Clustering is an important data exploration task. A prominent clustering algorithm is agglomerative hierarchical clustering. Roughly, in each iteration, it merges the closest pair of clusters. It was rst proposed way back in 1951, and since then there have been numerous mod-iications. Some of its good features are: a natural, simple, and non-parametric grouping of similar objects which is capab...

We propose a PDE chemotaxis model, which can be viewed as a regularization of the Patlak-Keller-Segel (PKS) system. Our modification is based on a fundamental physical property of the chemotactic flux function—its boundedness. This means that the cell velocity is proportional to the magnitude of the chemoattractant gradient only when the latter is small, while when the chemoattractant gradient ...

PURPOSE To develop and assess a "hybrid" method that combines a first-pass analytical approach and the Patlak plot (PP) to improve assessment of low blood-brain barrier permeability from dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) data. MATERIALS AND METHODS Seven patients with vestibular schwannoma were enrolled. T1 -W DCE imaging was acquired on a 1.5T scanner. Normal-a...

An Erratum to this paper has been published: https://doi.org/10.1007/s00259-021-05256-9

UNLABELLED 3'-Deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) is a thymidine analog that was developed for measuring tumor proliferation with PET. The aim of this study was to establish a kinetic modeling analysis method for quantitative (18)F-FLT PET studies in subcutaneous tumor models in mice. METHODS To explore the validity of an image-derived left ventricular input function, we measured equil...

PURPOSE Benign and malignant pulmonary lesions are not easy to distinguish in a clinical setting. We investigated the feasibility of using parametric imaging of the rate constant Ki to diagnose the nature of pulmonary lesions. METHODS Dynamic multi-bed scanning followed by a routine examination was performed on 21 patients with pulmonary lesions who were divided into two groups with malignant...

Many psychotropic compounds bind to sigma receptors and several new sigma ligands are in development for psychiatric indications such as anxiety, attention deficit hyperactivity disorder, depression and psychosis. Of special interest for drug development are tomographic methods that can quantify the binding of promising sigma ligands in a regional manner. Here we present the development of such...

BACKGROUND Quantification of kinetic parameters of positron emission tomography (PET) imaging agents normally requires collecting arterial blood samples which is inconvenient for patients and difficult to implement in routine clinical practice. The aim of this study was to investigate whether a population-based input function (POP-IF) reliant on only a few individual discrete samples allows acc...

BACKGROUND An inflammatory reaction in the airways and lung parenchyma, comprised mainly of neutrophils and alveolar macrophages, is present in some patients with chronic obstructive pulmonary disease (COPD). Thoracic fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) has been proposed as a promising imaging biomarker to assess this inflammation. We sought to introduce a fully quan...