title: Analysis of effective radiating area, power, intensity, and field characteristics of ultrasound transducers.
abstract: OBJECTIVE
  To characterize the ultrasound fields produced by a cohort of transducers from a single manufacturer via hydrophone and Schlieren technology.
  
  
  METHODS
  Descriptive study.
  
  
  METHODS
  Measurement laboratory.
  
  
  METHODS
  Seven same-model ultrasound transducers from a single manufacturer.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Effective radiating area (ERA), total power, spatial average intensity (SAI), beam nonuniformity ratio (BNR), and Schlieren beam widths at 1.0 and 3.3 MHz.
  
  
  RESULTS
  Values for ERA (1.0 MHz range, 3.62-4.38 cm(2); 3.3 MHz range, 3.74-4.76 cm(2)), total power (1.0 MHz range, 5.0-5.6 W; 3.3 MHz range, 4.7-5.7 W), SAI (1.0 MHz range, 1.2-1.4 W/cm(2); 3.3 MHz range, 1.0-1.5 W/cm(2)), and BNR (1.0 MHz range, 2.79-5.85; 3.3 MHz range, 2.51-4.56) fell within manufacturer's specifications and U.S. Food and Drug Administration (FDA) regulations. Schlieren analysis showed significantly larger beam widths at 3.3 MHz compared with 1.0 MHz and a large degree of variability in the ultrasound fields generated by the different transducers. There were no significant correlations between beam widths and ERA values.
  
  
  CONCLUSIONS
  ERA and total power values in a test cohort exist within a range that met FDA regulations. Individual variability in ERA and total power resulted in 50% variability in SAI. This variability may help explain previous reports of heating differences between transducers.
authors.affiliation: Department of Physical Therapy, Athletic Training/Sports Medicine Program, Quinnipiac University, Hamden, CT, USA. Lenn.Johns@quinnipiac.edu
authors.forename: Lennart D
authors.initials: LD
authors.lastname: Johns
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Straub
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Howard
mesh_terms: D000162:Acoustics; D000704:Analysis of Variance; D002138:Calibration; D006801:Humans; D055095:Optics and Photonics; D009991:Oscillometry; D017410:Practice Guidelines as Topic; D012031:Refractometry; D013059:Spectrum Analysis, Raman; D014159:Transducers / Q000592:standards* / Q000600:supply & distribution; D014464:Ultrasonic Therapy / Q000295:instrumentation* / Q000592:standards