Ultrasound monitoring of microcirculation: An original study from the laboratory bench to the clinic

Monitoring microvascular changes over time with a repositionable 3D ultrasonic capacitive micromachined row-column sensor

eHealth devices, including smartwatches and smart scales, have the potential to transform health care by enabling continuous, real-time monitoring of vital signs over extended periods. Existing technologies, however, lack comprehensive monitoring of the microvascular network, which is linked to conditions such as diabetes, hypertension, and small vessel diseases. This study introduces an ultrasound approach using a capacitive micromachined ultrasound transducer row-column array for continuous, ultrasensitive three-dimensional (3D) Doppler imaging of microvascular changes such as hemodynamic variations or vascular remodeling. In vitro tests and in vivo studies with healthy volunteers demonstrated the sensor's ability to image the 3D microvascular network at high resolution over different timescales with automatic registration and to detect microvascular changes with high sensitivity. Integrating this technology into wearable devices could, one day, enhance understanding, monitoring, and possibly early detection of microvascular-related health conditions.

Non-contrast ultrasound assessment of blood flow in clinical practice

Since the first clinical use of ultrasound in the 1940s, significant advancements have been made in its applications. Color Doppler imaging and power Doppler imaging are considered the first and second generations of flow ultrasound assessment tools, respectively. Subsequently, the introduction of contrastenhanced ultrasound has significantly improved the assessment of arterial and venous vascular patterns in lesions and vessels. 'Blood flow brightness-mode imaging' or 'B-flow', a non-Doppler ultrasound flow assessment mode introduced more recently, provides even more information for ultrasound users in flow assessment. Microvascular imaging, introduced about a decade ago, is the third generation of Doppler non-contrast ultrasound flow modes, and is growing in popularity. Using a special wall filter, microvascular imaging overcomes the limitations of color Doppler imaging and power Doppler imaging in the detection of slow flowing signals. Advanced dynamic flow is a third-generation non-contrast Doppler flow technology that has so far gained popularity in obstetric ultrasound, commonly used to evaluate fetal umbilical vessels and heart chambers. This review article presents some recent updates on the various non-contrast ultrasound flow modalities available in clinical practice. It focuses on the design principles of individual flow modalities, discussing their strengths, limitations, and clinical applications, along with a review of the relevant literature.

Analyses of gingival papilla blood flow via color doppler flow imaging and micro-flow imaging in patients with advanced periodontitis: a clinical pilot study

BACKGROUND

Research investigating the potential link between gingival microvascular blood flow and inflammatory status is scarce. This study aims to assess color doppler flow imaging (CDFI) and micro-flow imaging (MFI) as tools for the assessment of gingival papilla blood flow (GPBF) and to examine their diagnostic utility as a noninvasive means of detecting gingival bleeding.

METHODS

CDFI and MFI were used to assess the GPBF grade (0-4) of 140 anterior gingival papilla sites in advanced periodontitis patients. Correlations between GPBF grades and periodontal characteristics were examined, and diagnostic performance as a means of predicting bleeding on probing (BOP) was examined using receiver operating characteristic curves.

RESULTS

GPBF grades 0 and 1 assessed by the MFI were 14.29% and 15.71% respectively, lower than the 28.57% and 24.29% assessed by the CDFI. In contrast, MFI detected a higher frequency of GPBF grade 2 sites (40.71%) relative to CDFI (22.14%). The CDFI and MFI provided consistent results in 62.14% of the sites, while the MFI demonstrated higher ratings in rest 37.86% of the sites. A significant positive correlation was detected between GPBF grade and the modified gingival index (MGI), bleeding index (BI), BOP, and probing depth (PD). It showed high accuracy for CDFI or MFI to diagnosing BOP with a sensitivity of 80.51% and 96.43% and a specificity of 77.27% and 57.14%, respectively. Area under the receiver operator characteristic curve values when predicting BOP based on the GPBF grade determined using CDFI and MFI approaches 0.887 (95% CI 0.833-0.942) and 0.917 (95% CI 0.862-0.972), respectively, and there were no significant differences between these values (Z = - 1.502, p = 0.133).

CONCLUSIONS

Both MFI and CDFI can be employed for the evaluation of GPBF, and MFI is better suited to detecting mild inflammation. Trial registration ChiCTR2200066021 (Date of registration: 22/11/2022).

