Running across home plate at Fenway Park is an activity many of us can only dream of doing. Yet on Sunday morning, several thousand people will get to do just that, and for a good cause, too.The 2012 “Run-Walk to Home Base” gives participants the option of a 9-kilometer run or a 3-mile walk. Both end up at the same place, home plate at Fenway, and both help benefit the Red Sox Foundation and the Mass General Hospital Home Base Program.Through the Home Base Program, U.S. military veterans of the wars in Iraq and Afghanistan can receive treatment for post-traumatic stress disorder (PTSD) or traumatic brain injury (TBI).”Sadly, they’re quite common injuries, especially among those who served (multiple times)” Meg Vaillancourt, senior vice president of the Red Sox and executive director of the Red Sox Foundation, said on Wednesday.Vaillancourt added that shockwaves from improvised explosive devices (IEDs) can affect service members’ brains and “can be felt for a long time.””There are so many IEDs,” she said. “Less than 1 percent of Americans are serving and they are sent in time after time.”She also said that according to estimates, 10 to 30 percent of veterans returning from the conflicts have either PTSD or TBI.The Run-Walk to Home Base is in its third year (the walk was incorporated this year). It is rooted in the Red Sox visits to Walter Reed Hospital in Washington, D.C. during their White House appearances after winning the World Series in 2004 and 2007. Vaillancourt said that Sox chairman Tom Werner and the team were concerned about service members suffering from PTSD or TBI.”Tom Werner said, ‘There’s got to be something the team or charity can do to be part of a solution,” Vaillancourt said.Vaillancourt said that the total amount of money raised from the three years of the event will be over $7 million.”It says something about Red Sox Nation,” she said, “not just their passion for the sport but the compassion they have for members of the community.”Participants in the 2012 event had to commit to raising a minimum of $1,000 for the cause. (Fundraising is closed now.) There were two exceptions: Children ages 6 to 15 could participate in the walk for $125, and 500 members of the military could enter for $50.”They don’t have to do fundraising,” Vaillancourt said of the service members. “They gave at the office.”The chip-timed race begins at 8 a.m., with Gate B opening at 5:30 a.m., coffee and refreshments at 6:30 and opening ceremonies at 7:15.Runners will start in three waves on Yawkey Way, and the course incorporates a number of local landmarks, including Kenmore Square, the Mass Ave. Bridge and Memorial Drive.As for the finish, Vaillancourt said, runners cross a line in front of the Green Monster and then get a photo finish across home plate.Asked about the unusual number of kilometers – more than a 5K, a bit less than a 10K – Vaillancourt noted that nine was the uniform number for Red Sox legend Ted Williams, as well as the number of people on a baseball team and the number of innings in a ballgame.”It’s a pretty magical number in baseball,” she said.The public can attend to watch, Vaillancourt said, as well as participate in what she described as “family-friendly” activities such as making a care package or writing a thank-you note for service members. Visitors can meet Wally the Green Monster and former Red Sox pitching stars Jim Lonborg and Bill Lee, as well as check out World Series championship hardware.While the current team will be on the road in Philadelphia, ownership will be well-represented with Werner, president/CEO Larry Lucchino, and principal owner John Henry and his wife Linda Pizzuti Henry. The Red Sox front office will also be represented through “Team 9,” a fundraising team that has led all entrants for three years in a row. There will also be a team of runners from New England Sports Network, including reporters Tom Caron and Jenny Dell.Asked about the link between running and baseball, Vaillancourt said