title: Cavitation-enhanced back projection for acoustic rib detection and attenuation mapping.
abstract: High-intensity focused ultrasound allows for minimally invasive, highly localized cancer therapies that can complement surgical procedures or chemotherapy. For high-intensity focused ultrasound interventions in the upper abdomen, the thoracic cage obstructs and aberrates the ultrasonic beam, causing undesired heating of healthy tissue. When a phased array therapeutic transducer is used, such complications can be minimized by applying an apodization law based on analysis of beam path obstructions. In this work, a rib detection method based on cavitation-enhanced ultrasonic reflections is introduced and validated on a porcine tissue sample containing ribs. Apodization laws obtained for different transducer positions were approximately 90% similar to those obtained using image analysis. Additionally, the proposed method provides information on attenuation between transducer elements and the focus. This principle was confirmed experimentally on a polymer phantom. The proposed methods could, in principle, be implemented in real time for determination of the optimal shot position in intercostal high-intensity focused ultrasound therapy.
authors.affiliation: Imaging Division, UMC Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. Electronic address: p.ramaekers@umcutrecht.nl.
authors.forename: Pascal
authors.initials: P
authors.lastname: Ramaekers
authors.affiliation: Imaging Division, UMC Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: de Greef
authors.affiliation: Imaging Division, UMC Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
authors.forename: Chrit T W
authors.initials: CT
authors.lastname: Moonen
authors.affiliation: Imaging Division, UMC Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
authors.forename: Mario G
authors.initials: MG
authors.lastname: Ries
mesh_terms: D000818:Animals; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012272:Ribs / Q000000981:diagnostic imaging*; D013552:Swine; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*
keywords: Adaptive focusing; Attenuation; Cavitation; High-intensity focused ultrasound; Intercostal; Obstruction; Phased array; Reflection; Rib detection; Thoracic cage