Biomedical subjects

Anthony L Gerig

Publications and source records attributed to Anthony L Gerig.

3 recordsLinked to original sources

PubMed2005

Correlation of RF signals during angular compounding.

A theoretical analysis of the correlation between radio-frequency (RF) echo signal data acquired from the same location but at different angles is presented. The accuracy of the theoretical results is verified with computer simulations. Refinements to previous analyses of the correlation of RF signals originating from the same spatial location at different angular positions are made. We extend the analysis to study correlation of RF signals coming from different spatial locations and eventually correlation of RF signal segments that intersect at the same spatial location. The theory predicts a faster decorrelation with a change in the insonification angle for longer RF echo signal segments. As the RF signal segment becomes shorter, the decorrelation rate with angle is slower and approaches the limit corresponding to the correlation of RF signals originating from the same spatial location. Theoretical results provide a clear understanding of angular compounding techniques used to improve the signal-to-noise ratio in ultrasonic parametric imaging and in elastography.

Algorithms↗

PubMed2005

Optimization of angular and frequency compounding in ultrasonic attenuation estimations.

Previous reports have shown that the variance in ultrasound attenuation measurements is reduced when spatial and frequency compounding were applied in data acquisition and analysis. This paper investigates factors affecting the efficiency of compound attenuation imaging methods. A theoretical expression is derived that predicts the correlation between attenuation versus frequency slope (beta) estimates as a function of the increment between measurement frequencies (deltaf ) and the angular separation between beam lines (Delta (theta)). Theoretical results are compared with those from attenuation measurements on tissue-mimicking phantoms and from simulation data. Both predictions and measurement results show that the correlation between beta estimates as a function of (Delta f ) is independent of the length of the radio frequency (rf) data segment over which beta is derived. However, it decreases with an increase in the length of the data segment used in power spectra estimates. In contrast, the correlation between beta estimates as a function of delta(theta) decreases when the rf data segment length is longer or the frequency of the signal is higher. O 2005 Acoustical Society of America.

Acoustics↗

PubMed2004

Improved parametric imaging of scatterer size estimates using angular compounding.

The feasibility of estimating and imaging scatterer size using backscattered ultrasound signals and spectral analysis techniques was demonstrated previously. In many cases, size estimation, although computationally intensive, has proven to be useful for monitoring, diagnosing, and studying disease. However, a difficulty that is encountered in imaging scatterer size is the large estimator variance caused by statistical fluctuations in echo signals from random media. This paper presents an approach for reducing these statistical uncertainties. Multiple scatterer size estimates are generated for each image pixel using data acquired from several different directions. These estimates are subsequently compounded to yield a single estimate that has a reduced variance. In this feasibility study, compounding was achieved by translating a sectored-array transducer in a direction parallel to the acquired image plane. Angular compounding improved the signal-to-noise ratio (SNR) in scatterer size images. The improvement is proportional to the square root of the effective number of statistically independent views available for each image pixel.

Algorithms↗