Objective: The assessment of blood-flow volume (BFV) is clinically relevant for the diagnosis and monitoring of cardiovascular dysfunctions and the prevention of subsequent secondary diseases. Non-invasive BFV measurement based on ultrasound methods are appealing for lower cost, real-time operation, and equipment portability. Recently, complex ultrasound research scanners with 1024 channels controlling the elements of a 2-D matrix array probe, have been demonstrated suitable for off-line accurate BFV estimates. In this work, a streamlined approach, using a 256-channel research scanner paired with a 256-element 2-D sparse spiral array, is proposed and validated. Methods: This setup allows for simultaneous scanning of the vessel's longitudinal and transverse sections through an interleaved transmission sequence. In real-time, the longitudinal scan is used to determine the flow direction, while the transverse scan captures both the dynamic cross-sectional area and the local velocities by high frame rate color flow mapping. Results: Flow phantom experiments under steady and pulsatile flow conditions were conducted to assess the performance by comparing the measurements with the outputs of a reference flow sensor. The proposed method provided accurate and precise BFV values for both flow conditions, with mean percentage error and standard deviation always lower than 9.4% and 2.8%, respectively. Furthermore, preliminary in vivo experiments have produced results consistent with those reported in the literature. Conclusion: The proposed method based on the use of a sparse array has permitted accurate and precise phantom BFV measurements and has been shown suitable for real-time arterial BFV measurements.