Quantitative stray-field T1 relaxometry with the matrix pencil method

The matrix pencil method (MPM) is tested as an approach to quantitatively process multiexponential low-field nuclear magnetic resonance T₁ relaxometry data. The data is obtained by measuring T₁ saturation recovery curves in the highly inhomogeneous magnetic field of a stray-field sensor. 0.9% brine solutions, doped with different concentrations of a Gd³⁺ containing contrast agent, serve as test liquids. Relaxation-times as a function of contrast-agent concentration along with the T₁ relaxation curves for combinations of multiple different test liquids are measured, and the results from processing using MPM as well as inverse Laplace transformation as a benchmark are compared. The relaxation-time resolution limits of both procedures are probed by gradually reducing the difference between the relaxation-times of two liquids measured simultaneously. The sensitivity to quantify the relative contribution of each component to the magnetization build-up curve is explored by changing their volume ratio. Furthermore, the potential to resolve systems with more than two components is tested. For the systems under test, MPM shows superior performance in separating two or three relaxation components, respectively and effectively quantifying the time constants.

Diagnostic accuracy of two-dimensional coronary angiographic derived fractional flow reserve

Background

Non-invasive fractional flow reserve (NiFFR) is an emerging method for evaluating the functional significance of a coronary lesion during diagnostic coronary angiography (CAG). The method relies on the computational flow dynamics and the 3D reconstruction of the vessel extracted from CAG. In the present study, we sought to evaluate the diagnostic performance and applicability of 2D-based NiFFR.

Methods

In this prospective observational study, we evaluated 2D-based NiFFR in 279 candidates for invasive CAG and invasive FFR. NiFFR was calculated via 2 methods: variable NiFFR, in which the contrast transport time was extracted from the angiographic view, and fixed NiFFR, in which a prespecified frame count was applied.

Results

The final analysis was performed on 245 patients (250 lesions). Variable NiFFR had an area under the receiver operating characteristic curve of 81.5%, an accuracy of 80.0%, a sensitivity of 82.2%, a specificity of 82.2%, a negative predictive value of 91.4%, and a positive predictive value of 63.6%. The mean difference between FFR and NiFFR was −0.0244 ±0.0616 (P≤0.0001). A pressure wire-free hybrid strategy was possible in 68.8% of our population with variable NiFFR.

Conclusions

Our 2D-based NiFFR yielded results comparable to those derived from 3D-based software. Our findings should, however, be confirmed in larger trials.

Pressure wire-free hybrid strategy

Funding Acknowledgement

Type of funding source: None

Comparison between cheatham-platinum stent and self-expandable uncovered nitinol stent in patients with coarctation of aorta – a randomized controlled trial

Background

Endovascular treatment is considered the main therapeutic approach for native coarctation of aorta (CoA) in adult patients. Balloon-expandable stents (BE) have been introduced as the primary choice for coarctoplasty. However during the recent years, self-expandable (SE) stents with acceptable radial force have been suggested as an alternative. Still, no randomized controlled (RCT) trials have compared the efficacy and safety of both strategies.

Methods

The present study is a prospective, single center, parallel-group, open-label RCT on patients with native CoA (Figure). Patients were randomized into Bare Cheatham-Platinum Stents and Uncovered Nitinol Stent (SE). All patients were scheduled to be followed in 1-, 6-, 12-month and 36-month intervals. The present report, focuses on the one-year outcome of the study.

Results

Of 101 patients with native CoA referred to our center, 93 patients have been randomized into BE- (47 patients) and SE-arm (46 patients). One year follow up is scheduled to be completed on March 2020. In the preliminary analysis of 62 patients, 1 intraprocedural stent migration has occurred in each group. No aortic perforation was detected in the study. Vascular access site complications were similar between the two groups (3 (6.3%) in BE versus 1 (2.1%) in SE, p value= 0.432). One nonfatal stroke occurred in BE group. No mortality or bailout surgical repair happened in one year study in the two groups. One patient with re-coarctations were detected during one year follow up in each of the groups (p value=0.210). No aortic pseudoaneurysm or aneurysmal formation were observed in 12-month follow up aortic CT angiography.

Conclusion

The preliminary results showed no significant difference in efficacy and safety of both treatment modalities. The final result is pending.

