Location Of Point Targets Research Articles

Diffraction pattern recognition method for drastically improving image resolution and diagnostic sensitivity.

Compared with the two other mainstream medical imaging methods, CT and MRI, the worst weakness of ultrasound imaging is poor resolution—the ability to resolve tiny variations in tissue structure or texture. Due to sound wave diffraction and the way imaging ultrasound signal is retrieved, a point target in object domain does not generate point image in image domain, but an image spot with sophisticate spot pattern and considerable spot size as functions of point target location relative to the transducer—the most direct cause of poor resolution. The mainstream techniques aimed at reducing the image spot, either by shortening the impulse signal or by sharpening the beam focusing, are unavoidably accompanied by the deteriorated sensitivity and depth of penetration. It is a common consent in medical ultrasound community that ultrasound imaging is very close to its theoretical resolution limit. This article presents a different approach we named E-mode imaging that uses a diffraction-theory-based spot pattern recognition technique to account for the effects of image spot pattern in image processing. With the same set of ultrasound data that B imaging is based on, E-mode imaging achieved five to ten times better resolution and diagnostic power in computer simulations.

Time-reversal RAP-MUSIC imaging

Time-reversal imaging with the MUltiple SIgnal Classification (MUSIC) method for the location of point targets was first proposed by Devaney et al. In this paper, a recursive time-reversal MUSIC algorithm is proposed. The considered approach is based on the Recursively Applied and Projected (RAP) MUSIC which was first introduced for magnetoencephalographic (MEG) data processing. The main goal of this contribution is to test and study a time-reversal RAP-MUSIC approach for target location and imaging.

Time-reversal imaging with multiple signal classification considering multiple scattering between the targets

The time-reversal imaging with multiple signal classification method for the location of point targets developed within the framework of the Born approximation in Lehman and Devaney [“Transmission mode time-reversal super-resolution imaging,” J. Acoust. Soc. Am. 113, 2742–2753 (2003)] is generalized to incorporate multiple scattering between the targets. It is shown how the same method can be used in the location of point targets even if there is multiple scattering between them. On the other hand, both the conventional images and the calculated values of the target scattering amplitudes are scattering model-dependent.

Accuracy of an electromagnetic three-dimensional ultrasound system for carotid artery imaging

Freehand, three-dimensional (3-D) ultrasound (US) systems, which incorporate an electromagnetic tracking device to register the 3-D spatial location of images acquired using a standard linear array scan-probe, are a flexible and cost-effective solution for many clinical applications. The reconstruction accuracy of one such system was investigated by using a precision-made phantom. The error in 3-D distance measurements, under conditions appropriate to US investigations of the carotid arteries, was found to be −0.45 ± 1.30 mm, equivalent to −0.53 ± 3.39% (mean ± SD). The results are relevant to data acquired using a single sweep scan and for distances in the range 25.00 to 79.06 mm. Both the overall accuracy and precision in point-target location were found to be relatively unaffected by scan depth, and the precision of point-target location was found to be poorest in the elevational direction. In conclusion, the system tested in our laboratory performed with high accuracy, adopting a setup and scan-sweep identical to that used for imaging of the carotid arteries in 3-D. (E-mail: d.barratt@ic.ac.uk)

Human factors research in 3-D data presentation. ESD-TR-65-462.

Abstract : A series of experiments was performed to evaluate some of the operating characteristics and potential utility of a volumetric (i.e., real) three-dimensional display produced by projection of a CRT image onto a rotating translucent screen. Some of the variables tested were perceptibility of relative location of point targets in close proximity, perception of location of point targets relative to display boundaries and perception of absolute and relative motion of targets in the volume. Estimation of location and motion were found to be highly accurate and quite rapid. While the results do not point conclusively to specific applications, the utility of volumetric 3-D in making fine position and motion discriminations has been demonstrated. Further study would be required to ascertain utility in practical situations such as air traffic control, space surveillance, etc.