FMT Imaging Proves Accurate and Sensitive in Deep Tissue Regions

Fluorescence-reflectance imaging and hybrid fluorescence-mediated tomography (Source: F. Gremse et al. / Wiley).

Fluorescence-mediated tomography (FMT) is a promising imaging technology which allows three-dimensional assessment of the fluorescence distribution. FMT can be combined with an anatomical modality, a micro-computed tomography such as µCT, which enables more accurate and user-independent analysis because the µCT makes the images easier to interpret particularly for deep locations. Although FMT application is currently limited to rodents or parts of the human body such as hands and breasts, it already proved itself to be a very interesting and promising technique.

Scientists from the Institute for Experimental Molecular Imaging (ExMI) in Aachen, Germany recently performed a study to assess sensitivity and accuracy of µCT-FMT under realistic in vivo conditions in deeply-seated regions. “Our protocol, including imaging and analysis, is simple and reproducible” says Stefanie Rosenhain of ExMI. Due to the complex tissue properties and the presence of motion, an in vivo protocol is important for realistic assessment of sensitivity and accuracy, so her team used commercially available devices and a commercially available probe (OsteoSense) for their experiments to enhance the reproducibility for other research sites.

They acquired fluorescence reflectance images (FRI) and µCT-FMT scans of mice which were prepared with rectal insertions with different amounts of fluorescent dye. Default and high-sensitivity scans were acquired and the background signal was analyzed for three FMT channels (670 nm, 745 nm, and 790 nm). Analysis was performed for the original and an improved FMT reconstruction using the µCT data. While FRI and the original FMT reconstruction could detect 100 pmol, the improved FMT reconstruction could detect 10 pmol and significantly improved signal localization. By using a finer sampling grid and increasing the exposure time, the sensitivity could be further improved to detect 0.5 pmol.

With these results it was demonstrated that µCT-FMT is a highly sensitive, non-invasive procedure that provides accurate information in deep-tissue regions and thus appears to be suitable for imaging structures of the gastrointestinal tract. It might be used in preclinical imaging studies on colon cancer and inflammatory bowel diseases. The established protocol the team set up is helpful to assess sensitivity and accuracy for evaluating future improvements of the fluorescence reconstruction. Rosenhain and her team hope that a better understanding of the sensitivity and signal localization will help with planning and conducting future preclinical experiments using this interesting imaging technology. (Source: ExMI)

Reference: S. Rosenhain et al.: Sensitivity and accuracy of hybrid fluorescence-mediated tomography in deep tissue regions, J. Biophotonics 10 (9), online 21 November 2017; DOI: 10.1002/jbio.201600232

Link: The Institute for Experimental Molecular Imaging (ExMI), Aachen, Germany


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