1,211 research outputs found
Dynamic imaging and tracer kinetic modeling for emission tomography using rotating detectors
Author name used in this publication: Dagan FengAuthor name used in this publication: Daniel Pak-Kong LunCentre for Multimedia Signal Processing, Department of Electronic and Information EngineeringVersion of RecordPublishe
Advances in Clinical Molecular Imaging Instrumentation
In this article, we describe recent developments in the design of both single-photon emission computed tomography (SPECT) and positron emission tomography (PET) instrumentation that have led to the current range of superior performance instruments. The adoption of solid-state technology for either complete detectors [e.g., cadmium zinc telluride (CZT)] or read-out systems that replace photomultiplier tubes [avalanche photodiodes (APD) or silicon photomultipliers (SiPM)] provide the advantage of compact technology, enabling flexible system design. In SPECT, CZT is well suited to multi-radionuclide and kinetic studies. For PET, SiPM technology provides MR compatibility and superior time-of-flight resolution, resulting in improved signal-to-noise ratio. Similar SiPM technology has also been used in the construction of the first SPECT insert for clinical brain SPECT/MRI
Quantitative imaging of coronary blood flow
Positron emission tomography (PET) is a nuclear medicine imaging modality based on the administration of a positron-emitting radiotracer, the imaging of the distribution and kinetics of the tracer, and the interpretation of the physiological events and their meaning with respect to health and disease. PET imaging was introduced in the 1970s and numerous advances in radiotracers and detection systems have enabled this modality to address a wide variety of clinical tasks, such as the detection of cancer, staging of Alzheimer's disease, and assessment of coronary artery disease (CAD). This review provides a description of the logic and the logistics of the processes required for PET imaging and a discussion of its use in guiding the treatment of CAD. Finally, we outline prospects and limitations of nanoparticles as agents for PET imaging
Information technology applications in biomedical functional imaging
Author name used in this publication: (David) Dagan FengCentre for Multimedia Signal Processing, Department of Electronic and Information EngineeringVersion of RecordPublishe
Positron Emission Tomography: Current Challenges and Opportunities for Technological Advances in Clinical and Preclinical Imaging Systems
Positron emission tomography (PET) imaging is based on detecting two time-coincident high-energy photons from the emission of a positronemitting radioisotope. The physics of the emission, and the detection of the coincident photons, give PET imaging unique capabilities for both very high sensitivity and accurate estimation of the in vivo concentration of the radiotracer. PET imaging has been widely adopted as an important clinical modality for oncological, cardiovascular, and neurological applications. PET imaging has also become an important tool in preclinical studies, particularly for investigating murine models of disease and other small-animal models. However, there are several challenges to using PET imaging systems. These include the fundamental trade-offs between resolution and noise, the quantitative accuracy of the measurements, and integration with X-ray computed tomography and magnetic resonance imaging. In this article, we review how researchers and industry are addressing these challenges.This work was supported in part by National Institutes of Health grants R01-CA042593, U01-CA148131, R01CA160253, R01CA169072, and R01CA164371; by Human Frontier Science Program grant RGP0004/2013;
and by the Innovative Medicines Initiative under grant agreement 115337, which comprises financial
contributions from the European Union’s Seventh Framework Program (FP7/2007–2013
Advanced perfusion quantification methods for dynamic PET and MRI data modelling
The functionality of tissues is guaranteed by the capillaries, which supply the microvascular
network providing a considerable surface area for exchanges between blood and tissues.
Microcirculation is affected by any pathological condition and any change in the blood supply
can be used as a biomarker for the diagnosis of lesions and the optimization of the treatment.
Nowadays, a number of techniques for the study of perfusion in vivo and in vitro are
available. Among the several imaging modalities developed for the study of microcirculation,
the analysis of the tissue kinetics of intravenously injected contrast agents or tracers is the
most widely used technique. Tissue kinetics can be studied using different modalities: the
positive enhancement of the signal in the computed tomography and in the ultrasound
dynamic contrast enhancement imaging; T1-weighted MRI or the negative enhancement of
T2* weighted MRI signal for the dynamic susceptibility contrast imaging or, finally, the
uptake of radiolabelled tracers in dynamic PET imaging. Here we will focus on the perfusion
quantification of dynamic PET and MRI data. The kinetics of the contrast agent (or the tracer)
can be analysed visually, to define qualitative criteria but, traditionally, quantitative
physiological parameters are extracted with the implementation of mathematical models.
Serial measurements of the concentration of the tracer (or of the contrast agent) in the tissue
of interest, together with the knowledge of an arterial input function, are necessary for the
calculation of blood flow or perfusion rates from the wash-in and/or wash-out kinetic rate
constants. The results depend on the acquisition conditions (type of imaging device, imaging
mode, frequency and total duration of the acquisition), the type of contrast agent or tracer
used, the data pre-processing (motion correction, attenuation correction, correction of the
signal into concentration) and the data analysis method.
