With the development of bioengineering technologies, medical ultrasound systems have evolved and advanced over the years, including the transition of ultrasound machines from analog devices to digital systems and improvements in transducer assembly from piezoelectric ceramics to single crystals. In the past several years, the further miniaturization of ultrasound units has become possible with the advancement of computer chip manufacturing and production. Most recently, a new handheld ultrasound system has been developed by the startup company Butterfly Network, using an innovative CMUT/CMOS-based probe technique. This paper will review the history, technology and features of this new device, as well as discuss its future potential as a personal sonoscope.

Artificial intelligence (AI) is an area of computer science that emphasizes the creation of intelligent software or system based on big data information, machine learning and deep learning technologies. The rapid development of science and technology as well as internet communication has enabled AI and big data to gradually apply to many fields of health care. The modern imaging medicine is one of the first areas where AI can play an important role and applications. As cross-sectional imaging, ultrasound (US) is well suitable for AI technology to standardize imaging protocols and improve diagnostic accuracy. This article reviews current AI technology and related clinical applications in the fields of thyroid, breast and liver US.

Advances in modern clinical ultrasound include developments in ultrasound signal processing, imaging techniques and clinical applications. Improvements in ultrasound processing include contrast and high-fidelity ultrasound imaging to expand B-mode imaging and microvascular (or microluminal) discrimination. Similarly, volumetric sonography, automated or intelligent ultrasound, and fusion imaging developed from the innate limitations of planar ultrasound, including user-operator technical dependencies and complex anatomic spatial prerequisites. Additionally, ultrasound techniques and instrumentation have evolved towards expanding access amongst clinicians and patients. To that end, portability of ultrasound systems has become paramount. This has afforded growth into the point-of-care ultrasound and remote or tele-ultrasound arenas. In parallel, advanced applications of ultrasound imaging have arisen. These include high frequency superficial sonograms to diagnose dermatologic pathologies as well as various intra-cavitary or lesional interrogations by contrast-enhanced ultrasound. Properties such as realtime definition and ease-of-access have spurned procedural and interventional applications for vascular access. This narrative review provides an overview of these advances and potential future directions of ultrasound.

Objectives: To investigate the causes, differential diagnosis, and clinical significance of absent blood flow (ABF) in the testis detected by color Doppler ultrasound (CDU) in acute scrotum.
Methods: A total of 263 patients with ABF in the testis detected by CDU in our hospital were reviewed retrospectively. However, only 111 patients who underwent surgery were included in this study. The ultrasonographic features of the testis and paratesticular tissue were analyzed. The surgical or surgical-pathologic results were taken as the reference standard to determine the causes of ABF in the testis.
Results: The causes of ABF in the testis were testicular torsion (n = 98, torsion group) and non-testicular torsion related diseases (n = 13, non-torsion group, including 8 testicular rupture, 3 epididymitis-orchitis combination with testicular necrosis, and 2 tumors). Tunica albuginea of the testis, diffuse enlarged epididymis, whirlpool sign, and internal echo of the testis were the better parameters for diagnosing the causes of ABF in the testis detected by CDU. And the accuracies of these approaches were 93.7%, 91%, 83.8%, and 81.1%, respectively. Whirlpool sign had a 100% positive predictive value (PPV), and disrupted tunica albuginea of the testis and diffuse enlarged epididymis each had 100% specificity for predicting testicular torsion. When the ultrasonographic findings were combined with these methods to determine the causes, the accuracy was 96.4% (107/111).
Conclusion: ABF in the testis detected by CDU is not always indicative of testicular torsion in acute scrotum; Analyzing ultrasound findings of the testis and paratesticular tissue can help with differential diagnosis of the causes of ABF in the testis and guide clinical decision-making.

Ultrasound (US) technology, with major advances and new developments, has become an essential and first-line imaging modality for clinical diagnosis and interventional treatment. US imaging has evolved from one-dimensional, two-dimensional to three-dimensional display, and from static to real-time imaging, as well as from structural to functional imaging. Based on its portability and advanced digital imaging technique, US was first adopted by emergency medicine in the 1980s and gradually gained popularity among other specialists for clinical diagnosis and interventional treatment. Point-of-Care Ultrasound (POCUS) was then proposed as a new concept and developed for new uses, which greatly extended clinical US applications. Nowadays, artificial intelligence (AI), cloud computing, 5G network, robotics, and remote technologies are starting to be integrated into US equipment. US systems have gradually evolved to an intelligent terminal platform with powerful imaging and communication tools. In addition, specialized US machines tend to be more suitable and important to meet increasing demands and requirements by various clinical specialties and departments. In this article, we review current US technology and POCUS as new concepts and its future trends, as well as related technological developments and clinical applications.

