IMMOBILIZATION FOR ACCURATE TREATMENTS

Patient positioning and immobilization are critical factors in the accurate administration of radiation therapies, and ultimately, in positive healthcare outcomes. However, the traditional thermoplastics and processing methods used for the majority of immobilization masks rely on first-generation technology that cannot provide an optimal level of control, precision and quality. Drawbacks of these materials include an imprecise fit that leads to excessive movement; patient discomfort due to non-uniform shrinkage and adherence to the skin; and difficult challenges for the radiation therapist when preparing, shaping and adjusting the mask.

CHANGING THE STATUS QUO

To resolve the drawbacks of existing immobilization masks and achieve higher levels of patient immobilization, Orfit begins its creation of the Efficast masks with a special thermoplastic.

Instead of utilizing standard resin or relying on an outside compounder, Orfit compounds its specialized PCL-based thermoplastic in house. Orfit thermoplastic features controlled shrinkage and stretch, and optimized mechanical performance characteristics. Further, in-house compounding gives Orfit exceptional control over the quality and consistency of the material.

The next change is in processing of the compound. Most immobilization mask companies utilize compression molding, which is a batch process that involves injecting preheated resin into an open mold cavity, closing the mold, and applying pressure to force the material into all areas. This process can lead to uneven thicknesses of the materials that produce performance disparities and varying shrinkage behavior. To solve these quality issues, Orfit extrudes its compound using a Gravimetric feeder, a twinscrew extruder, and a large die to produce very large runs of sheet material.

The size of these runs versus small compression molded batches help to ensure uniformity of thickness, stretch and mechanical characteristics across the entire sheet.

Another point of differentiation is the relative thinness of the extruded Efficast material. At 1.6mm and 2.0mm, this material is thinner than the typical U-frame and S-frame masks commonly used, making them easier to drape and mold, and lighter and more comfortable to wear.

After extrusion, the sheet is perforated, die-cut and coated. Orfit utilizes a water-soluble special anti-stick coating that prevents adhesion of the mask to the patient's skin and hair. The company is also introducing a new anti-bacterial coating in Europe and Asia. Both the thermoplastic material and the coating are biodegradable and support environmental efforts.

ACCURATE IMMOBILIZATION

The ultimate goal of patient immobilization is treatment accuracy. Efficast masks meet the gold standard of immobilization by restricting movement to less than 2mm. The exceptional stability of the masks is the result of Orfit's formulation and processing technologies, and of the design of the masking system. Together, these elements provide significantly reduced stretch - 50% as opposed to 300% with conventional masks - as well as improved molding precision to eliminate areas of slack.

Also contributing to improved immobilization are Orfit's L-shaped profiles that are used to attach the mask to the base plate. The Lshaped profiles, made from acrylonitrile- butadiene-styrene (ABS) resin, are attached to the masks with an innovative laser welding process that provides a stable bond without the risk of the profile separating from the thermoplastic mask material.

Compared to commonly used push pins, these profiles - featuring wings or tabs that can be easily grasped with the fingers - make it easier to mold Efficast masks, position them precisely, and remove them quickly in case of emergency.

Efficast masks are designed with multiple, independent immobilization points that further enable precise and stable positioning of the mask to the patient's anatomy. Depending on the treatment, the masks may have three, four or five immobilization points; each secured using an L-shaped profile.

MASK MOLDING PROCES

The Efficast material relies on a crystallization process to enable shaping of the mask to the patient and subsequent hardening into the desired form. When the radiation therapist immerses the mask in 150°F water (which is 15°F to 20°F cooler than the temperature required for conventional thermoplastic material), the crystalline structure relaxes, allowing the material to be draped over the patient's anatomy. Only minimal effort and time are needed to shape and contour the mask.

Approximately 90% to 95% of all shrinkage occurs during the first five minutes that the Efficast mask is on the patient. The Orfit material crystallizes at the end of 24 hours, at which time the maximum precision of the immobilization is achieved. This speed of hardening also makes remasking easier. In the event that a modified mask shape is needed during treatment due to patient weight gain or loss, Efficast material can be re-immersed in warm water and reshaped.

This enables a single mask to be used for a full course of therapy, reducing costs.

QUALITY OF CARE

To keep pace with advances in radiation therapy and support quality of care goals, patient immobilization technology must continue to improve in precision, stability and ease-of-use. Although first-generation immobilization materials, processes and designs have been widely adopted and accepted, their disadvantages for oncologists, therapists and patients leave plenty of room for improvement.

The Orfit Efficast mask represents a major advancement in immobilization that can make a significant difference in treatment accuracy, ease of molding and remolding, and overall patient comfort and acceptance.

Orfit Industries of America
Jericho, NY
orfit.com