Fabrication and Performance of a Miniaturized and Integrated Endoscope Ultrasound Convex Array for Digestive Tract Imaging

Variable Curvature Flexible Transducer for Abdominal Expandable Imaging

Expanding the imaging field of view (FOV) of medical ultrasound transducers will more effectively detect pathological behaviors of tissues or organs. Conventional rigid transducers can be realized by increasing the number of array elements or the curvature; however, the imaging aperture is fixed by the original size and shape during the manufacturing process. This article presented a 128-element, 3-MHz flexible curvature abdominal array (FCAA) with the goal of dynamically expanding the FOV within a 120° range. The piezoelectric stack was divided into small pitches through a double-cut process, and two-component viscoelastic substrates (TCVSs) were filled between adjacent array elements to generate tensile and compressive stresses during decomposition deformation. A 3-D-printed push-pull device provides sufficient mechanical support, resulting in a conformal minimum curvature radius of 46 mm. The innovative rigid-flexible composite backing layer was used to balance mechanical flexibility and high bandwidth (BW) of -6 dB to 67.6%. The results showed that the axial and lateral resolutions of the commercial phantom line target are 0.35 and 0.77 mm, respectively, and the axial and lateral resolutions of FOV 120° are 0.36 and 1.02 mm, respectively. The imaging performance of FCAA was verified by B-model imaging of the kidneys, intestines, uterus, and bladder of volunteers with a different body mass index (BMI). In addition, the 5-mm renal artery phantom verified the Doppler imaging function of FCAA. All the results demonstrated that FCPA has great potential clinical value in abdominal ultrasound and gynecological examination.

A Two-Dimensional Circular Array Transducer for Endoscopic Ultrasound Imaging of Tube

The concept of endoscopic ultrasound (EUS) has been introduced to non-destructive testing for the inspection of tubular structure. However, the fixed normal focusing beam of the present EUS transducers obstructs imaging flexibility and limits the robustness of the inspection, particularly for planar reflectors. To address this challenge, a two-dimensional circular array (2-D CA) designed for three-dimensional focusing is developed in this paper. A prototype 2-D CA transducer is fabricated and validated, which is demonstrated has a central frequency of 10.10 MHz and an average pulse duration of no more than 344 ns. An independent-dual-focusing beamforming scheme is further proposed, providing delay laws in two orthogonal directions. The acoustic field simulation results confirm that the 2-D CA is capable of achieving focusing in any direction, thereby enhancing the flexibility of EUS imaging. The imaging performance of the 2-D CA is evaluated through the immersion EUS inspection of a stainless-steel tube specimen. All the quasi-planar reflectors, including ring grooves with narrow-width, small-diameter flat bottom holes, and longitudinal grooves, are successfully detected in the 2-D CA imaging results. These reflectors could hardly be recognized by the conventional CA with a fixed-normal beam, affirming the superior detection robustness of the 2-D CA. The detection signal-to-noise ratio and error of quantitative characterization of the 2-D CA are 26.12 dB higher and 40.37 % lower than those of conventional CA, respectively. The proposed 2-D CA enables novel and advanced EUS imaging modalities, which have potential applications in both medical imaging and non-destructive testing domains.

Research related to the diagnosis of prostate cancer based on machine learning medical images: A review

BACKGROUND

Prostate cancer is currently the second most prevalent cancer among men. Accurate diagnosis of prostate cancer can provide effective treatment for patients and greatly reduce mortality. The current medical imaging tools for screening prostate cancer are mainly MRI, CT and ultrasound. In the past 20 years, these medical imaging methods have made great progress with machine learning, especially the rise of deep learning has led to a wider application of artificial intelligence in the use of image-assisted diagnosis of prostate cancer.

METHOD

This review collected medical image processing methods, prostate and prostate cancer on MR images, CT images, and ultrasound images through search engines such as web of science, PubMed, and Google Scholar, including image pre-processing methods, segmentation of prostate gland on medical images, registration between prostate gland on different modal images, detection of prostate cancer lesions on the prostate.

CONCLUSION

Through these collated papers, it is found that the current research on the diagnosis and staging of prostate cancer using machine learning and deep learning is in its infancy, and most of the existing studies are on the diagnosis of prostate cancer and classification of lesions, and the accuracy is low, with the best results having an accuracy of less than 0.95. There are fewer studies on staging. The research is mainly focused on MR images and much less on CT images, ultrasound images.

DISCUSSION

Machine learning and deep learning combined with medical imaging have a broad application prospect for the diagnosis and staging of prostate cancer, but the research in this area still has more room for development.

A Circular Total Focusing Method With Eccentricity Correction and Intensity Compensation for Endoscopic Ultrasound Imaging of Dual-Layered Media

Present endoscopic ultrasound (EUS) imaging methods for circular array (CA) suffer from the nonuniform spatial resolution in the imaging of a dual-layered media, such as the tubes' immersion EUS inspection. The problem is mainly attributed to the restricted focus and beam de-focusing at the interface. In this article, a circular total focusing method (CTFM) is proposed, which leverages the concept of the conventional total focusing method (TFM) and makes three vital improvements to overcome the challenges. First, to obtain the accurate time-of-flight (TOF) in the dual-layered media, a fourth-order equation of Snell's law is built and solved in polar coordinate system. Second, a fast geometric approximation method is derived to correct the TOF distortion caused by the transducer's eccentricity. Third, the intensity compensation is applied to flatten the imaging intensity at different positions by considering the directivity of element, transmission at interface, and divergence in media. The CTFM is validated on a tube's immersion EUS using a 10 MHz CA with 128 elements. Experimental results demonstrate that the proposed CTFM outperforms existing imaging methods. The lateral and axial resolutions are 0.71 and 0.30 mm, which are 27.5% and 33.3% higher than those of the classic delay-and-sum (DAS) method. The CTFM image shows high and uniform signal-to-noise ratio (SNR) which is 33.6% higher than that of DAS images. The CTFM provides a novel EUS imaging modality which can be applied in both medical and nondestructive testing domains.

