Cram\'er-Rao Bound Optimized Subspace Reconstruction in Quantitative MRI

We extend the traditional framework for estimating subspace bases that maximize the preserved signal energy to additionally preserve the Cram\'er-Rao bound (CRB) of the biophysical parameters and, ultimately, improve accuracy and precision in the quantitative maps. To this end, we introduce an \textit{approximate compressed CRB} based on orthogonalized versions of the signal's derivatives with respect to the model parameters. This approximation permits singular value decomposition (SVD)-based minimization of both the CRB and signal losses during compression. Compared to the traditional SVD approach, the proposed method better preserves the CRB across all biophysical parameters with negligible cost to the preserved signal energy, leading to reduced bias and variance of the parameter estimates in simulation. In vivo, improved accuracy and precision are observed in two quantitative neuroimaging applications, permitting the use of smaller basis sizes in subspace reconstruction and offering significant computational savings

Obstacles in SME Financing: The Case of Masko

Small and medium sized enterprises (SMEs) have many benefits for the economy. They employ workforce, make investments, and pay taxes. Most of the time, they create innovative products that enhance competition. Therefore they can contribute to economy by providing innovative goods and services to the larger companies. However, they have short credit records and high risk as no concrete business is available. This kind of structure makes it difficult to finance projects if they don’t have sufficient shareholders’ equity. Bank loans are often not available, or they have high costs, bureaucracy and collateral requirements. Capital markets are also not accessible or provide low pricing for company stocks. Alternatives such as angel capital and crowd funding are available but they also have their limitations. This research has the goal to identify obstacles in SME financing and propose solutions in this field. A survey is made in Masko, an organized industrial zone in Ikitelli region, Istanbul, Turkey. The number of completed surveys are 416. There are information on sampling, scaling, reliability, factor analysis and regression analysis in the research. With the regression analysis the main hypothesis of the research: Solution Proposals for Financing of SMEs is being affected by other dimensions of the study. is accepted. The significant dependent variables that affect SME Financing are the frequency of using financial vehicles and Information on Financial Vehicles. A discussion section on research findings elaborates these results as well as some demographic variables such as gender, age, education, business operating period, having a finance department, obtaining loans and duration of loans. Some of the solution proposals available in the conclusion are lifelong learning and innovation, adjustments to the banking system, tax incentives, and transparency. Keywords: Corporate Finance, Furniture Industry, Regression Analysis, Small and Medium enterprises DOI: 10.7176/RJFA/10-20-11 Publication date:October 31st, 201

Generalized Bloch model: a theory for pulsed magnetization transfer

Purpose: The paper introduces a classical model to describe the dynamics of large spin-1/2 ensembles associated with nuclei bound in large molecule structures, commonly referred to as the semi-solid spin pool, and their magnetization transfer (MT) to spins of nuclei in Theory and Methods: Like quantum-mechanical descriptions of spin dynamics and like the original Bloch equations, but unlike existing MT models, the proposed model is based on the algebra of angular momentum in the sense that it explicitly models the rotations induced by radio-frequency (RF) pulses. It generalizes the original Bloch model to non-exponential decays, which are, e.g., observed for semi-solid spin pools. The combination of rotations with non-exponential decays is facilitated by describing the latter as Green's functions, comprised in an integro-differential equation. Results: Our model describes the data of an inversion-recovery magnetization-transfer experiment with varying durations of the inversion pulse substantially better than established models. We made this observation for all measured data, but in particular for pulse durations small than 300$\mu$s. Furthermore, we provide a linear approximation of the generalized Bloch model that reduces the simulation time by approximately a factor 15,000, enabling simulation of the spin dynamics caused by a rectangular RF-pulse in roughly 2$\mu$s. Conclusion: The proposed theory unifies the original Bloch model, Henkelman's steady-state theory for magnetization transfer, and the commonly assumed rotation induced by hard pulses (i.e., strong and infinitesimally short applications of RF fields) and describes experimental data better than previous models

