TomoTherapy integrates IMRT components in single product

May 1, 2002

First commercial unit ships this month The first two commercial shipments of a product incorporating a sophisticated form of intensity-modulated radiation therapy (IMRT) will go to Canadian institutions in May and June. Six more

First commercial unit ships this month

The first two commercial shipments of a product incorporating a sophisticated form of intensity-modulated radiation therapy (IMRT) will go to Canadian institutions in May and June. Six more of the device, called HI-ART (highly integrated adaptive radiotherapy system), are scheduled for shipment to U.S. facilities in the fourth quarter.

The technology, based on tomotherapy or "radiation by the slice," administers beams of radiation using a modified CT gantry. The intensity of the beam is first modulated to approximate that of a CT scanner, generating CT-equivalent images that ensure the patient is properly positioned for therapy. Beam intensity is then cranked to a level powerful enough to kill cancerous tumors and administered as 64 individually controlled "beamlets" directed at specific targets identified in the radiation therapy plan. The beam rotates around the patient once every 10 seconds in lockstep with the detector, which records dosage.

As in other forms of IMRT, tomotherapy relies on multileaf collimators to shape the beam to the exact dimensions of the tumor. The ability to both visualize target tissue and administer radiation by slices, however, provides unprecedented flexibility and accuracy.

"IMRT has a very high level of complexity," said John J. Barni, CEO of HI-ART developer, Wisconsin-based TomoTherapy. "We've been told that what the market needs is an easy-to-use product that integrates the imaging process with dose reconstruction and dose registration. That is exactly what TomoTherapy brings to the marketplace."

In the FDA application, which was cleared by regulators Jan. 29, the company claimed only that HI-ART was equivalent to current forms of IMRT. Barni hopes that research conducted at the company's expanding group of clinical sites will document the technology's superiority.

"The fact that we are taking a CT picture of patients on our couch and fusing that with the planning images should give us better registration," Barni said.

This will allow more precise targeting of the beam, he said, so that larger doses of cancer-killing radiation can be administered over fewer patient visits‹without increasing collateral damage to healthy tissue in the path of the beam. Research into radiobiology indicates that the more radiation delivered more accurately to the tumor, the better the outcome, Barni said. No clinical documentation of this effect yet exists, however, because the necessary equipment has not been available‹at least not until now.

Patient outcomes from the use of HI-ART will be measured at the five U.S. Comprehensive Cancer Centers (CCC) where the system will be installed over the coming months. Clinical data will also be added at the University of Wisconsin CCC in Madison, where a HI-ART system is already operating.

HI-ART evolved from research initially conducted at the university. TomoTherapy, a privately financed start-up established specifically to commercialize the product, licensed the technology from the Wisconsin Alumni Research Foundation. Some 120 patents, according to Barni, protect HI-ART.

Barni anticipates rising demand for HI-ART. The goal is to install 100 systems in key cancer centers over the next four years. Unit orders will likely exceed that number worldwide, as the company plans to market HI-ART to a wide range of cancer treatment centers, not just the upper echelon.

TomoTherapy staff assembles the product from components. Several of these, including the gantry and key electrical parts, are obtained from Analogic in Peabody, MA. TomoTherapy engineers focus on software development but also build the specially designed multileaf collimator. The 6-mV accelerator hooked into the HI-ART is obtained from Siemens Medical Solutions, although the product is compatible with any accelerator of similar power.

The systems soon will be built in a new 65,000-square-foot facility being constructed in Madison, and Barni and colleagues will move to the new facility from nearby Middleton. The TomoTherapy Customer and Technology Center is designed to produce up to 100 systems per year. It could easily be expanded, if demand exceeds that number, Barni said.