title: Mapping 3D Strains with Ultrasound Speckle Tracking: Method Validation and Initial Results in Porcine Scleral Inflation.
abstract: This study aimed to develop and validate a high frequency ultrasound method for measuring distributive, 3D strains in the sclera during elevations of intraocular pressure. A 3D cross-correlation based speckle-tracking algorithm was implemented to compute the 3D displacement vector and strain tensor at each tracking point. Simulated ultrasound radiofrequency data from a sclera-like structure at undeformed and deformed states with known strains were used to evaluate the accuracy and signal-to-noise ratio (SNR) of strain estimation. An experimental high frequency ultrasound (55 MHz) system was built to acquire 3D scans of porcine eyes inflated from 15 to 17 and then 19 mmHg. Simulations confirmed good strain estimation accuracy and SNR (e.g., the axial strains had less than 4.5% error with SNRs greater than 16.5 for strains from 0.005 to 0.05). Experimental data in porcine eyes showed increasing tensile, compressive, and shear strains in the posterior sclera during inflation, with a volume ratio close to one suggesting near-incompressibility. This study established the feasibility of using high frequency ultrasound speckle tracking for measuring 3D tissue strains and its potential to characterize physiological deformations in the posterior eye.
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Jun Liu, 270 Bevis Hall, 1080 Carmack Rd, Columbus, OH, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Cruz Perez
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Jun Liu, 270 Bevis Hall, 1080 Carmack Rd, Columbus, OH, USA.
authors.forename: Elias
authors.initials: E
authors.lastname: Pavlatos
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Jun Liu, 270 Bevis Hall, 1080 Carmack Rd, Columbus, OH, USA.
authors.forename: Hugh J
authors.initials: HJ
authors.lastname: Morris
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Jun Liu, 270 Bevis Hall, 1080 Carmack Rd, Columbus, OH, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.affiliation: Center for Biostatistics, The Ohio State University, Columbus, OH, USA.
authors.forename: Xueliang
authors.initials: X
authors.lastname: Pan
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Jun Liu, 270 Bevis Hall, 1080 Carmack Rd, Columbus, OH, USA.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Hart
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Jun Liu, 270 Bevis Hall, 1080 Carmack Rd, Columbus, OH, USA. liu.314@osu.edu.|Department of Ophthalmology, The Ohio State University, Columbus, OH, USA. liu.314@osu.edu.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
mesh_terms: D000818:Animals; D007429:Intraocular Pressure; D012590:Sclera / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D059629:Signal-To-Noise Ratio; D013552:Swine; D013718:Tensile Strength; D014463:Ultrasonography / Q000379:methods*
keywords: 3D strains; Inflation testing; Peripapillary sclera; Scleral biomechanics; Ultrasound speckle tracking