Department of Surgery, Leiden University Medical Center, Leiden, The Netherlands.
Department of Surgical Gastroenterology, Copenhagen University Hospital, Copenhagen, Denmark.
J Endovasc Ther. 2023 Jun;30(3):364-371. doi: 10.1177/15266028221081085. Epub 2022 Mar 3.
Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) is gaining popularity for the quantification of tissue perfusion, including foot perfusion in patients with lower extremity arterial disease (LEAD). However, the absolute fluorescence intensity is influenced by patient-and system-related factors limiting reliable and valid quantification. To enhance the quality of quantitative perfusion assessment using ICG NIR fluorescence imaging, normalization of the measured time-intensity curves seems useful.
In this cohort study, the effect of normalization on 2 aspects of ICG NIR fluorescence imaging in assessment of foot perfusion was measured: the repeatability and the region selection. Following intravenous administration of ICG, the NIR fluorescence intensity in both feet was recorded for 10 mins using the Quest Spectrum platform. The effect of normalization on repeatability was measured in the nontreated foot in patients undergoing unilateral revascularization preprocedural and postprocedural (repeatability group). The effect of normalization on region selection was performed in patients without LEAD (region selection group). Absolute and normalized time-intensity curves were compared.
Successful ICG NIR fluorescence imaging was performed in 54 patients (repeatability group, n = 38; region selection group, n = 16). For the repeatability group, normalization of the time-intensity curves displayed a comparable inflow pattern for repeated measurements. For the region selection group, the maximum fluorescence intensity (Imax) demonstrated significant differences between the 3 measured regions of the foot ( = .002). Following normalization, the time-intensity curves in both feet were comparable for all 3 regions.
This study shows the effect of normalization of time-intensity curves on both the repeatability and region selection in ICG NIR fluorescence imaging. The significant difference between absolute parameters in various regions of the foot demonstrates the limitation of absolute intensity in interpreting tissue perfusion. Therefore, normalization and standardization of camera settings are essential steps toward reliable and valid quantification of tissue perfusion using ICG NIR fluorescence imaging.
近红外（NIR）荧光成像是利用吲哚菁绿（ICG）来定量组织灌注，包括下肢动脉疾病（LEAD）患者的足部灌注。然而，绝对荧光强度受患者和系统相关因素的影响，限制了可靠和有效的定量。为了提高使用 ICG NIR 荧光成像进行定量灌注评估的质量，对测量的时间-强度曲线进行归一化似乎很有用。
在这项队列研究中，我们测量了 ICG NIR 荧光成像在评估足部灌注中的 2 个方面的归一化效果：重复性和区域选择。在静脉注射 ICG 后，使用 Quest Spectrum 平台在双脚上记录 10 分钟的 NIR 荧光强度。在术前和术后单侧血运重建的患者的未治疗脚上测量归一化对重复性的影响（重复性组）。在没有 LEAD 的患者中进行归一化对区域选择的影响（区域选择组）。比较绝对和归一化的时间-强度曲线。
54 例患者成功进行了 ICG NIR 荧光成像（重复性组，n = 38；区域选择组，n = 16）。对于重复性组，时间-强度曲线的归一化显示了重复测量的相似流入模式。对于区域选择组，足部 3 个测量区域的最大荧光强度（Imax）显示出显著差异（P <.002）。归一化后，双脚的时间-强度曲线在所有 3 个区域都具有可比性。
本研究表明，时间-强度曲线的归一化对 ICG NIR 荧光成像的重复性和区域选择都有影响。足部各个区域的绝对参数之间的显著差异表明，绝对强度在解释组织灌注方面存在局限性。因此，对相机设置进行归一化和标准化是使用 ICG NIR 荧光成像进行可靠和有效的组织灌注定量的必要步骤。
