Machine Design

Just what the doctor ordered: CAM software prescribes radiation blockers

A special version of the SurfCAM NC program generates toolpaths from medical CT scans rather than from CAD models. Moreover, the machining paths aren't one-for-one replicas of surfaces gleaned from CT data.

A special version of SurfCAM generates toolpaths that turn an aluminum block into a radiation compensator. Manufacturing engineers with CAMcad Technologies, Winter Springs, Fla. (www.camcadtech.com), produced the system called .decimal (digitally enhanced compensation intensity modulation with aluminum) using the API in the NC program.

Instead, the software uses the CT scans to figure out how to shape protective metal shields that sit over healthy tissue during radiation treatments. The brass or aluminum blocks, called tissue compensators, were invented by Southeastern Radiation Products, Sanford, Fla. (www.seradiation.com).

A problem with radiation therapy is that tumors reside at different depths and locations. "It's necessary to take tissue density into account before prescribing radiation treatments," explains Richard Sweat, SRP's president. "Bone is twice as dense as muscle, while lung tissue is only one-fifth as dense. It's important to factor all that into treatment to ensure the right amount of radiation reaches the target."

Sweat says the addition to SurfCAM CAD/CAM software, from Surfware Inc., Westlake Village, Calif. (www.surfware.com) generates geometry for compensators and toolpaths, and drives the NC machine. Cutting a compensator takes from 6 min to an hour depending on complexity. A four-axis Mazak machining center at the SRP facility cuts eight units in one setup. The company can pack a finished compensator for overnight delivery in just 9 hr after receiving the patient information. The company produces up to 150 devices a week. -- Paul Dvorak

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