Recent advancements in ultrasound technology have revolutionized both medical imaging and therapeutic applications. Among these, volumetric imaging using two-dimensional (2D) array ultrasound transducers has emerged as a powerful tool, enabling real-time three-dimensional (3D) visualization, which is also referred to as four-dimensional (4D) imaging. 4D ultrasound imaging represents the most advanced diagnostic technique in ultrasound and is considered one of the most essential tools for medical diagnostics, particularly for assessing blood flow in micro-sized blood vessels. Due to its real-time and volumetric imaging capabilities, 4D imaging offers a unique advantage for the early diagnosis of cardiovascular and cerebrovascular diseases. The row-column-addressed (RCA) array is a novel 2D ultrasound transducer designed for ultrafast 3D ultrasonic imaging. Compared to traditional fully-sampled 2D matrix arrays, RCA transducers reduce the number of electronic channels from M×N to M+N, thereby significantly lowering hardware costs and manufacturing complexity. This review explores the design, fabrication, and clinical applications of 2D arrays, including both fully-sampled 2D arrays and RCA arrays. We discuss their roles in cardiology, brain imaging, and interventional procedures, while also addressing current challenges and future developments in the field.