A new approach to ophthalmic imaging with concave array transducers

Abstract

Since a human eye is spherical in shape, transmitted ultrasound from the conventional arrays with either linear or convex shape is highly refracted from the anterior segment of the eye, especially the cornea. In ophthalmic imaging, therefore, one of the important issues is a loss of ultrasound energy occurring due to the refraction from the cornea. This paper proposes a concave array of which footprint meshes well with the shape of the cornea, thus allowing for minimizing a loss of ultrasound energy. The design of a concave array was conducted to obtain its optimal geometric parameters and key properties for the application of ophthalmic imaging. The design was verified using a Field II simulation program in terms of spatial resolution and lateral field of view. In addition, the spatial resolution including the levels of grating lobes was compared with that by a linear array with the similar design parameters. The concave array provided the −6 dB lateral beam width of 271 μm and the maximum level of grating lobes of −51.8 dB, which were compatible to those from the linear counterpart, i.e., 273 μm and −53.29 dB. On the other hand, the concave array provided the lateral field of view of 34 mm, but it was about 23 mm in the case of the linear counterpart. The designed concave array offered large enough lateral field of view with a reasonable spatial resolution for ophthalmic imaging. Due to its suitable geometry, the concave array may serve as a useful method to produce high-spatial, high-quality ophthalmic images.