TACOMA, Wash. — Staff Sgt. Jeff Ebert's entire body flinches as a roadside bomb explodes near his vehicle. Smoke obscures his view. Gunfire rattles around him.

This isn't on a road in Iraq but inside a room at Madigan Army Medical Center, where psychologists plan to begin using virtual reality — think immersive video games — to treat post-traumatic stress disorder by recreating the conditions of war.

Virtual-reality therapy provides doctors with a tool that uses visual, auditory and thermal cues to set the stage for treatment of veterans with the disorder, which causes nightmares and flashbacks. It can be so severe that some victims withdraw from society.

At Madigan, clinical psychologist Greg Reger hopes to begin offering the treatment later this summer.

"Just about everybody is affected by their deployment experience," said Reger, a former Army captain who recently came off active duty after spending a year in Iraq with the 62nd Medical Brigade. "The vast majority come home and there's a natural recovery that occurs, but for the significant minority that does need additional help, we do see a number of those individuals here in the clinic."

The research is being funded by the Office of Naval Research, which in 2005 provided $4 million to several groups to examine how virtual reality can help treat PTSD. The disorder affects an estimated 15 percent to 30 percent of Iraq war veterans.

Other research is being conducted in California, Hawai'i and Georgia. The Madigan program, Reger said, received a $200,000 grant for its work.

In clinical studies at San Diego's Naval Medical Center and Atlanta's Emory University, eight Iraq veterans with PTSD underwent virtual-reality treatment and six showed a reduction of symptoms, said Dr. Albert Rizzo, a University of Southern California psychologist developing a virtual-reality system.

"We're very enthusiastic that this is really going to start to make a difference," Rizzo said.

During a demonstration at Madigan, Ebert appears visibly jolted when a concussion from a bomb rocks his mock Humvee as he drives it in a military convoy. Ebert, who doesn't suffer from PTSD, sits in a chair atop a low platform that rumbles and shakes to simulate the vehicle's motion. He wears a headset that displays the scene.

The experience is "very realistic," he said, noting his palms became sweaty during the demonstration.

"I had my fair share of convoys," said the 28-year-old behavioral health specialist from Toledo, Ohio, who returned from a yearlong tour in Iraq in November 2004.

Next Ebert walks through a simulated Iraqi village and scans the area, his right hand instinctively moving to his hip where he would normally be carrying a sidearm while on patrol.

"Being through it before, it's just automatic reactions ... staying ready," Ebert said. "Just a sense of security."

At Madigan, treatment will involve interviewing the soldier to learn what may have triggered the PTSD symptoms, Reger said. He'll then tailor a virtual-reality scenario for that person.

"What this technology does is it gives us an environment to help facilitate soldiers' telling of their own story," Reger said.

Clinicians can also incorporate a slew of smells — body odor, gunfire or burning rubber, for example — to enhance the therapy sessions.

"You really can do a lot of things ... to heighten the level of realism of the experience," said Mark Wiederhold, president and director of Virtual Reality Medical Center in San Diego.

The company uses cognitive behavioral therapy along with virtual reality to treat people with a range of phobias, including fear of flying, heights and spiders. Its clinicians also have worked with patients involved in motor vehicle accidents who were later diagnosed with post-traumatic stress disorder.

Virtual-reality systems are also being used in the rehabilitation of disabled patients at Israel's Chaim Sheba Rehabilitation Hospital near Tel Aviv.

Previously, options for treating PTSD involved group or individual psychotherapy, or having a person imagine their experience, Wiederhold said.

"The issue is you want to access the fear hierarchy in patients," Wiederhold said. "Only about 15 percent of people are good imaginers. They have difficulty maintaining that state of imagining a scenario. Virtual reality is a much more vivid experience."

Veterans advocates, while not endorsing any specific treatment, welcome the technology for improving mental health.

"Being able to treat these people ... is very important," said Patrick Campbell, legislative director for Iraq and Afghanistan Veterans of America. "It's not just about the drugs."