Simultaneous Acquisition of Ultrasound and Gamma Signals with a Single-Channel Readout

Harmonic-Reduced Bias Circuit for Ultrasound Transducers

The gain of class-C power amplifiers is generally lower than that of class-A power amplifiers. Thus, higher-amplitude input voltage signals for class-C power amplifiers are required. However, high-amplitude input signals generate unwanted harmonic signals. Therefore, a novel bias circuit was proposed to suppress the harmonic signals generated by class-C power amplifiers, which improves the output voltage amplitudes. To verify the proposed idea, the input harmonic signals when using a harmonic-reduced bias circuit (-61.31 dB, -89.092 dB, -90.53 dB, and -90.32 dB) were measured and were found to be much lower than those when using the voltage divider bias circuit (-57.19 dB, -73.49 dB, -70.97 dB, and -73.61 dB) at 25 MHz, 50 MHz, 75 MHz, and 100 MHz, respectively. To further validate the proposed idea, the pulse-echo measurements were compared using the bias circuits. The peak-to-peak echo amplitude and bandwidth of the piezoelectric transducer, measured when using a harmonic-reduced bias circuit (27.07 mV and 37.19%), were higher than those achieved with a voltage divider circuit (18.55 mV and 22.71%). Therefore, the proposed scheme may be useful for ultrasound instruments with low sensitivity.

An Inverse Class-E Power Amplifier for Ultrasound Transducer

An inverse Class-E power amplifier was designed for an ultrasound transducer. The proposed inverse Class-E power amplifier can be useful because of the low series inductance values used in the output matching network that helps to reduce signal distortions. Therefore, a newly designed Class-E power amplifier can obtain a proper echo signal quality. The measured output voltage, voltage gain, voltage gain difference, and power efficiency were 50.1 V, 22.871 dB, 0.932 dB, and 55.342%, respectively. This low voltage difference and relatively high efficiency could verify the capability of the ultrasound transducer. The pulse-echo response experiment using an ultrasound transducer was performed to verify the capability of the proposed inverse Class-E power amplifier. The obtained echo signal amplitude and pulse width were 6.01 mV_p-p and 0.81 μs, respectively. The -6 dB bandwidth and center frequencies of the echo signal were 27.25 and 9.82 MHz, respectively. Consequently, the designed Class-E power amplifier did not significantly alter the performance of the center frequency of the ultrasound transducer; therefore, it could be employed particularly in certain ultrasound applications that require high linearity and reasonable power efficiency.

The current status and future prospects for molecular imaging-guided precision surgery

Molecular imaging technologies are increasingly used to diagnose, monitor, and guide treatment of i.e., cancer. In this review, the current status and future prospects of the use of molecular imaging as an instrument to help realize precision surgery is addressed with focus on the main components that form the conceptual basis of intraoperative molecular imaging. Paramount for successful interventions is the relevance and accessibility of surgical targets. In addition, selection of the correct combination of imaging agents and modalities is critical to visualize both microscopic and bulk disease sites with high affinity and specificity. In this context developments within engineering/imaging physics continue to drive the growth of image-guided surgery. Particularly important herein is enhancement of sensitivity through improved contrast and spatial resolution, features that are critical if sites of cancer involvement are not to be overlooked during surgery. By facilitating the connection between surgical planning and surgical execution, digital surgery technologies such as computer-aided visualization nicely complement these technologies. The complexity of image guidance, combined with the plurality of technologies that are becoming available, also drives the need for evaluation mechanisms that can objectively score the impact that technologies exert on the performance of healthcare professionals and outcome improvement for patients.

The Design of a Low Noise and Low Power Current Readout Circuit for Sub-pA Current Detection Based on Charge Distribution Model

In this article, we proposed an analytical model based on charge distribution for switched-capacitor trans-impedance amplifiers (SCTIAs). The changes in the load state of the amplifier under different operating conditions and the influence of the gain of the operational amplifier (Opamp) on the trans-impedance gain are analyzed to improve the design theory of switched-capacitor trans-impedance amplifiers. According to the conclusion drawn from the analysis, the trans-impedance amplifier (TIA) has been designed by adopting “correlated double sampling technology” and “cross-connection technology” to optimize input-referred noise current, power consumption, and trans-impedance gain. As a result, the trans-impedance gain reaches up to 206 dB, while the bandwidth is 3 kHz. The current readout system achieves an input-referred noise current floor of 2.96 fA/Hz at 1 kHz, and the power consumption of the system is 0.643 mW. The circuit has been simulated with the technology of 0.18 μm, and the layout area is 1000 μm × 500 μm.

