Vacuum Fixation Cushions: How to Choose

What Is a Vacuum Fixation Cushion?

In order to properly prepare a patient for radiation therapy, technicians must completely immobilize them to prevent the radiation beams from penetrating non-treatment areas of the body. Any movement from the patient, an improper angle, or differing positions each treatment could result in collateral tissue damage and/or ineffective treatment of the cancerous cells. The patient must remain motionless to ensure the beam of radiation hits its intended target (and nothing else). Many facilities, therefore, use vacuum fixation cushions.

Vacuum fixation cushions not only immobilize the patient, but they also provide comfort, as the patient often must stay in a fixed position for an extended period of time. This position may or may not be a natural body position, requiring the patient to lay in awkward positions in order for the radiation to target the intended cancerous area. Technicians can custom-create or adjust the cushions according to the needs of the individual case. Many times, the radiologist will position multiple fixation cushions under and/or around the patient’s body to achieve optimal results.

Vacuum cushions are highly configurable and can be quickly shaped around the patient’s body to mold against the natural curves of the patient. The inflated cushion is placed under the patient and once the correct positioning is achieved, a vacuum pump is attached to a cushion nozzle to evacuate all of the air. As the air is pulled from the cushion, the cushion shrinks/molds around the patient. The cushion then holds its shape and becomes rigid. If the cushion needs to be adjusted, the vacuum can be released to reposition the cushion.

Unlike fiber-filled or foam pillows, vacuum cushions can be easily cleaned and reused, saving the facility on supply costs and storage space. They are typically filled with small, polystyrene balls and are extremely lightweight. They are collapsible so they take up little room in a facility.

How to Choose the Right Cushion

One of the biggest challenges with radiation therapy is reproducibility. Reproducibility is referred to as “exposures made at the same kVp and mA stations of the same phantom thickness should produce the same optical density on the resulting image.” In layman’s terms, particularly to how it relates to radiation therapy, reproducibility is simply the ability to ensure the same results will be obtained when the patient is placed in the same position as the prior treatments.

Vacuum fixation cushions enable the radiologist to consistently position the patient so they receive the same treatment in the same spot(s). The cushions ensure greater accuracy by increasing the number of fixation points and reducing the volume of normal tissue treated. One study found that patients who received radiotherapy using individually-molded cushions experienced more accurate treatments than patients who were treated without fixation devices.

Clearly, vacuum fixation devices are effective. The next question is which kinds to choose. Because every patient body is different, facilities likely need a variety of cushions. The size of cushion is not the only determinant. Cushions also come in different filling amounts and some are made specifically for certain types of the body receiving treatment.

When choosing cushions, determine which types of radiation therapies your facility provides. Most facilities have the ability to treat every type of cancer and, therefore, require cushions made for the pelvis, thorax, and breast, for example. More general cushions should also be purchased, either to supplement the specific cushions or to create a custom configuration. For these purposes, cushions of multiple shapes and fill should be on hand. Most general cushions range from 100 x 100 cm to as small as 50 x 25 cm.

Beyond size, shape, and fill, we recommend looking at the structure of the cushions. They should be easy to set up and manipulate, as well as easy to clean for reuse. Of course, the cushions should also be durable so they do not rupture. The material should also not absorb the radiation.

Alternatives to Vacuum Fixation Cushions

There are options when it comes to fixation devices. Vacuum fixation cushions are inexpensive, customizable, and reusable, however, some facilities use other methods to immobilize patients for radiation therapy.

Standard patient positioning wedges, bolsters, and pads are pre-formed and made of molded polyurethane foam or plastic. Because they are fixed, they require ample storage space, are heavier than vacuum fixation cushions, and cannot be customized as accurately to the patient’s body. The plastic positioning devices are rigid and do not offer much in the way of patient comfort, either.

Wing boards and breast boards are often used to stabilize a patient’s arm(s) above their head and/or incline the patient. While these are sometimes used alone, many facilities use specialized vacuum cushions simultaneously for greater patient stability and comfort. The boards are also not sufficient for every type of treatment.

Facilities may also use custom casts of polyurethane foam. By mixing chemicals, foam is produced and hardens around the patient. Unlike vacuum fixation cushions, the casts take time, up to 15-20 minutes to harden. The casts must be made per patient and are not reusable.

Related: Thermoplastic Mask Oven: What It Is and How It’s Optimizing Workflows

Thermoplastic masks are another option for certain types of radiotherapy. One study found thermoplastic mask offer “better reproducibility with significantly less interfractional set up displacement than vacuum cushions.” This report, however, studied only stereotactic radiotherapy of one type of cancer, namely oligometastatic lung cancer. Even with its limitations, the study does show that thermoplastic masks can provide a good alternative to vacuum cushions in some instances.

Deciding which fixation devices to choose should be based on effectiveness, budget, storage space, ease of use, speed of use, and comfort. With the ultimate goal to increase fixation points to increase accuracy for optimal treatment, radiation facilities should invest in the devices that enable them to achieve the best patient outcomes. It is likely that no single fixation device is sufficient and a combination of multiple products will be necessary. Work with an experienced provider who can listen to your needs and work with you to develop a comprehensive solution.