This format combines the simple electronics of a linear scan, and the large image width in the farfield of the sector scan, with a big probe. Only a part of the probe is used for each beam, and the active part moves between beams. This type of probe is used especially with 3.5 and 5 MHz in abdominal and fetal imaging, see figure 16. The probe is characterized by its radius of curvature, and 4 - 60 mm is normal. It can also be used in probes inserted into the body (transvaginal and transrectal probes) as they are small and have radii of curvature in the range 10 to 20 mm. 
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<img src="/elaring/fag/ultralyd/teknologi/figur16.jpg" height="300">
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Figure 16: Curvilinear scan. Left side shows the scanning situation where a curved probe is held over a fetus in the uterus, and the right side shows the resulting ultrasound image.