With the rapid development of microelectronics, handheld ultrasound devices emerged and have a widespread use in the field of medicine and healthcare. The handheld ultrasound is a modality of medical ultrasonic device that is portable (i.e., carried by hand), easy to operate and in some cases even combine the scanner with the host system. It normally has the characteristics of light weight, small size and low power consumption. With the wireless imaging transmission technique, remote and intelligent diagnosis is possible for the doctors using handheld ultrasound devices. As soon as the low-cost, highperformance handheld ultrasound device was launched, it attracted clinical attention and received a warm welcome from primary doctors and clinicians, thereby accelerating the development of ultrasonic clinical visualization. In this paper, we will illustrate the status and roles of handheld ultrasound for its clinical settings and applications in the past, current, and future.

Ultrasound is a commonly used imaging modality for breast cancer diagnosis and prognosis but suffers from false positives, false negatives and interobserver variability. Deep learning (DL), a subset of artificial intelligence, has the potential to improve the efficiency and accuracy of breast ultrasound. This article provides a comprehensive overview of DL applications for breast cancer diagnosis and treatment in ultrasound, including methodological descriptions of various DL models, and clinical applications on noise reduction, lesion localization, risk assessment, diagnosis, response evaluation and outcome prediction. Furthermore, the review highlights the importance of interpretability and small sample size learning of DL-based systems in clinical practice; specific recommendations for further expanding the clinical impact of DL-based systems are also provided.

In 2009, Hitachi commercialized “Mappie^*1, the world’s first Capacitive Micro-machined Ultrasound Transducer (CMUT) using semiconductor based technology. It generated high quality diagnostic images of mammary glands, thanks to its broad-band characteristics^[1]. This year, the 4^th generation CMUT (4G CMUT) “SML44” has been brought to the market, achieved using advanced design and precise control of the fabrication process. When combined with new imaging technologies avail-able with the ARIETTA^*2 850, the SML44, in addition to excellent image quality, offers commonly used modalities and func- tions such as Tissue Harmonic Imaging (THI), Color Flow Mapping (CFM), Real-time Tissue Elastography^*3 (RTE), and Real-time Virtual Sonography^*4 (RVS). This report introduces the latest technology adopted in the 4G CMUT design.

Contrast-enhanced ultrasound (CEUS) is an imaging modality that has achieved considerable relevance in various clinical settings including the assessment of renal disease. CEUS is performed by injecting microbubble-based ultrasound contrast agents (UCAs) that create signals to display the microvasculature, allowing quantitative and qualitative assessment of parenchymal perfusion and real-time visualization of the renal anatomy. In recent years, CEUS has been widely accepted and applied for the assessment of kidney perfusion and the characterization of indeterminate renal masses, primarily due to its diagnostic efficacy, availability, low cost, reproducibility, and absence of nephrotoxicity. CEUS provides a higher spatial and temporal resolution than other cross-sectional imaging, resulting in high sensitivity and specificity for its applications in a variety of renal conditions including cancer monitoring following ablation, detection of transplant complications, hypoperfusion, acute traumatic injury, renal artery stenosis, parenchymal infection, and kidney intervention guidance. Additionally, the continuous investigation and development of new technologies surrounding this imaging technique have shown encouraging preliminary results for the use of CEUS in the evaluation of molecular expression in several disease processes, the dynamic analysis of blood flow kinetics, and the implementation of super-resolution imaging systems. The purpose of this article is to provide an overview of the current and potential clinical applications of renal CEUS.

