Biomedical Engineering

cancer treatment that precisely maps affected tissue, yet protects the cells around it by delivering hundreds of beams of radiation in an exact dose, may be at work in American hospitals by 2002. Called tomotherapy, it is the result of a collaboration between Professor of Biomedical Engineering, Human Oncology and Medical Physics Thomas 'Rock' Mackie (right) and UW-Madison oncologist Minesh Mehta (left). Unlike standard radiation treatments, which employ uniform radiation beams, tomotherapy provides doctors with hundreds of safe coordinates. They can bombard cancer cells while delivering less radiation to the surrounding tissue.

The treatment could eliminate some side effects from radiation exposure, and enable doctors to treat cancers such as pancreatic cancer, untreatable because many sensitive organs surround the pancreas. Tomotherapy also might improve treatments for prostate, liver and cervical cancers, and help doctors treat tumors more quickly.

Scientists at the university's Physical Sciences Laboratory are building a prototype tomotherapy machine, and with previous partner Paul Reckwerdt, Mackie founded TomoTherapy Inc. to bring the device to the medical marketplace. UW Hospital will begin tomotherapy trials this year.

Mackie, Mehta and a team of computer scientists have also perfected a software program that locks in a disease's coordinates, calculates the radiation dose and maps each radiation beam's destination. Called Pinnacle, it works on diseases besides cancer and helps doctors treat nearly 100,000 patients nationwide annually, including about 1,000 at UW Hospital. Mackie and staff members Cam Sanders, Mark Gehring and Reckwerdt recently began the local spin-off company, Geometrics, to pursue Pinnacle's commercial potential.

Systematic change: pH-sensitive valves operate on their own

Like microscopic floodgates, Assistant Professor David Beebe's hydrogel valves regulate fluid flow through channels in micro-fluidic systems, or thumbnail-sized "labs," without the help of external controls.

While conventional microactuators require external power to operate, Beebe's pH-sensitive hydrogel valves are "smart"; they swell and contract in response to changes in their environment, performing both sensing and actuation functions. Collaborating with Professor Jeff Moore of the University of Illinois, Beebe's group makes the valves--tiny hydrogel pillars--right inside the microchannels by flowing a mixture of monomers and a photoinitiator into the channels and irradiating the combination through a photomask. This capability to fabricate functional structures within microfluidic channels will make it significantly easier for scientists to build complex microfluidic systems, which can monitor, pump, mix or control small quantities of fluids.

Although a common example of a microfluidic system is an inkjet-printer nozzle, researchers can use microfluidic systems for on-the-spot analyses and in situations where substances or dangerous chemicals are only available or needed in small quantities. Beebe's work, funded by a DARPA grant, could extend to antigen-responsive hydrogels that could be devices in self-regulated drug delivery or biosensors.

Engineering "user-friendly" tissues

Although scientists already have manufactured artificial skin, cartilage and bone, and are close to perfecting the first artificial heart, they are still looking for ways to improve how those engineered tissues interact with the body. "A lot of the time, these devices are not working because the body has a way of defending itself from these foreign objects," says Assistant Professor Weiyuan John Kao. "If we want to improve these devices, first we have to understand what the body is doing."

Inflammation is one way the body interacts with foreign substances, he says. Collaborating with researchers in such areas as engineering, medicine and cell biology, Kao examines the body-biomaterial interaction at the molecular level, focusing on the fundamentals of inflammation. By learning how cells adhere to and activate on a tissue-engineered product on the molecular level, he attempts to mimic the interaction between host cells and material surfaces covered with proteins. Cells and proteins are basic means by which the body interacts with biomaterials such as artificial skin or organs.

Via this "biomimetism," Kao hopes to increase his understanding of designing advanced biomaterials. Ultimately that understanding will help to improve health-care by enhancing the compatibility and effectiveness of biomedical implants and tissue-engineered products.

Robert G. Radwin, Chair
Room 2130 Engineering Centers Building
1550 Engineering Drive
Madison, WI 53706-1609

Tel: 608/263-4660
Fax: 608/265-9239
E-mail: bme@engr.wisc.edu
www.engr.wisc.edu/bme