Browsing by Author "Hamze, H"
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- Item4D PET iterative deconvolution with spatiotemporal regularization for quantitative dynamic PET imaging(Elsevier, 2015-09-01) Reilhac, A; Charil, A; Wimberley, CA; Angelis, GI; Hamze, H; Callaghan, PD; Garcia, MP; Boisson, F; Ryder, W; Meikle, SR; Grégoire, MCQuantitative measurements in dynamic PET imaging are usually limited by the poor counting statistics particularly in short dynamic frames and by the low spatial resolution of the detection system, resulting in partial volume effects (PVEs). In this work, we present a fast and easy to implement method for the restoration of dynamic PET images that have suffered from both PVE and noise degradation. It is based on a weighted least squares iterative deconvolution approach of the dynamic PET image with spatial and temporal regularization. Using simulated dynamic [11C] Raclopride PET data with controlled biological variations in the striata between scans, we showed that the restoration method provides images which exhibit less noise and better contrast between emitting structures than the original images. In addition, the method is able to recover the true time activity curve in the striata region with an error below 3% while it was underestimated by more than 20% without correction. As a result, the method improves the accuracy and reduces the variability of the kinetic parameter estimates calculated from the corrected images. More importantly it increases the accuracy (from less than 66% to more than 95%) of measured biological variations as well as their statistical detectivity. © 2015 Elsevier Inc.
- ItemFluorine-18 radiolabelling and in vitro / in vivo metabolism of [18F]D4-PBR111(John Wiley & Sons, Inc, 2019-05-26) Wyatt, NA; Safavi-Naeini, M; Wotherspoon, ATL; Arthur, A; Nguyen, AP; Parmar, A; Hamze, H; Day, CM; Zahra, D; Matesic, L; Davis, E; Rahardjo, GL; Yepuri, NR; Shepherd, R; Murphy, RB; Pham, TQ; Nguyen, VH; Callaghan, PD; Holden, PJ; Grégoire, MC; Darwish, TA; Fraser, BHObjectives The purinergic receptor P2X ligand-gated ion channel type 7 (P2X7R) is an adenosine triphosphate (ATP)-gated ion-channel, and P2X7R is a key player in inflammation. P2X7R is an emerging therapeutic target in central nervous system (CNS) diseases including Alzheimer's disease (AD) and Parkinson's disease (PD), because P2X7R also plays a pivotal role in neuroinflammation. P2X7R represents a potential molecular imaging target for neuroinflammation via biomedical imaging technique positron emission tomography (PET), and several radioligands targeting P2X7R have been developed and evaluated in animals. In our previous work, we have developed and characterized [11C]GSK1482160 as a P2X7R radioligand for neuroinflammation,2 clinical evaluation of [11C]GSK1482160 in healthy controls and patients is currently underway, and the estimation of radiation dosimetry for [11C]GSK1482160 in normal human subjects has been reported.3 Since the half-life (t1/2) of radionuclide carbon-11 is only 20.4 min, it is attractive for us to develop derivatives of [11C]GSK1482160, which can be labeled with the radionuclide fluorine-18 (t1/2, 109.7 min), and a fluorine-18 ligand would be ideal for widespread use.4 To this end, a series of [18F]fluoroalkyl including [18F]fluoromethyl (FM), [18F]fluoroethyl (FE), and [18F]fluoropropyl (FP) derivatives of GSK1482160 have been prepared and examined as new potential P2X7R radioligands. © 2019 The Authors
- ItemImaging capabilities of the Inveon SPECT system using single-and multipinhole collimators(Society of Nuclear Medicine and Molecular Imaging, 2013-09-05) Boisson, F; Zahra, D; Parmar, A; Grégoire, MC; Meikle, SR; Hamze, H; Reilhac, AThe Inveon small-animal SPECT system comes with several types of multipinhole collimator plates. We evaluate here the performance measurements of the Inveon SPECT system using 6 different collimators: 3 dedicated for mouse imaging and 3 for rat imaging. Methods: The measured performance parameters include the sensitivity, the spatial resolution using line sources, the ultra-micro Derenzo phantom, the recovery coefficient and the noise measurements using the National Electrical Manufacturers Association NU-4 image quality phantom, obtained with the 2 reconstruction algorithms available with the Inveon Acquisition Workplace, version 1.5—the 3-dimensional ordered-subset expectation maximization (3DOSEM) and the 3-dimensional maximum a posteriori (3DMAP). Further, the overall performance of the system is illustrated by an animal experiment. Results: The results show that the Inveon SPECT scanner offers a spatial resolution, measured at the center of the field of view, ranging from 0.6 to 1 mm with the collimator plates dedicated to mouse imaging and from 1.2 to less than 2 mm with rat collimator plates. The system sensitivity varies from 29 to 404 cps/MBq for mouse collimators and from 53 to 175 cps/MBq for rat collimators. The image quality study showed that 3DMAP allows better noise reduction while preserving the recovery coefficient, compared with other regularization strategies such as the premature termination of the 3DOSEM reconstruction or 3DOSEM followed by gaussian filtering. Conclusion: The acquisition parameters, such as the collimator set and the radius of rotation, offer a wide range of possibilities to apply to a large number of biologic studies. However, special care must be taken because this increase in sensitivity can be offset by image degradation, such as image artifacts caused by projection overlap and statistical noise due to a higher number of iterations required for convergence. 3DMAP allowed better noise reduction while maintaining relatively constant recovery coefficients, as compared with other reconstruction strategies. © 2013 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
