A Unified Framework For Blood Data Modeling In Dynamic Positron Emission Tomography Studies

Quantification of dynamic PET images requires the measurement of radioligand concentrations in the arterial plasma. In general, this cannot be derived from PET images directly but it must be measured from blood samples taken from the subject’s radial artery. The aim of this thesis was to develop and validate a unified framework for the blood data modeling, which was both biologically and experimentally informed, in order to achieve a better description of the blood data

Longitudinal mouse-PET imaging: a reliable method for estimating binding parameters without a reference region or blood sampling

International audienceLongitudinal mouse PET imaging is becoming increasingly popular due to the large number of transgenic and disease models available but faces challenges. These challenges are related to the small size of the mouse brain and the limited spatial resolution of microPET scanners, along with the small blood volume making arterial blood sampling challenging and impossible for longitudinal studies. The ability to extract an input function directly from the image would be useful for quantification in longitudinal small animal studies where there is no true reference region available such as TSPO imaging.METHODS:Using dynamic, whole-body 18F-DPA-714 PET scans (60 min) in a mouse model of hippocampal sclerosis, we applied a factor analysis (FA) approach to extract an image-derived input function (IDIF). This mouse-specific IDIF was then used for 4D-resolution recovery and denoising (4D-RRD) that outputs a dynamic image with better spatial resolution and noise properties, and a map of the total volume of distribution (VT) was obtained using a basis function approach in a total of 9 mice with 4 longitudinal PET scans each. We also calculated percent injected dose (%ID) with and without 4D-RRD. The VT and %ID parameters were compared to quantified ex vivo autoradiography using regional correlations of the specific binding from autoradiography against VT and %ID parameters.RESULTS:The peaks of the IDIFs were strongly correlated with the injected dose (Pearson R = 0.79). The regional correlations between the %ID estimates and autoradiography were R = 0.53 without 4D-RRD and 0.72 with 4D-RRD over all mice and scans. The regional correlations between the VT estimates and autoradiography were R = 0.66 without 4D-RRD and 0.79 with application of 4D-RRD over all mice and scans.CONCLUSION:We present a FA approach for IDIF extraction which is robust, reproducible and can be used in quantification methods for resolution recovery, denoising and parameter estimation. We demonstrated that the proposed quantification method yields parameter estimates closer to ex vivo measurements than semi-quantitative methods such as %ID and is immune to tracer binding in tissue unlike reference tissue methods. This approach allows for accurate quantification in longitudinal PET studies in mice while avoiding repeated blood sampling

PET-BIDS, an extension to the brain imaging data structure for positron emission tomography

The Brain Imaging Data Structure (BIDS) is a standard for organizing and describing neuroimaging datasets, serving not only to facilitate the process of data sharing and aggregation, but also to simplify the application and development of new methods and software for working with neuroimaging data. Here, we present an extension of BIDS to include positron emission tomography (PET) data, also known as PET-BIDS, and share several open-access datasets curated following PET-BIDS along with tools for conversion, validation and analysis of PET-BIDS datasets

PET-BIDS, an extension to the brain imaging data structure for positron emission tomography

The Brain Imaging Data Structure (BIDS) is a standard for organizing and describing neuroimaging datasets. It serves not only to facilitate the process of data sharing and aggregation, but also to simplify the application and development of new methods and software for working with neuroimaging data. Here, we present an extension of BIDS to include positron emission tomography (PET) data (PET-BIDS). We describe the PET-BIDS standard in detail and share several open-access datasets curated following PET-BIDS. Additionally, we highlight several tools which are already available for converting, validating and analyzing PET-BIDS datasets.Competing Interest StatementThe authors have declared no competing interest

Methods and models for the characterization of arterial input function in dynamic PET studies

Dynamic PET quantfication often involves the cannulation of the radial artery of the patient, a practice considered invasive and cause of discomfort for the patient. For this reason in this study two alternatives to the arterial sampling, called ABIF and SIME respectively, were analyzed. The first consists in replacing the individual arterial measurements with the average of the AIFs of a population of subjects previously acquired; the second consists in estimating the input function and the tissue parameters of multiple ROIs simultaneously. Both methods were tested and a new model for the AIF description was propose

