[Research on Construction of Test Environment for Assessment of RF-Induced Heating Effects of Implants].

In magnetic resonance examination, the interaction between implants and the radio frequency (RF) fields induces heating in human tissue and may cause tissue damage. To assess the RF-induced heating of implants, three steps should be executed, including electromagnetic model construction, electromagnetic model validation, and virtual human body simulations. The crucial step of assessing RF-induced heating involves the construction of a test environment for electromagnetic model validation. In this study, a hardware environment, comprised of a RF generation system, electromagnetic field measurement system, and a robotic arm positioning system, was established. Furthermore, an automated control software environment was developed using a Python-based software development platform to enable the creation of a high-precision automated integrated test environment. The results indicate that the electric field generated in this test environment aligns well with the simulated electric field, making it suitable for assessing the RF-induced heating effects of implants.

Assessment of Perfusion Volumes by a New Automated Software for Computed Tomography Perfusion.

INTRODUCTION: To compare the perfusion volumes assessed by a new automated CT perfusion (CTP) software iStroke with the circular singular value decomposition software RAPID and determine its predictive value for functional outcome in patients with acute ischaemic stroke (AIS) who underwent endovascular treatment (EVT). METHODS: Data on patients with AIS were collected from four hospitals in China. All patients received CTP followed by EVT with complete recanalisation within 24 hours of symptom onset. We evaluated the agreement of CTP measures between the two softwares by Spearman's rank correlation tests and kappa tests. Bland-Altman plots were used to evaluate the agreement of infarct core volume (ICV) on CTP and ground truth on diffusion-weighted imaging (DWI). Logistic regression models were used to test the association between ICV on these two softwares and functional outcomes. RESULTS: Among 326 patients, 228 had DWI examinations and 40 of them had infarct volume >70 mL. In all patients, the infarct core and hypoperfusion volumes on iStroke had a strong correlation with those on RAPID (ρ=0.68 and 0.66, respectively). The agreement of large infarct core (volume >70 mL) was substantial (kappa=0.73, p<0.001) between these two softwares. The ICV measured by iStroke and RAPID was significantly correlated with independent functional outcome at 90 days (p=0.009 and p<0.001, respectively). In patients with DWI examinations and those with an ICV >70 mL, the ICV of iStroke and RAPID was comparable on individual agreement with ground truth. CONCLUSION: The automatic CTP software iStroke is a reliable tool for assessing infarct core and mismatch volumes, making it clinically useful for selecting patients with AIS for acute reperfusion therapy in the extended time window.

Evidence of economic development revealed in centennial scale sedimentary records of organic pollutants in Huguangyan Marr Lake.

Sedimentary records of polycyclic aromatic hydrocarbons (PAHs) and phthalates could reflect energy consumption and industrial production adjustment. However, there is limited knowledge about their effects on variations of PAH and phthalate compositions in the sediment core. The PAH and phthalate sedimentary records in Huguangyan Maar Lake in Guangdong, China were constructed, and random forest models were adopted to quantify the associated impact factors. Sums of sixteen PAH (∑16 PAH) and seven phthalate (∑7 PAE) concentrations in the sediment ranged from 28.8 to 1110 and 246-4290 µg/kg dry weight in 1900-2020. Proportions of 5-6 ring PAHs to the ∑16 PAHs increased from 32.0 %-40.7 % in 1900-2020 with increased coal and petroleum consumption, especially after 1980. However, those of 2-3 ring PAHs decreased from 30.7 % to 23.6 % due to the biomass substitution with natural gas. The proportions of bis (2-ethylhexyl) phthalate to the ∑7 PAEs decreased from 52.3 %-29.1 % in 1900-2020, while those of di-isobutyl phthalate increased (13.7 % to 42.3 %). The shift from traditional plasticizers to non-phthalates drove this transformation, though the primary plastic production is increasing. Our findings underscore the effectiveness of optimizing energy structures and updating chemical products in reducing organic pollution in aquatic environments.

Hemodynamic assessment for intracranial atherosclerosis from angiographic images: a clinical validation study.

BACKGROUND: Intracranial atherosclerotic stenosis (ICAS) is one of the leading causes of ischemic stroke. Conventional anatomical analysis by CT angiography, MRI, or digital subtraction angiography can provide valuable information on the anatomical changes of stenosis; however, they are not sufficient to accurately evaluate the hemodynamic severity of ICAS. The goal of this study was to assess the diagnostic performance of the pressure ratio across intracranial stenoses (termed as fractional flow (FF)) derived from cerebral angiography for the diagnosis of hemodynamically significant ICAS defined by pressure wire-derived FF. METHODS: This retrospective study represents a feasible and reliable method for calculating the FF from cerebral angiography (AccuFFicas). Patients (n=121) who had undergone wire-based measurement of FF and cerebral angiography were recruited. The accuracy of the computed pressure ratio was evaluated using wire-based FF as the reference standard. RESULTS: The mean value of wire-based FF was 0.78±0.19, while the computed AccuFFicas had an average value of 0.79±0.18. Good correlation (Pearson's correlation coefficient r=0.92, P<0.001) between AccuFFicas and FF was observed. Bland-Altman analysis showed that the mean difference between AccuFFicas and FF was -0.01±0.07, indicating good agreement. The area under the curve (AUC) of AccuFFicas in predicting FF≤0.70, FF≤0.75, and FF≤0.80 was 0.984, 0.986, and 0.962, respectively. CONCLUSION: Angiography-based FF computed from cerebral angiographic images could be an effective computational tool for evaluating the hemodynamic significance of ICAS.

