title: Real-time contrast ultrasound muscle perfusion imaging with intermediate-power imaging coupled with acoustically durable microbubbles.
abstract: BACKGROUND
  There is growing interest in limb contrast-enhanced ultrasound (CEU) perfusion imaging for the evaluation of peripheral artery disease. Because of low resting microvascular blood flow in skeletal muscle, signal enhancement during limb CEU is prohibitively low for real-time imaging. The aim of this study was to test the hypothesis that this obstacle can be overcome by intermediate- rather than low-power CEU when performed with an acoustically resilient microbubble agent.
  
  
  METHODS
  Viscoelastic properties of Definity and Sonazoid were assessed by measuring bulk modulus during incremental increases in ambient pressure to 200 mm Hg. Comparison of in vivo microbubble destruction and signal enhancement at a mechanical index (MI) of 0.1 to 0.4 was performed by sequential reduction in pulsing interval from 10 to 0.05 sec during limb CEU at 7 MHz in mice and 1.8 MHz in dogs. Destruction was also assessed by broadband signal generation during passive cavitation detection. Real-time CEU perfusion imaging with destruction-replenishment was then performed at 1.8 MHz in dogs using an MI of 0.1, 0.2, or 0.3.
  
  
  RESULTS
  Sonazoid had a higher bulk modulus than Definity (66 ± 12 vs 29 ± 2 kPa, P = .02) and exhibited less inertial cavitation (destruction) at MIs ≥ 0.2. On in vivo CEU, maximal signal intensity increased incrementally with MI for both agents and was equivalent between agents except at an MI of 0.1 (60% and 85% lower for Sonazoid at 7 and 1.8 MHz, respectively, P < .05). However, on progressive shortening of the pulsing interval, Definity was nearly completely destroyed at MIs ≥ 0.2 at 1.8 and 7 MHz, whereas Sonazoid was destroyed only at 1.8 MHz at MIs ≥ 0.3. As a result, real-time CEU perfusion imaging demonstrated approximately fourfold greater enhancement for Sonazoid at an MI of 0.3 to 0.4.
  
  
  CONCLUSIONS
  Robust signal enhancement during real-time CEU perfusion imaging of the limb is possible when using intermediate-power imaging coupled with a durable microbubble contrast agent.
authors.affiliation: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Division of Cardiology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Seol
authors.affiliation: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Division of Cardiology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Davidson
authors.affiliation: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Division of Cardiology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: J Todd
authors.initials: JT
authors.lastname: Belcik
authors.affiliation: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Division of Cardiology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Mott
authors.affiliation: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Division of Cardiology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Reid M
authors.initials: RM
authors.lastname: Goodman
authors.affiliation: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Division of Cardiology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Azzdine
authors.initials: A
authors.lastname: Ammi
authors.affiliation: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon; Division of Cardiology, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea. Electronic address: linderj@ohsu.edu.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Lindner
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D003199:Computer Systems; D003287:Contrast Media; D004285:Dogs; D055119:Elastic Modulus / Q000528:radiation effects; D005290:Ferric Compounds / Q000737:chemistry* / Q000528:radiation effects; D005466:Fluorocarbons / Q000737:chemistry* / Q000528:radiation effects; D006244:Hardness / Q000528:radiation effects; D007501:Iron / Q000737:chemistry* / Q000528:radiation effects; D008422:Materials Testing; D051379:Mice; D008810:Mice, Inbred C57BL; D045423:Microbubbles; D018482:Muscle, Skeletal / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000502:physiology*; D010087:Oxides / Q000737:chemistry* / Q000528:radiation effects; D055420:Perfusion Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013016:Sound; D014463:Ultrasonography / Q000379:methods*; D014783:Viscosity / Q000528:radiation effects
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; D005466:Fluorocarbons; D010087:Oxides; C069727:Sonazoid; D007501:Iron; C042852:perflutren
keywords: Contrast echocardiography; Contrast ultrasound; Microbubbles; Peripheral artery disease