Combining MRI with PET for partial volume correction improves image-derived input functions in mice.

Published on Jul 29, 2014in EJNMMI Physics3.309
· DOI :10.1186/2197-7364-1-S1-A84
Eleanor Evans2
Estimated H-index: 2
(University of Cambridge),
Guido Buonincontri14
Estimated H-index: 14
(University of Cambridge)
+ 6 AuthorsStephen J. Sawiak26
Estimated H-index: 26
(University of Cambridge)
Sources
Abstract
Kinetic modelling in PET requires the arterial input function (AIF), defined as the time-activity curve (TAC) in plasma. This measure is challenging to obtain in mice due to low blood volumes, resulting in a reliance on image-based methods for AIF derivation. We present a comparison of PET- and MR-based region-of-interest (ROI) analysis to obtain image-derived AIFs from the left ventricle (LV) of a mouse model. ROI-based partial volume correction (PVC) was performed to improve quantification. MRI and dynamic PET images were obtained from a recent study investigating treatment effects in 12 mice following myocardial infarction [1], where half the mice received a new treatment and half did not. Prospectively gated MRI (4.7T Bruker BioSpec, FLASH TR/TE 400/3ms, spatial resolution 140μm in 1mm slices) were acquired prior to PET acquisition (approx. 25MBq 18F-FDG bolus, 45 minute emission listmode acquisition reconstructed with 3DRP in four cardiac frames) on a split-magnet PET camera [2]. Images were co-registered using SPMMouse [3] (see Figure ​Figure11). Figure 1 Mouse heart MR (left) and fused with 18F-FDG static PET (right). Arrow indicates infarcted region. AIF extraction AIFs were obtained by taking mean time courses from LV Lumen ROIs, shown in Figure ​Figure2.2. The regional geometric transfer matrix (GTM) method was applied for PVC [4], using ROIs drawn on either the co-registered MR images or directly onto the last dynamic frame PET images. ROIs covered LV lumen, myocardium, lungs/body and background. Patlak [5] analysis was performed to evaluate glucose metabolism. Figure 2 AIFs and TACs derived for single subject using (A) MR ROIs, (B) PET ROIs with PVC and (C) MR ROIs with PVC. Insets detail first 500s Uncorrected AIFs and myocardial TACs produced by manual ROI delineation displayed contamination with myocardial signal. AIFs and myocardial curves became distinguishable if GTM PVC was applied. Only MR-based PVC produced significant differences (p<0.05) in Ki values between the treated and untreated groups (see Table ​Table11). Table 1 GTM-based PVC gives best results in mice when ROIs are based on MRI data, due to its high-resolution and excellent soft-tissue contrast.
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References5
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#1Carmen Methner (University of Cambridge)H-Index: 13
#2Guido Buonincontri (University of Cambridge)H-Index: 14
Last. Thomas Krieg (University of Cambridge)H-Index: 58
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Aim Stimulation of the nitric oxide (NO) – soluble guanylate (sGC) - protein kinase G (PKG) pathway confers protection against acute ischaemia/reperfusion injury, but more chronic effects in reducing post-myocardial infarction (MI) heart failure are less defined. The aim of this study was to not only determine whether the sGC stimulator riociguat reduces infarct size but also whether it protects against the development of post-MI heart failure. Methods and Results Mice were subjected to 30 min i...
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#8T. Adrian Carpenter (University of Cambridge)H-Index: 46
Features of a positron emission tomography-magnetic resonance (PET-MR) system in which a novel, superconducting magnet with a 'split' is combined with a multi-ring PET detector based on a microPETreg Focus 120 have been investigated. Those features include the impact on PET performance of: modification of the PET detector block, using a position-sensitive PMT in a nominal magnetic field of 10 Gauss (1mT), and - most significantly $operating the MR system whilst PET data is acquired. No effect on...
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#1Alun J. Lucas (University of Cambridge)H-Index: 7
#2Rob C. Hawkes (University of Cambridge)H-Index: 8
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As evidenced by the success of PET-CT, there are many benefits from combining imaging modalities into a single scanner. The combination of PET and MR offers potential advantages over PET-CT, including improved soft tissue contrast, access to the multiplicity of contrast mechanisms available to MR, simultaneous imaging and fast MR sequences for motion correction. In addition, PET-MR is more suitable than PET-CT for cancer screening due to the elimination of the radiation dose from CT.A key issue ...
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#1Olivier Rousset (Montreal Neurological Institute and Hospital)H-Index: 18
#2Yilong Ma (McGill University)H-Index: 48
Last. Alan C. Evans (McGill University)H-Index: 202
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The accuracy of PET for measuring regional radiotracer concentra tions in the human brain is limited by the finite resolution capability of the scanner and the resulting partial volume effects (PVEs). We designed a new algorithm to correct for PVEs by characterizing the geometric interaction between the PETsystem and the brain activity distribution. Methods: The partial volume correction (PVC) algo rithm uses high-resolution volumetric MR Âimages correlated with the PET volume. We used a PET sim...
A theoretical model of blood–brain exchange is developed and a procedure is derived that can be used for graphing multiple-time tissue uptake data and determining whether a unidirectional transfer process was dominant during part or all of the experimental period. If the graph indicates unidirectionality of uptake, then an influx constant (Ki) can be calculated. The model is general, assumes linear transfer kinetics, and consists of a blood–plasma compartment, a reversible tissue region with an ...
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