title: Physical and mechanical properties of ePTFE stretch vascular grafts determined by time-resolved scanning acoustic microscopy.
abstract: OBJECTIVE
  Determination of physical and mechanical characteristics and properties of thin-walled (0.39 mm) expanded polytetrafluoroethylene stretch vascular prostheses by time-resolved scanning acoustic microscopy (TR-SAM).
  
  
  METHODS
  Samples of Stretch Gore-Tex were mounted on polymethylmethaacrylate substrate, and ethyl alcohol was used as acoustic couplant. A 10 MHz ultrasound transducer mounted on a SAM50 scanning acoustic microscope generated short, pulsed sound waves. Reflected signals were used for imaging and for computer analysis of time resolved wave forms acquired by a digital sampling oscilloscope to calculate physical and mechanical characteristics of the material.
  
  
  RESULTS
  Graft wall thickness: 0.395 (0.352/0.401) mm; graft wall sound wave penetration velocity: 1111 (1083/1129) ms-1; acoustic impedance: 3.685 (2.975/4.370) 10(6) kg m-3s-1; attenuation coefficient: 0.144 (0.096/0.229) dB mm-1 MHz-1; material density: 3360 (2712/3982) kg m-3; elastic stiffness: 4.06 (3.35/4.83) GPa (median and (25/75) percentiles; n = 8 samples, 10 measurements spaced 100 microns apart in each sample).
  
  
  CONCLUSIONS
  TR-SAM can effectively quantify ePTFE graft wall properties, and new data on graft properties have been provided. The acoustic impedance and elastic stiffness of the ePTFE graft wall are 2.2 and 1.6 times higher, respectively, than in human coronary arteries, and it is highly reflective of ultrasound.
authors.affiliation: SAM Laboratory, Institute of Experimental Clinical Research, Aarhus University Hospital, Denmark.
authors.forename: C S
authors.initials: CS
authors.lastname: Jørgensen
authors.forename: W P
authors.initials: WP
authors.lastname: Paaske
mesh_terms: D000162:Acoustics; D001807:Blood Vessel Prosthesis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003331:Coronary Vessels / Q000502:physiology; D004548:Elasticity; D000431:Ethanol; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D008853:Microscopy; D009991:Oscillometry; D019904:Polymethyl Methacrylate; D011138:Polytetrafluoroethylene / Q000737:chemistry*; D011474:Prosthesis Design; D012815:Signal Processing, Computer-Assisted; D013314:Stress, Mechanical; D013499:Surface Properties; D014463:Ultrasonography
chemical_list: D000431:Ethanol; D011138:Polytetrafluoroethylene; D019904:Polymethyl Methacrylate