A Novel and Effective Brain Tumor Classification Model Using Deep Feature Fusion and Famous Machine Learning Classifiers

Brain tumors are difficult to treat and cause substantial fatalities worldwide. Medical professionals visually analyze the images and mark out the tumor regions to identify brain tumors, which is time-consuming and prone to error. Researchers have proposed automated methods in recent years to detect brain tumors early. These approaches, however, encounter difficulties due to their low accuracy and large false-positive values. An efficient tumor identification and classification approach is required to extract robust features and perform accurate disease classification. This paper proposes a novel multiclass brain tumor classification method based on deep feature fusion. The MR images are preprocessed using min-max normalization, and then extensive data augmentation is applied to MR images to overcome the lack of data problem. The deep CNN features obtained from transfer learned architectures such as AlexNet, GoogLeNet, and ResNet18 are fused to build a single feature vector and then loaded into Support Vector Machine (SVM) and K-nearest neighbor (KNN) to predict the final output. The novel feature vector contains more information than the independent vectors, boosting the proposed method's classification performance. The proposed framework is trained and evaluated on 15,320 Magnetic Resonance Images (MRIs). The study shows that the fused feature vector performs better than the individual vectors. Moreover, the proposed technique performed better than the existing systems and achieved accuracy of 99.7%; hence, it can be used in clinical setup to classify brain tumors from MRIs.

Novel dual-resistor-diode limtier circuit structures for high-voltage reliable ultrasound receiver systems

BACKGROUND:

The limiters have been used to protect the ultrasound receivers because of the inherent characteristic of the transducers which are required to use the high voltage excitation to obtain the reasonable echo signal amplitudes.

OBJECTIVE:

Among the variety of the limiters, the performances of discharge voltage degradation from the limiters gradually deteriorate the whole ultrasound systems according to the applied voltages of the ultrasonic transducers. This could cause the ultrasound systems to be unreliable for the long-term operations, resulting in possibly breaking the receiver systems.

METHODS:

Designed limiters were evaluated with insertion loss, total harmonic distortion, and pulse-echo responses with the ultrasound transducer devices.

RESULTS:

Designed new dual-resistor-diode limiters exhibited greater and faster suppression of the pulse width (1.15 V and 6.1 μs) for high-voltage signals.

CONCLUSIONS:

Our proposed dual-resistor-diode limiter could be one of the potential candidates for reliable ultrasound receiver system.

Generalized sidelobe canceler beamforming combined with eigenspace-wiener postfilter for medical ultrasound imaging

BACKGROUND:

The beamforming algorithm is key to the image quality of the medical ultrasound system. The generalized sidelobe canceler (GSC) beamforming can improve the image quality in lateral resolution, but the contrast is not improved correspondingly.

OBJECTIVE:

In our research, we try to optimize the generalized sidelobe canceler to obtain images that achieve an improvement in both lateral resolution and contrast.

METHODS:

We put forward a new beamforming algorithm which combines the generalized sidelobe canceler and Eigenspace-Wiener postfilter. According to eigenspace decomposition of the covariance matrix of the received data, the components of the Wiener postfilter can be calculated from the signal matrix and the noise matrix. Then, the adaptive weight vector of GSC is further constrained by the Eigenspace-Wiener postfilter, which make the output energy of the receiving array closer to the desired signal than the conventional GSC output.

RESULTS:

We compare the new beamforming algorithm with delay-and-sum (DS) beamforming, synthetic aperture (SA) beamforming, and GSC beamforming using the simulated and experimental data sets. The quantitative results show that our method reduces the FWHM by 85.5%, 80.5%, and 38.9% while improving the CR by 123.6%, 47.7%, 84.4% on basis of DS, SA, and GSC beamforming, respectively.

CONCLUSIONS:

The new beamforming algorithm can obviously improve the imaging quality of medical ultrasound imaging systems in both lateral resolution and contrast.

Fisheye lens design for solar-powered mobile ultrasound devices

BACKGROUND: Compared to benchtop ultrasound machines, mobile ultrasound machines require portable batteries when acquiring information regarding human tissues during outdoor activities. OBJECTIVE: A novel fisheye lens type was designed to address the charging issue where it is difficult to constantly track the sun. This method does not require the use of a mechanical motor that constantly tracks the sun to charge the portable batteries. METHODS: To obtain an optical solar power system, the numerical aperture (NA) and field angle must be increased. Therefore, we use the fisheye lens with the largest field angle. RESULTS: The NA of the designed fisheye lens system reaches 0.75, allowing light collection of approximately ± 48∘. Additionally, the efficiency ratio of the central and surrounding areas also satisfies more than 80% at a field angle of 85∘ and more than 70% at field angles of 85∘ to 90∘, respectively. CONCLUSIONS: We designed a novel fisheye lens for solar-powered mobile ultrasound machines used outdoors.

New Optical Design Method of Floating Type Collimator for Microscopic Camera Inspection

Recently released mobile phone cameras are capable of photographing objects at a fairly close distance. In addition, the field angle from the camera has increased. To measure the resolution of a mobile phone camera, the target must be photographed. To measure the resolution according to the object distance change from a mobile phone camera with a wide field angle, the target size must be large, whereas the target position must be moved. However, the target size cannot be changed. A virtual object for the target was created using a collimator. Moving a part of the lens group constituting the collimator also changes the virtual object distance. If the amount of change in the virtual object distance is large, the resolution of the collimator may also change. Therefore, a collimator that maintains the resolution even when the distance of the virtual object changes is designed as a floating type in which two lens groups move. Therefore, we propose a new floating collimator optical system that can inspect the resolution of mobile phone cameras from infinity to a close range to compensate for aberrations caused by object distance changes.