Objective: Thyroid nodules are a common medical problem in China and in other parts of the world. Many guidelines use ultrasound (US) as the first choice for evaluating thyroid nodules. A major limitation of US is operator dependency, resulting in a variety of discrepancies in diagnosing thyroid nodules in the literatures. Risk stratification of thyroid nodules is based on the patterns of US features in the 2015 American Thyroid Association (ATA) management guidelines for adult patients with thyroid nodules. We hypothesize that special training targeting features recognition may increase the inter-observer agreement.
Methods: The study was conducted on 52 participants from Peking Union Medical College Hospital (PUMCH) from March to May 2018.The participants were divided into two groups by their own decision for their convenience. Image featuresbased learning (IF-BL) was used to train the participants to learn special features including shape, margin, echo level, internal structure, calcification, vascularity through 10 standard images based on the 2015 ATA guideline. Group A (27 subjects) received IF-BL during the first month, and Group B (25 subjects) received IF-BL during the second month. All participants evaluated US features and risk stratification in 60 US images of 20 thyroid nodules before and after the training. The test results were graded by a teaching assistant according to the rule of 0.5 points assigned to every feature and 2 points assigned to risk stratification, with a total of 100 points. Inter-observer agreements of US features and risk stratification were assessed and compared before and after the training.
Results: After the first month, Group A had better scores than Group B, the control group of the month (75.4±9.4 vs 68.7±8.4, p = 0.01). At the end of the second month during which both groups were trained, there was no difference of scores between Group A and Group B (74.5±10.4 vs 75.1±7.4, P = 0.78). Scores of all participants were significantly higher than the initial (74.8±9.0 vs 65.8±13.6, P < 0.01). After the training, the kappa values of US features improved from 0.28-0.43 to 0.43-0.75, and those of risk stratification improved from 0.13 to 0.55.
Conclusion: IF-BL can effectively help trainees correctly recognize US features and evaluate the risk stratification of thyroid nodule and can improve the inter-observer agreement.

Objective: This study evaluated the performance of automated machine-learning to diagnose non-alcoholic fatty liver disease (NAFLD) by ultrasound and compared these findings to radiologist performance.
Methods: 96 patients with histologic (33) or proton density fat fraction MRI (63) diagnosis of NAFLD and 100 patients without evidence of NAFLD were retrospectively identified. The “Fatty Liver” label included 96 patients with 405 images and the “Not Fatty Liver” label included 100 patients with 500 images. These 905 images made up a “Comprehensive Image” group. A “Radiology Selected Image” group was then created by selecting only images considered diagnostic by a blinded radiologist, resulting in 649 images. Cloud AutoML Visionbeta (Google LLC, Mountain View, CA) was used for machine learning. The models were evaluated against three blinded radiologists.
Results: The “Comprehensive Image” group model demonstrated a sensitivity of 88.6% (73.3-96.8%) and a specificity of 95.3% (84.2-99.4%). Radiologist performance on this image group included a sensitivity of 81.0% (74.3-87.6%) and specificity of 86.0% (72.6-99.5%). The model’s overall accuracy was 92.3% (84.0-97.1%), compared with mean individual performance (83.8%, 78.4-89.1%). The “Radiology Selected Image” group model demonstrated a sensitivity of 88.6% (73.3 - 96.8%) and specificity of 87.9% (71.8-96.6%). Mean radiologist sensitivity was 92.4% (86.9-97.9%) and specificity was 91.9% (83.4-100%). The model’s overall accuracy was 88.2% (78.1-94.8%) which was comparable to the individual radiologist performance (92.2%, 90.1-94.2%) and consensus performance (95.6%, 87.6-99.1%).
Conclusions: An automated machine-learning algorithm may accurately detect NAFLD on ultrasound.

Many kinds of skin masses appeared as well-defined hypoechogenic lesion in ultrasound. Higher-frequency sound waves enable high resolution observation of the anatomical level and internal echogenic, In this study, 4 typical cases were observed by utilizing high resolution ultrasound (HRUS) at 10 to 20 MHz Ultrasound shows most Basal cell carcinoma (BCC ) was irregular-shaped while other kinds of cases appear as oval-shape, meanwhile, epidermoid cyst was located in the subcutaneous layer while the other three kinds of masses were located in the dermis. Color Doppler shows eccrine poromas and BCCs have flow signals, while dermatofibromas and eccrine poromas show a lack of vascularity. HRUS can provide noninvasive and effective diagnostic information for skin masses before surgery and can help the clinician evaluate whether the tumor was completely removed after surgery.

The spread of new coronavirus (SARS-Cov-2) follows a different pattern than previous respiratory viruses, posing a serious public health risk worldwide. World Health Organization (WHO) named the disease as COVID-19 and declared it a pandemic. COVID-19 is characterized by highly contagious nature, rapid transmission, swift clinical course, profound worldwide impact, and high mortality among critically ill patients. Chest X-ray, computerized tomography (CT), and ultrasound are commonly used imaging modalities. Among them, ultrasound, due to its portability and non-invasiveness, can be easily moved to the bedside for examination at any time. In addition, with use of 4G or 5G networks, remote ultrasound consultation can also be performed, which allows ultrasound to be used in isolated medial areas. Besides, the contact surface of ultrasound probe with patients is small and easy to be disinfected. Therefore, ultrasound has gotten lots of positive feedbacks from the frontline healthcare workers, and it has played an indispensable role in the course of COVID-19 diagnosis and follow up.

