Recent advances in vascular ultrasound imaging technology and their clinical implications

In Part I of this consensus article, the imaging methodology, evolving imaging technology, and development of novel targeted molecular probes relevant to the developing field of cardiovascular molecular imaging were reviewed. Novel reporter gene and reporter probe imaging approaches for tracking of cardiac transgene expression were also discussed and have important future implications for evaluation of gene- and cell-based therapies for the failing heart. The current role of metabolic and receptor imaging was also briefly reviewed, as these represent the beginning of our clinical application of molecular imaging within the cardiovascular system. Part II will summarize the available targeted imaging probes as well as specific future applications of molecular imaging for identification and evaluation of critical pathophysiological processes of the cardiovascular system.

Ultrasound (US) probes scan over the surface of the human body to acquire US images in clinical vascular US diagnosis. However, due to the deformation and specificity of different human surfaces, the relationship between the scan trajectory of the skin and the internal tissues is not fully correlated, which poses a challenge for autonomous robotic US imaging in a dynamic and external-vision-free environment. Here, we propose a decoupled control strategy for autonomous robotic vascular US imaging in an environment without external vision. The proposed system is divided into outer-loop posture control and inner-loop orientation control, which are separately determined by a deep learning (DL) agent and a reinforcement learning (RL) agent. First, we use a weakly supervised US vessel segmentation network to estimate the probe orientation. In the outer loop control, we use a force-guided reinforcement learning agent to maintain a specific angle between the US probe and the skin in the dynamic imaging processes. Finally, the orientation and the posture are integrated to complete the imaging process. Evaluation experiments on several volunteers showed that our RUS could autonomously perform vascular imaging in arms with different stiffness, curvature, and size without additional system adjustments. Furthermore, our system achieved reproducible imaging and reconstruction of dynamic targets without relying on vision-based surface information. Our system and control strategy provides a novel framework for the application of US robots in complex and external-vision-free environments.

The ultrasound (US) imaging technology, including contrast-enhanced US (CEUS) and fusion imaging, has experienced radical improvement, and advancement in technology thus overcoming the problem of poor conspicuous hepatocellular carcinoma (HCC). On CEUS, the presence or absence of enhancement distinguishes the viable portion from the ablative necrotic portion. Using volume data of computed tomography (CT) or magnetic resonance imaging (MRI), fusion imaging enhances the three-dimensional relationship between the liver vasculature and HCC. Therefore, CT/MR-US fusion imaging provides synchronous images of CT/MRI with real-time US, and US-US fusion imaging provides synchronous US images before and after ablation. Moreover, US-US overlay fusion can visualize the ablative margin because it focuses the tumor image onto the ablation zone. Consequently, CEUS and fusion imaging are helpful to identify HCC with little conspicuity, and with more confidence, we can perform ablation therapy. CEUS/fusion imaging guidance has improved the clinical effectiveness of ablation therapy in patients with poor conspicuous HCCs. Therefore; this manuscript reviews the status of CEUS/fusion imaging guidance in ablation therapy of poor conspicuous HCC.

Stroke is one of the leading causes of adult disability throughout the world and, even though neural mechanisms of loss of function have been extensively studied, many aspects of poststroke cerebral responses remain poorly understood. Of particular interest is the mounting evidence of the capacity of the adult brain to reorganize after injury, which is believed to contribute to limitation of the extent of neural dysfunction and to restoration of affected neural functions. Processes such as neuronal plasticity, glial proliferation, and neovascularization may be essential for preservation or recovery of function after stroke and may conceivably go hand-in-hand at nearby and remote sites of active tissue reorganization.1,2 Specifically, the acute initiation of neurovascular remodeling, stimulating the proliferation and growth of existing arteries/arterioles (ie, arteriogenesis) or new capillaries (ie, angiogenesis), may be critical to facilitate the survival and restructuring of neural tissue, which ultimately may contribute to functional recovery at later stages.3 A variety of vascular imaging strategies is available for in vivo detection, characterization, and quantification of these processes, which can significantly aid in elucidation of the role of neurovascular remodeling after stroke, as discussed in this review. Because most of the described imaging modalities are present in experimental and clinical settings, this raises significant opportunities for translational studies. Growth and remodeling of existing and nascent vascular networks in health and disease involve a number of critical steps that have been comprehensively described by Risau4 and Carmeliet.5 Arteriogenesis involves adaptive growth and proliferation of preexisting (collateral) arteries and arterioles in response to increase in intravascular shear forces. The increased shear stress leads to upregulation of cell adhesion molecules, followed by accumulation of monocytes and other leukocytes that release cytokines and growth factors around the proliferating and maturating arteries.6 Although arteriogenic growth of collateral …