Ex-Vivo Human-Sized Organ Machine Perfusion: A Systematic Review on the Added Value of Medical Imaging for Organ Condition Assessment

Machine perfused ex-vivo organs offer an excellent experimental platform, e.g., for studying organ physiology and for conducting pre-clinical trials for drug delivery. One main challenge in machine perfusion is the accurate assessment of organ condition. Assessment is often performed using viability markers, i.e., lactate concentrations and blood gas analysis. Nonetheless, existing markers for condition assessment can be inconclusive, and novel assessment methods remain of interest. Over the last decades, several imaging modalities have given unique insights into the assessment of organ condition. A systematic review was conducted according to accepted guidelines to evaluate these medical imaging methods, focussed on literature that use machine perfused human-sized organs, that determine organ condition with medical imaging. A total of 18 out of 1,465 studies were included that reported organ condition results in perfused hearts, kidneys, and livers, using both conventional viability markers and medical imaging. Laser speckle imaging, ultrasound, computed tomography, and magnetic resonance imaging were used to identify local ischemic regions and quantify intra-organ perfusion. A detailed investigation of metabolic activity was achieved using 31P magnetic resonance imaging and near-infrared spectroscopy. The current review shows that medical imaging is a powerful tool to assess organ condition.

Ultrasonic-responsive piezoelectric stimulation enhances sonodynamic therapy for HER2-positive breast cancer

INTRODUCTION

Breast cancer ranks second as the most common malignancy globally, after lung cancer. Among the various subtypes of breast cancer, HER2 positive breast cancer (HER2 BC)poses a particularly challenging prognosis due to its heightened invasiveness and metastatic potential. The objective of this study was to construct a composite piezoelectric nanoparticle based on poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) for imaging and treatment of HER2 BC.

METHOD

By reshaping the crystal structure of P(VDF-TrFE) piezoelectric nanoparticles, improving hydrophilicity, and incorporating imaging capabilities, we developed piezoelectric composite nanoparticles (PGd@tNBs) that integrate imaging and therapeutic functions. The in vitro characterization encompassed the assessment of piezoelectric properties, hydrophilicity, imaging performance, and therapeutic efficacy of these particles. The targeting and therapeutic effectiveness of PGd@tNBs particles were further validated in the SK-BR3 cell line and subsequently confirmed in HER2-positive tumor-bearing mice.

RESULTS

The nanoparticle demonstrated excellent biocompatibility and impressive multimodal imaging performance. Magnetic resonance imaging (MRI) observations revealed significant accumulation of PGd@tNBs particles in the HER2 positive tumor, exhibiting superior contrast-enhanced ultrasound performance compared to traditional ultrasound contrast agents, and small animal in vivo imaging showed that PGd@tNBs particles were primarily excreted through respiration and urinary metabolism. Piezoforce Microscopy characterization highlighted the outstanding piezoelectric properties of PGd@tNBs particles. Upon targeted binding to HER2-BC, ultrasound stimulation influenced the cell membrane potential, leading to reversible electroporation. This, in turn, affected the balance of calcium ions inside and outside the cells and the mitochondrial membrane potential. Following ingestion by cells, PGd@tNBs, when exposed to ultrasound, triggered the generation of reactive oxygen species (ROS), resulting in the consumption of glutathione and superoxide dismutase and achieving sonodynamic therapy. Notably, repeated ultrasound stimulation, post PGd@tNBs particles binding and entry into cells, increased ROS production and elevated the apoptosis rate by approximately 45%.

CONCLUSION

In conclusion, the PGd@tNBs particles developed exhibit outstanding imaging and therapeutic efficacy, holding potential for precise diagnosis and personalized treatment of HER2 BC.

Ultrasonography of Hepatocellular Carcinoma: From Diagnosis to Prognosis

Hepatocellular carcinoma (HCC) is a prominent contributor to cancer-related mortality worldwide. Early detection and diagnosis of liver cancer can significantly improve its prognosis and patient survival. Ultrasound technology, serving has undergone substantial advances as the primary method of HCC surveillance and has broadened its scope in recent years for effective management of HCC. This article is a comprehensive overview of ultrasound technology in the treatment of HCC, encompassing early detection, diagnosis, staging, treatment evaluation, and prognostic assessment. In addition, the authors summarized the application of contrast-enhanced ultrasound in the diagnosis of HCC and assessment of prognosis. Finally, the authors discussed further directions in this field by emphasizing overcoming existing obstacles and integrating cutting-edge technologies.

Microvascular flow ultrasound imaging for retinoblastoma

PURPOSE

To present the results of a pilot study of microvascular flow imaging (MFI) in characterizing tumor vasculature of retinoblastoma.

METHODS

The medical records of consecutive patients with retinoblastoma presenting at our institution between July 2019 and June 2022 that were imaged using MFI were reviewed retroactively. Each patient underwent diagnostic evaluation according to standard of care by examination under anesthesia with fluorescein angiography and ocular ultrasound imaging, including color Doppler and MFI.

