title: High frequency (20 MHz) ultrasonic devices: advantages and applications.
abstract: OBJECTIVE
  This paper investigates the problems, advantages and potential applications of 20 MHz ultrasonic devices.
  
  
  METHODS
  Aqueous gel and a thin appropriate membrane to enclose the front tip were used with 20 MHz probes without obvious decrease in resolution and sensitivity compared to the results obtained without a membrane and this considerably facilitates their routine use.
  
  
  RESULTS
  Many applications with linear scanning were evaluated in dermatology, ophthalmology (investigations of the anterior chamber of the eye, checking of corneal grafts), stomatology (detection and evaluation of periodontal disease) and in the field of measurement of very low velocities in small vessels by means of a duplex probe comprising two 20 MHz transducers: an imaging transducer and an inclined blood flow measurement transducer. Velocity profiles (velocities less than 0.50 mm/s) were measured in 100-300 microm diameter vessels using a cross-correlation method.
  
  
  CONCLUSIONS
  The use of 20 MHz frequency limits resolution but we have shown that this frequency allows the development of easy to handle probes.
authors.affiliation: Unité INSERM 316, Faculté de Médecine, 2 bis boulevard Tonnellé, 37032, Tours, France. berson@univ-tours.fr
authors.forename: M
authors.initials: M
authors.lastname: Berson
authors.forename: J M
authors.initials: JM
authors.lastname: Grégoire
authors.forename: F
authors.initials: F
authors.lastname: Gens
authors.forename: J
authors.initials: J
authors.lastname: Rateau
authors.forename: F
authors.initials: F
authors.lastname: Jamet
authors.forename: L
authors.initials: L
authors.lastname: Vaillant
authors.forename: F
authors.initials: F
authors.lastname: Tranquart
authors.forename: L
authors.initials: L
authors.lastname: Pourcelot
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D003880:Dermatology / Q000295:instrumentation; D004867:Equipment Design; D005782:Gels; D006801:Humans; D008567:Membranes, Artificial; D009885:Ophthalmology / Q000295:instrumentation; D019242:Oral Medicine / Q000295:instrumentation; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation*
chemical_list: D005782:Gels; D008567:Membranes, Artificial