Two women and two boys were injured in a two-vehicle, head-on collision in East Dennis around 10 a.m. Saturday, Dennis police said. Trude Maloney, 69, of Dennis, apparently drifted over the center line at 312 Setucket Road while driving alone westbound in a 2007 Toyota Matrix, according to police Sergeant John Emerson. He said a witness told police that her vehicle collided with a 2003 Ford Taurus driven by Rita Taylor, 83, also of Dennis. Maloney suffered serious abdominal and chest injuries and was taken by helicopter to a Boston hospital, Emerson said. Police are investigating whether a medical issue caused Maloney to cross over the marked lane, he said. Emerson said he did not know her current condition. Taylor was traveling with her grandsons — ages 5 and 12 — from Middle Grove, N.Y. The boys suffered minor injuries in the crash, Emerson said. Taylor suffered more serious injuries to her leg and neck. All three were taken to Cape Cod Hospital.