An ultrasound image is created from backscattered echoes originating from both diffuse and directional scattering. It is potentially useful to separate these two components for the purpose of tissue characterization. This article presents several models for visualization of scattering fields on 3-dimensional (3D) ultrasound imaging. By scanning the same anatomy from multiple directions, we can observe the variation of specular intensity as a function of the viewing angle. This article considers two models for estimating the diffuse and specular components of the backscattered intensity: a modification of the well-known Phong reflection model and an existing exponential model. We examine 2-dimensional implementations and also propose novel 3D extensions of these models in which the probe is not constrained to rotate within a plane. Both simulation and experimental results show that improved performance can be achieved with 3D models.Key Words-diffuse; scattering; specular; 3-dimensional ultrasound imaging specular, and quasiperiodic structures by using harmonic models for particle movements. This method gives two types of diffuse images: a diffuse friction coefficient image and a diffuse forced frequency image, with the latter showing better contrast between tissues. Other methods 2,4,8 exist for detecting specular reflectors; however, these methods using generalized spectrum techniques often do not aim to detect the class of specular reflectors that are directionally dependent. Instead, any reflection that is strong compared to the surrounding weak reflections is viewed as specular, and the goal is to identify all such strong reflections.Recently, multidirectional ultrasound echo signals have been considered for differentiation and characterization of specular reflection. 1 In this work, the authors have utilised limited-angle spatial compound imaging at each point of the image plane as a function of angle of insonification. A symmetric 2-dimensional (2D) exponential model is fitted in terms of least squares to the measured backscatter over different angles of insonification. The above procedure has promising prospects for differentiation of scar tissues from the surroundings based on the specular reflections.In this article, we are extending this work to consider an alternative reflection model. Our motivation for this research comes from the Phong reflection model 9 that has become the de facto standard as an illumination model in computer graphics applications. This model is an empirical model and considers that the specular reflection is stronger in one direction and falls off rapidly as we move away from it. This approach has the advantage of being conceptually simple and in a different context 10 has previously been used as a reflection model for deconvolution of a single 2D ultrasound image. That approach estimates the specular direction using an edge detection approach from the image data. In comparison, we use multiple scans from different directions to determine the true reflection properties of the un...