Cost-effectiveness of thrombectomy alone versus alteplase before thrombectomy in acute ischemic stroke: results from the DIRECT-MT.

OBJECTIVE: The use of thrombectomy alone (endovascular thrombectomy [EVT]) was found to be noninferior to combination therapy (EVT plus intravenous thrombolysis [IVT] with alteplase before thrombectomy [EVT+IVT]) in the DIRECT-MT (Direct Intra-Arterial Thrombectomy in Order to Revascularize AIS Patients With Large Vessel Occlusion Efficiently in Chinese Tertiary Hospitals: A Multicenter Randomized Clinical Trial), yet the economic value of omitting alteplase was unclear. Thus, in this paper the authors assessed the cost-effectiveness of EVT alone versus EVT+IVT in the DIRECT-MT. METHODS: In the context of the Chinese healthcare system, the authors conducted a post hoc economic analysis of the DIRECT-MT based on an intention-to-treat approach. Index stroke costs were collected at the individual level, while costs after discharge were complemented with published literature and government websites. Utility weights assessed at 90 days using the 5-Level EQ-5D questionnaire were prospectively collected. For long-term modeled cost-effectiveness analysis, a Markov model with 7 health states corresponding to the 7 modified Rankin Scale scores was used. Deterministic and probabilistic sensitivity analyses were performed. All costs are expressed in 2019 US dollars, discounted using the annual Consumer Price Index in China. RESULTS: During the index hospitalization, the mean medication cost in the EVT-alone group was $487 lower than that in the EVT+IVT group ($2453 [95% CI $2205-$2701] vs $2940 [95% CI $2703-$3178], p = 0.01), but the mean overall costs were similar between the groups ($15,565 [95% CI $14,876-$16,254] vs $15,472 [95% CI $14,714-$16,230], p = 0.73). Within 90 days of the trial, there were no significant differences in total costs (difference -$222 [95% CI -$603 to $161], p = 0.06, bootstrapping) or utility values (median 0.84 [IQR 0.48-0.95] vs median 0.85 [IQR 0.26-1.00]; beta coefficient < 0.01 [95% CI -0.06 to 0.07]) between EVT alone and EVT+IVT. Over the lifetime horizon, EVT alone and EVT+IVT yielded comparable lifetime QALYs (2.02 QALYs [95% CI -0.07 to 4.55 QALYs] vs 1.90 QALYs [95% CI -0.09 to 4.55 QALYs]) and costs ($26,795 [95% CI $15,281-$54,463] vs $27,632 [95% CI $14,558-$52,251]). CONCLUSIONS: In this economic analysis based on a trial conducted in China, the authors found that EVT alone was not associated with economic dominance over EVT+IVT in patients with anterior circulation large-vessel occlusion.

Noninvasive Assessment of Carotid Plaques Calcification by 18F-Sodium Fluoride Accumulation: Correlation with Pathology.

BACKGROUD: Vascular calcification is currently recognized as an important pathobiological process in atherosclerosis, but the mechanism remains elusive. Given the similarities in vascular calcification and bone formation, 18F-sodium fluoride (18F-NaF) is now considered a novel marker of vascular calcification. This study aimed to correlate 18F-NaF accumulation with the histological characterization of vascular calcification in carotid plaques. METHODS: A total of 8 patients who were undergoing carotid endarterectomy (CEA) for carotid artery stenosis were recruited. Before CEA, 18F-NaF positron emission tomography and computed tomography (PET-CT) studies were conducted. 18F-NaF uptake was measured by the maximum standardized uptake value and the target-to-background ratio. The Hounsfield unit (HU) value was also measured. Postoperative carotid plaques were investigated by hematoxylin and eosin staining, alizarin red staining, and immunohistochemistry (alpha-smooth muscle actin and CD68). RESULTS: 18F-NaF uptake was observed in the bilateral carotid bifurcation of all patients. Compared with the pathology results, there was a significant correlation between tracer activity in the carotid plaques and the calcification in the corresponding histological sections (integrated optical density [IOD]: r = .781, P = .022; positive area: r = .765, P = .027). A negative correlation was observed between 18F-NaF uptake and smooth muscle cell staining (IOD: r = -.710, P = .049). 18F-NaF uptake did not correlate with carotid artery stenosis, HU value, or inflammation. CONCLUSIONS: 18F-NaF PET-CT is a noninvasive imaging method for the assessment of calcification in human carotid atherosclerotic plaques and a promising approach to studying calcification in atherosclerotic lesions.