The dimension of the ultrasound beam and the transducer array are the origin of the beam width artifact or volume averaging artifact. When the ultrasound beam is wider than the diameter of the lesion being scanned, normal tissues which lie immediately adjacent to the lesion arc included within the beam width, and their echotexture is averaged in with that of the lesion.
Thus, what appears to be the echogenicity of the lesion is really that of the lesion plus the averaged normal tissues. Because of volume averaging, cystic lesions may falsely appear to be solid, and some subtle solid lesions may become impossible to distinguish from surrounding normal tissue and, therefore, not identified at all.

See also Ultrasound Picture and Vector Array Transducer.

A curved or curvilinear array transducer is similar to a linear array except that the image created has a sector-type format. A curvilinear array gives a large footprint and near field with a wide sector. Usually, curved transducers are described by the radius of curvature in mm. The transducer elements control the characteristics and direction of the sound beam.
Curvilinear transducers have a wider field of view from the transducer face. Sector scanners are most useful for cardiac ultrasound examinations where the beam is directed between the ribs to image the heart.
Also called convex transducer.

Duplex ultrasonography (duplex scan) consists of two ultrasound modalities to study blood flow and the perivascular tissue. This includes B-mode / gray scale imaging used in combination with spectral Doppler / pulsed-wave Doppler.
The real-time visualization of the vessels and tissue by the B-mode component improves the PW Doppler positioning and the direction of blood flow can be inferred. The angle between the direction of the PW Doppler signal and the estimated direction of blood flow can be measured.
Duplex techniques are available on phased array, linear array, and mechanical scanners. A phased array probe is able to create nearly simultaneous images and flow information. A linear array transducer can also do this if the Doppler probe is attached separately to one end of the scanhead. A mechanical transducer freeze the image; the crystals must be static to produce a Doppler image. The first two transducers are therefore the best choice for Duplex.

See also Compound B-Mode, and Duplex Scanner.

From ESAOTE S.p.A.;
'The 260 Corvus is perfectly suited for multiple applications in black & white ultrasound. The digital console system is standard equipped with three probe connectors for a choice of various linear, convex, annular and annular phased array transducers. The 260 Corvus can be fully integrated into a digital hospital network (PACS) using the optional DICOM® compatible ImageLab™ module.'

Sonography of the gallbladder is a reliable technique for diagnosing e.g., gallstones, cholecystitis, tumors, polyps, or ductal obstruction. Patient should be examined with empty stomach and on a low fat diet the night before. Barium studies, endoscopy, ERCP, colonoscopy, and abdominal CT should be performed after this examination.
Gallbladder ultrasound is best performed with a 5 MHz curved array or a linear array transducer in cases of a very superficial gallbladder. In obese patients or in patients with difficult sonographic access, a 3.5 MHz sector or curved linear transducer is advantageous.
Gallbladder and biliary tree are usually imaged in supine and posterior oblique (LPO) positions. Sometimes very small gallstones are better visible in upright and prone position.