Sökresultat

Filtyp

Din sökning på "*" gav 535696 sökträffar

Basic Atomic and Nuclear Physics

Nuclear medicine and molecular imaging are mostly based on radioactive elements that, when decaying due to an excess of energy, emit radiation in the form of electromagnetic radiation (photons), or by charge-particles (electron, positrons, or alpha particles). The first part of this chapter describes in general the atom and its components and states some definitions important for further reading.

Benefits, Challenges and Applications of Ultra-High Field Magnetic Resonance

Human ultra-high field (UHF) MR at 7T and above has been on a rapid rise since the first installations in the 1990s, motivated by the opportunities created by SNR gains and contrast changes. Research efforts were for long focused mainly on technological developments to cope with the challenges posed by UHF. This has brought 7T MR neuroimaging to maturity and into an application dominated realm, fu

Bias correction of 20 years of IMERG satellite precipitation data over Canada and Alaska

Study regionWe define two northern study areas: one covering all of Canada and Alaska and a second, smaller subregion surrounding the Peace-Athabasca Delta for testing.Study focusThis study aims to use bias correction to improve satellite precipitation data over a relatively data-sparse high latitude region using a network of in-situ rain gauges. We evaluate the satellite data and derive a linear

Survival of the Un-Fittest? A Study of Social Media-Based New Crisis Initiatives in the COVID 19 Pandemic

Focusing on Sweden in the COVID 19 pandemic, this paper explores theorganizational/communicational practices of new crisis initiatives, defined as informal,emergent, and loosely coordinated interactions between individuals and/or organizations using social media to engage in crisis relief efforts. By manually tracing crisis relief efforts on Facebook in the spring of 2020 and the fall of 2021, we

Evaluation of genetic demultiplexing of single-cell sequencing data from model species

Single-cell sequencing (sc-seq) provides a species agnostic tool to study cellular processes. However, these technologies are expensive and require sufficient cell quantities and biological replicates to avoid artifactual results. An option to address these problems is pooling cells from multiple individuals into one sc-seq library. In humans, genotype-based computational separation (i.e., demulti

Academic freedom and the anti-Israeli BDS movement

Raphael Cohen-Almagor looks at the Boycott, Divestment, Sanctions (BDS) campaign to boycott Israeli academics and ban Israel tout court. He argues that there is no justification for any academic organisation to do this. Any such decision would be unjust, unfair, and counterproductive

Baseline Serum Prostate-specific Antigen Value Predicts the Risk of Subsequent Prostate Cancer Death-Results from the Norwegian Prostate Cancer Consortium

BACKGROUND: Prostate-specific antigen (PSA) levels in midlife are strongly associated with the long-term risk of lethal prostate cancer in cohorts not subject to screening. This is the first study evaluating the association between PSA levels drawn as part of routine medical care in the Norwegian population and prostate cancer incidence and mortality.OBJECTIVE: To determine the association between

Basics of Radiation Interactions in Matter

Both electromagnetic radiation (photons) and charged particles interact with matter and by different interaction processes result in energy deposition. This is the core of virtually all nuclear medicine applications because it is from the charged-particle interactions and related energy depositions that we can measure the scintillation light in SPECT and PET systems and from this create diagnostic

Gamma Spectrometry

Gamma spectrometry primarily is used for identification and quantification of gamma-emitting radionuclides present in samples collected from a specific environment. The objective is often to determine, with a certain confidence, whether the activity concentration of the present gamma emitters exceed some reference level: for example, a criterion for the highest level of impurity of gamma emitters

Properties of the Digital Image

The digital image has become an important carrier of information that supports diagnostics and therapeutics in medicine. Today there are a number of different imaging modalities that each reflects different tissue properties and are based on different technical principles. Together these techniques form a tremendous arsenal for patient diagnostics. Although the underlying physical and technical pr

Machine Learning

Machine learning, a sub-field of artificial intelligence, is the study of computer algorithms that improve automatically through experience. Although the term was coined in 1959, machine learning builds on questions/methods that were developed earlier in linear algebra, mathematical analysis, optimization, and mathematical statistics. In this chapter we will give a brief overview of machine learni

Single Photon Emission Computed Tomography (SPECT) and SPECT/CT Hybrid Imaging

Images created using a standard collimator-based scintillation camera are essentially 2D images, lacking information regarding the source depth, since the value in a particular pixel in the image represents detection of photons along a line determined by the collimator. However, it is possible to reconstruct a set of 2D images that together form a 3D image of the underlying activity distribution f

The male bias can be attenuated in reading : on the resolution of anaphoric expressions following gender-fair forms

Despite the increased use of different types of gender-fair forms in French, studies investigating their interpretation in context remain few. To fill this gap, we conducted a pre-registered study using a timed sentence evaluation task to examine speakers' possibilities to establish an anaphoric relationship between a gendered anaphoric expression (women or men) and non-stereotyped role nouns as a

Activity Quantification from Planar Images

Planar imaging was for a long time the most-used technique for image-based activity quantification. Owing to its simplicity and speed, the possibility to acquire dynamic image sequences, and to generate whole-body images at a reasonable acquisition time, it is still frequently used in nuclear-medicine imaging. Today, planar imaging is most commonly used for diagnostic examinations with qualitative

Multicentre Studies

The first part of the chapter provides an introduction on the implementation of quality-assurance programmes in nuclear medicine (NM) services. It is argued that participation in interlaboratory comparisons has two main benefits. First, on top of existing local quality-assurance programmes, participation can add a level of reassurance on quality. Second, interlaboratory comparisons are prerequisit

Monte Carlo Simulation of Nuclear Medicine Imaging Systems

This chapter describes the use of the Monte Carlo method to simulate nuclear medicine imaging systems, mainly the scintillation camera – SPECT (Single-Photon Emission Computed Tomography) and PET (Positron Emission Tomography) – systems that are major tools in nuclear medicine to produce images of activity distributions. The first part describes the principles behind the Monte Carlo method, in par

Principles behind Computed Tomography (CT)

The use of Computed tomography (CT) for anatomical information in a combination with the SPECT system has in many ways added substantial information to many nuclear medicine imaging procedures. The information from the CT system can provide information on the location of lesions and can be used for attenuation correction. Modern SPECT/CT and PET/CT today have CT scanners that provide diagnostic qu