Cram\'er-Rao bound-informed training of neural networks for quantitative MRI

Neural networks are increasingly used to estimate parameters in quantitative MRI, in particular in magnetic resonance fingerprinting. Their advantages over the gold standard non-linear least square fitting are their superior speed and their immunity to the non-convexity of many fitting problems. We find, however, that in heterogeneous parameter spaces, i.e. in spaces in which the variance of the estimated parameters varies considerably, good performance is hard to achieve and requires arduous tweaking of the loss function, hyper parameters, and the distribution of the training data in parameter space. Here, we address these issues with a theoretically well-founded loss function: the Cram\'er-Rao bound (CRB) provides a theoretical lower bound for the variance of an unbiased estimator and we propose to normalize the squared error with respective CRB. With this normalization, we balance the contributions of hard-to-estimate and not-so-hard-to-estimate parameters and areas in parameter space, and avoid a dominance of the former in the overall training loss. Further, the CRB-based loss function equals one for a maximally-efficient unbiased estimator, which we consider the ideal estimator. Hence, the proposed CRB-based loss function provides an absolute evaluation metric. We compare a network trained with the CRB-based loss with a network trained with the commonly used means squared error loss and demonstrate the advantages of the former in numerical, phantom, and in vivo experiments.Comment: Xiaoxia Zhang, Quentin Duchemin, and Kangning Liu contributed equally to this wor

Rapid quantitative magnetization transfer imaging: utilizing the hybrid state and the generalized Bloch model

Purpose: To improve spatial resolution and scan time of quantitative magnetization transfer (qMT) imaging without constraints on model parameters. Theory and Methods: We combine two recently-proposed models in a Bloch-McConnell equation: the dynamics of the free spin pool is confined to the hybrid state and the dynamics of the semi-solid spin pool is described by the generalized Bloch model. We numerically optimize the flip angles and durations of a train of radio frequency pulses to enhance the encoding of three marked qMT parameters while accounting for an 8-parameter model. We sparsely sample each time frame along this spin dynamics with a 3D radial koosh-ball trajectory, reconstruct the data with sub-space modeling, and fit the qMT model with a neural network for computational efficiency. Results: We were able to extract qMT parameter maps of the whole brain with a nominal resolution of 1mm isotropic and high SNR from a 12.6 minute scan. In lesions of multiple sclerosis subjects, we observe a decreased size of the semi-solid spin pool and slower relaxation, consistent with previous reports. Conclusion: The encoding power of the hybrid state, combined with regularized image reconstruction, and the accuracy of the generalized Bloch model provide an excellent basis for highly efficient quantitative magnetization transfer imaging

Analysis of Serum Cytokine Levels in Larynx Squamous Cell Carcinoma and Dysplasia Patients

ABSTRACT Background: Although the imbalance of cytokines in Head and Neck Squamous Cell Carcinoma (HNSCC) is well known, there is scarce data regarding its occurrence during dysplasia, before the malignant transformation. Objective: To determine whether laryngeal dysplasia patients show a different cytokine profile than patients with cancer and healthy controls. Methods: Seventeen newly diagnosed, untreated larynx squamous cell carcinoma (SCC) and six laryngeal dysplasia patients as well as 22 healthy controls were analyzed for circulating cytokines. A flowcytometry Th1/Th2 cytokine array kit was used to quantitatively measure Interleukin-2 (IL-2), IL-4, IL-6, IL-10, Tumor Necrosis Factor-α (TNF-α) and Interferon-γ (IFN-γ) levels. Additionally, IL-8 levels were determined through ELISA. Results: IL-6, IL-8 and IL-10 were determined to be statistically increased in SCC patients (p<0.05). IL-8 and IL-10 levels were also higher in SCC patients than dysplasia patients (p<0.05). Additionally, IL-6 and IL-10 were all found to be markedly increased in dysplasia patients compared with controls (p<0.05). Conclusion: Our results demonstrate an imbalance of IL-6 and IL-10 not only in HNSCC but also in laryngeal dysplasia

