An intravascular ultrasound (IVUS) catheter that can provide forward viewing volumetric ultrasound images would be an invaluable clinical tool for guiding interventions. Single chip integration of front-end electronics with capacitive micromachined ultrasonic transducers (CMUTs) is highly desirable to reduce the interconnection complexity and enable miniaturization in IVUS catheters. For this purpose we use the monolithic CMUT-on-CMOS integration where CMUTs are fabricated directly on top of pre-processed CMOS wafers. This minimizes parasitic capacitances associated with connection lines. We have recently implemented a system design including all the required electronics using 0.35-µm CMOS process integrated with a 1.4-mm diameter CMUT array. In this study, we present the experimental volumetric imaging results from an ex-vivo chicken heart phantom. The imaging results demonstrate that the single-chip forward looking IVUS (FL-IVUS) system with monolithically integrated electronics has potential to visualize the front view of coronary arteries.