Ultrasound has developed as an invaluable tool in diagnosis and proper management in the intensive care unit (ICU). Application of critical care ultrasonography is quite distinct from the routine comprehensive diagnostic ultrasound exam, because the urgent setting mandates a goal-directed approach. Performing accurate and efficient critical care ultrasound requires ultrasound providers to first understand the pathophysiology of the disease and related imaging findings, and then follow the protocols to perform a focused ultrasound exam. In the ongoing coronavirus disease 2019 (COVID-19) pandemic, ultrasound plays an essential role in diagnosing and monitoring critically ill COVID-19 patients in the ICU. Our review focuses on the basics and clinical application of critical care ultrasound in diagnosing common lung disease, COVID-19 pulmonary lesions, pediatric COVID-19, and cardiovascular dysfunction as well as its role in ECMO and interventional ultrasonography.

Contrast-enhanced ultrasound (CEUS) applications in cancer management have expanded over the past two decades. Through detection of vascularization and perfusion changes, CEUS provides a potentially reliable means of early prediction of response to different cancer therapies including systemic chemotherapy and locoregional therapies. Ultrasound-induced cavitation of contrast agents has a range of effects on the surrounding microenvironment. These effects can be manipulated to sensitize the tumors to radio- and chemotherapy, as well as achieve targeted delivery through drug-loaded contrast agents. Newer forms of drug carriers are being developed with improved drug-carrying capacity and tissue penetration. This review aims at providing a synopsis of the latest developments in CEUS’ use in oncologic therapy. While the majority of work described in this review is still in the pre-clinical phases, results have been encouraging and show potential translational benefit for cancer patients in the near future.

By virtue of advantages including no exposure to radiation and low toxicity and side effects, hyperthermia has been increasingly applied in treating cancer and other diseases. However, the challenge of continuous temperature monitoring during hyperthermia limits its further application. Currently, temperature monitoring in the clinic is primarily carried out using invasive thermometry, which is hampered by incomplete detection and pain. To overcome the obvious limitations of invasive thermometry, a variety of noninvasive thermometry methods with suitable accuracy have been explored. Among these, ultrasonic thermal strain imaging (UTSI), which exploits the temperature dependence of ultrasonic echo time shift to form thermal strain images, shows significant potential. It not only possesses the merits of ultrasonography but also displays different tissue characteristics (thermal properties of tissue and sound velocity) from other ultrasound imaging methods, so it has been investigated extensively over the past few years. This paper reviews recent advances in UTSI for noninvasive thermometry and discusses its main limitations, hoping to show the strong clinical application potential of UTSI from solid basic theory and practical research results.

Objective: Ultrasonography is widely used for the diagnosis of many diseases including thyroid and breast cancers. Delineation of lesion boundaries from ultrasound images plays an important role in calculation of clinical indices and early diagnosis of diseases. However, accurate automatic segmentation of lesions is challenging because of their heterogeneous appearance and lack of background contrast.
Method: In this study, we employed a pre-trained deep convolutional neural network (PCNN) to automatically segment lesions from ultrasound images. Specifically, our PCNN based method used whole images of normal tissues and lesions as inputs and then generated the segmentation probability maps as outputs. A pre-training strategy was used to improve the performance of the PCNN based model. Additionally, we compared the performance of our approach with that of the common convolutional neural network segmentation methods on the same dataset.
Results: We validated on ultrasound images of thyroid nodules and breast nodules. The experimental results were shown in true positive rate (TP), false positive rate (FP), overlap metric (OM) and dice ratio (DR). Specifically, for thyroid nodule segmentation, our method could achieve an average of OM, DR, TP, FP as 0.8943, 0.9558, 0.9694, 0.0569 on overall folds, respectively. For breast nodule segmentation, our method could achieve an average of OM, DR, TP, FP as 0.8572, 0.9001, 0.9497, 0.8619, respectively.
Conclusion: Our proposed method is fully automatic without any user interaction and may be good enough to replace the timeconsuming and tedious manual segmentation approach, demonstrating the potential clinical applications.

Real-time ultrasound imaging has been used for the evaluation of pulmonary abnormalities and other complications during the outbreak of COVID-19. However, conventional ultrasound examination requires operators to conduct scanning either in the examination room or patient ward, which may increase the potential infective risk. Tele-operated ultrasound robotics can provide a unique technique for doctors to remotely scan patients. During the COVID-19 pandemic, we attempted to apply a 5G network-based scanning robot to conduct remote ultrasound examination on COVID-19 patients and to explore the feasibility of this technique for teleultrasound diagnosis and consultation during critical infectious situations.

