The selection of well-vascularized tissue during DIEP flap harvest remains controversial. While several studies have elucidated cross-midline perfusion, further characterization of perfusion to the ipsilateral hemiabdomen is necessary for minimizing rates of fat necrosis or partial fat necrosis in bilateral DIEP flaps. Eighteen patients (29 flaps) underwent DIEP flap harvest using a prospectively designed protocol. Perforators were marked and imaged with a novel system for quantitatively measuring tissue oxygenation, the Digital Light Hyperspectral Imager. Images were then analyzed to determine if perforator selection influenced ipsilateral flap perfusion. Flaps based on a single lateral row perforator (SLRP) were found to have a higher level of hemoglobin oxygenation in Zone I (mean %HbO2 = 76.1) compared to single medial row perforator (SMRP) flaps (%HbO2 = 71.6). Perfusion of Zone III relative to Zone I was similar between SLRP and SMRP flaps (97.4% vs. 97.9%, respectively). These differences were not statistically significant (p>0.05). Perfusion to the lateral edge of the flap was slightly greater for SLRP flaps compared SMRP flaps (92.1% vs. 89.5%, respectively). SMRP flaps had superior perfusion travelling inferiorly compared to SLRP flaps (88.8% vs. 83.9%, respectively). Overall, it was observed that flaps were better perfused in the lateral direction than inferiorly. Significant differences in perfusion gradients directed inferiorly or laterally were observed, and perforator selection influenced perfusion in the most distal or inferior aspects of the flap. This suggests broader clinical implications for flap design that merit further investigation.
Visible DLP® hyperspectral reflectance imaging in medical applications is limited by the lack of penetration of visible
light for visualization of deeper vessels and tissues. The longer, near infrared (NIR) wavelengths, capable of facilitating
chromophore and fluorophore visualization, penetrate deeper allowing visualization of anatomical structures in surgical
settings. Digital micromirror device (DMD) chips allow for digital programming of complex spectral illuminations with
bandwidths as low as 7nm. Furthermore, fluorescence can be maximized by programming the DMD chip to illuminate
with light precisely configured to contain excitation spectra. We have developed a "mid-range" system that extends from
the visible light range into the NIR (525nm - 1050nm) and has been characterized and configured for fluorescence of
indocyanine green (ICG). The DMD-based light source was found to be within the manufacturer's spectral specifications
and proved to be very versatile in both spectral behavior and application. Fluorescence of ICG was successfully
optimized by this system and demonstrated in capillary tubes and excised tissue.