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Ultrasound cavitation induced nucleation in metal solidification: An analytical model and validation by real-time experiments.

ABSTRACT: Microstructural refinement of metallic alloys via ultrasonic melt processing (USMP) is an environmentally friendly and promising method. However, so far there has been no report in open literature on how to predict the solidified microstructures and grain size based on the ultrasound processing parameters.In this paper, an analytical model is developed to calculate the cavitation enhanced undercooling and the USMP refined solidification microstructure and grain size for Al-Cu alloys. Ultrafast synchrotron X-ray imaging and tomography techniques were used to collect the real-time experimental data for validating the model and the calculated results. The comparison between modeling and experiments reveal that there exists an effective ultrasound input power intensity for maximizing the grain refinement effects for the Al-Cu alloys, which is in the range of 20-45 MW/m². In addition, a monotonous increase in temperature during USMP has negative effect on producing new nuclei, deteriorating the benefit of microstructure refinement due to the application of ultrasound.

SUBMITTER: Huang H

PROVIDER: S-EPMC8633372 | biostudies-literature | 2021 Dec

REPOSITORIES: biostudies-literature

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Ultrasound cavitation induced nucleation in metal solidification: An analytical model and validation by real-time experiments.

Huang Haijun H Qin Ling L Tang Haibin H Shu Da D Yan Wentao W Sun Baode B Mi Jiawei J

Ultrasonics sonochemistry 20211116

Microstructural refinement of metallic alloys via ultrasonic melt processing (USMP) is an environmentally friendly and promising method. However, so far there has been no report in open literature on how to predict the solidified microstructures and grain size based on the ultrasound processing parameters.In this paper, an analytical model is developed to calculate the cavitation enhanced undercooling and the USMP refined solidification microstructure and grain size for Al-Cu alloys. Ultrafast s ...[more]

PMID: 34826724

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Project description:Background : Focused ultrasound (FUS) in combination with microbubbles has recently shown great promise in facilitating blood-brain barrier (BBB) opening for drug delivery and immunotherapy in Alzheimer's disease (AD). However, it is currently limited to systems integrated within the MRI suites or requiring post-surgical implants, thus restricting its widespread clinical adoption. In this pilot study, we investigate the clinical safety and feasibility of a portable, non-invasive neuronavigation-guided FUS (NgFUS) system with integrated real-time 2-D microbubble cavitation mapping. Methods : A phase 1 clinical study with mild to moderate AD patients (N = 6) underwent a single session of microbubble-mediated NgFUS to induce transient BBB opening (BBBO). Microbubble activity under FUS was monitored with real-time 2-D cavitation maps and dosing to ensure the efficacy and safety of the NgFUS treatment. Post-operative MRI was used for BBB opening and closure confirmation as well as safety assessment. Changes in AD biomarker levels in both blood serum and extracellular vesicles (EVs) were evaluated, while changes in amyloid-beta (Aβ) load in the brain were assessed through 18F-florbetapir PET. Results : BBBO was achieved in 5 out of 6 subjects with an average volume of 983 ± 626 mm3 following FUS at the right frontal lobe both in white and gray matter regions. The outpatient treatment was completed within 34.8 ± 10.7 min. Cavitation dose significantly correlated with the BBBO volume (R 2 > 0.9, N = 4), demonstrating the portable NgFUS system's capability of predicting opening volumes. The cavitation maps co-localized closely with the BBBO location, representing the first report of real-time transcranial 2-D cavitation mapping in the human brain. Larger opening volumes correlated with increased levels of AD biomarkers, including Aβ42 (R 2 = 0.74), Tau (R 2 = 0.95), and P-Tau181 (R 2 = 0.86), assayed in serum-derived EVs sampled 3 days after FUS (N = 5). From PET scans, subjects showed a lower Aβ load increase in the treated frontal lobe region compared to the contralateral region. Reduction in asymmetry standardized uptake value ratios (SUVR) correlated with the cavitation dose (R 2 > 0.9, N = 3). Clinical changes in the mini-mental state examination over 6 months were within the expected range of cognitive decline with no additional changes observed as a result of FUS. Conclusion : We showed the safety and feasibility of this cost-effective and time-efficient portable NgFUS treatment for BBBO in AD patients with the first demonstration of real-time 2-D cavitation mapping. The cavitation dose correlated with BBBO volume, a slowed increase in pathology, and serum detection of AD proteins. Our study highlights the potential for accessible FUS treatment in AD, with or without drug delivery.

Project description:The purpose of these clinical studies was to validate a Tissue Change Monitoring (TCM) algorithm in vivo. TCM is a quantitative tool for the real-time assessment of HIFU dose. TCM provides quantitative analysis of the backscatter pulse echo signals (pre and immediately post HIFU) for each individual ablative site, using ultrasonic tissue characterization as a surrogate for monitoring tissue temperature. Real-time analysis generates an energy difference parameter (?E in dB) that is proportional to tissue temperature.Post in vitro studies, two clinical studies were conducted to validate the TCM algorithm on the Sonablate® device. Studies enrolled histologically confirmed, organ confined prostate cancer patients. The first clinical study was conducted in two phases for whole gland ablation. First eight patients' data were used to measure the algorithm performance followed by 89 additional patients for long term outcome. The second clinical study enrolled five patients; four patients with focal cancer had hemi-ablation only and one had whole gland ablation. Four 3 Fr. needles containing three thermocouples each were placed transperineally in the prostate to record tissue temperatures in the focal zone, posterior to the focal zone and on the lateral gland where no HIFU was applied. Tissue temperatures from the focal zone were correlated to the ?E parameter.In the first clinical study, the average TCM rate was 86%. Pre and 6 months post HIFU, median PSA was 7.64 and 0.025 ng/ml respectively and 97% patients had negative biopsy. For the second clinical study, the measured prostate tissue temperatures (Average, Max, and Min) in the ablation zones were 84°, 114° and 60 °C and the corresponding ?E (dB/10) parameters were 1.05, 2.6 and 0.4 resulting in 83% of temperatures in the range of 75°-100 °C and 17% in the 60°-74 °C range. Outside the focal zone, the average temperature was 50 °C and in the lateral lobe where no HIFU was applied, peak temperature was 40.7 °C.The TCM algorithm is able to estimate tissue changes reliably during the HIFU procedure for prostate tissue ablation in real-time and can be used as a guide for HIFU dose delivery and tissue ablation control.

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Ultrasound cavitation induced nucleation in metal solidification: An analytical model and validation by real-time experiments.

Publications

Ultrasound cavitation induced nucleation in metal solidification: An analytical model and validation by real-time experiments.

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