Effect of strain on phase selection in High Entropy Alloys

High-entropy alloys are potential candidates for high temperature application which form solid solutions with FCC, BCC, and HCP crystal structures. In order to investigate the applicability of Hume-Rothery rules and approaches to these alloys, we devise a set of experiments for understanding the role of strain and valence-electron concentrations. In this study, we explore the role of strain by varying the Ti:Zr ratio in pseudo-quaternary AlCuNi(TixZr1-x) alloys. The alloys were synthesized using different techniques in order to assess the role of kinetics in phase selection. The samples were analyzed via x-ray diffraction and scanning electron microscopy. All compositions tested were found to consist of a primary BCC phase and a secondary FCC phase. With the addition of Ti significant peak broadening was observed

Deep Learning How to Fit an Intravoxel Incoherent Motion Model to Diffusion-Weighted MRI

Purpose: This prospective clinical study assesses the feasibility of training a deep neural network (DNN) for intravoxel incoherent motion (IVIM) model fitting to diffusion-weighted magnetic resonance imaging (DW-MRI) data and evaluates its performance. Methods: In May 2011, ten male volunteers (age range: 29 to 53 years, mean: 37 years) underwent DW-MRI of the upper abdomen on 1.5T and 3.0T magnetic resonance scanners. Regions of interest in the left and right liver lobe, pancreas, spleen, renal cortex, and renal medulla were delineated independently by two readers. DNNs were trained for IVIM model fitting using these data; results were compared to least-squares and Bayesian approaches to IVIM fitting. Intraclass Correlation Coefficients (ICC) were used to assess consistency of measurements between readers. Intersubject variability was evaluated using Coefficients of Variation (CV). The fitting error was calculated based on simulated data and the average fitting time of each method was recorded. Results: DNNs were trained successfully for IVIM parameter estimation. This approach was associated with high consistency between the two readers (ICCs between 50 and 97%), low intersubject variability of estimated parameter values (CVs between 9.2 and 28.4), and the lowest error when compared with least-squares and Bayesian approaches. Fitting by DNNs was several orders of magnitude quicker than the other methods but the networks may need to be re-trained for different acquisition protocols or imaged anatomical regions. Conclusion: DNNs are recommended for accurate and robust IVIM model fitting to DW-MRI data. Suitable software is available at (1)

Extracranial applications of diffusion-weighted magnetic resonance imaging

Diffusion-weighted MRI has become more and more popular in the last couple of years. It is already an accepted diagnostic tool for patients with acute stroke, but is more difficult to use for extracranial applications due to technical challenges mostly related to motion sensitivity and susceptibility variations (e.g., respiration and air-tissue boundaries). However, thanks to the newer technical developments, applications of body DW-MRI are starting to emerge. In this review, we aim to provide an overview of the current status of the published data on DW-MRI in extracranial applications. A short introduction to the physical background of this promising technique is provided, followed by the current status, subdivided into three main topics, the functional evaluation, tissue characterization and therapy monitorin

Ear pain in patients with oropharynx carcinoma: how MRI contributes to the explanation of a prognostic and predictive symptom

Reflex otalgia is a predictive and prognostic parameter for local control in patients with oropharynx carcinoma. Can a morphologic correlate of this important symptom be detected by MRI? Thirty-six patients were prospectively evaluated by MRI before radical radiotherapy. Sixteen patients had reflex otalgia; 20 did not. The oropharynx and adjacent regions were analyzed. Alteration was defined as effacement of anatomical structures, signal alteration or enhancement after contrast medium administration. The χ 2-test was used to compare categorical parameters. In patients with reflex otalgia, alteration of the following structures innervated by the glossopharyngeal nerve were found significantly more often: nasopharynx, hard palate, superior constrictor pharyngis muscle, palatine tonsil, palatopharyngeus muscle, palatoglossus muscle, stylopharyngeus muscle, hyoglossus muscle and preepiglottic space. No difference was found for the muscles of mastication, levator and tensor veli palatini muscles, styloglossus muscle, genioglossus muscle, intrinsic muscles of the tongue, digastric muscles, mucosal surface of the lateral and posterior pharyngeal wall, uvula, valleculae, parapharyngeal space and larynx. An alteration of structures innervated by the glossopharyngeal nerve was visualized on MRI significantly more often when reflex otalgia was present. Involvement of structures innervated by other cranial nerves did not show the same association with ear pai

Mental flexibility depends on a largely distributed white matter network: Causal evidence from connectome-based lesion-symptom mapping.

Mental flexibility (MF) refers to the capacity to dynamically switch from one task to another. Current neurocognitive models suggest that since this function requires interactions between multiple remote brain areas, the integrity of the anatomic tracts connecting these brain areas is necessary to maintain performance. We tested this hypothesis by assessing with a connectome-based lesion-symptom mapping approach the effects of white matter lesions on the brain's structural connectome and their association with performance on the trail making test, a neuropsychological test of MF, in a sample of 167 first unilateral stroke patients. We found associations between MF deficits and damage of i) left lateralized fronto-temporo-parietal connections and interhemispheric connections between left temporo-parietal and right parietal areas; ii) left cortico-basal connections; and iii) left cortico-pontine connections. We further identified a relationship between MF and white matter disconnections within cortical areas composing the cognitive control, default mode and attention functional networks. These results for a central role of white matter integrity in MF extend current literature by providing causal evidence for a functional interdependence among the regional cortical and subcortical structures composing the MF network. Our results further emphasize the necessity to consider connectomics in lesion-symptom mapping analyses to establish comprehensive neurocognitive models of high-order cognitive functions