Ecografia con mezzo di contrasto delle piccole articolazioni : analisi cinetica

Le articolazioni della mano possono essere sede di diversi processi patologici che vanno dall'osteoartrosi fino alle varie forme di artriti, con conseguenze variabili da semplici artralgie a deformazioni anche gravi, causa di invalidità. La possibilità di identificare precocemente una artrite e di definirne il tipo e il grado di attività, può permettere di impostare una terapia adeguata, di monitorarla nel tempo e quindi di prevenire i danni causati dalla malattia bloccandone l'evoluzione. Il miglioramento degli interventi terapeutici e l'utilizzo di nuovi e potenti farmaci nella terapia dell'artrite reumatoide (RA), fanno sentire l'esigenza di un migliore approccio clinico all'artrite, in particolare per quanto riguarda la diagnosi, l'attività di malattia e il monitoraggio della terapia. La RA è una malattia cronica autoimmune caratterizzata da infiammazione sistemica e danno articolare, che colpisce circa l'1% della popolazione [1]. Le articolazioni più precocemente e frequentemente colpite sono le metacarpofalangee (MCF) e le interfalangee prossimali (IFP). Il riscontro di alterazioni in queste articolazioni può essere considerato indice di danno articolare diffuso. La radiologia tradizionale riveste un ruolo centrale nella diagnosi e nel monitoraggio della malattia, essa infatti consente di valutare la morfologia e la struttura dei capi ossei ed è ancora utilizzata come criterio classificativo ACR della RAdal 1987. Negli ultimi anni, tuttavia, è stato dimostrato che nelle fasi precoci il primo segno ad apparire è la sinovite e solo successivamente si consolida il danno osseo. Un evento cruciale nella patogenesi del danno articolare nella RA consiste nella formazione del panno e la neoangiogenesi è una condizione molto precoce che accompagna l'iperplasia sinoviale, con conseguente distruzione di cartilagine e osso. La vascolarizzazione sinoviale sembra correlare con l'attività e l'aggressività del panno reumatoide. Da qui la necessità di avere tecniche di imaging sensibili, capaci di valutare il grado e l'estensione della neovascolarizzazione intraarticolare, non visualizzabile attraverso la radiografia tradizionale. I primi tentativi di rilevare l'infiammazione e la proliferazione sinoviale attuati attraverso indagini di risonanza magnetica (MRI) hanno dimostrato che alcune alterazioni della sinovia correlano con l'evoluzione del danno articolare. Successivamente l'uso di mezzo di contrasto ha permesso di ottenere maggiori informazioni sulla presenza di vasi nello spazio sinoviale. La MRI è però un esame lungo, costoso, e presenta controindicazioni nel caso di impianti metallici, elettronici e nel caso di pazienti disabili o claustrofobici. Tra le nuove strategie diagnostiche, l'ecografia appare una tecnica molto promettente, che tuttavia non ha ancora raggiunto un grado di validazione e standardizzazione adeguato

Kinetic modeling without accounting for the vascular component impairs the quantification of [(11)C]PBR28 brain PET data

The positron emission tomography radioligand [(11)C]PBR28 targets translocator protein (18 kDa) (TSPO) and is a potential marker of neuroinflammation. [(11)C]PBR28 binding is commonly quantified using a two-tissue compartment model and an arterial input function. Previous studies with [(11)C]-(R)-PK11195 demonstrated a slow irreversible binding component to the TSPO proteins localized in the endothelium of brain vessels, such as venous sinuses and arteries. However, the impact of this component on the quantification of [(11)C]PBR28 data has never been investigated. In this work we propose a novel kinetic model for [(11)C]PBR28. This model hypothesizes the existence of an additional irreversible component from the blood to the endothelium. The model was tested on a data set of 19 healthy subjects. A simulation was also performed to quantify the error generated by the standard two-tissue compartmental model when the presence of the irreversible component is not taken into account. Our results show that when the vascular component is included in the model the estimates that include the vascular component (2TCM-1K) are more than three-fold smaller, have a higher time stability and are better correlated to brain mRNA TSPO expression than those that do not include the model (2TCM)