title: Calculation of tissue attenuation with a clinical ultrasound unit.
abstract: OBJECTIVE
  Five alternative methods for estimating tissue attenuation with a clinical ultrasound unit were evaluated.
  
  
  METHODS
  Two homogeneous tissue mimicking phantoms (with known attenuations of 0.25 and 0.54 db/cm/MHz) and 22 human placentas were scanned. Attenuation coefficients were computed by linear regression of 1) L(f), the log spectral difference; 2) Fav (d), the average spectral frequency; 3) log[P(d)], the logarithm of the spectral power; 4) Fav (d) x log[P(d)]; and 5) (Fav(d) + log[P(d)])/2.
  
  
  RESULTS
  Each of these five heuristics provided accurate estimates for the relative attenuations of the two phantoms. For placental tissue, method 3 provided better regression fits than methods 1 and 2. Methods 4 and 5 provide the best regression fits (P < .01).
  
  
  CONCLUSIONS
  The combination of both frequency and power information in methods 4 and 5 compensates, in part, for nonlinearities introduced by tissue heterogeneity. A parameter that combines both frequency and time domain information is likely to provide more reliable estimates of attenuation than power or frequency measurements alone.
authors.affiliation: Department of Radiology, Jefferson Medical College, Philadelphia, PA 19107-5244.
authors.forename: E J
authors.initials: EJ
authors.lastname: Halpern
mesh_terms: D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008961:Models, Structural; D010920:Placenta / Q000000981:diagnostic imaging*; D011247:Pregnancy; D014463:Ultrasonography