Quantification of steal flow on Doppler ultrasound in patients with arteriovenous graft for hemodialysis.

PURPOSE: Arteriovenous fistula (AVF) is the preferred treatment for long-term hemodialysis patients to allow reliable vascular access. Arteriovenous graft (AVG) is monitored using Doppler sonography to check a vessel's condition and predict complications such as steal syndrome. In this study, we developed an analysis algorithm and method to quantify steal syndrome using Doppler sonography. METHODS: Doppler sonography was used to determine the pattern of anterograde and retrograde flow. The ratio of blood volumes was calculated with a vision analysis software. First, performance of the developed algorithm was validated by comparing it with commercial Doppler sonography data. Doppler sonography was performed for an artificial vessel to analyze the steal flow. RESULTS: A total of 58 patients with steal flow were enrolled in this study. Of these patients, 23 did not have a difference in fingertip temperature between both sides. The median difference in temperature of 35 patients was 0.8°C (range, 0.3-1.9°C). The ratio of retrograde flow volume/antegrade flow volume in patients with the presence of temperature difference was significantly higher compared to that in patients without the temperature difference (p < .001). The ROC curve for the difference in flow volume had an AUC of 0.770. The optimal cutoff of difference in the flow volume between the two groups was 0.24 (sensitivity of 91.4 % and specificity of 52.2%). The flow volume difference was significantly positively correlated to temperature difference (r = 0.487, p < .003). CONCLUSION: Our algorithm could measure steal flow volume of a bidirectional waveform by antegrade arterial flow and retrograde reversal flow.

Noninvasive wearable sensor for the continuous monitoring of human sound and movement signals in real-time.

Recently, with the development of non-invasive human health monitoring technology including wearable devices, a flexible sensor that monitors 'human sound and movement signals' such as human voice and muscle movement is attracting attention. In this experiment, electrospun nanofibers were mixed with highly conductive nanoparticles and coated with polyaniline to detect the patient's electrical signals. Due to the high piezoelectric effect, nanofiber-based sensors do not require charging through a separate battery, so they can be used as self-powered devices. In addition, the LCR meter test confirmed that the sensor has a high capacitance due to its high conductivity and high sensitivity to electrical signals. The sensor produced in this study can visually estimate the electrical signal of the actual human body through real-time comparison with electromyography (EMG) measuring equipment, and it was confirmed that the error is small. This sensor is expected to be widely used in the medical field, from simple sound and movement signals to disease monitoring.

Validation of Signal Intensity Gradient from TOF-MRA for Wall Shear Stress by Phase-Contrast MR.

To validate the correlation between the signal intensity gradient (SIG) from time-of-flight magnetic resonance angiography (TOF-MRA) and wall shear stress (WSS) determined by phase contrast magnetic resonance (PC-MR), we conducted both experimental and human studies. In the experimental study, we measured WSS in four tubes of different sizes with variable flow rates using PC-MR and TOF-MRA. The flow rates of water in the experimental study ranged from 0.06 to 12.75 mL/s, resulting in PC-WSS values between 0.1 and 1.6 dyne/cm2. The correlation between PC-WSS and SIG was statistically significant, showing a coefficient of 0.86 (P < 0.001, R2 = 0.75). The line fit provided the conversion equation as Y = 1.6287X - 1.1563 (Y = PC-WSS, X = SIG). For the human study, 28 subjects underwent TOF-MRA and PC-MR examinations of carotid and vertebral arteries. Arterial PC-WSS and SIG were determined in the same segment for each subject. The arterial PC-WSS ranged from 1.9 to 21.0 dyne/cm2. Both carotid and vertebral arteries showed significant correlations between PC-WSS and SIG, with coefficients of 0.85, 0.86, 0.91, and 0.81 in the right and left carotid and vertebral arteries, respectively. Our results show that SIG from TOF-MRA and SIG-WSS derived from the conversion equation provide concurrent in vivo hemodynamic information on arterial shear stress. This study was registered on ClinicalTrials.gov with the identifier NCT04585971 on October 14, 2020.

Findings of Angiography and Carotid Vessel Wall Imaging Associated with Post-Procedural Clinical Events after Carotid Artery Stenting.

PURPOSE: Vessel wall imaging (VWI) for carotid plaque is better for detecting unstable carotid plaque such as intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and thin/ruptured fibrous cap. However, the role of VWI before carotid artery stenting (CAS) is unclear. Thus, this study aimed to determine the findings of symptomatic carotid stenosis before CAS on angiography and carotid VWI and to evaluate the imaging findings associated with post-procedural clinical events after CAS. MATERIALS AND METHODS: This retrospective study included 173 consecutive patients who underwent carotid VWI, CAS, and post-procedural diffusion-weighted imaging (DWI) after CAS. Findings of unstable plaque on carotid VWI and unstable findings on angiography were analyzed. We also analyzed the incidence of post-procedural clinical events, any stroke, myocardial infarction (MI), and death within 30 days of CAS. RESULTS: Of 173 patients, 101 (58.4%) had initial ischemic symptoms and positive findings on DWI. Symptomatic patients were significantly higher in patients with IPH than in patients without IPH (62.4% vs. 45.8%, P=0.031). Degree of stenosis, thrombus of the stenotic lesion, flow delay of internal carotid artery, and flow arrest by filter thrombus had significantly higher prevalence in the symptomatic group. Twenty patients (11.6%) had post-procedural clinical events such as any stroke, clinical symptoms, and/or MI. Hyperlipidemia and intraluminal thrombus on angiography were identified as significant factors influencing post-procedural events after CAS. CONCLUSION: An intraluminal thrombus on angiography was identified as a significant factor influencing post-procedural clinical events after CAS.

Post-diffusion and perfusion magnetic resonance imaging of emboli to distal territories after endovascular thrombectomy.

BACKGROUND AND PURPOSE: This study aimed to investigate the clinical outcomes of emboli to distal territories (EDT) after aspiration thrombectomy in patients with acute anterior circulation occlusion. MATERIALS AND METHODS: From January 2016 to December 2022, all eligible patients who underwent endovascular treatment (EVT) due to acute anterior circulation occlusion were retrospectively reviewed. During this period, patients with EDT after EVT underwent magnetic resonance (MR) perfusion with angiography and diffusion-weighted imaging within 12 hours from recanalization. Hypoperfusion was defined as a Tmax value > 6-second volume. RESULTS: Of the 104 eligible patients (65 males, median age 74 years), 79 (76.0 %; 2a: 19, 2b: 55, 2c: 5) had hypoperfusion on perfusion MR (PWI). Complete mismatch on diffusion-weighted imaging (DWI) of the hypoperfusion area was significantly higher in patients with successful recanalization than in patients with incomplete recanalization (58.3 % vs. 31.6 %, p = 0.0437). Of the 79 patients with hypoperfusion, 24 had EDT in the M2, 39 in the M3, and 16 in the M4. Complete mismatch on DWI and PWI was significantly higher in patients with a distal EDT (M3 or M4) than in patients with an M2 EDT (65.8 % vs. 20.8 %, p < 0.001). CONCLUSIONS: EDT to the M3 or more distal branches after EVT had a higher rate of complete DWI-PWI mismatch on early follow-up MRI than EDT to M2.