Objective: To investigate the value of lung ultrasound (LUS) in asymptomatic patients with confirmed COVID-19.
Methods: A retrospective analysis was performed on nine patients in a designated isolation hospital in Sanya from February 22nd, 2020 to February 23rd, 2020. All patients were confirmed with COVID-19 pneumonia by PCR test, but none had the typical symptoms of COVID-19. All patients first underwent LUS examination and then chest computed tomography (CT) scanning. The application value of LUS in asymptomatic confirmed patients with COVID-19 was evaluated, compared with chest CT which was regarded as the golden standard.
Results: Among nine asymptomatic patients with COVID-19, there were two cases (22.22%) with abnormal ultrasonic manifestations, of which one (11.11%) showed a fusion B3-line in zone 5 of the right lung, and the other showed localized pulmonary consolidation in zone 6 of the left lung. The remaining seven cases (77.78%) showed no abnormal changes in LUS, but only clear pleura sliding sign and A-line. Chest CT showed abnormal changes in three cases (33.33%). Two of them (22.22%) showed flocculent high-density shadow at the base of both lungs (especially in the right lung), while the other case showed ground-glass opacity with thickened interlobular septal in the left lower lobe, involving the pleura. There were no abnormalities on chest CT of the remaining six cases (66.67%). The two (22.22%) LUS-positive patients were in complete coincidence with CT-positive patients. This study showed that the coincidence rate of the two examination methods was 88.89%. Taking chest CT as golden standard, the sensitivity, specificity, positive predictive value, negative predictive value, and Kappa value of lung ultrasound in the diagnosis of COVID-19 were 66.67%, 100%, 100%, 85.71%, and 0.727, respectively.
Conclusion: LUS can evaluate lung lesions in asymptomatic patients with COVID-19. Compared with chest CT, the diagnostic coincidence rate and diagnostic consistency of LUS are relatively higher. For this asymptomatic type of patient, ultrasound can be used as a diagnosis method, which can avoid the risk of radiation exposure in a short period of time. As a rapid and dynamic assessment method, LUS can cooperate with remote consultation to provide timely and accurate guidance for clinical diagnosis and treatment when necessary.

Objective: To report our initial experience using the ultrasound (US)-guided single-needle lavage technique for treating calcific Achilles tendinitis.
Methods: Eighteen patients with chronic ankle pain refractory to medical treatment were treated percutaneously using a fine needle lavage technique under US guidance. Patients were evaluated using the visual analogue scale (VAS) pain score both before and 3 months after the procedure. Treatment-related complications were also recorded.
Results: All 18 cases of US-guided single-needle lavage were performed successfully. The range of recovery time was 30-45 days, and there was a significant reduction in the VAS pain score.
Conclusion: The US-guided single-needle lavage technique seems to be an effective and minimally invasive way to treat calcific Achilles tendinitis.

In recent years, ultrasound imaging has become an important means of medical diagnosis because of its safety and radiation-free advantages. With the continuous progress of deep learning, Artificial Intelligence (AI) models can process large amounts of ultrasound data quickly and accurately, providing decision support for clinicians in diagnosis. From the perspective of ultrasound image classification, detection and segmentation, this paper systemically introduces the latest progress of AI technology in ultrasound imaging, and summarizes the recent high-level related work. At the same time, we also discuss the development prospect and bottleneck of AI in ultrasound imaging processing, which provides the future research directions for researchers in related fields.

This case report describes a patient with severe coronavirus disease 2019 (COVID-19) concomitated with spontaneous pneumothorax, along with retrospective analysis of effective diagnosis and treatment. The case shows how chest radiography and computed tomography can play an important role in diagnosing and providing useful information for clinical management. The patient’s outcome and prognosis was related to his clinical management. In particular, early comprehensive treatment was certainly key to reducing complications and mortality in severe novel coronavirus pneumonia.

Objectives To assess the clinical efficacy and safety of ultrasound-guided stellate ganglion block in the treatment of allergic rhinitis.

Methods Sixty patients with allergic rhinitis were selected as study subjects and were treated with stellate ganglion blocking. We observed the appearance and time of the patient's Horner syndrome, and compared the patient's clinical symptom scores before and after one month treatment, and calculated the clinical efficacy and overall effective rate.

