Radiotherapy is one of the treatment methods for treating cancer. High energy x-ray or gamma-ray is used to kill the cancer cell. This treatment is given either once or a few times for each patient.

Thus, radiotherapy treatment must be delivered accurately. To ensure treatment is given accurately, some accessory devices are needed following the parts of body that will be getting treatment.

These accessory devices are used to determine the patient’s position during treatment, to prevent any movement and to make sure patient is comfortable using it. Each patient will use a definite set of accessory which differs according to the type of cancer and area of treatment. This accessory must be durable and can be used repeatedly by the patient until treatment completes. For some patient, own accessory set is made especially for them.

This radiotherapy accessory device can be divided into immobilization device, patient positioning aid device, tissue compensation device and organ protection device.

Immobilization Device

In this explanation, only the immobilization device will be defined while the rest of the accessories will be clarified according to category in another explanation.

Immobilization device is a tool that is used to ensure the position of the patient is stable and can be maintained, without any movement. Patient is only allowed to breathe normally. The shaping of this device must be able to maintain patient’s position. This is vital because any movement that can be made by the patient who puts on the device can result in inaccurate treatment delivery. Inaccurate treatment results in cancer cell not getting radiation and may be harmful to nearby sensitive organs that should not receive radiation.

The following are some immobilization devices that are frequently used. These devices can be used by pediatric or adult patient.

Beam Direction Shell

Beam direction shell (BDS) is made from thermoplastic and is often known as thermoplastic mask. Thermoplastic used for BDS have holes which enable patient to breathe through them. The thermoplastic came in the form of a flat and even sheet that makes it easier to be soaked in the heating container. The nature of thermoplastic is quick to soften and easy to shape when it is warmed which simplifies the BDS formation. There is a frame to hold the thermoplastic sheet which is used for clipping the mask onto the head rest or body holder.

The shaping process of BDS begins by soaking the thermoplastic sheet in hot water at temperature of 60 to 70 degree Celsius. Then, in the soften and slightly warm condition, it is placed on the body part in the treatment area and the BDS is shaped according to the patient’s body contour. The patient needs to wait for 15 to 20 minutes until the BDS stiffen. It is important for the patient to give cooperation during this device fabrication. The patient is allowed to breathe normally and is asked to stay calm. This BDS is usually used for treatment of head, thorax and pelvis region. The pictures below are the examples of various BDS.

a)BDS for head region b) BDS for pelvis region c) BDS for head and neck region


Vac-Lok Cushion

Vac-Lok cushion is an accessory that is shaped like a pillow or mattress. The cushion cover is made from nylon and inside the cushion are polystyrene beads. Vac-Lok cushion is of various size and shape depending on body part that is treated. It also came in small size for pediatric patients’ usage.

Vac-Lok cushion is formed following the patient’s body shape when air is removed by a vacuum pump through its valve. This vac lok will be hardened when the determined position of the patient is achieved. For maintaining the shape that has been produced, there is a stopper on the valve to prevent air from entering the Vac-Lok cushion. Vac-Lok cushion that has been shaped will be stored and hung on a special rack. For each treatment, the patient will be laid on the Vac-Lok cushion to maintain the position and to prevent any movement

Vac-Lok cushion before air is pumped out. Vac-Lok cushion after air is pumped out.



Through this introduction about the immobilization device, it is hoped that the patient understands the importance and its requirement in radiotherapy treatment. It also hopes that the patient is prepared to give co-operation during this non-painful device fabrication process to give the best outcome.


  1. http://www.artcorporationsa.com
  2. http://www.civco.com
  3. http://www.osl.uk.com


Last Reviewed : 17 March 2017
Translator : Halimah binti Mohd Zarawi
Accreditor : Sarah Lee Abdullah