Caveats when interpreting intravenous urograms following ileal orthotopic bladder substitution

The aim of this study was to evaluate the appearance of the upper urinary tract following cystectomy and ileal orthotopic bladder substitution. Intravenous urograms (IVUs) performed preoperatively and at regular intervals postoperatively on 87 long-term survivors (minimum survival, 5 years) following ileal orthotopic bladder substitution were reviewed. Distention of the collecting system with blunted or rounded fornices was defined as dilatation. If in addition contrast medium excretion was delayed on the 5-min film, this was defined as obstruction. Collecting system dilatation was present on all IVU films obtained from most patients (80%) within 6 months of surgery, even in the absence of urinary tract obstruction. In contrast, dilatation was commonly seen only on the 20-min postinjection films (79%) on urograms performed more than 1 year following surgery, but not encountered on the other two postinjection radiographs (at 5 and 60min). Five years after surgery, permanent obstruction was observed in only five (3%) renoureteral units. Dilatation of the upper urinary tract after ileal orthotopic bladder substitution is a frequent finding on the 5-min, 20-min, and 60-min films during the early postoperative period but is found only on the 20-min film 1 year and later after surgery. These findings should not be overinterpreted as obstructio

Diffusion-weighted MR imaging including bi-exponential fitting for the detection of recurrent or residual tumour after (chemo)radiotherapy for laryngeal and hypopharyngeal cancers

Objectives: To assess whether diffusion-weighted magnetic resonance imaging (DW-MRI) including bi-exponential fitting helps to detect residual/recurrent tumours after (chemo)radiotherapy of laryngeal and hypopharyngeal carcinoma. Methods: Forty-six patients with newly-developed/worsening symptoms after (chemo)radiotherapy for laryngeal/hypopharyngeal cancers were prospectively imaged using conventional MRI and axial DW-MRI. Qualitative (visual assessment) and quantitative analysis (mono-exponentially: total apparent diffusion coefficient [ADCT], and bi-exponentially: perfusion fraction [FP] and true diffusion coefficient [ADCD]) were performed. Diffusion parameters of tumour versus post-therapeutic changes were compared, with final diagnosis based on histopathology and follow-up. Mann-Whitney U test was used for statistical analysis. Results: Qualitative DW-MRI combined with morphological images allowed the detection of tumour with a sensitivity of 94% and specificity 100%. ADCT and ADCD values were lower in tumour with values 120 ± 49 × 10−5mm2/s and 113 ± 50 × 10−5mm2/s, respectively, compared with post-therapeutic changes with values 182 ± 41 × 10−5mm2/s (P < 0.0002) and 160 ± 47 × 10−5mm2/s (P < 0.003), respectively. FP values were significantly lower in tumours than in non-tumours (13 ± 9% versus 31 ± 16%, P < 0.0002), with FP being the best quantitative parameter for differentiation between post-therapeutic changes and recurrence. Conclusions: DW-MRI in combination with conventional MRI substantially improves detection and exclusion of tumour in patients with laryngeal and hypopharyngeal cancers after treatment with (chemo)radiotherapy on both qualitative and quantitative analysis, with FP being the best quantitative parameter in this context. Key Points : • DW-MRI is increasingly used to detect tumour recurrence. • DW-MRI allows accurate post-treatment recurrence detection in laryngeal or hypopharyngeal cancer • ADC values in recurrent tumour are lower than in benign tissue alterations • Both qualitative and quantitative DW-MRI approaches allow detection of recurrence • DW-MRI can easily be added to daily clinical routine imagin

Retrospective analysis of patients for development of nephrogenic systemic fibrosis following conventional angiography using gadolinium-based contrast agents

Purpose: The purpose was to retrospectively review the data of 27 patients with renal insufficiency who underwent conventional angiography with gadolinium-based contrast agents (GDBCA) as alternative contrast agents and assess the occurrence of nephrogenic systemic fibrosis (NSF) together with associated potential risk factors. Methods: This HIPAA-compliant study had institutional review board approval, and informed consent was waived. Statistical analysis was performed for all available laboratory and clinical data, including dermatology reports. Type and amount of the GDBCA used were recorded for angiography and additional MRI studies, if applicable. Serum creatinine levels (SCr) pre- and post-angiography were recorded, and estimated glomerular filtration rates (eGFR) were calculated. Results: Ten female and 17 male patients who underwent angiography with GDBCA were included. The mean amount of GDBCA administered was 44 ± 15.5ml (range 15-60ml) or 0.24 + 0.12mmol/kg (range 0.1-0.53mmol/kg). At the time of angiography all patients had renal insufficiency (eGFR <60ml/min/1.73m2). Mean eGFR pre-angiography was 26ml/min/1.73m2 and 33ml/min/1.73m2 post-angiography. The mean follow-up period covers 28months, range 1-84months. Additional MRI studies with GDBCA administration were performed in 15 patients. One patient with typical skin lesions had developed biopsy-confirmed NSF. Conclusion: Conventional arterial angiography with GDBCA may play a role in the development of NSF in patients with renal insufficiency. Alternative contrast agents, such as CO2 angiography or rather the use of low doses of iodinated contrast agents, should be considered in these patient