title: A combination of parabolic and grid slope interpolation for 2D tissue displacement estimations.
abstract: Parabolic sub-sample interpolation for 2D block-matching motion estimation is computationally efficient. However, it is well known that the parabolic interpolation gives a biased motion estimate for displacements greater than |y.2| samples (y = 0, 1, …). Grid slope sub-sample interpolation is less biased, but it shows large variability for displacements close to y.0. We therefore propose to combine these sub-sample methods into one method (GS15PI) using a threshold to determine when to use which method. The proposed method was evaluated on simulated, phantom, and in vivo ultrasound cine loops and was compared to three sub-sample interpolation methods. On average, GS15PI reduced the absolute sub-sample estimation errors in the simulated and phantom cine loops by 14, 8, and 24% compared to sub-sample interpolation of the image, parabolic sub-sample interpolation, and grid slope sub-sample interpolation, respectively. The limited in vivo evaluation of estimations of the longitudinal movement of the common carotid artery using parabolic and grid slope sub-sample interpolation and GS15PI resulted in coefficient of variation (CV) values of 6.9, 7.5, and 6.8%, respectively. The proposed method is computationally efficient and has low bias and variance. The method is another step toward a fast and reliable method for clinical investigations of longitudinal movement of the arterial wall.
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, Lund University, Ole Römers väg 3, 221 00, Lund, Sweden. John.Albinsson@bme.lth.se.
authors.forename: John
authors.initials: J
authors.lastname: Albinsson
authors.affiliation: Department of Medical Imaging and Physiology, Skåne University Hospital, Lund University, Malmö, Sweden.
authors.forename: Åsa Rydén
authors.initials: ÅR
authors.lastname: Ahlgren
authors.affiliation: Clinical Sciences Lund, Biomedical Engineering, Lund University, Lund, Sweden.|Medical Services, Skåne University Hospital, Lund, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Jansson
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, Lund University, Ole Römers väg 3, 221 00, Lund, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Cinthio
mesh_terms: D000465:Algorithms; D017536:Carotid Artery, Common / Q000000981:diagnostic imaging* / Q000502:physiology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D009038:Motion; D009068:Movement / Q000502:physiology*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*
keywords: Block matching; In silico; In vivo; Speckle tracking; Sub-sample estimation; Ultrasound