Noninvasive blood flow imaging for feedback during laser therapy of port wine stain birthmarks

A port wine stain (PWS) is a congenital disease characterized by progressive vascular malformations. With laser therapy, a reduction in size and degree of redness of PWS skin occurs in ∼60% of patients. After ten treatment sessions, complete disappearance of the PWS occurs in only ∼10% of patients.;The objective of my dissertation research was to determine the acute vascular response to laser therapy. During laser therapy of port wine stain (PWS) birthmarks, we postulate that regions of persistent perfusion exist. Furthermore, we hypothesize that such regions, which are not readily visible, exist even during laser surgery performed by highly experienced clinicians. We anticipate that the presence of such regions correlates with a poor treatment outcome.;To achieve the objective, we developed a clinic-friendly laser speckle imaging (LSI) instrument to provide the clinician with real-time images of blood flow during laser therapy. We acquired images from patients undergoing laser therapy of PWS birthmarks at Scripps Clinic (San Diego, CA) and Beckman Laser Institute and Medical Clinic. We extracted blood flow maps from the acquired imaging data. Collectively, we have observed two regimes of patient response to therapy: (1) an immediate increase in perfusion within minutes after laser therapy; and (2) an overall decrease in blood perfusion approximately one hour after laser therapy, with distinct regions of persistent perfusion apparent in the majority of post-treatment blood-flow images. We used numerical and experimental approaches to characterize the depth sensitivity of our LSI instrument, which was found to be approximately 0.5 mm using a 633 nm wavelength laser. This data validate the approach of using LSI to acquire images from PWS birthmarks and demonstrate that our LSI instrument is capable of imaging the degree of photocoagulation achieved with laser therapy.