Study Flow Chart

Funding Acknowledgement

Type of funding source: None

Fast and robust quantification of liquid inside thin fibrous porous materials with single-sided NMR

Single-sided NMR with the NMR-MOUSE is employed for the characterization of fluids in fibrous and open foam materials. One of the key aspects of this study is the quantification of the fluid amount. To this end critical information was provided by a relaxation study. Using 2 mM/L of a Gd³⁺ relaxation agent the repetition time could be shortened to 250 ms, improving the correlation coefficient between liquid amount and signal amplitude from R² = 0.893 to R² = 0.982. To assess reproducibility and instrument precision, calibration experiments were repeated several times and their variation investigated. The results showed that the device is highly precise and robust with a standard deviation for liquid quantification of less than 1%.

Revealing how interfaces in stacked thin fibrous layers affect liquid ingress and transport properties by single-sided NMR

Offering multifaceted applications, thin fibrous porous materials are mostly used in stacks of layers, each layer having a defined functionality. Since only a few pores exist across a layer a couple of hundred microns thick, the interface between layers may significantly affect liquid ingress. Thus, the main objective of the study is to substantiate that an interface layer is present during liquid infiltration between stacked thin fibrous layers and that it affects the fluid transport properties. A compact single-sided NMR device with a low static gradient of about 2 T/m perpendicular to the sensor surface and a uniform magnetic field in lateral directions was used to profile a 2-mm thick slice in one shot. The liquid ingress into the thin fibrous layers and their interfaces was visualized by Fourier-transforming the NMR signal and processing the time-dependent 1D profiles with a newly developed mathematical method. The flow characteristics and liquid distribution profiles of a 400-µm thick layer were compared with those of two stacked 200-µm thick layers from the same material but with an interface between them. The results show major differences in distributions and flow dynamics for the single and dual layer cases, which reveal the importance of the interface in fluid flow.

Continuum-Scale Modeling of Liquid Redistribution in a Stack of Thin Hydrophilic Fibrous Layers

Macroscale three-dimensional modeling of fluid flow in a thin porous layer under unsaturated conditions is a challenging task. One major issue is that such layers do not satisfy the representative elementary volume length-scale requirement. Recently, a new approach, called reduced continua model (RCM), has been developed to describe multiphase fluid flow in a stack of thin porous layers. In that approach, flow equations are formulated in terms of thickness-averaged variables and properties. In this work, we have performed a set of experiments, where a wet 260 - μ m -thin porous layer was placed on top of a dry layer of the same material. We measured the change of average saturation with time using a single-sided low-field nuclear magnetic resonance device known as NMR-MOUSE. We have employed both RCM and the traditional Richards equation-based models to simulate our experimental results. We found that the traditional unsaturated flow model cannot simulate experimental results satisfactorily. Very close agreement was obtained by including the dynamic capillary term as postulated by Hassanizadeh and Gray in the traditional equations. The reduced continua model was found to be in good agreement with the experimental result without adding dynamic capillarity term. Moreover, the computational effort needed for RCM simulations was one order of magnitude less than that of traditional models.

The Assessment of Relations between Socioeconomic Status and Number of Complications among Type 2 Diabetic Patients

BACKGROUND

The prevalence of diabetes mellitus among Iranian aged 25-64 estimated to be about 7.7%. The aim of current study was the assessment of socioeconomic status of diabetic patients and their complications.

METHODS

A cross sectional study was conducted on type 2 diabetic patients with complications in four major teaching hospitals affiliated to Tehran University of Medical Sciences (TUMS) during July 2009 to March 2010. All patients (530) were interviewed through a questionnaire with 85% response rate (450 patients). Skilled nurses were assigned as responsible for data collection. Collected data analyzed by Exact Fisher and χ2 tests using SPSS version 11.5.

RESULTS

The majority of patients had experienced one or more complications. Findings revealed that 50%, 33.6% and 16.4% of the patients suffered from one, two, and three complications of type 2 diabetes, respectively. Patients with cardiovascular complications included 22.2%, with both cardiovascular and eye complications (12.7%), and with cardiovascular, eye and foot ulcer together 14% of the respondents. Frequency of complications demonstrated significant relation with sex, age, educational level, type of occupation, duration of diabetes (P<0.001) and social class (P=0.002). The majority of patients (54.2%) belonged to low income group.

CONCLUSION

It seems patients with low socioeconomic status face more challenges in their social environment together with less psychological support. Health care systems are responsible to empower them to control their illness and feel a better life to live.