通过饮食和波长选择最小化临床前成像中的近红外自发荧光。

SIGNIFICANCE: Preclinical fluorescence imaging with NIR-I (700 to 900 nm) illumination and short-wave infrared or NIR-II (1000 to 1700 nm) emission increases tissue penetration depth and improves resolution through decreased scattering. Background autofluorescence decreases signal-to-background ratios (SBR) in fluorescence imaging; maximizing SBR will further improve the impact of deep tissue imaging. AIM: The impact of rodent diet, illumination wavelength, and emission range on the background fluorescence and contrast agent SBR were determined to assist with the experimental design of future imaging studies. APPROACH: Following illumination with 670, 760, or 808 nm, autofluorescence in the NIR-I ( ), NIR-II ( ), and NIR-II LP ( ) regions was assessed in mice fed chow or a purified diet using an IR VIVO preclinical imager (Photon, Etc.). Comparison of the SBR of liver-localized indocyanine green in the various imaging conditions indicated when gut autofluorescence was a problematic confounder. RESULTS: Mice fed chow exhibit high levels of background autofluorescence in the gastrointestinal tract and, to a lesser extent, skin when illuminated with 670 nm light for NIR-I imaging (700 to 975 nm), interfering with the identification of fluorescently labeled tissue. Background autofluorescence was reduced by more than two orders of magnitude by any of the following changes: (1) purified diet; (2) excitation with 760 or 808 nm illumination; or (3) emission in the NIR-II (1000 to 1600 or 1250 to 1600 nm). Although the SBR was generally sufficient for feature identification except when imaging of chow-fed mice with 670 nm excitation and NIR-I emission, switching to a purified diet, using longer excitation wavelengths, or using longer emission wavelengths improved SBR significantly. CONCLUSIONS: Systematic comparison of imaging conditions and diet highlights the reduction in autofluorescence and increase in SBR enabled by intentional choices in the experimental parameters including diet, excitation wavelength, and emission wavelength range.

意义：使用近红外-I（700 至 900nm）照明和短波红外或近红外-II（1000 至 1700nm）发射的临床前荧光成像增加了组织穿透深度，并通过减少散射提高了分辨率。背景自发荧光降低了荧光成像中的信号与背景比（SBR）；最大限度地提高 SBR 将进一步提高深部组织成像的效果。

目的：确定啮齿动物饮食、照明波长和发射范围对背景荧光和造影剂 SBR 的影响，以协助未来成像研究的实验设计。

方法：在使用 670、760 或 808nm 照明后，使用近红外-I（）、近红外-II（）和近红外-II LP（）区域的自发荧光在食用标准饮食或纯化饮食的小鼠中进行评估，使用 IR VIVO 临床前成像仪（Photon，Etc.）。比较不同成像条件下肝脏定位吲哚菁绿的 SBR，表明肠道自发荧光是一个有问题的混杂因素。

结果：当用 670nm 光进行近红外-I 成像（700 至 975nm）时，喂食标准饮食的小鼠在胃肠道中表现出高水平的背景自发荧光，在皮肤中也有较低程度的背景自发荧光，干扰了荧光标记组织的识别。通过以下任何一种变化都可以将背景自发荧光降低两个数量级以上：（1）纯化饮食；（2）用 760 或 808nm 照明激发；或（3）在近红外-II（1000 至 1600nm 或 1250 至 1600nm）中发射。尽管 SBR 通常足以进行特征识别，除非用 670nm 激发和近红外-I 发射对喂食标准饮食的小鼠进行成像，但是切换到纯化饮食、使用较长的激发波长或使用较长的发射波长会显著提高 SBR。

结论：对成像条件和饮食的系统比较突出了通过实验参数的有意选择（包括饮食、激发波长和发射波长范围）降低自发荧光和提高 SBR 的能力。