Factor analysis is an efficient technique to the analysis of dynamic structures in medical image sequences and recently
has been used in contrast-enhanced ultrasound (CEUS) of hepatic perfusion. Time-intensity curves (TICs) extracted by
factor analysis can provide much more diagnostic information for radiologists and improve the diagnostic rate of focal
liver lesions (FLLs). However, one of the major drawbacks of factor analysis of dynamic structures (FADS) is
nonuniqueness of the result when only the non-negativity criterion is used. In this paper, we propose a new method of
replace-approximation based on apex-seeking for ambiguous FADS solutions. Due to a partial overlap of different
structures, factor curves are assumed to be approximately replaced by the curves existing in medical image sequences.
Therefore, how to find optimal curves is the key point of the technique. No matter how many structures are assumed, our
method always starts to seek apexes from one-dimensional space where the original high-dimensional data is mapped.
By finding two stable apexes from one dimensional space, the method can ascertain the third one. The process can be
continued until all structures are found. This technique were tested on two phantoms of blood perfusion and compared to
the two variants of apex-seeking method. The results showed that the technique outperformed two variants in
comparison of region of interest measurements from phantom data. It can be applied to the estimation of TICs derived
from CEUS images and separation of different physiological regions in hepatic perfusion.
In this paper, we proposed an adaptive watermarking algorithm to embed invisible digital watermarking in the wavelet domain of ultrasonic image. By analyzing the characteristic of detail sub-band coefficients of the ultrasonic image after discrete wavelet transform (DWT), we use the mean and variance of the detail sub-bands to modify the wavelet coefficients adaptively, and the embedded watermark is invisible to human visual system (HVS) and adapted to the original image. We can derive the just noticeable different (JND), which describes the maximum signal intensity that the various parts of image can tolerate the digital watermarking. By using this digital watermarking technique we can embed a certainty or confidentiality information directly into original ultrasonic images so that the replication and transmission of ultrasonic image can be tracked efficiently. Therefore, the copyright and ownership of ultrasonic images can be protected, which is critical for the authorization usage of the source of ultrasonic images. The experimental results and attack analysis showed that the proposed algorithm is effective and robust to ultrasonic image processing operations and geometric attacks.
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