title: A simple uniformity test for ultrasound phased arrays.
abstract: OBJECTIVE
  It is difficult to test phased array ultrasound transducers for non functioning elements. We aimed to modify a widely performed test to improve its ease and effectiveness for these arrays.
  
  
  METHODS
  A paperclip was slowly moved along the transducer array, with the scanner operating in M-mode, imaging at a fundamental frequency with automatic gain and grey scale adjustment disabled. Non-functioning elements are identified by a dark vertical line in the image. The test was repeated several times for each transducer, looking for consistency of results. 2 transducers, with faults already shown by electronic transducer testing, were used to validate the method. 23 transducers in clinical use were tested.
  
  
  RESULTS
  The results of the modified test on the 2 faulty transducers agreed closely with electronic transducer testing results. The test indicated faults in 5 of the 23 transducers in clinical use: 3 with a single failed element and 2 with non-uniform sensitivity. 1 transducer with non-uniform sensitivity had undergone lens repair; the new lens was visibly non-uniform in thickness and further testing showed a reduction in depth of penetration and a loss of elevational focus in comparison with a new transducer.
  
  
  CONCLUSIONS
  The modified test is capable of detecting non-functioning elements. Further work is required to provide a better understanding of more subtle faults.
authors.affiliation: Radiation Protection & Radiology Physics, United Lincolnshire Hospitals NHS Trust, Greetwell Road, Lincoln LN2 5QY, UK; Multi-Medix, 33 Turn Street, Syston, Leicester LE7 1HP, UK. Electronic address: nick.dudley@ulh.nhs.uk.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Dudley
authors.affiliation: Multi-Medix, 33 Turn Street, Syston, Leicester LE7 1HP, UK.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Woolley
mesh_terms: D000465:Algorithms; D002138:Calibration; D004867:Equipment Design; D019544:Equipment Failure Analysis; D009068:Movement; D015203:Reproducibility of Results; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods* / Q000592:standards
keywords: Phased array; Quality assurance; Ultrasound