Evans Eleanor, Sawiak Stephen J, Ward Alexander O, Buonincontri Guido, Hawkes Robert C, Carpenter T Adrian
Wolfson Brain Imaging Centre, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
Wolfson Brain Imaging Centre, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK ; Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK.
Nucl Instrum Methods Phys Res A. 2014 Jan 11;734(B):137-140. doi: 10.1016/j.nima.2013.08.076.
Accurate kinetic modelling of in vivo physiological function using positron emission tomography (PET) requires determination of the tracer time-activity curve in plasma, known as the arterial input function (AIF). The AIF is usually determined by invasive blood sampling methods, which are prohibitive in murine studies due to low total blood volumes. Extracting AIFs from PET images is also challenging due to large partial volume effects (PVE). We hypothesise that in combined PET with magnetic resonance imaging (PET/MR), a co-injected bolus of MR contrast agent and PET ligand can be tracked using fast MR acquisitions. This protocol would allow extraction of a MR AIF from MR contrast agent concentration-time curves, at higher spatial and temporal resolution than an image-derived PET AIF. A conversion factor could then be applied to the MR AIF for use in PET kinetic analysis. This work has compared AIFs obtained from sequential DSC-MRI and PET with separate injections of gadolinium contrast agent and F-FDG respectively to ascertain the technique's validity. An automated voxel selection algorithm was employed to improve MR AIF reproducibility. We found that MR and PET AIFs displayed similar character in the first pass, confirmed by gamma variate fits (p<0.02). MR AIFs displayed reduced PVE compared to PET AIFs, indicating their potential use in PET/MR studies.
使用正电子发射断层扫描（PET）对体内生理功能进行准确的动力学建模需要确定血浆中的示踪剂时间-活度曲线，即动脉输入函数（AIF）。AIF通常通过侵入性血液采样方法确定，由于小鼠总血容量较低，这种方法在小鼠研究中不可行。由于存在较大的部分容积效应（PVE），从PET图像中提取AIF也具有挑战性。我们假设，在PET与磁共振成像（PET/MR）联合使用时，可以通过快速磁共振采集追踪共注射的磁共振造影剂和PET配体团注。该方案将允许从磁共振造影剂浓度-时间曲线中提取磁共振AIF，其空间和时间分辨率高于基于图像的PET AIF。然后可以将一个转换因子应用于磁共振AIF，用于PET动力学分析。这项工作比较了分别注射钆造影剂和F-FDG后通过序列动态对比增强磁共振成像（DSC-MRI）和PET获得的AIF，以确定该技术的有效性。采用了一种自动体素选择算法来提高磁共振AIF的可重复性。我们发现，通过伽马变量拟合证实（p<0.02），磁共振和PET AIF在首次通过时表现出相似的特征。与PET AIF相比，磁共振AIF的PVE降低，表明它们在PET/MR研究中的潜在用途。