Continuous vascular imaging is critical for the early diagnosis and monitoring of disease progression. Vascular ultrasound imaging is usually performed by an array with a high central frequency due to its better imaging quality. However, conventional ultrasonic arrays are rigid and operator-dependent. Existing flexible and wearable ultrasonic arrays are often manufactured with a relatively low central frequency since the element pitch is still limited by processing difficulties. Moreover, the lack of an acoustic lens, matching layer and backing layer also affects performance. Here, we report a 128-channel flexible wearable ultrasonic array designed with a 10 MHz central frequency, 150 μm pitch, shielding layer, backing layer, piezoelectric layer and matching layer. The array has been tested in several ultrafast vascular ultrasound imaging situations, with multi-angle coherent plane-wave transmission adopted. In vitro phantom experiments illustrate its effectiveness in power Doppler and color Doppler imaging of blood flow. Cross-sectional and longitudinal section imaging of the human carotid artery in vivo can be achieved, and Doppler imaging as well as pulsatility measurements have been performed to obtain hemodynamics. Furthermore, long-term continuous ultrasound monitoring of the human carotid artery has been performed over 9 h using the wearable array. Preliminary in vivo ultrasound localization microscopy results for rabbit brain carried out with the array indicate its potential in microvascular imaging. This wearable ultrasonic array will offer more flexibility for ultrasound vascular imaging detection and diagnosis.

Recent advances in vascular ultrasound imaging technology and their clinical implications

Image segmentation for object to extract data from ultrasound acquired is an essential preprocessing step for the effective diagnosis. Various image segmentation methods have been studied. In this study, interactive image segmentation method by graph cut algorithm is proposed to develop a variety of applications of vascular ultrasound imaging and diagnostics. General imaging and vascular ultrasound imaging segmentation by entering constrain condition such as foreground and background. In the future it will be able to develop new ultrasound diagnostics.

Vascular occlusion is the major complication of percutaneous cardiac catheterization in children. This is a prospective study to evaluate post catheterization vascular complications in 120 consecutive children with the help of vascular ultrasound and Doppler imaging. Ultrasound imaging of both iliac and femoral veins and arteries was done one hour prior and 24 hours after cardiac catheterization. Patients with prior thrombus or occlusion of femoral/iliac vein or artery due to previous cardiac catheterization were excluded from the study. Age of the patients ranged from 22 days to 12 years with a mean of 56 months and weight ranged from 3 to 57 kg with a mean of 14.3 kg. Procedure time was less than 60 minutes in 74 patients (61.66%) and more than 60 minutes in 46 patients (38.33%). 4F sized arterial sheath was used in 108 patients. 5F or bigger sized arterial sheath was used in remaining 12 patients. Incidence of arterial occlusion was higher in patients weighing less than 10 kg (16%) as compared with patients weighing more than 10 kg (5.5%) {P = 0.031}. Arterial thrombosis was more in infants (16%) as compared with older children (7%) {P = 0.203} Prolonged procedure time or use of larger sized sheath did not have higher incidence of arterial occlusion. Venous thrombosis was found in 2 patients (1.66%) who had 5F venous sheath. One patient had arterio venous fistula. Our study shows vascular ultrasound imaging can provide anatomical details of femoral and iliac vessels and is a easier and accurate method of assessing post-catheterization vascular complications in children.

Objective: To analyze the diagnostic, monitoring, and procedural applications of ultrasound (US) imaging in neurocritical care (NCC) patients.Method: US imaging has been extensively validated in various subset of critically ill patients, but not specifically in the NCC population. We reviewed the clinical applications of US imaging for heart, vascular, brain, and lung evaluation and for possible procedural uses in NCC patients. Major neurosurgical books, journals, testimonials, authors’ personal experience, and scientific databases were analyzed.Results: Cardiac US imaging provides accurate information at NCC arrival to stratify risk factors, including presence of atrial septal defect/patent formen ovale, abnormal ventricular function, or pericardial effusion, and to monitor cardiac anatomy and function during the NCC stay for guiding goal-directed therapy. Vascular US in NCC patients has three especially relevant indications: to screen anatomy and flow in extracranial supra-aortic arteries, to diagnose deep vein thrombosis, and to optimize the safety of central venous catheterization. Brain US has important clinical applications in the NCC, including transcranial Doppler and emerging techniques for cerebral blood flow evaluation with contrast-enhanced US imaging. Lung US, as demonstrated in other intensive care unit patients, provides accurate diagnosis of anatomical and functional abnormalities and enables diagnosis of pleural effusion, pneumothorax, lung consolidation, pulmonary abscess and interstitial-alveolar syndrome, and lung recruitment/derecruitment. US imaging can effectively guide percutaneous tracheostomy.Conclusion: In conclusion, US imaging is an important diagnostic tool that provides real-time information at the bedside to stratify risk, monitor for complications, and guide invasive procedures in NCC patients.

