High-performance III-V MOSFET with nano-stacked high-k gate dielectric and 3D fin-shaped structure.

A three-dimensional (3D) fin-shaped field-effect transistor structure based on III-V metal-oxide-semiconductor field-effect transistor (MOSFET) fabrication has been demonstrated using a submicron GaAs fin as the high-mobility channel. The fin-shaped channel has a thickness-to-width ratio (TFin/WFin) equal to 1. The nano-stacked high-k Al2O3 dielectric was adopted as a gate insulator in forming a metal-oxide-semiconductor structure to suppress gate leakage. The 3D III-V MOSFET exhibits outstanding gate controllability and shows a high Ion/Ioff ratio > 105 and a low subthreshold swing of 80 mV/decade. Compared to a conventional Schottky gate metal-semiconductor field-effect transistor or planar III-V MOSFETs, the III-V MOSFET in this work exhibits a significant performance improvement and is promising for future development of high-performance n-channel devices based on III-V materials.

Correlations among acoustic, texture and morphological features for breast ultrasound CAD.

Acoustic, textural and morphological features of the breast in ultrasound imaging were extracted for computer-aided diagnosis. In addition, correlations among different categories of features were analyzed. Clinical data from 14 patients (7 malignant and 7 benign samples) were acquired. A custom-made experimental apparatus was used for simultaneous data acquisition of B-mode ultrasound and limited-angle tomography images. Textural features were extracted from B-mode images, including five parameters derived from the gray-level concurrence matrix and five parameters derived from a nonseparable wavelet transform. Morphological features were also extracted from B-mode images, including the depth-to-width ratio and normalized radial gradient. Acoustic features were estimated using limited-angle tomography, including the sound velocity and attenuation coefficient. Generally, the correlation coefficients for features within the textural feature group were relatively high (0.48-0.79), whereas those between different feature categories were relatively low (0.17-0.40). This suggests that combining different sets of features would improve the computer-aided diagnosis of breast cancer.

Performance evaluation of coherence-based adaptive imaging using clinical breast data.

Sound-velocity inhomogeneities degrade both the spatial resolution and the contrast in diagnostic ultrasound. We previously proposed an adaptive imaging approach based on the coherence of the data received in the channels of a transducer array, and we tested it on phantom data. In this study, the approach was tested on clinical breast data and compared with a correlation-based method that has been widely reported in the literature. The main limitations of the correlation-based method in ultrasonic breast imaging are the use of a near-field, phase-screen model and the integration errors due to the lack of a two-dimensional (2-D) array. In contrast, the proposed coherence-based method adaptively weights each image pixel based on the coherence of the receive-channel data. It does not make any assumption about the source of the focusing errors and has been shown to be effective using 1-D arrays. This study tested its in vivo performance using clinical breast data acquired by a programmable system with a 5 MHz, 128-channel linear array. Twenty-five cases (6 fibroadenomas, 10 carcinomas, 6 cysts, and 3 abscesses) were investigated. Relative to nonweighted imaging, the average improvements in the contrast ratio and contrast-to-noise ratio for the coherence-based method were 8.57 dB and 23.2%, respectively. The corresponding improvements when using the correlation-based method were only 0.42 dB and 3.35%. In an investigated milk-of-calcium case, the improvement in the contrast was 4.47 dB and the axial and lateral dimensions of the object were reduced from 0.39 to 0.32 mm and from 0.51 to 0.43 mm, respectively. These results demonstrate the efficacy of the coherence-based method for clinical ultrasonic breast imaging using 1-D arrays.

Reconstruction of ultrasonic sound velocity and attenuation coefficient using linear arrays: clinical assessment.

The aim of this study was to determine the efficacy of using sound velocity and tissue attenuation to clinically discriminate breast cancer from healthy tissues. The methods for reconstructing the sound-velocity and attenuation-coefficient distributions were previously proposed and tested on tissue-mimicking phantoms. The methods require only raw channel data acquired by a linear transducer array and can therefore be implemented on existing clinical systems. In this paper, these methods are tested on clinical data. A total of 19 biopsy-proven cases, consisting of five carcinomas (CAs), seven fibroadenomas (FAs), six adipose tissue (fat) and one oil cyst, were evaluated. A single imaging setup consisting of a 5-MHz, 128-channel linear array was used to simultaneously obtain B-mode image data, time-of-flight data and attenuation data. The sound velocity and attenuation coefficient can be reconstructed inside and outside a region of interest manually selected in the B-mode image. To reduce distortion caused by tissue inhomogeneities, an optimal filter derived from pulse-echo data-with water replacing the breast tissue-is applied. We found that the sound velocities in CA, FA and fat tissues relative to those in the surrounding tissues were 49.8 +/- 35.2, 2.6 +/- 27.3 and -25.1 +/- 44.9 m/s (mean +/- SD), respectively, whereas the relative attenuation coefficients were 0.21 +/- 0.58, 0.27 +/- 0.62 and -0.02 +/- 0.59 dB/cm/MHz. These results indicate that CA can be discriminated from FA and fat by choosing an appropriate threshold for the relative sound velocity (i.e., 18.5 m/s). However, the large variations in the attenuation within the same type of tissue make simple thresholding ineffective. Nevertheless, the method described in this paper has the potential to reduce negative biopsies and to improve the accuracy of breast cancer detection in clinics.