Lossy data compression generates distortion or error on the reconstructed image and the distortion becomes visible as the compression ratio increases. Even at the same compression ratio, the distortion appears differently depending on the compression method used. Because of the nonlinearity of the human visual system and lossy data compression methods, we have evaluated subjectively the quality of medical images compressed with two different methods, an intraframe and interframe coding algorithms. The evaluated raw data were analyzed statistically to measure interrater reliability and reliability of an individual reader. Also, the analysis of variance was used to identify which compression method is better statistically, and from what compression ratio the quality of a compressed image is evaluated as poorer than that of the original. Nine X-ray CT head images from three patients were used as test cases. Six radiologists participated in reading the 99 images (some were duplicates) compressed at four different compression ratios, original, 5:1, 1 0: 1 , and 1 5 : 1 . The six readers agree more than by chance alone and their agreement was statistically significant, but there were large variations among readers as well as within a reader. The displacement estimated interframe coding algorithm is significantly better in quality than that of the 2-D block DCT at significance level 0.05. Also, 10: 1 compressed images with the interframe coding algorithm do not show any significant differences from the original at level 0.05.
A 10-touch performance is achieved by using a mutual-capacitive touch sensor. To increase the immunity to display-generated noise, an integrator is used with the input node isolated from touch sensor panel (TSP) during the high-LCD-noise period, controlled by the gate-driver clock. This increases SNR by more than 15 dB.
In this study, we have explored two compression techniques, i.e., 3-D displacement estimated interframe coding algorithm (DEICA) and 2-D DCT algorithm, applied them in ultrasound image compression and assessed their feasibility. A sequence of 96 128 x 128 x 8-bit parallel slices and a set of 25360 x 264 x 8-bit timesequence images have been used in our experiments, and compression ratios in the range of 6 -20 to 1 and 4 -5 to 1 have been obtained in DEICA, while the mean square error was kept to be less than 4.0. While DEICA has achieved higher compression ratios in X-ray CT images than the 2-D DCT algorithm at the same distortion, DEICA has not shown any improvement in compressing ultrasound images. This is mainly due to the fact that statistics within the difference image are sometimes degraded in ultrasound images. After fine-tuning the DEICA by adjusting key parameters based on the statistics of ultrasound images and reducing the speckle noise, higher compression ratios are expected. In the future, 3-D or time-sequence images will have more frame-byframe correlation and less speckle noise patterns with the technical advances in ultrasound probes and data acquisition & image computing technologies. Furthermore, 3-D ultrasound imaging systems will become more popular and the amount of data generated by these devices will increase even further. These new developments might make DEICA more attractive.
The diffusion experiment of Al x Ga 1-x N (x = 0.00, 0.04, 0.45, 0.65, 0.86, 1.00) samples using a solid source of Al 4 C 3 layer was performed by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). The Al x Ga 1-x N (x≦0.45) samples were proven to be a p-type. In second ion mass spectroscopy (SIMS) analysis, the carbon profile is different from the simple complementary error function, but is the double of the complementary error function, meaning AlC or AlCO plus C. The diffusion length (L) was drastically decreased by increasing Al. The diffusion coefficient (D) was also calculated as a function of Al mole fraction.
A C-doped p-AlGaInN light-emitting diode (LED) fabricated from III–V nitride was grown by metalorganic vapor phase epitaxy (MOVPE) by the insertion of Al4C3/Al2O3(0001). Al4C3/Al2O3(0001) with a size of 1×1 mm2 was placed at the center of a 2-in. Al2O3(0001) substrate before growing the LED. An InGaN/GaN multi quantum well (MQW) was used as an active layer. The concentrations of C and Si were different with the distance of Al4C3. Maximum C (p≧1018 cm-3) and Si (n≧1019 cm-3) intensities were observed at the edge and the half of center and edge on the grown wafer, respectively. The voltage of the C-doped AlGaInN LED was 6.9 V at 10 mA. The peak electroluminescence (EL) wavelength and the full-width at half-maximum (FWHM) were 395 nm and about 30 nm, respectively. It was clearly proven that u-Al0.19Ga0.81N became p-Al0.19Ga0.81N.
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