Unmarked Image Research Articles

Combined ultrasound and near infrared diffused light imaging in a test object

We have investigated the use of combining near infrared (NIR) diffuse light and ultrasound imaging methods to increase the detection sensitivity and to reduce the false alarm rate in small target detection. A line-of-sight optical projection through a test object is identified from an amplitude null and a sharp phase transition produced by diffusive waves originating from two in-phase (initial phase 0 degrees ) and out-of-phase (initial phase 180 degrees ) light emitting diode sources. This line-of-sight is scanned across a scattering phantom. A complete ultrasound B-scan image is recorded at each projected line in the optical scan. Each acoustic image plane is bisected by the optical beam path and lies in the optical scan plane. The scattering phantom simulates acoustic and optical properties of homogeneous tissue. A single small cylinder-like object simulating some acoustic and optical breast tumor properties is inserted at various places in the scattering phantom. With this single object, the optical scanning identifies the line-of-sight passing through the simulated tumor quite well. Most of these simulated tumors were at or below the threshold for acoustic detection and were not seen consistently with unguided ultrasound. For tests in which a target was apparently detected optically, the selected line-of-sight was indicated in each of three adjacent ultrasound images. Two radiologist observers were statistically more accurate (83%) in identifying the target location on the optically-selected ultrasound images than in the unmarked images (52%). That is, in these single-targets of homogeneous scattering background, the optical technique usually provided the correct line-of-sight, and ultrasound generally showed the location along that line.

Copyright protection of digital images by embedded unperceivable marks

Digital watermarking has been proposed as a solution to the problem of copyright protection of multimedia documents in a networked environment. It makes it possible to tightly associate a code to an image, allowing the identification of the data creator, owner and so on. In this paper, after a review of some important watermarking techniques, a new watermarking algorithm for digital images is presented: the method, which enhances a previous technique proposed by Cox et al. [1] [I.J. Cox, J. Kilian, T. Leighton, T. Shamoon, Secure spread spectrum watermarking for multimedia, NEC Research Institute Technical Report 95-10], operates in the frequency domain, by embedding in a selected set of DCT coefficients a sequence of randomly generated real numbers. By exploiting their statistical characteristics, it is possible to reliably extract the embedded sequences without resorting to the original unmarked image. Experimental results demonstrate that the watermark is robust to several image transformations.