- ItemIn vivo PET imaging with [18F]FDG to explain improved glucose uptake in an apolipoprotein A-I treated mouse model of diabetes(Springer Nature, 2016-05-18) Cochran, BJ; Ryder, WJ; Parmar, A; Tang, S; Reilhac, A; Arthur, A; Charil, A; Hamze, H; Barter, PJ; Kritharides, L; Meikle, SR; Grégoire, MC; Rye, KAType 2 diabetes is characterised by decreased HDL levels, as well as the level of apolipoprotein A-I (apoA-I), the main apolipoprotein of HDLs. Pharmacological elevation of HDL and apoA-I levels is associated with improved glycaemic control in patients with type 2 diabetes. This is partly due to improved glucose uptake in skeletal muscle.© 2016 Springer Nature
- ItemNEMA NU 4-2008 validation and applications of the PET-SORTEO Monte Carlo simulations platform for the geometry of the Inveon PET preclinical scanner(IOP Publishing, 2013-09-10) Boisson, F; Wimberley, CA; Lehnert, W; Zahra, D; Pham, TQ; Perkins, G; Hamze, H; Grégoire, MC; Reilhac, AMonte Carlo-based simulation of positron emission tomography (PET) data plays a key role in the design and optimization of data correction and processing methods. Our first aim was to adapt and configure the PET-SORTEO Monte Carlo simulation program for the geometry of the widely distributed Inveon PET preclinical scanner manufactured by Siemens Preclinical Solutions. The validation was carried out against actual measurements performed on the Inveon PET scanner at the Australian Nuclear Science and Technology Organisation in Australia and at the Brain and Mind Research Institute and by strictly following the NEMA NU 4-2008 standard. The comparison of simulated and experimental performance measurements included spatial resolution, sensitivity, scatter fraction and count rates, image quality and Derenzo phantom studies. Results showed that PET-SORTEO reliably reproduces the performances of this Inveon preclinical system. In addition, imaging studies showed that the PET-SORTEO simulation program provides raw data for the Inveon scanner that can be fully corrected and reconstructed using the same programs as for the actual data. All correction techniques (attenuation, scatter, randoms, dead-time, and normalization) can be applied on the simulated data leading to fully quantitative reconstructed images. In the second part of the study, we demonstrated its ability to generate fast and realistic biological studies. PET-SORTEO is a workable and reliable tool that can be used, in a classical way, to validate and/or optimize a single PET data processing step such as a reconstruction method. However, we demonstrated that by combining a realistic simulated biological study ([11C]Raclopride here) involving different condition groups, simulation allows one also to assess and optimize the data correction, reconstruction and data processing line flow as a whole, specifically for each biological study, which is our ultimate intent. © 2017 IOP Publishing
- ItemThe role of earthquakes and climate in the formation of diamictic sediments in a New Zealand mountain lake(Elsevier, 2018-03-03) Woodward, CA; Slee, A; Gadd, PS; Zawadzki, A; Hamze, H; Parmar, A; Zahra, DWe used Itrax XRF, magnetic susceptibility, grain size, and micro-CT scanning to provide a facies classification for a Late Holocene sediment sequence from Lake Chappa'ai in the Southern Alps, New Zealand. The record contained multiple diamictic layers and our objective was to determine the environmental significance of these deposits. Clast fabric analysis indicated that the diamicts comprise dropstones transported to the centre of the lake by ice rafting. Diamicts belonging to Facies 1 represent rock falls onto lake ice triggered by earthquakes that produced MMI (Modified Mercalli Intensity) > 8 shaking in the catchment. MMI >8 earthquakes may need to occur when the lake has ice cover to produce Facies 1 diamicts. MMI >8 earthquakes in the ice free season or MMI 7–8 earthquakes may also result in an increased flux of large (>1 mm) clasts to the centre of the lake, but may not produce a Facies 1 diamict. More work is required to establish the role of climate related processes on the formation of non-Facies 1 diamicts in Lake Chappa'ai. Climate change may directly lead to diamict formation by changing lake ice cover and facilitating transport of large clasts by anchor ice, or increasing the likelihood of rain on snow events in the spring. Changing ice cover conditions will also affect how mountain lakes record past earthquake events. Lakes that are ice free will not produce earthquake diamicts and lakes that have perennial ice cover may produce a single diamict representing multiple earthquakes if the lake becomes ice free. A reduction in the duration of winter ice cover will also decrease the probability of capturing primary rockfall deposits from earthquakes. Additional data, such as a diatom or chironomid record from Lake Chappa'ai may help to resolve the contribution of climate processes to diamict formation. We should consider the Lake Chappa'ai record as an indicator of minimum earthquake activity until we can disentangle the effects of climate change on non-Facies 1 diamict formation. This study highlights the multiple mechanisms that can lead to diamict formation in mountain lake sediments. These processes should always be considered before attributing the presence of diamict deposits to ice-rafted debris in a pro-glacial lake. This is particularly true in seismically active settings where earthquake triggered rockfalls may lead to diamict formation. Crown Copyright ©2017 Published by Elsevier Ltd