RESULTS

Thirteen eyes of 10 patients with retinoblastoma were included. MFI showed a prominent feeder vessel in 8 eyes, basket vasculature in 6 eyes and tumor bed vascularity in 10 eyes. MFI showed a more extensive vascular branching pattern that was not visible on color Doppler and fluorescein angiography in all eyes.

CONCLUSIONS

MFI of retinoblastoma patients could add information about tumor vascularity not detectable by color Doppler or fluorescein angiography. Further study is needed to determine whether this information could be used to predict prognosis for ocular salvage and tumor response to treatment.

Non-contrast ultrasound image analysis for spatial and temporal distribution of blood flow after spinal cord injury

Ultrasound technology can provide high-resolution imaging of blood flow following spinal cord injury (SCI). Blood flow imaging may improve critical care management of SCI, yet its duration is limited clinically by the amount of contrast agent injection required for high-resolution, continuous monitoring. In this study, we aim to establish non-contrast ultrasound as a clinically translatable imaging technique for spinal cord blood flow via comparison to contrast-based methods and by measuring the spatial distribution of blood flow after SCI. A rodent model of contusion SCI at the T12 spinal level was carried out using three different impact forces. We compared images of spinal cord blood flow taken using both non-contrast and contrast-enhanced ultrasound. Subsequently, we processed the images as a function of distance from injury, yielding the distribution of blood flow through space after SCI, and found the following. (1) Both non-contrast and contrast-enhanced imaging methods resulted in similar blood flow distributions (Spearman's ρ = 0.55, p < 0.0001). (2) We found an area of decreased flow at the injury epicenter, or umbra (p < 0.0001). Unexpectedly, we found increased flow at the periphery, or penumbra (rostral, p < 0.05; caudal, p < 0.01), following SCI. However, distal flow remained unchanged, in what is presumably unaffected tissue. (3) Finally, tracking blood flow in the injury zones over time revealed interesting dynamic changes. After an initial decrease, blood flow in the penumbra increased during the first 10 min after injury, while blood flow in the umbra and distal tissue remained constant over time. These results demonstrate the viability of non-contrast ultrasound as a clinical monitoring tool. Furthermore, our surprising observations of increased flow in the injury periphery pose interesting new questions about how the spinal cord vasculature reacts to SCI, with potentially increased significance of the penumbra.

Microvascular assessment of fascio-cutaneous flaps by ultrasound: A large animal study

Objectives: Blood perfusion quality of a flap is the main prognostic factor for success. Microvascular evaluation remains mostly inaccessible. We aimed to evaluate the microflow imaging mode, MV-Flow, in assessing flap microvascularization in a pig model of the fascio-cutaneous flap. Methods: On five pigs, bilateral saphenous fascio-cutaneous flaps were procured on the superficial femoral vessels. A conventional ultrasound evaluation in pulsed Doppler and color Doppler was conducted on the ten flaps allowing for the calculation of the saphenous artery flow rate. The MV-Flow mode was then applied: for qualitative analysis, with identification of saphenous artery collaterals; then quantitative, with repeated measurements of the Vascularity Index (VI), percentage of pixels where flow is detected relative to the total ultrasound view area. The measurements were then repeated after increasing arterial flow by clamping the distal femoral artery. Results: The MV-Flow mode allowed a better follow-up of the saphenous artery's collaterals and detected microflows not seen with the color Doppler. The VI was correlated to the saphenous artery flow rate (Spearman rho of 0.64; p = 0.002) and allowed to monitor the flap perfusion variations. Conclusion: Ultrasound imaging of microvascularization by MV-Flow mode and its quantification by VI provides valuable information in evaluating the microvascularization of flaps.

FlowMorph: Morphological Segmentation of Ultrasound-Monitored Spinal Cord Microcirculation

Imaging of spinal cord microvasculature holds great potential in directing critical care management of spinal cord injury (SCI). Traditionally, contrast agents are preferred for imaging of the spinal cord vasculature, which is disadvantageous for long-term monitoring of injury. Here, we present FlowMorph, an algorithm that uses mathematical morphology techniques to segment non-contrast Doppler-based videos of rat spinal cord. Using the segmentation, it measures single-vessel parameters such as flow velocity, rate, and radius, with visible cardiac cycles in individual vessels showcasing the spatiotemporal resolution. The segmentation outlines vessels well with little extraneous labeling, and outlines are smooth through time. Radius measurements of perforating vessels are similar to what is seen in the literature through other methods. Verification of the algorithm through comparison to manual measurement and in vitro microphantom standards highlights points of future improvement. This method will be vital for future work studying the vascular effects of SCI and can be adopted to other species as well.