As for the MRI, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a
non-invasive imaging technique that can be used to measure properties of tissue
microvasculature. It is sensitive to differences in blood volume and vascular permeability that
can be associated with tumour angiogenesis. DCE-MRI has been investigated for a range of
clinical oncologic applications (breast, prostate, cervix, liver, lung, and rectum) including
cancer detection, diagnosis, staging, and assessment of treatment response. Tumour
microvascular measurements by DCE-MRI have been found to correlate with prognostic
factors (such as tumour grade, microvessel density, and vascular endothelial growth factor
expression) and with recurrence and survival outcomes. Furthermore, DCE-MRI changes
measured during treatment have been shown to correlate with outcome, suggesting a role as
a predictive marker. The accuracy of DCE-MRI relies on the ability to model the
pharmacokinetics of an injected contrast agent using the signal intensity changes on
sequential magnetic resonance images. DCE-MRI data are usually quantified with the
application of the pharmacokinetic two-compartment Tofts model (also known as the
standard model), which represents the system with the plasma and tissue (extravascular
extracellular space) compartments and with the contrast reagent exchange rates between
them. This model assumes a negligible contribution from the vascular space and considers
the system in, what-is-known as, the fast exchange limit, assuming infinitely fast
transcytolemmal water exchange kinetics. In general, the number, as well as any assumption
about the compartments, depends on the properties of the contrast agent used (mainly
gadolinium) together with the tissue physiology or pathology studied. For this reason, the
choice of the model is crucial in the analysis of DCE-MRI data. The value of PET in clinical oncology has been demonstrated with studies in a variety of
cancers including colorectal carcinomas, lung tumours, head and neck tumours, primary and
metastatic brain tumours, breast carcinoma, lymphoma, melanoma, bone cancers, and other
soft-tissue cancers. PET studies of tumours can be performed for several reasons including
the quantification of tumour perfusion, the evaluation of tumour metabolism, the tracing of
radiolabelled cytostatic agents. In particular, the kinetic analysis of PET imaging has showed,
in the past few years, an increasing value in tumour diagnosis, as well as in tumour therapy,
through providing additional indicative parameters. Many authors have showed the benefit
of kinetic analysis of anticancer drugs after labelling with radionuclide in measuring the
specific therapeutic effect bringing to light the feasibility of applying the kinetic analysis to
the dynamic acquisition. Quantification methods can involve visual analysis together with
compartmental modelling and can be applied to a wide range of different tracers. The
increased glycolysis in the most malignancies makes 18F-FDG-PET the most common
diagnostic method used in tumour imaging. But, PET metabolic alteration in the target tissue
can depend by many other factors. For example, most types of cancer are characterized by
increased choline transport and by the overexpression of choline kinase in highly proliferating
cells in response to enhanced demand of phosphatidylcholine (prostate, breast, lung, ovarian
and colon cancers). This effect can be diagnosed with choline-based tracers as the 18Ffluoromethylcholine
(18F-FCH), or the even more stable 18F-D4-Choline. Cellular
proliferation is also imaged with 18F-fluorothymidine (FLT), which is trapped within the
cytosol after being mono phosphorylated by thymidine kinase-1 (TK1), a principal enzyme
in the salvage pathway of DNA synthesis. 18F-FLT has been found to be useful for noninvasive
assessment of the proliferation rate of several types of cancer and showed high
reproducibility and accuracy in breast and lung cancer tumours.
The aim of this thesis is the perfusion quantification of dynamic PET and MRI data of patients
with lung, brain, liver, prostate and breast lesions with the application of advanced models.
This study covers a wide range of imaging methods and applications, presenting a novel
combination of MRI-based perfusion measures with PET kinetic modelling parameters in
oncology. It assesses the applicability and stability of perfusion quantification methods,
which are not currently used in the routine clinical practice.
The main achievements of this work include: 1) the assessment of the stability of perfusion
quantification of D4-Choline and 18F-FLT dynamic PET data in lung and liver lesions,
respectively (first applications in the literature); 2) the development of a model selection in
the analysis of DCE-MRI data of primary brain tumours (first application of the extended
shutter speed model); 3) the multiparametric analysis of PET and MRI derived perfusion
measurements of primary brain tumour and breast cancer together with the integration of
immuohistochemical markers in the prediction of breast cancer subtype (analysis of data
acquired on the hybrid PET/MRI scanner).
The thesis is structured as follows:
- Chapter 1 is an introductive chapter on cancer biology. Basic concepts, including the causes
of cancer, cancer hallmarks, available cancer treatments, are described in this first chapter.
