A curvilinear (convex) array transducer has elements arranged along a curved surface, producing a fan-shaped (sector) image that widens with depth. Operating at lower frequencies (typically 2–6 MHz), curvilinear transducers provide good penetration for imaging deep abdominal organs, the obstetric uterus, and pelvic structures. The wide field of view at depth makes them the standard probe for general abdominal and obstetric sonography.