A method for generating a composite image using an intravascular imaging device includes receiving reflected echo signals from at least one transducer along a first of a plurality of radial scan lines. The received echo signals are passed through a plurality of signal processing channels to form a plurality of filtered signals. The filtered signals include a high-resolution tissue structure signal and at least one first pre-blood-flow-mask signal. High-resolution tissue structure signals are processed to form a high-resolution tissue structural image. First pre-blood-flow-mask signals are cross-correlated with second pre-blood-flow-mask signals from an adjacent radial scan line to form blood-flow-mask signals. Blood-flow-mask signals are processed to form a blood-flow mask. For each pixel of the composite image, it is determined whether to use a corresponding pixel of the high-resolution tissue structural image or a corresponding pixel of the cross-correlated blood flow mask to generate the composite image pixel.