Lipid-coated microbubbles are widely used as an ultrasound contrast agent, as well as drug delivery carriers. However, the two main limitations in ultrasound diagnosis and drug delivery using ...microbubbles are the short half-life in the blood system, and the difficulty of surface modification of microbubbles for active targeting. The exosome, a type of extracellular vesicle, has a preferentially targeting ability for its original cell. In this study, exosome-fused microbubbles (Exo-MBs) were developed by embedding the exosome membrane proteins into microbubbles. As a result, the stability of Exo-MBs is improved over the conventional microbubbles. On the same principle that under the exposure of ultrasound, microbubbles are cavitated and self-assembled into nano-sized particles, and Exo-MBs are self-assembled into exosome membrane proteins-embedded nanoparticles (Exo-NPs). The Exo-NPs showed favorable targeting properties to their original cells. A photosensitizer, chlorin e6, was loaded into Exo-MBs to evaluate therapeutic efficacy as a drug carrier. Much higher therapeutic efficacy of photodynamic therapy was confirmed, followed by cancer immunotherapy from immunogenic cell death. We have therefore developed a novel ultrasound image-guided drug delivery platform that overcomes the shortcomings of the conventional ultrasound contrast agent and is capable of simultaneous photodynamic therapy and cancer immunotherapy.
The realization of a parallel-beamforming (pBF) method in ultra-compact ultrasound imaging systems is challenging to achieve uncompromised beamforming accuracy in limited hardware and power ...resources. In this paper, we present a new hardware- and power-efficient pBF method that utilizes a shared first-in-first-out block on a post-fractional delay filtering architecture (pBF-sFIFO). For an analog-to-digital conversion (ADC) rate given, the proposed pBF-sFIFO method yielded beamforming accuracy comparable to that by an unconstrained pBF (pBF-CON) method, with up to 15% less power consumption. Otherwise, a conventional time-sharing pBF method (pBF-TS) was more vulnerable to aliasing artifacts. Even though increasing ADC rate in the pBF-TS method could recover the beamforming accuracy, exponential need in power consumption was inevitable. Therefore, the pBF-sFIFO method would be an effective solution to enable advanced imaging features in ultra-compact ultrasound imaging systems.
CdMnTe(CMT) is a promising alternative material for use as a room-temperature radiation detector. Frisch-grid detectors have a simple configuration and outstanding spectral performance compared with ...other single-carrier collection techniques. The energy resolution of large-volume virtual Frisch-grid CMT detectors was tested by using several isotopes such as
57
Co,
22
Na,
133
Ba, and
137
Cs together or separately. Energy resolutions of 6.7% and 2.1% were obtained for 122-keV
57
Co and 662-keV
137
Cs gamma rays, respectively, without using any additional signal processing techniques. Also, a 12-mm-thick CMT detector detected the 511-keV and 1.277-MeV gamma peaks of
22
Na with values of the full width at half maximum (FWHM) of 2.7% and 1.5%, respectively. In addition, multiple low- and high-energy gamma peaks of
133
Ba were well separated. The mobilitylifetime product calculated from the shift of the 662-keV photo-peak vs. bias by using Hecht’s equation was 7 × 10
−3
cm
2
/V. These results show the possibility of using CMT detectors in response to various requirements for gamma-ray detection at room-temperature.
•A new frequency domain passive acoustic mapping method using Hilbert beamforming.•The data rate can be reduced to its frequency bandwidth utilized for PAM reconstruction.•Redundant FFT computation ...for unutilized frequency bins was eliminated.•Less hardware utilization for implementing FFT than conventional frequency domain PAM.
