title: Substantial fluctuation of acoustic intensity transmittance through a bone-phantom plate and its equalization by modulation of ultrasound frequency.
abstract: For safe and efficient sonothrombolysis therapies, accurate estimation of ultrasound transmittance through the human skull is essential. The present study clarifies uncertainty surrounding this transmittance and experimentally verifies the equalization of transmittance through the modulation of ultrasound frequency. By changing three factors (ultrasound frequency, the thickness of a bone-phantom plate, and the distance between a transducer and a bone-phantom plate), we measured the intensity of ultrasound passing through the plate. Two activating methods, sinusoidal waves at 500 kHz and modulated waves, were compared. When we changed (1) the distance between a transducer and a bone-phantom plate and (2) the thickness of the bone-phantom plate, ultrasound transmittance through the plates substantially fluctuated. The substantial fluctuation in transmittance was observed also for a cut piece of human temporal skull bone. This fluctuation significantly declined for the modulated wave. In conclusion, modulation of ultrasound frequency can equalize the transmittance with an approximately 30-65% fluctuation drop and an approximately 40% fluctuation drop for a bone-phantom plate and for a cut piece of skull bone, respectively. By using modulated waves, we can develop safer and more effective sonothrombolysis therapies.
authors.affiliation: Division of Medical Engineering, Research Center for Medical Sciences, The Jikei University School of Medicine, 3-25-8, Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Saito
authors.affiliation: Division of Medical Engineering, Research Center for Medical Sciences, The Jikei University School of Medicine, 3-25-8, Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Zuojun
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Neurology, The Jikei University School of Medicine, 3-25-8, Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Mitsumura
authors.affiliation: Department of Emergency Medicine, The Jikei University School of Medicine, 3-25-8, Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Takeki
authors.initials: T
authors.lastname: Ogawa
authors.affiliation: Department of Neurology, The Jikei University School of Medicine, 3-25-8, Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Iguchi
authors.affiliation: Division of Medical Engineering, Research Center for Medical Sciences, The Jikei University School of Medicine, 3-25-8, Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan. Electronic address: masajun2093ryo@jikei.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yokoyama
mesh_terms: D000162:Acoustics; D006801:Humans; D012886:Skull / Q000000981:diagnostic imaging*; D013010:Sonication / Q000379:methods; D013701:Temporal Bone / Q000000981:diagnostic imaging; D015912:Thrombolytic Therapy / Q000379:methods*; D014464:Ultrasonic Therapy / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*
keywords: Acute ischemic stroke; Modulation; Sonothrombolysis; Thrombolysis; Transcranial transmittance