Results After ultrasound-guided stellate ganglion blocking treatment, 97% of patients occurred Horner syndrome within 2 minutes. The scores of sneezing, runny nose, nasal itching, and nasal congestion significantly reduced at one month after treatment compared with those before treatment, in which there was statistically significant difference (P<0.05). The clinical efficacy rate also reached 96.7% after procedures. No serious complications occurred in this study.

Conclusions Ultrasound-guided stellate ganglion block can significantly improve the clinical symptoms and the life quality for patients with allergic rhinitis, and it is worthy of extensive clinical application.

An autonomous functioning thyroid nodule (AFTN) is a benign disease. It can autonomously secrete excessive thyroid hormones without the need for TSH stimulation. It is not subject to the hypothalamic-pituitary-thyroid axis and is rare during pregnancy. Here we report a case of a 36-year-old pregnant woman with hyperthyroidism detected in early pregnancy, According to ultrasound and laboratory results, she was diagnosed with an AFTN. Ultrasound-guided (US-guided) microwave ablation (MWA) was used to treat AFTN during the second trimester of pregnancy. Hyperthyroidism crisis and other complications did not occur due to MWA. Thyroid function was normal at 2, 3 and 4 months after MWA. The volume reduction rate (VRR) was 83.67% at 4 months after MWA. The patient gave birth normally at 40 weeks gestation. All indices of thyroid function were normal during postpartum and lactation. US-guided MWA is a feasible and safe method for the treatment of AFTN during pregnancy, specifically in the second trimester.

Appendiceal mucocele is a rare disease. Sometimes it is discovered accidentally and sometimes it resembles acute appendicitis. The incidence is 0.2% to 0.7% of all appendectomies specimens. A case report of A 35-year female presented to the emergency room with a history of progressively increasing abdominal pain on and off for 3 months. Tenderness in the right lower quadrant of the abdomen was noted with a palpable mass in the right iliac fossa. An abdominal ultrasound examination was performed, and the patient was found to have an Appendicular mucocele-onion peel sign (sonographic layering within a cystic mass). The patient underwent surgery, and the diagnosis was confirmed by the histopathological report. If mucocele is treated incorrectly, pseudomyxoma peritonei which is characterized by a malignant process may develop. The term mucocele is widely used in diagnosing both benign and malignant lesions.

The cholinergic anti-inflammatory pathway is a neuro-immune regulatory pathway that mediates anti-inflammatory effects based on the vagus nerve, acetylcholine and α7 nicotinic acetylcholine receptors. In recent years, the effect of nerve stimulation by ultrasound has attracted much attention and has been widely studied. Ultrasound can stimulate the vagus nerve or spleen nerve and activate the cholinergic anti-inflammatory pathway, exerting anti-inflammatory and organ protection effects, which is expected to provide a new treatment for many inflammatory diseases. The purpose of this review is to introduce the composition, mechanisms and regulation methods of cholinergic anti-inflammatory pathway, and discuss its therapeutic implications.

Artificial intelligence-based pelvic floor ultrasound helps the diagnosis, preoperative assessment, and postoperative monitoring of female pelvic floor dysfunction (FPFD). The application of artificial intelligence in pelvic floor ultrasound mainly includes automatic segmentation and measurement, the diagnosis of muscle injury, childbirth prediction and postoperational evaluation. It can not only overcome the problem of operator experience dependence but also improve work efficiency and simplify the workflow, which has popularized the application of pelvic floor ultrasound. However, most of the current research is still limited to the automatic segmentation of three-dimensional axial plane levator hiatus (LH). The automatic reconstruction, real-time tracking of 3D/4D images and the imaging navigation of pelvic floor surgery remain major challenges for researchers.

The Coronavirus Disease 2019 (COVID-19) has spread rapidly throughout the world. COVID-19 is a highly contagious and potentially lethal infection, and as a result, individuals infected with it are treated in isolation units. Teleultrasound (TUS), particularly with the support of the fifth generation (5G) wireless transmission technology, can provide timely monitoring, fast clinical progress assessment, and help to guide interventional produces for patients with COVID-19 in isolation units. It can also reduce the risk of medical workers infection and save medical resources such as equipment and supplies. The purpose of this paper is to present an overview of operating procedures and ongoing planning with TUS for COVID-19 patients in China.

The purpose of this article is to review the use of lung ultrasonography (US) in the workup of COVID-19 pneumonia. The scanning protocol, normal US appearance of lung, major US features of COVID-19 pneumonia, diagnostic performance of lung US and potential pitfalls when explaining US results are descripted and discussed. Lung US is increasingly accepted as a useful tool in the workup of COVID-19 pneumonia. Certain US imaging features allow to confirm or rule out the diagnosis for clinical management; on other hand, most US findings are nonspecific with technical limitations. Thus, it is important to recognize these drawbacks since the ignorance of potential pitfalls of lung US may lead to over diagnosis or missed diagnosis.