Design and Fabrication of a High-Frequency Microconvex Array Transducer for Small Animals Imaging

High-frequency convex array transducer, featuring both high spatial resolution and wide field of view, has been successfully developed for ophthalmic imaging. To further expand its application range to small animals' imaging, this work develops a high-frequency microconvex array transducer possessing smaller aperture size and wider scanning angle. This transducer featured 128 array elements arranged in a curvilinear 2-2 piezoelectric composite configuration, yielding a maximum view angle of 97.8°. The array was composed of two front matching layers, a nonconductive backing layer, and a customized flexible circuit that electrically connected array elements to coaxial cables. The center frequency and the -6-dB fractional bandwidth were about 18.14 MHz and 69.15%, respectively. The image of a tungsten wire phantom resulted in approximately 62.9- [Formula: see text] axial resolution and 121.3- [Formula: see text] lateral resolution. The image of the whole kidney of a rat as well as its internal arteries was acquired in vivo, demonstrating the imaging capability of the proposed high-frequency microconvex array transducers for small animals' imaging applications.

Development of Cardiac Phased Array With Large-Size PZN-5.5 %PT Single Crystals

In recent years, the manufacturing process of lead zinc niobate-lead titanate [Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃, also called PZN-PT], has been enhanced with improvements in size, consistency, and a suitable compromise between piezoelectric properties and phase transition temperature, which means that it is possible to obtain PZN-PT single crystals in sufficient size for performance characterization studies and batch manufacturing to produce high-performance medical ultrasonic transducers. This article mainly focuses on the development of the 64-element phased array ultrasonic transducer based on novel large-size PZN-PT piezoelectric single crystals. The composition of the single crystal was chosen as PZN-5.5 %PT. The designed center frequency of the phased array is 3.0 MHz, which is suitable for cardiac ultrasound imaging. The array elements were spaced at a 0.254-mm pitch, and interconnected through a custom-designed flexible circuit. Double matching layers with a light backing structure were applied in the transducer fabrication process to improve the performance of the array. The test results of the developed phased array showed a center frequency of 3.0 MHz, and an average -6 dB fractional bandwidth of 72%. In the vicinity of the center frequency, the two-way insertion loss (IL) was about -46 dB, while a crosstalk between the adjacent elements was less than -31 dB. The wire phantom can be distinctly imaged with the phased array, and the axial and lateral resolutions were measured to be 660 and [Formula: see text], respectively. The image of a standard phantom was acquired to present the imaging performance of the transducer. The final results indicate that the transducer arrays based on novel large-size PZN-PT single crystals are quite promising for use in medical ultrasound imaging applications.

Transparent capacitive micromachined ultrasound transducer linear arrays for combined realtime optical and ultrasonic imaging

Transparent ultrasound transducers could enable many novel applications involving both ultrasonics and optics. Recently, we reported transparent capacitive micromachined ultrasound transducers (CMUTs) and demonstrated through-illumination photoacoustic imaging. This work presents the feasibility of transparent CMUTs for combined ultrasound imaging and through-array white-light imaging with a miniature camera placed behind the array. Transparent CMUT devices are fabricated with an adhesive wafer bonding technique and provide high transparency up to 90% in visible wavelengths. Fabricated linear arrays have a central operating frequency of 9 MHz with 128 active elements. Realtime plane-wave imaging is performed for ultrasound imaging, and lateral and axial resolutions of, respectively, 234 and 338 µm are achieved. Transparent CMUT has demonstrated a high transmit sensitivity of 1.4 kPa/V per channel with a 100 VDC bias voltage. The signal-to-noise ratio for a beamformed image of wire targets is determined to be 28.4 dB. To the best of our knowledge, this is the first report of combined realtime optical and ultrasonic imaging with transparent arrays. This technology may enable one to visually see what is being scanned and scan what one sees without co-registration errors. Future applications could include multi-modality probes for interventional and surgical procedures.

1.5-Dimensional Circular Array Transducer for In Vivo Endoscopic Ultrasonography

OBJECTIVE

Traditional endoscopic ultrasonography (EUS), which uses one-dimensional (1-D) curvilinear or radial/circular transducers, cannot achieve dynamic elevational focusing, and the slice thickness is not sufficient. The purpose of this study was to design and fabricate a 1.5-dimensional (1.5-D) circular array transducer to achieve dynamic elevational focusing in EUS in vivo.

METHODS

An 84 × 5 element 1.5-D circular array transducer was successfully developed and characterized in this study. It was fabricated with PZT-5H 1-3 composite that attained a high-electromechanical coupling factor and low-acoustic impedance. The acoustic field distribution was measured with different transmission modes to validate the 1.5-D elevational beam focusing capability. The imaging performance of the 84 × 5 element 1.5-D circular array transducer was evaluated by two wire phantoms, an agar-based cyst phantom, an ex vivo swine pancreas, and an in vivo rhesus macaque rectum based on multifocal ray-line imaging method with five-row elevational beam steering.

RESULTS

It was demonstrated that the transducer exhibited a central frequency of 6.47 MHz with an average bandwidth of 50%, a two-way insertion loss of 23 dB, and crosstalk of <-26 dB around the center frequency.

CONCLUSION

Dynamic elevational focusing and the enhancement of the slice thickness in EUS were obtained with a 1.5-D circular array transducer.

SIGNIFICANCE

This study promotes the development of multirow and two-dimensional array EUS probes for a more precise clinical diagnosis and treatment.