A computed tomography (CT) or ultra sound imaging system and method are configured to construct images of an object. The imaging system includes: a radiation or ultrasound source including a collimating or a blocking device configured to generate both a narrow beam and a wide beam; a detector configured to detect radiation or ultrasound wave from the radiation or ultrasound wave from the radiation or ultrasound source; and at least one processing circuit configured to: determine a scatter-to-primary ratio (SPR) of the wide beam based on the narrow beam; determine a primary component of the wide beam based on the SPR to thereby separate the primary component from a scattered component of the wide beam; and construct an image of an object inside a patient using the primary component to thereby improve a contrast of the object.