Comparison of Multispectral Reflectance Imaging and Indocyanine Green Angiography

Background:

Intra-operative assessment of tissue viability is critical to improve outcomes of cosmetic and reconstructive procedures. A widely used objective method to predict tissue viability is intra-operative angiography. We present an alternative method that determines the relative proportions of oxyhemoglobin to deoxyhemoglobin through multispectral reflectance imaging (MSRI). This cost-effective and hand-held device does not require injectable material and may be used in the operative, inpatient or clinic setting. In initial studies, this method has been successful for wound and flap assessment.¹ In this study, we compare the accuracy of predicting flap necrosis using MSRI and indocyanine green (ICG) angiography in clinical patients and experimental animals.

 

Methods: Authors evaluated patients undergoing procedures performed by a single surgeon. All patients were evaluated intra-operatively with both SPY angiography and MSRI using Kent imaging KD203. For SPY analysis, ICG was injected intravenously and perfusion was quantified using absolute florescence values.

 

Authors also evaluated 300-400 gram male Sprague-Dawley rats undergoing reverse McFarlane skin flaps.² The flap is supplied by caudal sacral perforators and is raised to ensure a gradient of flap necrosis on the dorsum of the rat within 72 hours. Imaging with SPY angiography and MSRI were performed pre-surgery, immediately post-surgery and 30-minutes post-surgery.  Rats were then evaluated by 3 independent plastic surgeons for flap necrosis 72-hours post-surgery.

 

In both clinical and animal studies, objective data were compared to post-surgical clinical outcomes to determine which method more accurately predicted flap necrosis.

 

Results:

19 patients were included in the study. 16 patients had direct-to-implant pre-pectoral breast reconstruction, two patients had breast reductions, and one patient had lower leg reconstruction. MSRI and SPY both predicted actual necrosis in 2 patients while SPY over-predicted the extent in both. SPY predicted ischemia incorrectly in an additional 2 patients who did not develop necrosis.

 

Overall, 9 out of 11 rats survived to 72-hours post-surgery. Initial data analysis demonstrated that at a fixed 90% sensitivity for predicting necrosis immediately upon raising the flap, the 95% confidence intervals of the specificities were [76% - 85%] and [77% - 93%] for MSRI and SPY, respectively. This analysis is preliminary as it only includes one surgeon’s post-operative evaluation. However, with this analysis, it seems that while SPY is on average more specific for predicting viability compared to Kent, it shows more variability.

 

Conclusions:

In this initial assessment, MSRI was useful in detecting compromised tissue viability. With the advantages of non-invasiveness, portability, affordability and lack of disposables, MSRI has an exciting potential for widespread use in cosmetic and reconstructive procedures.

 

References

1. Payette JR, Kohlenberg E, Leonardi L, et al. Assessment of skin flaps using optically based methods for measuring blood flow and oxygenation. Plast Reconstr Surg. 2005;115(2):539-46.
2. Mcfarlane RM, Deyoung G, Henry RA. The Design of a Pedicle Flap in the Rat to Study Necrosis and its Prevention. Plast Reconstr Surg. 1965;35:177-82.