A linear probe contains one or more acoustic linear array transducer elements arranged in a line to send pulses of sound into a material. The linear array gives a large probe surface (footprint) and near field. In Doppler mode, a linear probe operates a subset of its elements as a linear phased array and can thus steer the Doppler beam at a selected angle to the imaging beam. This is a popular configuration for peripheral vascular and perivascular scanning.

From SIUI Inc.;
'The SIUI CTS-200 is one of few 'linear only' units to be developed with a digital scan converter to process all incoming signals. With a digital processor, not only is the incoming signal processed faster but less noise is introduced into the signal path. The images are cleaner, crisper than you have experienced, even in machines at many times the price.'
'CTS-200 is suitable to a wide range of examination of liver, gallbladder, kidney, spleen, pancreas, thyroid gland, breast, uterus, urinary bladder, OB/GYN, etc. It is a portable ultrasound scanner of high performance.'

From SIUI Inc.;
'Dedicated to ultrasound industry, Shantou Institute of Ultrasonic Instruments, Inc. (SIUI) has launched Apogee 3500, the Digital Color Doppler Ultrasound Imaging System.
With latest imaging technologies, high-definition image quality and excellent practical functions, the Apogee 3500 offers optimal solutions for clinical ultrasonic examination.'

'The Apogee 3500 is available with many high-density, super broadband and multi-frequency probes, such as convex, micro-convex, linear, vaginal, rectal and phased array probes, which are widely applied for different clinical diagnoses, including abdomen (liver, kidney, gall-bladder, pancreas), gynecology (uterus, ovary), obstetrics (early pregnancy, basic OB, complete OB, multi gestation, fetal echo), cardiology (adult and pediatric cardiology), small parts (thyroid, galactophore, testicles, neonate), peripheral vascular and prostate.'

The acoustic lens is placed at the time the transducer is manufactured and cannot be changed. The acoustic lens is generally focused in the mid field rather than the near or far fields. The exact focal length varies with transducer frequency, but is generally in the range of 4-6 cm for a 5 MHz curved linear probe and 7-9 cm for a 3.5 MHz curved transducer.
Placing the elevation plane (z-plane) focal zone of the acoustic lens in the very near or far field would improve the beam width at precisely those depths. However, this would degrade the beam width to a much greater and unacceptable degree at all other depths.
There are some chemicals in ultrasound couplants that can degrade the acoustic lens, destroy bonding, or change the acoustic properties of the lens. Problematic chemicals include mineral oil, silicone oil, alcohol, surfactants, and fragrances. Fragrance can affect the transducer's acoustic lens or face material by absorption over time into elastomer and plastic materials, thus changing the material's weight, size, density, and acoustic impedance. Surfactants can degrade the bond between the lens and the piezoelectric elements and contribute to the accelerated degeneration of the lens.

See also Retrolenticular Afterglow.

From SIUI Inc.;
'The CTS-310B is designed for the diagnosis of liver, gall, kidney, pancreas, thyroid, breast, uterus, bladder, ovary, etc. It is a versatile ultrasound scanner with both linear array scanning and convex scanning.'
Features:
'Powerful image processing circuit & High quality image
A wide range of probes for selection
Cineloop
Probe frequency conversation option
Computer image communication
Various measuring function
Backlit keyboard'