Passive acoustic mapping (PAM) is the current state-of-the-art imaging tool for monitoring cavitation activity during focused ultrasound therapy such as blood-brain barrier opening. However, PAM incurs huge computational complexity. To address this issue, frequency-domain PAM (FD-PAM) was proposed. Nevertheless, FD-PAM still requires a large number of fast Fourier transforms (FFTs) to produce the frequency components utilized for cavitation monitoring with PAM. Hence, in this paper, we proposes a frequency domain PAM method using passive Hilbert beamforming (PHB-PAM), which can significantly reduce the number of input samples for FFT by down-sampling the analytic signal of the received RF samples at each channel at a rate equal to the bandwidth of the frequency components of interest. The experimental results show that the proposed PHB-PAM provides comparable image quality to that of FD-PAM (correlation coefficient > 0.98). Additionally, the study experimentally verifies that the pre-processing block for generating the decimated analytic signal and FFT in PHB-PAM can be realized using lesser logic resources than FFT in FD-PAM when implemented in an FPGA. Especially, with 128-fold decimation, PHB-PAM reduces the amount of LUTs and DSP slices to implement the pre-processing block by 72.16% and 53.4%, respectively, compared to those of FD-PAM, which allows the 64-channel implementation of the pre-processing block in a low-cost single FPGA. Finally, a hardware-efficient architecture for the pre-processing block of PHB-PAM is described, which can be implemented by replacing the two lowpass filters of an off-the-shelf analog front-end component for ultrasound imaging with a pair of band-pass filters. If PHB-PAM is realized using such a component, it can truly minimize the computational complexity of FD-PAM.
The implementation of dynamic delay calculations (DDCs) is challenging for ultra-compact ultrasound imaging due to the enormous computation and power consumption requirements. Here, we present an ...efficient pseudo-DDC method based on optimal zone segmentation (PDC-Optimal), which significantly decreases these requirements relative to an unconstrained DDC method: reductions in flip-flops of 84.35% and in look-up tables of 94.19%, respectively. The reductions lead to an up to 94.53% lower dynamic power consumption and provide image quality comparable to the unconstrained DDC method. The proposed PDC-Optimal method also provides adaptive flexibility between beamforming accuracy and battery life using the delay error allowance, a user-definable parameter. A conventional pseudo-DDC method using uniform zone segmentation (PDC-Conv) presented substantial image degradation in the near imaging field when the same number of zone segments was used. Therefore, the PDC-Optimal method provides an efficient yet flexible DDC solution to improve the experiences for ultra-compact ultrasound imaging system users.
In this paper, we present a smart US imaging system (SMUS) based on an android-OS smartphone, which can provide maximally optimized efficacy in terms of weight and size in point-of-care diagnostic ...applications. The proposed SMUS consists of the smartphone (Galaxy S5 LTE-A, Samsung., Korea) and a 16-channel probe system. The probe system contains analog and digital front-ends, which conducts beamforming and mid-processing procedures. Otherwise, the smartphone performs the back-end processing including envelope detection, log compression, 2D image filtering, digital scan conversion, and image display with custom-made graphical user interface (GUI). Note that the probe system and smartphone are interconnected by the USB 3.0 protocol. As a result, the developed SMUS can provide real-time B-mode image with the sufficient frame rate (i.e., 58 fps), battery run-time for point-of-care diagnosis (i.e., 54 min), and 35.0°C of transducer surface temperature during B-mode imaging, which satisfies the temperature standards for the safety and effectiveness of medical electrical equipment, IEC 60601-1 (i.e., 43°C).
High quality ultrasound imaging is required throughout entire imaging depths for abdominal ultrasound. In general, sector scanning with a convex array transducer is performed by using a focused ...ultrasound beam to obtain a wide field-of-view. However, the conventional focusing (CF) method suffers from the degraded spatial resolution except for the vicinity of the focal depth due to the diffractive propagation of the focused ultrasound. Plane wave synthetic focusing (PWSF) method has been initially proposed for a linear array transducer to give a solution to the diffraction problem of interrogating beam. In this paper, to our best knowledge, we present the first report on the PWSF method for B-mode convex array imaging as well as the optimization strategies for enhancing image quality. The validation study was performed by acquiring data from a tissue-mimicking phantom (040GSE, CIRS Inc., USA) using an ultrasonic research platform (Vantage 128, Verasonics Inc., USA) with a C5-2 convex array transducer. The evaluation results indicate that the PWSF method can be successfully employed to convex array imaging and it exhibits substantially improved image quality compared to that of CF method.
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