Avid phantom promises improved treatment planning

3D product could speed radiotherapy prep

MDX Medical has begun beta testing a phantom that promises to verify in 3D the accuracy of planned radiosurgical procedures, according to the Vancouver, BC, company. The work-in-progress 3D Avid Phantom System is intended initially for head and neck applications. If successful, the basic design may be expanded to simulate the thyroid, breast, prostate, and other organs.

David M. Phillips, president and CEO of MDX, believes the Avid phantom will provide the most cost-effective means yet of validating treatment plans without requiring a site to replace its own treatment planning software.

"There are tools available that enable verification at a single point or in 2D," Phillips said. "But the phantom must then be removed from the radiosurgical equipment and placed in a scanner for quantitative measurements. These procedures are laborious and time-consuming and must be repeated many times to verify the accuracy of a radiosurgical procedure over a 3D volume."

Verification using the Avid system is much faster: Setup takes 10 minutes, and data are acquired in 15. The entire procedure takes less than a half-hour, Phillips said.

Although still a work-in-progress, the product has already attracted vendor interest.

"The fact that it's a 3D rather than a 2D phantom is certainly an advance," said Harry Tschopik, director of global marketing for Philips Medical Systems. "The anthropomorphic shape improves quality assurance because you're looking at a dose in an irregular shape rather than a dose in just a cube, as with other systems."

While Philips does not routinely use such phantoms, it does recommend them to its customers, Tschopik said.

"I think this phantom has some potential beyond just stereotactic radiosurgery in intensity modulated radiotherapy (IMRT)," he said. "If you could use this for IMRT, that would really be an advance over 2D systems."

The new phantom is built around a detector fashioned largely of "solid water," a material that has the same radiographic character as human tissue. This detector is placed inside an anthropomorphic shell representing the head and neck. Specially cut radiographic films are positioned inside the detector and irradiated using high-energy x-rays delivered in accordance with the treatment plan. The films are then removed and scanned using a standard digitizer. The resulting data, analyzed with proprietary software, can be downloaded into the treatment planning workstation. The information can be superimposed over reference CT or MR scans and viewed by the radiosurgical team using a graphics interface, according to Phillips.

Testing of the phantom's potential is under way at the Mayo Clinic in Jacksonville, FL, and the Medical College of Virginia Hospitals in Richmond. After completion of clinical assessment and design review, possibly by the end of 1Q 2002, MDX will apply for FDA premarket notification.

"For an early-stage medical device company to establish beta testing agreements with these institutions provides an exceptional opportunity," Phillips said. "For MDX to have access to such expertise and to receive cooperation and assistance is particularly encouraging."

The Avid system is expected to list for $20,000 to $30,000. Marketing could begin by the end of 2002. The initial market will include the 700 to 800 radiosurgical systems in operation worldwide, Phillips said.

MDX will have to establish an agreement with a medical device distribution agency to provide effective marketing and reliable after-sales support. But sales may be the least of the company's challenges.

"We foresee demand for these units quickly exceeding our ability to address it successfully at this stage in our corporate development," Phillips said.