Molecular ultrasound imaging or targeted contrast-enhanced ultrasound (CEUS) is a relatively new technique that has varied applications to augment both diagnostics and therapeutics. Ultrasound contrast agents are conjugated to ligands that bind with specific biomarkers in the areas of interest which can then be quantified using ultrasound technology. This technique has numerous clinical applications including studying pathophysiology of disease, improving diagnostic sensitivity and specificity, and improving localized drug delivery. This technology, most notably, has proven useful in numerous oncologic and cardiovascular applications. Given ultrasound’s advantages over other radiographic studies including its low cost, lack of ionizing radiation, portability, ability to provide real-time imaging, and non-invasiveness, recent investigations have expanded the utility of molecular ultrasound. In this review, we briefly review targeted ultrasound contrast agents and explore the current applications of molecular ultrasound as well as future applications based on the currently published literature.

The ultrasound contrast agents currently used in clinics are microbubbles with a large particle size and short circulation time, and their approved clinical applications are limited to endovascular diagnosis and therapy only. The development of ultrasound-responsive nanodroplets (NDs) provides a new approach for extravascular diagnosis and therapy, especially for molecular imaging and targeted therapy of tumors. The NDs with a nano-scaled particle size and a liquid core can maintain their shape and initial diameter during injection, enhancing their EPR effects and facilitating the accumulation of NDs at the tumor site. When exposed to ultrasound, NDs can vaporize and exhibit contrast enhancement at the sites of interest. In addition, the destruction of microbubbles can provide a driving force to facilitate the release of drugs or genes from the microbubbles into target cells, allowing the NDs to act as drug carriers. The development of ultrasound-responsive NDs has shown rapid progress in recent years, while a variety of NDs with excellent properties have been fabricated for targeted diagnosis and drug delivery. In this article, the development of ultrasound-responsive NDs was reviewed in terms of their structure, phase transition properties, and applications in targeted tumor diagnosis and therapy.

Artificial intelligent (AI) based on deep learning has been used in medical imaging analysis for years. Improvements have been made in the diagnosis of various diseases with the help of deep learning. Multimodal medical imaging combines two or more imaging modalities, providing comprehensive diagnostic information of the diseases. However, some modality problems always exist in clinical practice. Recently, AI-based deep learning technologies have realized the modality conversion. Investigations on modality conversion have gradually been reported in order to acquire multimodal information. MRI images could be generated from CT images while ultrasound elastography could be generated from B mode ultrasonography. Continuous researches and development of new technologies around deep learning are still under investigation and provide huge clinical potentials in the future. The purpose of this review is to summarize an overview of the current applications and prospects of deep learning-based modality conversion of medical imaging.

Objective: To explore the clinical value of ultrasonography for early detection and monitoring of angular pregnancy during the first-trimester.

Methods: For this retrospective study, we enrolled 23 patients with asymptomatic angular pregnancy who were diagnosed by ultrasound at early pregnancy and who underwent ultrasound follow-up to determine its clinical outcome. An ultrasound unit E8 (GE Healthcare, Milwaukee, WI) associated with a 5-9 MHz convex array transvaginal probe was used to image the gestational sac by both two-dimensional and three-dimensional modes. Transvaginal sonographic observation included the location, size, and shape of the gestational sac, as well as the relationship between the gestational sac and the endometrium. When the gestational sac was located close to or at the corners of the uterus, the wall thickness of the corner was measured and documented for follow-up during the first-trimester.

Results: Angular pregnancy (n=23) was detected by first ultrasonography at 37-50 days of gestation. All patients then underwent dynamic sonographic monitoring and were closely followed every 5-10 days for 1-3 weeks. In 3 cases, ultrasound showed embryo demise at follow-up examination. Seven cases were converted to intrauterine pregnancies based on sonographic findings and carried to term. In 13 cases, ultrasonography showed the gestational sacs grew outward in the corner of the uterus where the wall was thinning and had asymmetrical corners. Based on the ultrasound results, thesepregnancies were terminated (by surgery [n=6] or medication [n=7]).

Conclusions: Sonography is a valuable clinical tool for early detection and monitoring of angular pregnancy. Follow-up ultrasound can provide useful information for observing the transformation of angular pregnancy to guide clinical management, including whether to continue or terminate pregnancy.

