Improvement of Resolution of Ultrasound images
This work has been supported by NSF under grant MIP-9553227, the
We consider the problem of improving the resolution of ultrasound (
Since ultrasound is widely used in nondestructive testing of materials, improving its resolution will also be beneficial in areas such as flaw detection in metals and material characterization.
This research is funded by the National Science Foundation, the Whitaker
Foundation, and the
Dr. John M. Reid , Biomedical Engineering and Science Inst., Drexel University
Dr. Flemming Forsberg, Radiology Department, Thomas Jefferson University Hospital, Philadelphia PA.
Dr. Barry Goldberg, Radiology Department,
Some results on distrotion estimation and subsequent image deconvolution are shown below.
ULTRASOUND RF ECHO MODELING AND TISSUE CHARACTERIZATION
Supported by the National Institute of Health under grant grant CA52823
Ultrasound is a widely used medical imaging technique because of its low cost, relative safety, and versatility. Since biological tissues are composed of characteristic structures whose ultrasonic properties often change due to diseases, the ultrasound RF echo contains information that can be used to study the underlying tissue. The goal is to model and process the ultrasound RF echo in order to extract tissue characterization features that are observer-independent.
In this project, we propose a new model for the radio-frequency (RF) ultrasound echo, namely the shot noise process with narrow-band power-law filter function. This model can be justified by considering the tissue as a collection of point scatterers embedded in a uniform medium and assuming a power-law decay instead of exponential decay for attenuation. The model is characterized by the exponent n of the power-law filter and Poisson rate l. Based on this model, the in-phase and quadrature components of the echo can be shown to exhibit 1/f b -type spectral behavior with b = 2(1-n). The envelope also exhibits this type of spectral behavior but with a different exponent and furthermore if the power-law exponent n is equal to 0.5 the envelope follows the well-known Rayleigh statistic. Although the shot noise model has been used in the past for modeling the RF echo, this is the first time that a power-law impulse response filter is used and the resulting power-law spectral behavior of the RF echo is investigated. The theoretical derivations were validated via simulations, while the validity of the proposed model was tested based on clinical ultrasound images of the breast.
The spectral exponents in the
proposed model are associated to tissue
attenuation, whereas l is associated to the
number of scatterers. Since both properties change
due to disease, the estimates of these parameters are
natural candidates for tissue signatures. We have proposed algorithms
for estimating b and l from the data, and investigated the
potential significance of the model parameters in characterizing breast tissue.
We conducted experiments based on clinical ultrasound images of the breast,
provided to us by our collaborators at Thomas Jefferson University Hopsittal in
Although the results on differentiating between normal and abnormal tissue are very good, the ability of model parameters in differentiating between malignant and benign tumor regions is moderate. ROC areas of 72.5%, 70%, and 68% were obtained respectively for the exponent of the envelope, the in-phase component and l. Our results were based on 56 images, 28 of which contained benign tumors and rest contained malignant tumors. We are currently investigating the amount of independent information carried by b and l and the potential advantages of combining the two parameters to obtain a better tissue signature.
Key papers (Improvement of Resolution of Ultrasound images)
U.R. Abeyratne, A.P. Petropulu, T. Golas, J.M. Reid, E. Conant and F. Forsberg, "Higher-Order Vs. Second Order Statistics in Ultrasound Image Deconvolution," IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control , November 1997. Abstract.
U. R. Abeyratne, A.P. Petropulu and J.M. Reid," On modeling the tissue response from ultrasound b-scan images, " IEEE Trans. on Medical Imaging, vol. 14(4), pp. 479-490, August 1996. Abstract.
sU. R. Abeyratne,
A.P. Petropulu and J.M. Reid," Higher-Order Spectra
Based Deconvolution of Ultrasound Images," IEEE
Transactions on Ultrasonics, Ferroelectrics, and
Frequency Control, vol. 42(6), November 1995. Abstract.
Key papers (ULTRASOUND RF ECHO MODELING AND TISSUE CHARACTERIZATION)
Gefen, O. Tretiak, C.W. Piccoli,
K. Donohue, A.P. Petropulu, P.M.
M.A. Kutay, A.P. Petropulu and C.W. Piccoli, "On Modeling Biomedical Ultrasound RF-Echoes Using a Power-Law Shot-Noise Model and Application to Tissue Characterization," Pattern Recognition Letters, vol. 24, no. 4-5, pp. 741-756, February 2003.
MATLAB code for parameter estimation and constrcution of ROC graphs can be obtained by clicking HERE