title: Image-Guided Ultrasound Characterization of Volatile Sub-Micron Phase-Shift Droplets in the 20-40 MHz Frequency Range.
abstract: Phase-shift perfluorocarbon droplets are designed to convert from the liquid to the gas state by the external application of acoustic or optical energy. Although droplet vaporization has been investigated extensively at ultrasonic frequencies between 1 and 10 MHz, few studies have characterized performance at the higher frequencies commonly used in small animal imaging. In this study, we use standard B-mode imaging sequences on a pre-clinical ultrasound platform to both image and activate sub-micron decafluorobutane droplet populations in vitro and in vivo at center frequencies in the range of 20-40 MHz. Results show that droplets remain stable against vaporization at low imaging pressures but are vaporized at peak negative pressures near 3.5 MPa at the three frequencies tested. This study also found that a small number of size outliers present in the distribution can greatly influence droplet performance. Removal of these outliers results in a more accurate assessment of the vaporization threshold and produces free-flowing microbubbles upon vaporization in the mouse kidney.
authors.affiliation: Physical Sciences Department, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada. Electronic address: pssheeran@gmail.com.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Sheeran
authors.affiliation: Physical Sciences Department, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Yasaman
authors.initials: Y
authors.lastname: Daghighi
authors.affiliation: Physical Sciences Department, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Kimoon
authors.initials: K
authors.lastname: Yoo
authors.affiliation: Physical Sciences Department, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Ross
authors.initials: R
authors.lastname: Williams
authors.affiliation: Physical Sciences Department, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Cherin
authors.affiliation: Physical Sciences Department, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
authors.forename: F Stuart
authors.initials: FS
authors.lastname: Foster
authors.affiliation: Physical Sciences Department, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Burns
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000737:chemistry* / Q000528:radiation effects; D005740:Gases / Q000138:chemical synthesis* / Q000528:radiation effects; D019220:High-Energy Shock Waves; D007668:Kidney / Q000737:chemistry / Q000000981:diagnostic imaging*; D051379:Mice; D008809:Mice, Inbred C3H; D053758:Nanoparticles / Q000737:chemistry* / Q000528:radiation effects / Q000648:ultrastructure; D009374:Neoplasms, Experimental / Q000737:chemistry / Q000000981:diagnostic imaging; D044367:Phase Transition / Q000528:radiation effects; D012996:Solutions; D013010:Sonication / Q000379:methods; D014463:Ultrasonography / Q000379:methods*
chemical_list: D003287:Contrast Media; D005740:Gases; D012996:Solutions
keywords: Acoustic droplet vaporization; Perfluorocarbon; Phase-shift droplets; Ultrasound contrast agents