Phased Array ultrasonics

Ultrasound

Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

 is an advanced method of ultrasonic testing that has applications in medical imaging

Medical ultrasonography

Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...

 and industrial nondestructive testing

Nondestructive testing

Nondestructive testing or Non-destructive testing is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage....

. In medicine a common application of phased array is the imaging of the heart (images of the fetus

Fetus

A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 in the womb are usually made by curvilinear array, a multi-element probe that does not actually phase the signals). When applied to metals the PA image shows a slice view that may reveal defects hidden inside a structure or weld

Welding

Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...

.

Principle of operation

The PA probe consists of many small ultrasonic elements, each of which can be pulsed individually. By varying the timing, for instance by pulsing the elements one by one in sequence along a row, a pattern of constructive interference is set up that results in a beam at a set angle. In other words, the beam can be steered electronically. The beam is swept like a search-light through the tissue or object being examined, and the data from multiple beams are put together to make a visual image showing a slice through the object.

Features of phased array

• The method most commonly used for medical ultrasonography
  Medical ultrasonography
  Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
  
  .
• Multiple probe elements produce a steerable, tightly focused, high-resolution beam.
• Produces an image that shows a slice through the object.
• Compared to conventional, single-element ultrasonic inspection
  Ultrasonic inspection
  In ultrasonic testing , very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz are launched into materials to detect internal flaws or to characterize materials...
  
   systems, PA instruments and probes are more complex and expensive.
• In industry, PA technicians require more experience and training than conventional technicians.

Standards

European Committee for Standardization

European Committee for Standardization

The European Committee for Standardization or Comité Européen de Normalisation , is a non-profit organisation whose mission is to foster the European economy in global trading, the welfare of European citizens and the environment by providing an efficient infrastructure to interested parties for...

 (CEN)

• prEN 16018, Non destructive testing - Terminology - Terms used in ultrasonic testing with phased arrays
• ISO/WD 13588 - prEN 13588, Non-destructive testing of welds – Ultrasonic testing – Use of (semi-) automated phased array technology

External links

• Industrial applications of portable phased array [technical paper]
• Construction Weld Testing Procedures Using Phased Array [technical paper; based on computer modelling]
• Introduction to theory for medical phased array, Martin E. Anderson, Duke University
• Phased array animated simulator [registration required after 5 minutes' use]

Books

• ASME Boiler and Pressure Vessel Code. American Society Of Mechanical Engineers, 2004. Section V — Nondestructive Examination. [See Article 4 — Ultrasonic Examination Methods for Welds. Para E-474 UT-Phased Array Technique]
• ASME Code Case 2235-9, Use of Ultrasonic Examination in Lieu of Radiography — Section I and Section VIII, Divisions 1 and 2. American Society Of Mechanical Engineers, Approval Date: October 11, 2005. [See page 1, footnote 1 on phased array] (PDF here)

See also

• Phased array
  Phased array
  In wave theory, a phased array is an array of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.An antenna array...
  
   (general theory and electromagnetic telecommunications).
• Phased array optics
  Phased array optics
  Phased array optics is the technology of controlling the phase of light waves transmitting or reflecting from a two-dimensional surface by means of adjustable surface elements. It is the optical analog of phased array radar...