Quantitative evaluation of enhanced laser tattoo removal by skin optical clearing

Lasers have been widely used for tattoo removal,but the limited light penetration depth calused by high skin scattering property restricts the therapeutic outcome of deep tattoo.Skin optical clearing method,by introducing optical clearing agent(OCA)into skin,has shown some im-provement in the effect of laser tattoo removal.In this study,the enhanced laser tattoo removal has been quantitatively assessed.OCA was applied to the skin of tattoo animal model and Q switched Nd:YAG laser(1064 nm)irradiation was used to remove the tattoo.The skin evaluation instrument(Mexameter probe,MPA580)was applied to measure the content of tattoo pigment before and after laser treatment,and then the clearance rate of pigment was calculated.Further,Monte Carlo(MC)method was utilized to simulate the efecet of skin optical clearing on light transmission in tattoo skin model.By comparing the pigment change of tattoo areas respectively treated with OCA plus laser and single laser,it was found that pigment clearance of the former tattoo area was increased by 1.5-fold.Further,the MC simulation verifed that the reduced light scattering in skin could increase the effective dose of lumninous fux reaching to the deep tattoo regions.It can be concluded from both experiment and theoretical simulations that skin optical clearing technique could improve the outcome of laser tattoo re moval,which should be beneficial for clinical laser tattoo removal and other laser pigment elimination.

Assessing low-light cameras with photon transfer curve method

Low-light camera is an indispensable component in various°uorescence microscopy techniques.However,choosing an appropriate low-light camera for a speci¯c technique(for example,single molecule imaging)is always time-consuming and sometimes confusing,especially after the commercialization of a new type of camera called sCMOS camera,which is now receiving heavy demands and high praise from both academic and industrial users.In this tutorial,we try to provide a guide on how to fully access the performance of low-light cameras using a well-developed method called photon transfer curve(PTC).We¯rst present a brief explanation on the key parameters for characterizing low-light cameras,then explain the experimental procedures on how to measure PTC.We also show the application of the PTC method in experimentally quantifying the performance of two representative low-light cameras.Finally,we extend the PTC method to provide o®set map,read noise map,and gain map of individual pixels inside a camera.

QUANTIFYING THE SHORT LIFETIME WITH TCSPC-FLIM:FIRST MOMENT VERSUS FITTING METHODS

Combing the time corelated single photon counting(TCSPC)with fuorescence lifetime imaging microscopy(FLIM)provides promising opportunities in revealing important information on the microenvironment of cells and tissues,but the applications are thus far mainly limited by the accuracy and precision of the TCSPC-FLIM technique.Here we present a comprehensive in-vestigation on the perforance of two data analysis methods,the first moment(M_(1))method and the conventional least squares(Fitting)method,in quantifying fuorescence lifetime.We found that the Mp method is more superior than the Fitting method when the lifetime is short(70-400ps)or the signal intensity is weak(<10^(3) photons).