Ultrasound transducers transmits high frequency sound waves and recieve back echoes, which forms ultrasound images.

Types -
Linear transducer-
High frequency (7 to 12MHz) - Better resolution, lower depth.
Hockey stick probe - small foot print linear transducer. Used for MSK ultrasound and peripheral nerve imaging.
Convex aka Curvilinear transducer-
Lower frequency ( 2 to 7 MHz) - Better depth, relatively poor resolution.
2D convex probes used for - Abdominal imaging, neurosonogram, Obstetric scan.
3D imaging - Gynec and obstetric imaging.
Phased array transducers -
Low frequency, small foot print (2.5 MHz to 7.5MHz).
Narrow beam which expands - giving a triangular image.
Used for cardiac and brain imaging.
Endocavitatory transducers-
Endovaginal, endorectal probes.
Small curvilinear footprint.
Frequency range from 3 to 12MHz.
Transesophageal transducers -
Used for transesophageal echocardiography.
4 D transducers -
It is seeing 3D images in motion.
Endovascular transducers -
Very high frequency compact transducers attached to a catheter.
Imaging blood vessels and characterizing plaque morphology, extent of luminal stenosis etc