Quantitative analysis of positron emission tomography (PET) with the second generation translocator protein (TSPO) ligand [18F]GE-180 A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy (PhD) in the Faculty of Biology, Medicine and Health 2016 Sujata Sridharan School of Health Sciences Contents Contents ......................................................................................................................................................... 2 List of tables ................................................................................................................................................. 7 List of figures ............................................................................................................................................... 8 Abstract....................................................................................................................................................... 10 Declaration ................................................................................................................................................ 11 Copyright statement .............................................................................................................................. 11 Acknowledgements................................................................................................................................ 12 Abbreviations ........................................................................................................................................... 14 1 Introduction ................................................................................................................................. 16 1.1 Rationale for the alternative format ................................................................ 16 1.1.1 Aims ......................................................................................................................... 16 1.1.2 Structure of the thesis ...................................................................................... 16 1.2 Role of the author .................................................................................................... 17 1.3 Inflammation and microglia ................................................................................ 19 1.4 The 18 kDa translocator protein ....................................................................... 21 1.5 PET imaging ............................................................................................................... 23 1.5.1 [11C]-(R)-PK11195 ............................................................................................. 26 1.5.2 Specific and non-specific binding ................................................................ 26 1.5.3 The TSPO polymorphism ................................................................................ 27 1.6 TSPO expression in neurological disease ...................................................... 28 1.6.1 Multiple sclerosis ............................................................................................... 28 1.6.2 Preclinical studies .............................................................................................. 31 1.7 Plasma and metabolites of [11C]-(R)-PK11195 ........................................... 32 1.8 Kinetic analysis and modelling of TSPO data ............................................... 34 1.8.1 Overview of techniques ................................................................................... 35 1.8.2 Plasma input functions .................................................................................... 36 1.8.2.1 Compartment models ........................................................................... 36 1.8.2.2 Graphical analysis – Logan plots...................................................... 38 1.8.2.3 Graphical analysis – Patlak plots ..................................................... 39 1.8.2.4 Spectral analysis ..................................................................................... 39 1.8.2.5 Key results from studies using plasma input functions ......... 41 1.8.2.6 Summary of plasma input approaches .......................................... 43 1.8.3 ROI analysis vs. parametric mapping ......................................................... 44 1.8.4 Image-derived input functions ..................................................................... 44 2 1.8.5 Reference tissue input functions ................................................................. 45 1.8.5.1 The simplified reference tissue model .......................................... 46 1.8.5.2 Reference tissue graphical analysis ................................................ 47 1.8.5.3 Reference tissue input parametric images .................................. 49 1.8.5.4 Key results from studies using reference input functions .... 50 1.8.5.5 Summary of reference tissue input approaches........................ 52 1.8.6 Cluster analysis ................................................................................................... 52 1.8.6.1 Unsupervised clustering ..................................................................... 53 1.8.6.2 Supervised clustering ........................................................................... 55 1.8.6.3 Key results from studies using cluster analysis ........................ 57 1.8.6.4 Summary of cluster analysis approaches ..................................... 59 1.8.7 Summary of kinetic analysis approaches ................................................. 59 1.9 Summary and rationale for study ..................................................................... 62 2 Comparative evaluation of three TSPO PET radiotracers in a LPS-induced model of mild neuroinflammation in rats ........................................................................ 63 2.1 Abstract ....................................................................................................................... 63 2.2 Introduction ............................................................................................................... 65 2.3 Materials and methods .......................................................................................... 68 2.3.1 Tracer synthesis ................................................................................................. 68 2.3.2 Animals ................................................................................................................... 68 2.3.3 LPS and AMPA administration ..................................................................... 68 2.3.4 Scanning protocol .............................................................................................. 69 2.3.5 Image analysis ..................................................................................................... 70 2.3.6 Data-driven method for the extraction of reference tissue kinetics71 2.3.7 PET data modelling ........................................................................................... 72 2.3.8 Immunohistochemistry ................................................................................... 72 2.3.9 Autoradiography ................................................................................................ 73 2.3.10 Statistical analysis.............................................................................................. 74 2.4 Results .......................................................................................................................... 75 2.4.1 PET imaging ......................................................................................................... 75 2.4.1.1 Non-paired scans ................................................................................... 77 2.4.1.2 Dual scans.................................................................................................. 77 2.4.2 Kinetic analysis ................................................................................................... 77 2.4.2.1 SRTM with contralateral reference input .................................... 78 2.4.2.2 SRTM with cerebellar reference input .......................................... 78 2.4.2.3 SRTM with data-driven clustering reference input ................. 78 2.4.3 Autoradiography ................................................................................................ 79 3 2.4.4 Immunohistochemistry ................................................................................... 79 2.5 Discussion ................................................................................................................... 82 2.5.1 PET imaging and ex vivo observations ...................................................... 82 2.5.2 PET data modelling ........................................................................................... 84 2.6 Conclusions ................................................................................................................ 86 Supplementary materials .................................................................................................................... 88 3 Characterisation of a blood sampling system for generating [18F]DPA-714 TSPO-PET plasma input functions in the rat brain ...................................................... 90 3.1 Abstract ....................................................................................................................... 90 3.2 Introduction ..............................................................................................................