Quantitative perfusion assessment using indocyanine green during surgery - current applications and recommendations for future use.

PURPOSE: Incorrect assessment of tissue perfusion carries a significant risk of complications in surgery. The use of near-infrared (NIR) fluorescence imaging with Indocyanine Green (ICG) presents a possible solution. However, only through quantification of the fluorescence signal can an objective and reproducible evaluation of tissue perfusion be obtained. This narrative review aims to provide an overview of the available quantification methods for perfusion assessment using ICG NIR fluorescence imaging and to present an overview of current clinically utilized software implementations. METHODS: PubMed was searched for clinical studies on the quantification of ICG NIR fluorescence imaging to assess tissue perfusion. Data on the utilized camera systems and performed methods of quantification were collected. RESULTS: Eleven software programs for quantifying tissue perfusion using ICG NIR fluorescence imaging were identified. Five of the 11 programs have been described in three or more clinical studies, including Flow® 800, ROIs Software, IC Calc, SPY-Q™, and the Quest Research Framework®. In addition, applying normalization to fluorescence intensity analysis was described for two software programs. CONCLUSION: Several systems or software solutions provide a quantification of ICG fluorescence; however, intraoperative applications are scarce and quantification methods vary abundantly. In the widespread search for reliable quantification of perfusion with ICG NIR fluorescence imaging, standardization of quantification methods and data acquisition is essential.

Quantification of near-infrared fluorescence imaging with indocyanine green in free flap breast reconstruction.

BACKGROUND: One of the complications of free flap breast reconstruction is the occurrence of skin and fat necrosis. Intra-operative use of near-infrared (NIR) fluorescence imaging with Indocyanine Green (ICG) has the potential to predict these complications. In this study, the quantification of the fluorescence intensity measured in free flap breast reconstruction was performed to gain insight into the perfusion patterns observed with ICG NIR fluorescence imaging. METHODS: ICG NIR fluorescence imaging was performed in patients undergoing free flap breast reconstruction following mastectomy. After completion of the arterial and venous anastomosis, 7.5 mg ICG was administered intravenously. The fluorescence intensity over time was recorded using the Quest Spectrum Platform®. Four regions of interest (ROI) were selected based on location and interpretation of the NIR fluorescence signal: (1) The perforator, (2) normal perfusion, (3) questionable perfusion, and (4) low perfusion. Time-intensity curves were analyzed, and two parameters were extracted: Tmax and Tmax slopes. RESULTS: Successful ICG NIR fluorescence imaging was performed in 13 patients undergoing 17 free flap procedures. Region selection included 16 perforators, 17 normal perfusions, 8 questionable perfusions, and 5 low perfusion ROIs. Time-intensity curves of the perforator ROIs were comparable to the ROIs of normal perfusion and demonstrated a fast inflow. No outflow was observed for the ROIs with questionable and low perfusion. CONCLUSION: This study provides insight into the perfusion patterns observed with ICG NIR fluorescence imaging in free flap breast reconstruction. Future studies should correlate quantitative parameters with clinical perfusion assessment and outcome.

Enzyme histochemistry on muscle biopsies as an aid in the diagnosis of diseases of the equine neuromuscular system: a study of six cases.

Muscle biopsies from six horses with clinical histories of muscle atrophy, muscle tremors, myopathic symptoms, unsteadiness of pelvic limbs and progressive ataxia were examined. Muscle biopsies were studied with enzyme histochemical techniques to evaluate the diagnostic values of these methods in cases suspected of suffering from neuromuscular disorders. Hypertrophy, atrophy, fibre splitting, waxy degeneration, phagocytosis and necrosis were seen in haematoxylin eosin stained sections of the different cases. Fibre type predominance and fibre type grouping were seen in the calcium ion stimulated myosine ATP-ase (Ca-ATP-ase) stained sections of some cases. 'Moth-eaten fibres' were demonstrated in three cases by staining with NADH: nitro blue tetrazolium oxidoreductase (NADH-TR), succinate dehydrogenase (SDH), NADH dependent malate dehydrogenase, cytochrome c oxidase and by lactate dehydrogenase. The catabolic enzymes, acid phosphatase (ACP) and 5'-nucleotidase were active in cases with fibre phagocytosis. The oxidative part of the pentose phosphate pathway in myopathic tissue seemed to be important in three cases, demonstrated by the increased activity of glucose-6-phosphate dehydrogenase (GPDH) and 6-phosphogluconate dehydrogenase (PGDH). The important feature of diseased horse muscle was that the pathohistochemical changes were exactly the same as in diseased skeletal muscles of humans. The application of tissue saving enzyme histochemical techniques can be recommended in the study of muscle tissue from horses suffering from suspected neuromuscular disorders.