobilization devices used in radiotherapy such as thermoplastic masks, breast boards, belly boards, Vac-Lok systems, and treatment chairs. Proper immobilization is crucial for accurate radiation treatment by reducing setup errors and patient movement. The advantages of each device are described in terms of patient comfort, reproducibility of positioning, and reduction of radiation exposure to surrounding healthy tissues.

1. GONO BISHWABIDYALAY
Dept. of Medical Physics and Biomedical engineering
Radiation treatment planning (MPBME-322)
Assignment on immobilizing device used in radiotherapy
Submittedby: Submittedto:
Mohammad Ullah Shemanto Abu kawser
Roll: 328 Teaching assistant
Semester: 6th Dept. of MPBME
Batch: 16th Gono biswabidyalay

2. IMMOBILIZATION: 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.
ROLE OF IMMOBILIZATION:
• Patient positioning and immobilization are said to be the most
crucial parts of radiation therapy treatment.
• For accurate delivery of a prescribed radiation dose to a target
volume, while sparing sourrounding normal and critical tissues.
• Without proper immobilization ,the patient nwanted side effects
• Immobilization such as molds, casts, headrests, and other devices
are constructed to reduce setup error and patient movement
during treatment.
• Although the primary goal of immobilization system is to limit
patient motion and reduce the probability of major positioning
errors, there are other benefits as well..
• A well constructed immobilizing system can reduce the time for
daily patient set up.
• It can make the patient feel more secure and less apprehensive.

3. • It can reduce the reliance on patient co-operation and alertness,
and it can help to stabilize the relationship between external skin
marks and internal structures
Frameless immobilization devices:
• Orfit cast
• Vac lok
• Velcro Straps
• Alfa cradle
• Pituitary board
• Breast board
• Customized foam pads

4. Current methods for positioning and immobilization
Thermoplastic mask of the head Treatment chair

5. Positioning aids Head rest Belly boards
Pelvic board Extremities
Breast board

6. Head Fixation Devices
Invasive

7. VAC-LOk
Thermoplastic mask of the head:
This device is made from a rigid plastic that becomes pliable when placed
in warm water. When it is placed over the patient body and conforms to
the contour of the treatment area.
Advantage of Thermoplastic mask of the head:
 Low-temperature orthopedic plastics.
 Polycaprolactone
 Softens at 60 C (working temp)
 Melts at 150 C (melting point)
 Solid sheets or a flat plastic mesh of diff thicknesses.
Breast board:
Breast board 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 carbon fibre allowing the device to be
lightweight and durable.

8. Advantage of breast board:
 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.
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.
Advantage of 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.
Vac lok:
 A complete vacuum is drawn through the quick-release valve,
cushion becomes a rigid and comfortable mold, offering accurate
reproducibility throughout the course of simulation and treatment.
 Made up of Nylon-urethane material, can be cleaned and reused.

9. Benefits of VAC-LOK:
• cost-effective
• re-usable
• quick to set up
• full range of sizes
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.
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