Gorbach Alexander M, Wang Hengliang, Dhanani Nadeem N, Gage Fred A, Pinto Peter A, Smith Paul D, Kirk Allan D, Elster Eric A
Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, USA.
J Surg Res. 2008 Oct;149(2):310-8. doi: 10.1016/j.jss.2008.02.007. Epub 2008 Mar 13.
Currently visual and tactile clues such as color, mottling, and tissue turgor are used in the operating room for subjective assessments of organ ischemia. Studies have demonstrated that infrared (IR) imaging is a reliable tool to identify perfusion of brain tumors and kidneys during human surgery. Intraoperative IR imaging has the potential for more objective real-time detection and quantitative assessment of organ viability including early ischemia. We hypothesize, by detecting variations of the IR signal, we can assess the degree to which renal surface temperature reflects underlying renal ischemia. To address this hypothesis, IR imaging-derived temperature fluctuations were evaluated during laparotomy in a porcine model (n = 15). These temperature profiles then underwent spectral (frequency) analysis to assess their relationship to well-described oscillations of the microcirculation.
An IR camera was positioned 30-60 cm above the exposed kidneys. Images (3-5 mum wavelength) were collected (1.0/s) at baseline, during warm renal ischemia, and during reperfusion. Dominant frequency (DF) of the tissue temperature fluctuations were determined by a Fourier transformation (spectral) analysis.
IR images immediately showed which segments of the kidney were ischemic. DF at approximately 0.008 Hz that corresponds to blood flow oscillations was observed in thermal profiles. The oscillations were diminished or disappeared after 25 min of warm ischemia and were recovered with reperfusion in a time-dependent fashion. Oscillations were attenuated substantially in ischemic segments, but not in perfused segments of the kidney.
The described oscillations can be measured noninvasively using IR imaging in the operating room, as represented by the DF, and may be an early marker of critical renal ischemia.
目前，在手术室中，颜色、斑纹和组织弹性等视觉和触觉线索被用于对器官缺血进行主观评估。研究表明，红外（IR）成像在人体手术期间是识别脑肿瘤和肾脏灌注情况的可靠工具。术中红外成像有可能对包括早期缺血在内的器官活力进行更客观的实时检测和定量评估。我们假设，通过检测红外信号的变化，可以评估肾表面温度反映潜在肾缺血的程度。为了验证这一假设，在猪模型（n = 15）的剖腹手术过程中评估了红外成像得出的温度波动情况。然后对这些温度曲线进行频谱（频率）分析，以评估它们与已充分描述的微循环振荡之间的关系。
将一台红外摄像机放置在暴露的肾脏上方30 - 60厘米处。在基线、肾热缺血期间和再灌注期间，以1.0/秒的频率收集图像（波长3 - 5微米）。通过傅里叶变换（频谱）分析确定组织温度波动的主导频率（DF）。
红外图像立即显示出肾脏的哪些节段发生了缺血。在热曲线中观察到对应于血流振荡的约0.008赫兹的主导频率。在热缺血25分钟后，振荡减弱或消失，并在再灌注过程中随时间恢复。振荡在肾脏的缺血节段显著减弱，但在灌注节段未减弱。
如主导频率所示，在手术室中使用红外成像可以无创地测量上述振荡，其可能是严重肾缺血的早期标志物。
