CNR Institute of Bioimaging and Molecular Physiology, Milan, Genoa Section, Genoa, Italy.
Eur J Nucl Med Mol Imaging. 2012 Jan;39(1):91-101. doi: 10.1007/s00259-011-1955-1. Epub 2011 Oct 20.
Conflicting results have been reported about the clinical value of fluorodeoxyglucose (FDG) imaging in predicting the risk of rupture of abdominal aortic aneurysm (AAA). The present study tests the hypothesis that FDG uptake is low in asymptomatic noninflammatory AAA due to the low cell density in aneurysmal walls.
Positron emission tomography (PET)/CT imaging was performed in 12 consecutive candidates for AAA surgical repair and in 12 age- and sex-matched controls. At intervention, aneurysmal walls were cut into three sequential blocks. Block A was frozen to cut three 5-μm slices for incubation with 2-3 MBq of FDG for 5 min. Block C was first incubated with the same tracer solution for the same time and subsequently frozen to cut three 5-μm slices. Autoradiographic images were coregistered with immunohistochemical pictures of cell density, type and DNA synthesis as assessed on block B.
No visible uptake in abdominal aorta occurred in any patient or control subject. Immunohistochemistry documented a severe loss of wall structure, with low numbers of cells. Tracer retention directly correlated with overall cell density and with prevalence of cells synthesizing DNA. The metabolic nature of FDG uptake was confirmed by the selective effect of preliminary freezing that decreased tracer content by 90% in regions with high cell density and only by 34% in cold acellular areas.
The loss of tissue structure and the marked decrease in cell density account for the low prevalence of positive findings at FDG PET imaging, at least in asymptomatic patients bearing AAAs whose diameter is close to surgical indication.
关于氟脱氧葡萄糖（FDG）成像在预测腹主动脉瘤（AAA）破裂风险方面的临床价值，已有相互矛盾的结果报道。本研究检验了以下假设，即由于AAA 壁中的细胞密度低，无症状非炎症性 AAA 中的 FDG 摄取较低。
对 12 名连续接受 AAA 手术修复的候选者和 12 名年龄和性别匹配的对照者进行正电子发射断层扫描（PET）/CT 成像。在干预时，将动脉瘤壁切成三个连续的块。将块 A 冷冻以切取三个 5μm 切片，用于孵育 2-3MBq 的 FDG 5min。首先将块 C 用相同的示踪剂溶液孵育相同的时间，然后冷冻以切取三个 5μm 切片。将放射性自显影图像与块 B 评估的细胞密度、类型和 DNA 合成的免疫组织化学图片进行配准。
在任何患者或对照者中，腹部主动脉均未出现可见摄取。免疫组织化学证明了壁结构的严重丧失，细胞数量减少。示踪剂保留与总细胞密度和合成 DNA 的细胞的流行率直接相关。FDG 摄取的代谢性质通过初步冷冻的选择性作用得到证实，该作用使高细胞密度区域中的示踪剂含量降低了 90%，而在冰冷的无细胞区域中仅降低了 34%。
至少在接近手术指征的无症状患者中，组织结构的丧失和细胞密度的显著下降解释了 FDG PET 成像中阳性发现的低流行率。
