focal zone


Also found in: Dictionary, Thesaurus, Legal, Encyclopedia.

focal zone

in ultrasonography, the distance along the beam axis of a focused transducer assembly, from the point where the beam area first becomes equal to four times the focal area to the point beyond the focal surface where the beam area again becomes equal to four times the focal area.

focal

1. limited to a small area or volume.
2. pertaining to or emanating from focus.

focal distance
see focal-film distance.
focal length
the distance between the lens and an object from which all rays of light are brought to a focus.
focal liver disease
widely disseminated micro-abscesses or abscesses, migration paths of helminth larvae.
focal macular melanosis
dark colored spots on the skin, not elevated above the skin surface but apt to be confused with melanosis.
focal myelitis-encephalitis
widely disseminated inflammatory lesions, usually the result of blood-borne infection, in brain and spinal cord.
focal symmetrical encephalomalacia
see focal symmetrical encephalomalacia.
focal symmetrical spinal poliomalacia
see focal symmetrical spinal poliomalacia.
focal ulcerative dermatitis
manifest by ulcers in the unfeathered anterior breast skin of 4 to 5 months old male turkeys. The incidence is influenced by litter type. Called also breast buttons.
focal zone
in ultrasound, the area of the transducer where the sound beam is most sharply focussed and where the area under examination will give the best image.
References in periodicals archive ?
In the case when the focal distance changes and the aperture is stable in the axis of the ultrasonic beam, the pressure module reaches the maximum in the focal area and the increased pressure zone remains in the whole focal zone length, decreasing almost in a straight direction in terms of increase in focal distance.
The image was focused at all times - eliminating the need to look for focal zones, and the B-Flow technology allowed me to clearly visualize the blood flow.
As the ciliary muscle loses some of its ability to adjust to different distance ranges--think of how you hold a book a little farther away from your eyes than you used to--multi-focal lenses can help, because they are made with several focal zones to assist with a variety of distances.