Steganographic coding scheme based on dither convolutional trellis under resampling mechanism.

With the rapid development of mobile internet and cloud computing, numerous digital me-dia files in mobile social networking and media sharing software have become the important carriers of steganography. However, these digital media files may be resampled by the media server when being pushed to the intelligent mobile terminals. The resampling of digital media files is a transfor-mation which enlarges or shrinks objects by a scale factor that is the same in all dimensions. In order to reduce embedding distortion while ensuring the correct extraction of secret messages under resam-pling mechanism, a steganographic coding scheme based on dither convolutional trellis is proposed in this paper. The resampling mapping is estimated with finite sample pairs. The resampling stego media files with secret messages embedded are generated from the estimated resampling cover media files by syndrome-trellis codes (STCs). According to the estimated resampling mapping, the dither convolutional trellis for one dimensional resampling is constructed to generate the source stego me-dia files from source cover media files and resampling stego media files. The steganographic coding scheme is also extended to the circumstance of two dimensional resampling such as image scaling. The experimental results show that the proposed steganographic scheme can achieve less embedding dis-tortion while ensuring the accuracy of secret messages extraction under multi-dimensional resampling mechanism.

Diagnostic Value of Prospective Electrocardiogram-triggered Dual-source Computed Tomography Angiography for Infants and Children with Interrupted Aortic Arch.

BACKGROUND: Accurate assessment of intra- as well as extra-cardiac malformations and radiation dosage concerns are especially crucial to infants and children with interrupted aortic arch (IAA). The purpose of this study is to investigate the value of prospective electrocardiogram (ECG)-triggered dual-source computed tomography (DSCT) angiography with low-dosage techniques in the diagnosis of IAA. METHODS: Thirteen patients with suspected IAA underwent prospective ECG-triggered DSCT scan and transthoracic echocardiography (TTE). Surgery was performed on all the patients. A five-point scale was used to assess image quality. The diagnostic accuracy of DSCT angiography and TTE was compared with the surgical findings as the reference standard. A nonparametric Chi-square test was used for comparative analysis. P <0.05 was considered as a significant difference. The mean effective radiation dose (ED) was calculated. RESULTS: Diagnostic DSCT images were obtained for all the patients. Thirteen IAA cases with 60 separate cardiovascular anomalies were confirmed by surgical findings. The diagnostic accuracy of TTE and DSCT for total cardiovascular malformations was 93.7% and 97.9% (P > 0.05), and that for extra-cardiac vascular malformations was 92.3% and 99.0% (P < 0.05), respectively. The mean score of image quality was 3.77 ± 0.83. The mean ED was 0.30 ± 0.04 mSv (range from 0.23 mSv to 0.39 mSv). CONCLUSIONS: In infants and children with IAA, prospective ECG-triggered DSCT with low radiation exposure and high diagnostic efficiency has higher accuracy compared to TTE in detection of extra-cardiac vascular anomalies.

Comparison of low-dose sequences of dual-source CT and echocardiography for preoperative evaluation of aortic valve disease.

BACKGROUND: Accurate evaluation of coronary artery, aortic valve annulus diameter (AVAD), and cardiac function in patients with aortic valve disease is of great significance for surgical strategy. In this study, we explored the preoperative evaluation of low-dose sequence (MinDose sequence) scan of dual-source CT (DSCT) for those patients. METHODS: Forty patients suspected for aortic valve disease (the experimental group) underwent MinDose sequence of DSCT to observe coronary artery, AVAD, and left ventricular ejection fraction (LVEF). Another 33 subjects suspected for coronary artery disease (the control group) underwent conventional retrospective electrocardiographically-gated sequence of DSCT. Two-dimensional transthoracic echocardiography (2D-TTE) and four-dimensional transthoracic echocardiography (4D-TTE) were applied in the experimental group to measure AVAD and LVEF and compared with MinDose-DSCT. RESULTS: There was a strong correlation between LVEFs measured by 2D-TTE and MinDose-DSCT (r = 0.87, P < 0.01), as well as between 4D-TTE and MinDose-DSCT (r = 0.90, P < 0.01). AVAD measured by MinDose-DSCT was in good agreement with corresponding measurements by 2D-TTE (r = 0.90, P < 0.01). The effective dose in the experimental group was 63.54% lower than that in the control group. CONCLUSIONS: MinDose sequence of DSCT with a low radiation dose serving as a one-stop preoperative evaluation makes effective assessment of the coronary artery, AVAD, and LVEF for patients with aortic valve disease.