Department of Internal Medicine, Academic Medical Center, 1100DD Amsterdam, The Netherlands.
J Nucl Med. 2013 Feb;54(2):208-12. doi: 10.2967/jnumed.112.111849. Epub 2013 Jan 14.
Brown adipose tissue (BAT) has become a focus of research in the hope of finding a new target to fight obesity. Metabolic BAT activity can be visualized with (18)F-FDG PET/CT. Furthermore, the sympathetic innervation of BAT can be visualized with the radiolabeled norepinephrine analog (123)I-metaiodobenzylguanidine ((123)I-MIBG). We aimed to determine whether (123)I-MIBG SPECT/CT and (18)F-FDG PET/CT identify the same anatomic regions as active BAT in adult humans. Furthermore, we investigated whether the magnitude of BAT activity measured by these techniques correlated. Finally, we tried to establish the optimal time interval between (123)I-MIBG administration and subsequent SPECT/CT acquisition to visualize sympathetic stimulation of BAT.
Ten lean (body mass index, 19-25 kg/m(2)), healthy Caucasian men (age, 18-32 y) underwent one (18)F-FDG PET/CT and two (123)I-MIBG-SPECT/CT scans within a 2-wk interval. On 2 separate occasions, the subjects were exposed to mild cold (17°C) for 2 h after an overnight fast. After 1 h of cold exposure, (18)F-FDG (one occasion) or (123)I-MIBG (other occasion) was administered. (18)F-FDG PET/CT was performed at 1 h after (18)F-FDG administration, and (123)I-MIBG-SPECT/CT was performed at 4 and 24 h after (123)I-MIBG injection.
(18)F-FDG uptake in BAT was observed in 8 of 10 subjects, whereas (123)I-MIBG uptake was observed in 7 of 10 subjects in both the SPECT/CT scans acquired at 4 h after (123)I-MIBG administration and the SPECT/CT scans acquired at 24 h after (123)I-MIBG administration. All subjects who showed (123)I-MIBG uptake in BAT also showed (18)F-FDG uptake in BAT. There was no statistically significant correlation between maximal standardized uptake value of (18)F-FDG and semiquantitative uptake of (123)I-MIBG at 4 h after administration. However, a positive correlation was found between the maximal standardized uptake value of (18)F-FDG and semiquantitative uptake of (123)I-MIBG at 24 h after administration (r = 0.64, P = 0.04).
(123)I-MIBG SPECT/CT, as a marker of sympathetic activity, and (18)F-FDG PET/CT, as a marker of metabolic activity, identified the same anatomic regions as active BAT. Moreover, when (123)I-MIBG SPECT/CT was performed at 24 h after (123)I-MIBG administration, the magnitude of BAT activity measured with these techniques correlated strongly. This finding not only supports that BAT activity in humans is sympathetically influenced but also identifies (123)I-MIBG SPECT/CT, when performed 24 h after (123)I-MIBG injection, as a method to visualize and quantify sympathetic stimulation of BAT.
确定 (123)I-MIBG SPECT/CT 和 (18)F-FDG PET/CT 是否能在成年人体内识别出与活性 BAT 相同的解剖区域。方法：10 名体质量指数（BMI）为 19-25kg/m2 的健康白种男性（年龄 18-32 岁）在 2 周内接受了一次 (18)F-FDG PET/CT 和两次 (123)I-MIBG-SPECT/CT 扫描。在 2 次不同的情况下，受检者在禁食过夜后，在 17°C 的环境中暴露于轻度寒冷中 2 小时。在寒冷暴露 1 小时后，给予 (18)F-FDG（一次）或 (123)I-MIBG（另一次）。(18)F-FDG PET/CT 在给予 (18)F-FDG 后 1 小时进行，(123)I-MIBG-SPECT/CT 在给予 (123)I-MIBG 后 4 小时和 24 小时进行。
10 名受检者中有 8 名在 8 名受检者中观察到 BAT 的 (18)F-FDG 摄取，在 10 名受检者中有 7 名在给予 (123)I-MIBG 后 4 小时和给予 (123)I-MIBG 后 24 小时进行的 SPECT/CT 扫描中观察到 BAT 的 (123)I-MIBG 摄取。所有在 BAT 中显示 (123)I-MIBG 摄取的受检者也在 BAT 中显示 (18)F-FDG 摄取。(18)F-FDG 的最大标准化摄取值与给予 (123)I-MIBG 后 4 小时的半定量摄取之间没有统计学上的显著相关性。然而，在给予 (123)I-MIBG 后 24 小时，发现 (18)F-FDG 的最大标准化摄取值与 (123)I-MIBG 的半定量摄取之间存在正相关（r=0.64，P=0.04）。
(123)I-MIBG SPECT/CT 作为交感神经活性的标志物，(18)F-FDG PET/CT 作为代谢活性的标志物，与活性 BAT 相同的解剖区域。此外，当在给予 (123)I-MIBG 后 24 小时进行 (123)I-MIBG SPECT/CT 时，这两种技术测量的 BAT 活性之间具有很强的相关性。这一发现不仅支持人类 BAT 活动受到交感神经的影响，而且还确定了在给予 (123)I-MIBG 后 24 小时进行 (123)I-MIBG SPECT/CT 作为可视化和量化 BAT 交感神经刺激的方法。
