In one embodiment, a method is provided. The method includes transmitting a first set of ultrasound waves to determine whether there is fluid flow at a target area. The first set of ultrasound waves are transmitted at a first pulse repetition frequency. The method also includes determining whether there is fluid flow in a second area based on the first set of ultrasound waves. The second area is between the target area and an ultrasound probe. The method further includes transmitting a second set of ultrasound waves to detect fluid flow at the target area in response to determining that there is fluid flow in the second area between the target area and the ultrasound probe. The second set of ultrasound waves are directed towards the target area. The second set of ultrasound waves are transmitted at a second pulse repetition frequency.