Postoperative Quantitative Assessment of Reconstructive Tissue Status in a Cutaneous Flap Model Using Spatial Frequency Domain Imaging

Abstract

Background The purpose of this study is to investigate the capabilities of a novel optical wide-field imaging technology known as Spatial Frequency Domain Imaging (SFDI) to quantitatively assess reconstructive tissue status. Methods Twenty two cutaneous pedicle flaps were created on eleven rats based on the inferior epigastric vessels. After baseline measurement, all flaps underwent vascular ischemia, induced by clamping the supporting vessels for two hours (either arterio-venous or selective venous occlusions) normal saline was injected to the control flap, and hypertonic hyperoncotic saline solution to the experimental flap. Flaps were monitored for two hours after reperfusion. The SFDI system was used for quantitative assessment of flap status over the duration of the experiment. Results All flaps demonstrated a significant decline in oxy-hemoglobin and tissue oxygen saturation in response to occlusion. Total hemoglobin and deoxy-hemoglobin were markedly increased in the selective venous occlusion group. After reperfusion and the solutions were administered, oxy-hemoglobin and tissue oxygen saturation in those flaps that survived gradually returned to the baseline levels. However, flaps for which oxy-hemoglobin and tissue oxygen saturation didn’t show any signs of recovery appeared to be compromised and eventually became necrotic within 24–48 hours in both occlusion groups. Conclusion SFDI technology provides a quantitative, objective method to assess tissue status. This study demonstrates the potential of this optical technology to assess tissue perfusion in a very precise and quantitative way, enabling wide-field visualization of physiological parameters. The results of this study suggest that SFDI may provide a means for prospectively identifying dysfunctional flaps well in advance of failure.

Diffuse optical imaging using spatially and temporally modulated light

“…111,112 In one study, bilateral groin skin flaps with a separate but singular vascular supply based on the inferior epigastric vessels were created. 111 An external clamp for inducing an occlusion in addition to a cannula inserted into the femoral artery provided the ability to control flap perfusion. A clamp was placed for 2 h to induce either a venous or arterio-venous occlusion, after which hypertonic hyperoncotic saline solution was administered to induce necrosis.…”

Noncontact imaging of burn depth and extent in a porcine model using spatial frequency domain imaging

“…Moreover, SFDI can spatially resolve these properties with modest resolution (<1 mm) over large fields of view (>10 s of cm), allowing for the visualization of the lateral extent of a wound. SFDI has been demonstrated in several applications including skin flaps, [25][26][27] port-wine stains, 28 and cancer. 29 In the area of burns, SFDI has been demonstrated to track acute changes in tissue chromophores for different burn severities 30 and to identify the onset of infection due to burn injury.…”

Visible spatial frequency domain imaging with a digital light microprojector

“…Further filtering of the remitted light with either a series of bandpass filters or with a liquid-crystal tunable filter allows unique spectra of μ a and μ 0 s to be found in different tissue types. 1,2 Recent applications of SFDI to skin imaging include in vivo monitoring of burn wounds, 3,4 determining flap perfusion during surgical procedures, 5,6 and assessing cutaneous vascular abnormalities. 7 SFDI has also been used for characterizing brain in small animal models of stroke, 8 glioblastoma, 9 and Alzheimer's disease.…”