Port wine stain (PWS) birthmarks are one class of benign congenital vascular malformation. Laser therapy is the most successful treatment modality of PWS. Unfortunately, this approach has limited efficacy, with only 10% of patients experiencing complete blanching of the PWS. To address this problem, several research groups have developed technologies and methods designed to study treatment outcome and improve treatment efficacy. This paper reviews seven optical imaging techniques currently in use or under development to assess treatment efficacy, focusing on: Reflectance spectrophotometers/tristimulus colorimeters, Laser Doppler flowmetry (LDF) and Laser Doppler imaging (LDI), Cross-polarized diffuse reflectance color imaging system (CDR), Reflectance Confocal Microscopy (RCM), Optical Coherence Tomography (OCT), Spatial Frequency Domain Imaging (SFDI), and Laser Speckle Imaging (LSI).
The use of tissue transfer flaps has become a common and effective technique for reconstructing
or replacing damaged tissue. While the overall failure rate associated with these procedures is
relatively low (5-10%), the failure rate of tissue flaps that require additional surgery is
significantly higher (40-60%). The reason for this is largely due to the absence of a technique for
objectively assessing tissue health after surgery. Here we have investigated spatial frequency
domain imaging (SFDI) as a potential tool to do this. By projecting wide-field patterned
illumination at multiple wavelengths onto a tissue surface, SFDI is able to quantify absolute
concentrations of oxygenated and deoxygenated hemoglobin over a large field of view. We have
assessed the sensitivity of SFDI in a swine pedicle flap model by using a controlled vascular
occlusion system that reduced blood flow by 25%, 50%, 75%, or 100% of the baseline values in either
the vein or artery. SFDI was able to detect significant changes for oxygenated hemoglobin,
deoxygenated hemoglobin, or tissue oxygen saturation in partial arterial occlusions of at least 50%
and partial venous occlusions of at least 25%. This shows SFDI is sensitive enough to quantify
changes in the tissue hemoglobin state during partial occlusions and thus has the potential to be a
powerful tool for the early prediction of tissue flap failure.
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