The importance of long-term monitoring to evaluate the microvascular response to light-based therapies.

NIH Public Access Author Manuscript J Invest Dermatol. Author manuscript; available in PMC 2012 November 09. Published in final edited form as: J Invest Dermatol. 2008 February ; 128(2): 485–488. doi:10.1038/sj.jid.5700991. The Importance of Long-Term Monitoring to Evaluate the Microvascular Response to Light-Based Therapies $watermark-text Bernard Choi 1,2 , Wangcun Jia 1 , Jennifer Channual 1 , Kristen M. Kelly 1,3 , and Justin Lotfi 1 Bernard Choi: choib@uci.edu 1 Beckman Laser Institute and Medical Clinic, University of California, Irvine, California, USA 2 Department of Biomedical Engineering, University of California, Irvine, California, USA 3 Department of Dermatology, University of California, Irvine, California, USA TO THE EDITOR $watermark-text Optimization of laser therapy for disfiguring vascular birthmarks is one specific clinical application (Kelly et al ., 2005). Current treatment protocols involve the use of high-power pulsed laser irradiation with parameters chosen to induce selective photocoagulation of the targeted blood vessels, a method known as selective photothermolysis (Anderson and Parrish, 1983). Protocol design is based largely on results from numerical modeling studies (van Gemert et al ., 1997), which are designed to predict the laser light distribution within the skin and subsequent photothermal response leading toward selective photocoagulation. However, current modeling methods do not incorporate adequately the complex dynamics associated with changes in light absorption due to conversion of hemoglobin to methemoglobin (Barton et al ., 2001; Kimel et al ., 2005) and convective mixing of blood during pulsed laser irradiation (Kimel et al ., 2003), limiting their overall predictive capability. Furthermore, these models do not consider the chronic, biological response of the microvasculature to therapeutic laser intervention, which remains a poorly researched field. Knowledge of the biological response is critical to understand the repair processes initiated with photothermal injury and to assess the ultimate efficacy of the treatment. $watermark-text Animal models used as a platform to study light-based, microvascular-targeted therapies include the chick chorioallantoic membrane (Kimel et al ., 1994, 2003), hamster cheek pouch (Suthamjariya et al ., 2004), and rodent dorsal window chamber (Barton et al ., 1998, 1999, 2001; Choi et al ., 2004; Babilas et al ., 2005; Smith et al ., 2006). Optical imaging modalities used to evaluate noninvasively therapeutic outcome include video imaging, fluorescence microscopy, Doppler optical coherence tomography, and laser speckle imaging. Typically, short-term ( 24 hour after intervention) monitoring periods usually are not performed with nontumor-bearing window chambers, presumably due to the reduced clarity of the chamber imposed by poor maintenance of window integrity secondary to infection. However, we hypothesized that the short-term response of the microvasculature is a poor predictor of the long-term response. With emphasis on aseptic methods, we have been able to maintain clear window chamber preparations for as long as 45 days after intervention. CONFLICT OF INTEREST The authors state no conflict of interest.