A vaginal transducer is a small ultrasound probe that is inserted directly into the vagina. The vaginal transducer is used in gynecological ultrasound scans and has a long and slender shape to fit into the vagina. A cover is used to ensure sterility, and the transducer is lubricated with a water-soluble gel.

See also Transvaginal Sonography.

A transducer assembly is the configuration of an ultrasound transducer. Electronic array transducers are composed of multiple crystal elements e.g., linear array and phased array transducer assemblies. A handheld mechanical probe may contain a mechanically driven single element transducer, or a rotating wheel transducer. Static B-scanner (obsolete) had a cylindrical probe with a single disk-shaped piezoelectric crystal.
Some probes are designed to be inserted in body cavities (vagina, rectum, esophagus) so that they can get closer to the organ being examined (uterus, prostate gland, heart); getting closer to the region of interest allow for a more detailed view.

See also Endocavitary Echography, Endoscopic Ultrasound, Vaginal Transducer and Rectal Probe.

Transducers used for the real-time mode are different than for the A-mode, B-, or M-modes. A linear array transducer with multiple piezoelectric crystal elements that are different arranged and fired, transmits the needed larger sound beam.
A subgroup of x adjacent elements (8-16; or more in wide-aperture designs) is pulsed simultaneously; the inner elements pulse delayed with respect to the outer elements. The interference of the x small divergent wavelets generates a focused beam. The delay time determining the focus depth of a real-time transducer can be changed during imaging.
Similar delay factors applied during the receiving phase, result in a dynamic focusing effect on the return. This forms a single scan line in the real-time image. To produce the following scan line, another group of x elements is selected by shifting one element position along the transducer array from the previous group. This pattern is then repeated for the groups along the array, in a sequential and repetitive way.

Linear array transducer elements are rectangular and arranged in a line. Linear array probes are described by the radius of width in mm. A linear array transducer can have up to 512 elements spaced over 75-120 mm. The beam produced by such a narrow element will diverge rapidly after the wave travels only a few millimeters. The smaller the face of the transducer, the more divergent is the beam. This would result in poor lateral resolution due to beam divergence and low sensitivity due to the small element size.
In order to overcome this, adjacent elements are pulsed simultaneously (typically 8 to 16; or more in wide-aperture designs). In a subgroup of x elements, the inner elements pulse delayed with respect to the outer elements. The interference of the x small divergent wavelets produces a focused beam. The delay time determines the depth of focus for the transmitted beam and can be changed during scanning.
Linear arrays are usually cheaper than sector scanners but have greater skin contact and therefore make it difficult to reach organs between ribs such as the heart. One-dimensional linear array transducers may have dynamic, electronic focusing providing a narrow ultrasound beam in the image plane. In the z-plane (elevation plane - perpendicular to the image plane) focusing may be provided by an acoustic lens with a fixed focal zone.
Rectangular or matrix transducers with unequal rows of transducer elements are two-dimensional (2D), but they are termed 1.5D, because the number of rows is much less than the number of columns. These transducers provide dynamic, electronic focusing even in the z-plane.

See also Rectangular Array Transducer.

Vector array transducers have phasing applied to linear sequenced arrays to steer pulses in various directions.