Initial experience of perfusion assessment in a rabbit model of orthopaedic trauma surgery using fluorescent microspheres and hyperspectral imaging cryomacrotome

Timely assessment of bone perfusion in orthopaedic trauma surgery plays an important role in successful treatment outcome. For guiding accurate debridement of bones with impaired blood supply, fluorescence-guided surgery (FGS) technique have gained increasingly popularity. Compared to other imaging modalities like computed tomography and nuclear magnetic resonance imaging that are time consuming and less practical during surgery, fluorescence imaging can be performed intraoperatively and is able to visualize the bone blood flow in real time. In order to link the blood flow fluorescence imaging to quantitative bone perfusion numbers, in this study we are using a modified fluorescent microsphere (FM) approach called microsphere quantification using imaging cryomacrotome (mQUIC). Bone perfusion is assessed by identifying the density of deposited microspheres in reconstructed imaging volumes, which are proportional to the regional blood flow. In the rabbit model presented here, cryoimaging was used to scan femurs injected with three colors of microspheres corresponding to three conditions: baseline, post-osteotomy and post-periosteal stripping. Image processing, such as top-hat transform and object-based colocalization, was used to enable accurate counting of FMs to produce their 3D-localization within the bones. FM density volumes were converted to bone perfusion units (mL/min/100g) using the reference organ technique. This study provides a groundwork for direct comparison with our DCE-FI technique for measuring bone perfusion in orthopaedic trauma surgery models.