In medical ultrasound imaging, high-performance beamforming is important to enhance spatial and contrast resolutions. A modern receive dynamic beamfomer uses a constant sound speed that is typically assumed to 1540 m/s in generating receive focusing delays [1], [2]. However, this assumption leads to degradation of spatial and contrast resolutions particularly when imaging obese patients or breast since the sound speed is significantly lower than the assumed sound speed [3]; the true sound speed in the fatty tissue is around 1450 m/s. In our previous study, it was demonstrated that the modified nonlinear anisotropic diffusion is capable of determining an optimal sound speed and the proposed method is a useful tool to improve ultrasound image quality [4], [5]. In the previous study, however, we utilized at least 21 iterations to find an optimal sound speed, which may not be viable for real-time applications. In this paper, we demonstrates that the number of iterations can be dramatically reduced using the GSS(golden section search) method with a minimal error. To evaluate performances of the proposed method, in vitro experiments were conducted with a tissue mimicking phantom. To emulate a heterogeneous medium, the phantom was immersed in the water. From the experiments, the number of iterations was reduced from 21 to 7 with GSS method and the maximum error of the lateral resolution between direct and GSS was less than 1%. These results indicate that the proposed method can be implemented in real time to improve the image quality in the medical ultrasound imaging.
Optical coherence tomography (OCT) is a tool currently used for noninvasive diagnosis of human disease as well as for
monitoring treatment during or after therapy. In this study, OCT was used to examine penetration and accumulation of
cosmetic creams on human hand skin. The samples varied in collagen content with one formulation containing soluble
collagen as its primary active ingredient. Collagen is a major connective tissue protein that is essential in maintaining
health vitality and strength of many organs. The penetration and localization of collagen in cosmetic creams is thought to
be the main determinant of the efficacy of new collagen synthesis. Detection and quantification of collagen in cosmetic
creams applied to skin may thus help predict the eventual efficacy of the product in skin collagen regeneration. We
hypothesize that the topically applied collagen may be detectable by OCT through its modulation of skin scattering
properties. To test this hypothesis, we used a FDML swept-source optical coherence tomography (SS-OCT) system. A
particular location on the skin of two male adult volunteers was used to investigate 4 different cosmetic creams. The
duration of OCT monitoring of cosmetic penetration into skin ranged from 5 minutes to 2 hours following topical
application. The results showed that OCT can discriminate between a cream with collagen and other collagen-free
formulations. Thus it seems feasible that OCT intensity can monitor the in vivo effects of topical application of collagen
contained in cosmetic formulations.
KEYWORDS: Ultrasonography, Signal to noise ratio, Phased arrays, Image quality, Tissues, In vivo imaging, Functional imaging, Transducers, In vitro testing, Image enhancement
In medical ultrasound imaging, a multi-beamforming (MBF) method is used for supporting high frame rate imaging
or functional imaging where multiple scanlines are reconstructed from a single excitation event. For efficient MBF, a
time-sharing technique (i.e., MBF-TS) can be applied. However, the MBF-TS could degrade image quality due to the
decreased beamforming frequency. In this paper, the multi-access register-based MBF (MBF-MAR) method running on
the post-fractional filtering (PFF) architecture is presented. In PFF-MBF-MAR, instead of lowering beamforming
frequency, a multi-access register at each channel is utilized for generating multiple scanlines simultaneously. To
evaluate the performance of the proposed PFF-MBF-MAR method, the phantom experiment was conducted where 64-
channel pre-beamformed radio-frequency (RF) data were captured from a tissue mimicking phantom by using a modified
commercial ultrasound system (SONOLINE G40, Siemens Inc., USA) using a 3-MHz phased array probe. From the
phantom experiment, the PFF-MBF-MAR method showed 4.7 dB and 0.6 improvements in the signal-to-noise ratio
(SNR) and the contrast-to-noise ratio (CNR), respectively, compared to the PFF-MBF-TS method, while slightly
increasing the hardware complexity (<5.2%). The similar results were achieved with the in vivo thyroid data. These
results indicate that the proposed PFF-MBF-MAR method can be used for high frame rate imaging or functional imaging
without sacrificing image quality while slightly increasing the hardware complexity.
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