Stegger Lars, Heijman Edwin, Schäfers Klaus P, Nicolay Klaas, Schäfers Michael A, Strijkers Gustav J
Department of Nuclear Medicine, University Hospital Münster, and European Institute of Molecular Imaging, University of Münster, Münster, Germany.
J Nucl Med. 2009 Jan;50(1):132-8. doi: 10.2967/jnumed.108.056051. Epub 2008 Dec 17.
PET has become an important noninvasive imaging technique in cardiovascular research for the characterization of mouse models in vivo. This modality offers unique insight into biochemical changes on a molecular level, with excellent sensitivity. However, morphologic and functional changes may be of equal importance for a thorough assessment of left ventricular (LV) pathophysiology. Although echocardiography and MRI are widely considered the imaging techniques of choice for the assessment of these parameters, their use with PET considerably increases study complexity and decreases cost- and time-efficiency. In this study, a novel method for the additional quantification of LV volumes and ejection fraction (EF) from PET was evaluated using cardiac MRI as the reference method.
The radiolabeled glucose derivative 18F-FDG was injected into 33 mice (6 mice with previous permanent occlusion of the left anterior descending artery [LAD], 15 mice with a temporary 30-min occlusion of the LAD, and 12 mice without previous surgery). 18F-FDG uptake within the LV myocardium was measured using a dedicated small-animal PET scanner. After we reconstructed the images into 16 electrocardiogram (ECG)-gated frames, we determined the LV cavity volumes in end-diastole (EDV) and end-systole (ESV) and the EF using a semiautomatic segmentation algorithm based on elastic surfaces. A 6.3-T cardiac MRI examination was performed in the same animals using an ECG-triggered and respiratory-gated multislice cine sequence. The MR images were segmented with a semiautomatic algorithm using commercially available software.
Overall, measurements from PET agreed well with those obtained by MRI. Mean EDV and ESV were slightly overestimated by PET (86+/-43 microL and 44+/-42 microL), compared with MRI (73+/-44 microL and 41+/-46 microL); mean (+/-SD) EF was similar (PET, 55+/-19 microL; MRI, 54+/-18 microL). Correlation between PET and MRI was excellent for EDV (0.97) and ESV (0.96) and good for EF (0.86). The slope of the regression line was nearly perfect for EDV (0.98) and EF (1.01) and slightly below 1 for ESV (0.90), indicating a good separation of abnormal and normal values with PET. The y-intercept was above zero for EDV (15 microL) and ESV (7 microL) and near to zero for EF (0.2%).
The quantification of LV volumes and EF in mice with PET is both efficient and accurate. This method allows for combined molecular and functional imaging of the left ventricle within a single scan, obviating additional sophisticated MRI in many cases.
正电子发射断层扫描（PET）已成为心血管研究中一种重要的非侵入性成像技术，用于体内小鼠模型的特征描述。这种成像方式能够在分子水平上对生化变化提供独特的见解，具有出色的灵敏度。然而，形态学和功能变化对于全面评估左心室（LV）病理生理学可能同样重要。尽管超声心动图和磁共振成像（MRI）被广泛认为是评估这些参数的首选成像技术，但将它们与PET一起使用会大大增加研究的复杂性，并降低成本和时间效率。在本研究中，使用心脏MRI作为参考方法，评估了一种从PET额外定量左心室容积和射血分数（EF）的新方法。
将放射性标记的葡萄糖衍生物18F-FDG注入33只小鼠体内（6只先前左前降支动脉[LAD]永久性闭塞的小鼠，15只LAD临时闭塞30分钟的小鼠，以及12只未进行过手术的小鼠）。使用专用的小动物PET扫描仪测量左心室心肌内的18F-FDG摄取量。在将图像重建为16个心电图（ECG）门控帧后，我们使用基于弹性表面的半自动分割算法确定舒张末期（EDV）和收缩末期（ESV）的左心室腔容积以及EF。使用ECG触发和呼吸门控的多层电影序列对同一批动物进行6.3-T心脏MRI检查。使用市售软件通过半自动算法对MR图像进行分割。
总体而言，PET测量结果与MRI获得的结果非常吻合。与MRI（73±44微升和41±46微升）相比，PET对平均EDV和ESV略有高估（86±43微升和44±42微升）；平均（±标准差）EF相似（PET为55±19微升；MRI为54±18微升）。PET与MRI之间对于EDV（0.97）和ESV（0.96）的相关性极佳，对于EF（0.86）的相关性良好。回归线的斜率对于EDV（0.98）和EF（1.01）几乎完美，对于ESV（0.90）略低于1，表明PET能够很好地区分异常值和正常值。EDV（15微升）和ESV（7微升）的y轴截距大于零，EF（0.2%）的y轴截距接近零。
用PET对小鼠左心室容积和EF进行定量既高效又准确。这种方法允许在单次扫描中对左心室进行分子和功能联合成像，在许多情况下无需额外进行复杂的MRI检查。
