Separable nonlinear least squares fitting with linear bound constraints and its application in magnetic resonance spectroscopy data quantification

AbstractAn application in magnetic resonance spectroscopy quantification models a signal as a linear combination of nonlinear functions. It leads to a separable nonlinear least squares fitting problem, with linear bound constraints on some variables. The variable projection (VARPRO) technique can be applied to this problem, but needs to be adapted in several respects. If only the nonlinear variables are subject to constraints, then the Levenberg–Marquardt minimization algorithm that is classically used by the VARPRO method should be replaced with a version that can incorporate those constraints. If some of the linear variables are also constrained, then they cannot be projected out via a closed-form expression as is the case for the classical VARPRO technique. We show how quadratic programming problems can be solved instead, and we provide details on efficient function and approximate Jacobian evaluations for the inequality constrained VARPRO method

Local-Global Vectors to Improve Unigram Terminology Extraction

The present paper explores a novel method that integrates efficient distributed representations with terminology extraction. We show that the information from a small number of observed instances can be combined with local and global word embeddings to remarkably improve the term extraction results on unigram terms. To do so, we pass the terms extracted by other tools to a filter made of the local-global embeddings and a classifier which in turn decides whether or not a term candidate is a term. The filter can also be used as a hub to merge different term extraction tools into a single higher-performing system. We compare filters that use the skipgram architecture and filters that employ the CBOW architecture for the task at hand

Term Evaluator: A Tool for Terminology Annotation and Evaluation

There are several methods and available tools for terminology extraction, but the quality of the extracted terms is not always high. Hence, an important consideration in terminology extraction is to assess the quality of the extracted terms. In this paper, we propose and make available a tool for annotating the correctness of terms extracted by three term-extraction tools. This tool facilitates term annotation by using a domain-specific dictionary, a set of filters, and an annotation memory, and allows for post-hoc evaluation. We present a study in which two human judges used the developed tool for term annotation. Their annotations were then analyzed to determine the efficiency of term extraction tools by measures of precision, recall, and F-score, and to calculate the inter-annotator agreement rate

Dilated cardiomyopathy in a patient with acromegaly – association or causality

Carol Davila University of Medicine and Pharmacy, Bucharest, Romania, The 8th International Medical Congress for Students and Young Doctors, September 24-26, 2020Background. Acromegaly is a rare endocrine disorder that carries a significant burden of cardiovascular morbidity and mortality. Abnormalities of the growth hormone/insulin-like growth factor-1 (IGF-1) axis in acromegaly lead to the characteristic cardiovascular manifestations. One hallmark feature of the disease is acromegalic cardiomyopathy; a syndrome of progressive cardiac dysfunction characterized by left ventricular (LV) hypertrophy, diastolic dysfunction, and combined systolic and diastolic dysfunction in advanced stages. Dilated cardiomyopathy (DCM) is relatively rare in this setting but is associated with increased mortality. Case report. We report the case of a 44 y.o man who was admitted to the cardiology department because of progressive dyspnea on exertion and paroxysmal nocturnal dyspnea with recent onset. Physical examination revealed systolic murmurs in mitral and tricuspid areas and jugular vein distension. Laboratory findings showed moderate hepatic cytolysis. Electrocardiogram showed sinus rhythm (SR) and LV hypertrophy. Echocardiography revealed DCM with severe LV dysfunction (LV ejection fraction (LVEF) = 20%), LV hypertrophy, restrictive diastolic dysfunction, biatrial enlargement, moderate mitral regurgitation and pulmonary hypertension (systolic pulmonary artery pressure (PAPs) = 60 mmHg). A coronary angiography was performed to rule out coronary disease. It revealed normal coronary arteries. Optimal heart failure (HF) treatment was started. The patient did not attend follow-up visits. Ten years later, he presented with NYHA class III HF symptoms. Mandibular enlargement with widened space between the lower incisor teeth, macroglossia, enlargement of his hands and feet over the last 10 years was noted on physical examination. Laboratory findings revealed hepatic cytolysis and elevated NT-proBNP (9668 pg/ml). Electrocardiogram identified atrial fibrillation. Echocardiography showed dilated cardiomyopathy with further deterioration of LV function (LVEF=15%) and pulmonary hypertension. Magnetic resonance imaging showed non-specific LV myocardial fibrosis. Genetic tests, carried out to exclude a genetic DCM (170 genes evaluated), did not identify any pathogenic variants. At this point an endocrinology evaluation was requested. It revealed active acromegaly (IGF-I = 416 ng/ml) due to pituitary microadenoma. Considering a high surgical risk, conservative treatment with somatostatin analogue was initiated. Follow up at 5, 10 and 18 months revealed improved clinical status, spontaneous restauration of SR, progressive improvement in LVEF (30%, 33% and 40%), normalization of PAPs and of NT-proBNP = 186 pg/ml. Conclusions. Here we report the case of a patient with acromegaly and severe non-ischemic DCM. Treatment with somatostatin analogue resulted in early improvement of clinical status and LV systolic function sustaining a probable causal relation between endocrinological dysfunction and DCM. This is a one of the few reported cases of acromegalic DCM with significant improvement under somatostatin analogue therapy as an initial option