- ItemSimultaneous scanning of two mice in a small-animal PET scanner: a simulation-based assessment of the signal degradation(IOP science publishing, 2016-01-21) Reilhac, A; Boisson, F; Wimberley, CA; Parmar, A; Zahra, D; Hamze, H; Davis, E; Arthur, A; Bouillot, C; Charil, A; Grégoire, MCIn PET imaging, research groups have recently proposed different experimental set ups allowing multiple animals to be simultaneously imaged in a scanner in order to reduce the costs and increase the throughput. In those studies, the technical feasibility was demonstrated and the signal degradation caused by additional mice in the FOV characterized, however, the impact of the signal degradation on the outcome of a PET study has not yet been studied. Here we thoroughly investigated, using Monte Carlo simulated [18F]FDG and [11C]Raclopride PET studies, different experimental designs for whole-body and brain acquisitions of two mice and assessed the actual impact on the detection of biological variations as compared to a single-mouse setting. First, we extended the validation of the PET-SORTEO Monte Carlo simulation platform for the simultaneous simulation of two animals. Then, we designed [18F]FDG and [11C]Raclopride input mouse models for the simulation of realistic whole-body and brain PET studies. Simulated studies allowed us to accurately estimate the differences in detection between single- and dual-mode acquisition settings that are purely the result of having two animals in the FOV. Validation results showed that PET-SORTEO accurately reproduced the spatial resolution and noise degradations that were observed with actual dual phantom experiments. The simulated [18F]FDG whole-body study showed that the resolution loss due to the off-center positioning of the mice was the biggest contributing factor in signal degradation at the pixel level and a minimal inter-animal distance as well as the use of reconstruction methods with resolution modeling should be preferred. Dual mode acquisition did not have a major impact on ROI-based analysis except in situations where uptake values in organs from the same subject were compared. The simulated [11C]Raclopride study however showed that dual-mice imaging strongly reduced the sensitivity to variations when mice were positioned side-by-side while no sensitivity reduction was observed when they were facing each other. This is the first study showing the impact of different experimental designs for whole-body and brain acquisitions of two mice on the quality of the results using Monte Carlo simulated [18F]FDG and [11C]Raclopride PET studies. © 2016 Institute of Physics and Engineering in Medicine
- ItemTest-retest reliability and inter scanner variability of 11C-raclopride striatal binding potentials between two INVEON PET/CT imaging systems for naïve Sprague Dawley rats(Wiley, 2014-04-16) Callaghan, PD; Zahra, D; Wimberley, CA; Arthur, A; Rahardjo, GL; Hamze, H; Davis, E; Nguyen, A; Boisson, F; Perkins, G; Pascali, G; Reilhac, A; Grégoire, MCBackground: 11C-raclopride is a routine tracer for quantification of dopamine D2 receptors in neurological and psychiatric disease. D2 imaging in key longitudinal models has significant utility of understanding mechanisms and therapeutic interventions. Aims: Optimisation of preclinical imaging and data analysis protocols for 11C-raclopride in rat brain. Methods: a) Test-retest reliability: Naïve male Sprague Dawley rats (n = 6) underwent test-retest assessment of binding potential variability, with two scans, 1 week apart. Rats were anaesthetised (1–5% isoflurane) and received 11C-raclopride (>0.1 nmol, 20–40 MBq) during 1 hour image acquisition (Siemens Inveon PET/CT), followed by a 10 minute CT scan. b) Assessment of the intersystem variability of the INVEON scanners (n = 12). Test-retest experiments were performed on a second INVEON system. c) Assessment of inter system variability with arterial blood sampling (n = 5). Acquisitions were performed (as above) with prior femoral artery cannulation: 23 blood samples (∼30 ul) were collected during PET acquisition, and plasma metabolite corrected input functions generated. PET list mode data were histogrammed (23 frames) and reconstructed with 2D filtered backprojection algorithm. The impact of some post-reconstruction image processing techniques, such iterative deconvolution of the image and data denoising techniques, onto the accuracy and reliability of the computed parameter of interest were also investigated. Binding potential parametric maps were calculated from the dynamic PET data (using either a standard reference tissue modelling using the cerebellum TAC (test-retest), and or a 2 compartment kinetic modelling with input function). Preliminary results: Significant improvements were seen for tissue activity data after denoising /iterative deconvolution (see figure). Analysis of binding potential data are currently in progress. Conclusion: Assessment of within and intersystem variability will aid the appropriate statistical design of future longitudinal 11C-raclopride imaging studies. Improvements from post-reconstruction image processing techniques show significant benefits. © 1999-2022 John Wiley & Sons, Inc.