Objectives: To determine the efficacy of Doppler-based renal resistive index (RRI) in the prediction of acute kidney injury (AKI) in critically ill patients.
Methods: A systematic review and meta-analysis of cohort studies was conducted. Relevant studies were identified in PubMed, Embase and Cochrane Library from inception to November 1, 2020, and reference lists of identified primary studies. Prospective studies that examined the diagnostic accuracy of RRI in AKI were included.
Results: Among the 126 articles identified, 18 were included, with a total of 1656 patients. Bivariate analysis yielded pooled sensitivity and specificity of 0.81 (95% CI 0.74-0.86) and 0.75 (95% CI 0.65-0.83), respectively. The summary positive likelihood ratio was 3.2 (95% CI 2.2-4.6), and negative likelihood ratio was 0.26 (95% CI 0.19-0.36).
Conclusion: Elevated RRI may be an early predictor of AKI in critically ill patients. Further large-scale prospective studies are needed to confirm the predictive efficacy and determine the performance and optimal cutoff value of RRI among the included studies.

Objective: To evaluate and compare the diagnostic performance of B-mode ultrasound (B-mode US), strain elastography (SE), color Doppler ultrasound (color Doppler US) and the combination of these modalities in differentiation between fibroadenomas and phyllodes tumors.

Methods: This retrospective study included 220 breast lesions, between January 2016 and January 2018. B-mode US, strain elastography, and color Doppler US were realized to evaluate each lesion. The results of three modalities were compared between the B-mode US and the combination of B-mode US, elastography, and color Doppler US: sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the receiver operating characteristic curve (AUC). The pathological findings were used as the reference standard.

Results: Among 220 breast masses, 189 of the lesions were fibroadenomas, 31 were phyllodes tumors. Addition of strain elastography and color Doppler US to B-mode US increased the specificity from 27.5% (95% confidence interval [CI]: 21.15%, 33.88%) to 95.24% (95% CI: 92.20%, 98.27%; P < 0.001); PPV from 16.46% (95% CI: 10.79%,22.14%) to 60.87% (95% CI: 40.92%, 80.82%; P < 0.001) and AUC from 0.584 (95% CI: 0.481, 0.687) to 0.886 (95% CI: 0.824, 0.948; P < 0.001).

Conclusion: The combination B-mode US, strain elastography and color Doppler US increase the diagnostic performance in distinguishing fibroadenomas from phyllodes tumors.

Ultrasound imaging has attracted great interest of researchers due to their application in cancer diagnosis and treatment. Ultrasound contrast agents, microbubbles and nanobubbles are widely explored as a multifunctional platform, not only carrying other contrast agents for multimodal imaging to complement the disadvantages of each imaging modality, but also carrying drug/gene for cancer theragnostic. In this article, the characteristics and differences of microbubbles and nanobubbles are briefly introduced and reviewed. Besides, the microbubbles and nanobubbles driven multimodal imaging and theragnostic of cancer are summarized.

Protective measures that are needed when treating patients with highly contagious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) add difficulty when performing interventional procedures in isolation wards. We describe two cases of ultrasonography-guided nasogastric tube placement in severe COVID-19 patients, both disabled elderly patients who were unconscious and had complicated underlying diseases. The first is an 83-year-old patient with Alzheimer's, hemiplegia, and epilepsy; the second is a 67-year-old patient with hemiplegia and thoracic deformity. Nasogastric tube indwelling for severe patients like this was essential but challenging. With the help of ultrasonography, intubation proceeded successfully and rapidly. Operator’s confidence of appropriate placement was established because of definite tube visualization. These cases demonstrated that bedside ultrasonography in isolation wards can not only facilitate diagnosis but also assist interventional operations.

The sentinel lymph node (SLN) concept hypothesizes that metastatic cancer cells will spread through the lymphatic system to the SLN being the first one in the lymphatic chain to receive the metastatic cells, indicating that if the SLN is free of cancer cells the rest of the lymphatic chain is also without metastatic disease. Diagnostic ultrasound imaging (US) has been used to evaluate lymph nodes (LN) to determine level of suspicion and to guide LN biopsies. However, conventional US cannot be used for lymphatic mapping, which requires administration of a tracer. This has been changed with the use of contrast-enhanced US (CEUS) to detect lymphatic channels and SLNs after subcutaneous injections of microbubble-based US contrast agents (UCAs). The aim of this review is to examine the clinical evidence on the role of subcutaneous injection of UCA, known as lymphosonography, to be used as preoperative identification of SLNs in patients with breast and other cancers.