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Is there any benefit of paraaortic field irradiation in pelvic lymph node positive endometrial cancer patients? A propensity match analysis

We evaluated the survival outcomes and recurrence patterns of endometrial cancer (EC) patients with pelvic lymph node metastases who received postoperative radiotherapy (RT) to the pelvis (P-RT) or to the pelvis plus paraaortic lymph nodes (PA-RT) with or without systemic chemotherapy (ChT). The data from 167 patients with stage IIIC1 EC treated with postoperative RT or RT and ChT were collected retrospectively. Those patients with pelvic lymph node metastases were treated with either P-RT (106 patients, 63%) or PA-RT (61 patients, 37%). The median follow-up time for the entire cohort was 49 (range = 5–199) months. The patients receiving adjuvant ChT and RT had significantly higher 5-year OS rates (77% vs. 33%, p < .001) and 5-year PFS rates (71% vs. 30%, p < .001) when compared to those receiving adjuvant RT alone. The patients receiving P-RT and ChT had significantly higher 5-year OS rates and 5-year PFS rates when compared to those treated with adjuvant PA-RT in the entire cohort and matched cohort. Adjuvant ChT together with RT is the strongest predictor of the OS and PFS. Prophylactic PA-RT is unnecessary, even if ChT is used together with P-RT in EC patients with pelvic lymph node metastasis.Impact statement What is already known on this subject? Local and distant recurrence risks are relatively higher in patients with stage IIIC disease, postoperative adjuvant treatment is required to reduce the recurrence risk. Adjuvant RT is a common approach for patients with locally advanced EC. Optimal target volume for RT in patients with stage IIIC EC remains controversial. We demonstrated that extended field RT is unnecessary, even if ChT is used together with pelvic RT in stage IIIC EC patients. What do the results of this study add? We demonstrated that adjuvant ChT together with RT is the strongest predictor of the OS and PFS for EC patients with pelvic lymph node metastases. Extended field RT is unnecessary, even if ChT is used together with pelvic RT in EC patients with pelvic lymph node metastases. What are the implications of these findings for clinical practice and/or further research? Although adjuvant treatment modalities are associated with improvements in survival, distant metastasis still remains the most common site of recurrence in advanced EC patients. Thus, further research is warranted to identify improved combined modality strategies to optimise the outcomes for EC patients with pelvic lymph node metastasis

Generalized Bloch model: A theory for pulsed magnetization transfer

PurposeThe paper introduces a classical model to describe the dynamics of large spin-1/2 ensembles associated with nuclei bound in large molecule structures, commonly referred to as the semi-solid spin pool, and their magnetization transfer (MT) to spins of nuclei in water.Theory and methodsLike quantum-mechanical descriptions of spin dynamics and like the original Bloch equations, but unlike existing MT models, the proposed model is based on the algebra of angular momentum in the sense that it explicitly models the rotations induced by radiofrequency (RF) pulses. It generalizes the original Bloch model to non-exponential decays, which are, for example, observed for semi-solid spin pools. The combination of rotations with non-exponential decays is facilitated by describing the latter as Green's functions, comprised in an integro-differential equation.ResultsOur model describes the data of an inversion-recovery magnetization-transfer experiment with varying durations of the inversion pulse substantially better than established models. We made this observation for all measured data, but in particular for pulse durations smaller than 300&nbsp;μs. Furthermore, we provide a linear approximation of the generalized Bloch model that reduces the simulation time by approximately a factor 15,000, enabling simulation of the spin dynamics caused by a rectangular RF-pulse in roughly 2&nbsp;μs.ConclusionThe proposed theory unifies the original Bloch model, Henkelman's steady-state theory for MT, and the commonly assumed rotation induced by hard pulses (i.e., strong and infinitesimally short applications of RF-fields) and describes experimental data better than previous models