A Real-Time Circuit Phase Delay Correction System for MEMS Vibratory Gyroscopes

With the development of the designing and manufacturing level for micro-electromechanical system (MEMS) gyroscopes, the control circuit system has become a key point to determine their internal performance. Nevertheless, the phase delay of electronic components may result in some serious hazards. This study described a real-time circuit phase delay correction system for MEMS vibratory gyroscopes. A detailed theoretical analysis was provided to clarify the influence of circuit phase delay on the in-phase and quadrature (IQ) coupling characteristics and the zero-rate output (ZRO) utilizing a force-to-rebalance (FTR) closed-loop detection and quadrature correction system. By deducing the relationship between the amplitude-frequency, the phase-frequency of the MEMS gyroscope, and the phase relationship of the whole control loop, a real-time correction system was proposed to automatically adjust the phase reference value of the phase-locked loop (PLL) and thus compensate for the real-time circuit phase delay. The experimental results showed that the correction system can accurately measure and compensate the circuit phase delay in real time. Furthermore, the unwanted IQ coupling can be eliminated and the ZRO was decreased by 755% to 0.095°/s. This correction system realized a small angle random walk of 0.978°/√h and a low bias instability of 9.458°/h together with a scale factor nonlinearity of 255 ppm at room temperature. The thermal drift of the ZRO was reduced to 0.0034°/s/°C at a temperature range from -20 to 70 °C.

A Novel Deep Learning Method for Recognition and Classification of Brain Tumors from MRI Images

A brain tumor is an abnormal growth in brain cells that causes damage to various blood vessels and nerves in the human body. An earlier and accurate diagnosis of the brain tumor is of foremost important to avoid future complications. Precise segmentation of brain tumors provides a basis for surgical planning and treatment to doctors. Manual detection using MRI images is computationally complex in cases where the survival of the patient is dependent on timely treatment, and the performance relies on domain expertise. Therefore, computerized detection of tumors is still a challenging task due to significant variations in their location and structure, i.e., irregular shapes and ambiguous boundaries. In this study, we propose a custom Mask Region-based Convolution neural network (Mask RCNN) with a densenet-41 backbone architecture that is trained via transfer learning for precise classification and segmentation of brain tumors. Our method is evaluated on two different benchmark datasets using various quantitative measures. Comparative results show that the custom Mask-RCNN can more precisely detect tumor locations using bounding boxes and return segmentation masks to provide exact tumor regions. Our proposed model achieved an accuracy of 96.3% and 98.34% for segmentation and classification respectively, demonstrating enhanced robustness compared to state-of-the-art approaches.

A New Approach to Power Efficiency Improvement of Ultrasonic Transmitters via a Dynamic Bias Technique

To obtain a high-quality signal from an ultrasound system through the transmitter, it is necessary to achieve an appropriate operating point of the power amplifier in the ultrasonic transmitter by applying high static bias voltage. However, the power amplifier needs to be operated at low bias voltage, because a power amplifier operating at high bias voltage may consume a large amount of power and increase the temperature of the active devices, worsening the signal characteristics of the ultrasound systems. Therefore, we propose a new method of increasing the bias voltage for a specific period to solve this problem by reducing the output signal distortion of the power amplifier and decreasing the load on the active device. To compare the performance of the proposed method, we measured and compared the signals of the amplifier with the proposed technique and the amplifier only. Notably, improvement was achieved with 11.1% of the power added efficiency and 3.23% of the total harmonic distortion (THD). Additionally, the echo signal generated by the ultrasonic transducer was improved by 2.73 dB of amplitude and 0.028% of THD under the conditions of an input signal of 10 mW. Therefore, the proposed method could be useful for improving ultrasonic transmitter performance using the developed technique.

Novel Bandwidth Expander Supported Power Amplifier for Wideband Ultrasound Transducer Devices

Ultrasound transducer devices have their own frequency ranges, depending on the applications and specifications, due to penetration depth, sensitivity, and image resolution. For imaging applications, in particular, the transducer devices are preferable to have a wide bandwidth due to the specific information generated by the tissue or blood vessel structures. To support these ultrasound transducer devices, ultrasound power amplifier hardware with a wide bandwidth can improve the transducer performance. Therefore, we developed a new bandwidth expander circuit using specially designed switching architectures to increase the power amplifier bandwidth. The measured bandwidth of the power amplifier with the help of the bandwidth expander circuit increased by 56.9%. In addition, the measured echo bandwidths of the 15-, 20-, and 25-MHz transducer devices were increased by 8.1%, 6.0%, and 9.8%, respectively, with the help of the designed bandwidth expander circuit. Therefore, the designed architecture could help an ultrasound system hardware with a wider bandwidth, thus supporting the use of different frequency ultrasound transducer devices with a single developed ultrasound system.