Furthermore, there are basic concepts of brain, breast, prostate and lung cancers (which are
the lesions that have been analysed in this work). - Chapter 2 is about Positron Emission Tomography. After a brief introduction on the basics
of PET imaging, together with data acquisition and reconstruction methods, the chapter
focuses on PET in the clinical settings. In particular, it shows the quantification techniques
of static and dynamic PET data and my results of the application of graphical methods,
spectral analysis and compartmental models on dynamic 18F-FDG, 18F-FLT and 18F-D4-
Choline PET data of patients with breast, lung cancer and hepatocellular carcinoma.
- Chapter 3 is about Magnetic Resonance Imaging. After a brief introduction on the basics of
MRI, the chapter focuses on the quantification of perfusion weighted MRI data. In particular,
it shows the pharmacokinetic models for the quantification of dynamic contrast enhanced
MRI data and my results of the application of the Tofts, the extended Tofts, the shutter speed
and the extended shutter speed models on a dataset of patients with brain glioma.
- Chapter 4 introduces the multiparametric imaging techniques, in particular the combined
PET/CT and the hybrid PET/MRI systems. The last part of the chapter shows the applications
of perfusion quantification techniques on a multiparametric study of breast tumour patients,
who simultaneously underwent DCE-MRI and 18F-FDG PET on a hybrid PET/MRI scanner.
Then the results of a predictive study on the same dataset of breast tumour patients integrated
with immunohistochemical markers. Furthermore, the results of a multiparametric study on
DCE-MRI and 18F-FCM brain data acquired both on a PET/CT scanner and on an MR
scanner, separately. Finally, it will show the application of kinetic analysis in a radiomic
study of patients with prostate cancer
An integrated MR/PET system: prospective applications
Radiology is strongly depending on medical imaging technology and consequently directing technological progress. A novel technology can only be established, however, if improved diagnostic accuracy influence on therapeutic management and/or overall reduced cost can be evidenced. It has been demonstrated recently that Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) can technologically be integrated into one single hybrid system. Some scientific arguments on the benefits are obvious, e.g., that simultaneous imaging of morphological and functional information will improve tissue characterization. However, crossfire of questions still remains: What unmet radiological needs are addressed by the novel system? What level of hardware integration is reasonable, or would software-based image co-registration be sufficient? Will MR/PET achieve higher diagnostic accuracy compared to separate imaging? What is the added value compared to other hybrid imaging modalities like PET/CT? And finally, is the system economically reasonable and has the potential to reduce overall costs for therapy planning and monitoring? This article tries to highlight some perspectives of applying an integrated MR/PET system for simultaneous morphologic and functional imaging
Methodological considerations in quantification of oncological FDG PET studies
Contains fulltext :
87741.pdf (publisher's version ) (Closed access)
Contains fulltext :
87741-1.pdf (postprint version ) (Open Access)PURPOSE: This review aims to provide insight into the factors that influence quantification of glucose metabolism by FDG PET images in oncology as well as their influence on repeated measures studies (i.e. treatment response assessment), offering improved understanding both for clinical practice and research. METHODS: Structural PubMed searches have been performed for the many factors affecting quantification of glucose metabolism by FDG PET. Review articles and references lists have been used to supplement the search findings. RESULTS: Biological factors such as fasting blood glucose level, FDG uptake period, FDG distribution and clearance, patient motion (breathing) and patient discomfort (stress) all influence quantification. Acquisition parameters should be adjusted to maximize the signal to noise ratio without exposing the patient to a higher than strictly necessary radiation dose. This is especially challenging in pharmacokinetic analysis, where the temporal resolution is of significant importance. The literature is reviewed on the influence of attenuation correction on parameters for glucose metabolism, the effect of motion, metal artefacts and contrast agents on quantification of CT attenuation-corrected images. Reconstruction settings (analytical versus iterative reconstruction, post-reconstruction filtering and image matrix size) all potentially influence quantification due to artefacts, noise levels and lesion size dependency. Many region of interest definitions are available, but increased complexity does not necessarily result in improved performance. Different methods for the quantification of the tissue of interest can introduce systematic and random inaccuracy. CONCLUSIONS: This review provides an up-to-date overview of the many factors that influence quantification of glucose metabolism by FDG PET.01 juli 201
Molecular SPECT Imaging: An Overview
Molecular imaging has witnessed a tremendous change over the last decade. Growing interest and emphasis are placed on this specialized technology represented by developing new scanners, pharmaceutical drugs, diagnostic agents, new therapeutic regimens, and ultimately, significant improvement of patient health care. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) have their signature on paving the way to molecular diagnostics and personalized medicine. The former will be the topic of the current paper where the authors address the current position of the molecular SPECT imaging among other imaging techniques, describing strengths and weaknesses, differences between SPECT and PET, and focusing on different SPECT designs and detection systems. Radiopharmaceutical compounds of clinical as well-preclinical interest have also been reviewed. Moreover, the last section covers several application, of μSPECT imaging in many areas of disease detection and diagnosis
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