title: Superresolution of ultrasound images using the first and second harmonic signal.
abstract: This paper presents a new method of blind two-dimensional (2-D) homomorphic deconvolution and speckle reduction applied to medical ultrasound images. The deconvolution technique is based on an improved 2-D phase unwrapping scheme for pulse estimation. The input images are decomposed into minimum-phase and allpass components. The 2-D phase unwrapping is applied only to the allpass component. The 2-D phase of the minimum-phase component is derived by a Hilbert transform. The accuracy of 2-D phase unwrapping is also improved by processing small (16 x 16 pixels) overlapping subimages separately. This takes the spatial variance of the ultrasound pulse into account. The deconvolution algorithm is applied separately to the first and second harmonic images, producing much sharper images of approximately the same resolution and different speckle patterns. Speckle reduction is made by adding the envelope images of the deconvolved first and second harmonic images. Neither the spatial resolution nor the frame rate decreases, as the common compounding speckle reduction techniques do. The method is tested on sequences of clinical ultrasound images, resulting in high-resolution ultrasound images with reduced speckle noise.
authors.affiliation: Section for Medical Image Analysis and Informatics, Dept. of Physiology, University of Bergen, Arstadveien 19, 5009 Bergen, Norway. Torfinn.Taxt@fys.uib.no
authors.forename: Torfinn
authors.initials: T
authors.lastname: Taxt
authors.forename: Radovan
authors.initials: R
authors.lastname: Jirík
mesh_terms: D000465:Algorithms; D004452:Echocardiography / Q000379:methods; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging; D010179:Pancreas / Q000000981:diagnostic imaging; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D014463:Ultrasonography / Q000379:methods*