Real-time photothermal imaging and response in pulsed dye laser treatment for port wine stain patients.

BACKGROUND: This study was performed to assess the photothermal response of highly focused laser energy using infrared thermal imaging instrument to detect and assess the actual temperature distribution during flash lamp pumped pulsed dye laser (FLPPDL) treatment for port wine stain (PWS) patients and avoiding its complications. METHODS: A retrospective review of 40 patients with PWS birthmark treated with FLPPDL (l = 585 nm, tp = 1500 ms, 7 mm spot) was conducted over a 2-year period. Subjects' ages ranged between 28 and 46 years (mean 29 years); there were 24 females and 16 males. Twenty patients received non-cooling laser treatment (NC-LT) using light dosages of 5-12 J/cm 2 . Another 20 patients received cryogen spray cooling laser treatment (CSC-LT) using light dosages of 5-12 J/cm 2 . A real-time infrared thermal imaging and the thermal wave equation were used for assessment. The results of temperature distributions related to the energy change were analyzed. RESULTS: Proper temperature measurement using infrared thermal imaging instrument and thermal wave equation in non-cooled PWS patients showed that the energy density of pulsed dye laser (PDL) higher than 7 J/cm 2 can reach >44°C and result in burn injury. However, when energy densities beyond 10 J/cm 2 were administered, along with using CSC, thermal damage was could still be minimized without the risk of damage to the treated area. CONCLUSION: Using infrared thermal imaging instrument and thermal wave equation, we can predict the skin temperature distribution in FLPPDL for PWS patients during the treatment. In conjunction with CSC, the complications can be minimized.

High-resolution optical Doppler tomography for in vitro and in vivo fluid flow dynamics.

BACKGROUND: The objective of our research was to use a noninvasive tomographic imaging technique with high spatial resolution (2-15 microm) to characterize and monitor fluid flow and the microvasculature in highly scattering biological tissues at user-specified discrete locations. METHODS: The technique of optical Doppler tomography (ODT) combines laser Doppler flowmetry (LDF) with optical coherence tomography to obtain high-resolution tomographic velocity and structural images of static and moving constituents in highly scattering biological tissues. We present ODT structural and velocity images using in vitro turbid samples of a circular conduit infused with a suspension of polymer microspheres. At a thin rectangular cross-section of the conduit, the Intralipid flow was measured. Blood flow velocity was measured in vivo in the ear of rodent skin. RESULTS: In first model, the ODT velocity images demonstrated beads near the center of the conduit moving faster than those near the circular wall. In the second model, the ODT velocity images indicated that laminar flow was fastest along the central axis of the conduit. Blood flow in 2 small veins with diameters of 70 and 40 microm, respectively, and an artery with diameter of 25 microm, was clearly identified in a rodent model. CONCLUSION: In our preliminary in vitro and in vivo studies on turbid samples and model vasculatures, we determined that the application of ODT to characterize and image blood flow with high spatial resolution at discrete user-specified locations in highly scattering biological tissues is feasible.