The study aimed to explore the value of ultrasound (US) texture analysis in the differential diagnosis of triple-negative breast cancer (TNBC) and non-TNBC.Retrospective analysis was done on 93 patients with breast cancer (35 patients with TNBC and 38 patients with non-TNBC) who were admitted to Taizhou people's hospital from July 2015 to June 2019. All lesions were pathologically proven at surgery. US images of all patients were collected. Texture analysis of US images was performed using MaZda software package. The differences between textural features in TNBC and non-TNBC were assessed. Receiver operating characteristic curve analysis was used to compare the diagnostic performance of textural parameters showing significant difference.Five optimal texture feature parameters were extracted from gray level run-length matrix, including gray level non-uniformity (GLNU) in horizontal direction, vertical gray level non-uniformity, GLNU in the 45 degree direction, run length non-uniformity in 135 degree direction, GLNU in the 135 degree direction. All these texture parameters were statistically higher in TNBC than in non-TNBC (P <.05). Receiver operating characteristic curve analysis indicated that at a threshold of 268.9068, GLNU in horizontal direction exhibited best diagnostic performance for differentiating TNBC from non-TNBC. Logistic regression model established based on all these parameters showed a sensitivity of 69.3%, specificity of 91.4% and area under the curve of 0.834.US texture features were significantly different between TNBC and non-TNBC, US texture analysis can be used for preliminary differentiation of TNBC from non-TNBC.

The introduction of ultrasound (US) microbubble contrast agents has dramatically expanded the possibilities for US detection of prostate cancer. Recent advances in US technology have increased the value of US contrast agents. Many newer US techniques, which are quite sensitive for detection of microbubbles, are yet to be explored for prostate applications. A critical evaluation of the current status of transrectal US imaging for the detection of prostate cancer and background information for US contrast agents and imaging techniques are presented. Early results have demonstrated the feasibility of US contrast agents to enhance US imaging of prostatic disease. The application of US contrast agents for the detection and clinical staging of prostate cancer is promising. Future clinical trials are needed to determine whether the promise of contrast-enhanced US of the prostate will evolve into widespread clinical application.

With advances in imaging technology, images from ultrasound (US) and computed tomography (CT) or magnetic resonance imaging (MRI) can be displayed simultaneously and in real time, according to the angle of the transducer. CT/MR-US fusion imaging improves the visualization of inconspicuous hepatocellular carcinoma (HCC) and helps us to understand the three-dimensional relationship between the liver vasculature and HCC. US fusion imaging guidance facilitates improvement in the treatment response for HCC with poor conspicuity, and the rates of technical success of ablation and local tumor progression for inconspicuous HCC range from 94.4 to 100% and 0 to 8.3%, respectively. Moreover, the development of image fusion has made it possible to compare and overlay pre- and post-ablation US images. This US-US fusion imaging allows side-by-side comparison of the ablative margin, while US-US overlay fusion can visualize the ablative margin because the tumor image is projected onto the ablative hyperechoic zone. Thus, US-US overlay fusion guidance is highly effective for safety margin achievement in local ablation therapy for HCC, providing a lower risk of local tumor progression. This manuscript reviews the current status of ultrasound fusion imaging for percutaneous ablation therapy of HCC.

Guidelines for Noninvasive Vascular Laboratory Testing: A Report from the American Society of Echocardiography and the Society of Vascular Medicine and Biology

For diagnostic and interventional procedures ultrasound (US) image fusion can be used as a complementary imaging technique. Image fusion has the advantage of real time imaging and can be combined with other cross-sectional imaging techniques. With the introduction of US contrast agents sonography and image fusion have gained more importance in the detection and characterization of liver lesions. Fusion of US images with computed tomography (CT) or magnetic resonance imaging (MRI) facilitates the diagnostics and postinterventional therapy control. In addition to the primary application of image fusion in the diagnosis and treatment of liver lesions, there are more useful indications for contrast-enhanced US (CEUS) in routine clinical diagnostic procedures, such as intraoperative US (IOUS), vascular imaging and diagnostics of other organs, such as the kidneys and prostate gland.

Advancements in Noncontrast Ultrasound Imaging for Low-Velocity Flow: A Technical Review and Clinical Applications in Vascular Medicine.