Evaluation of photothermal tomography for imaging the microvasculature of human skin

Photothermal tomography (PTT) can provide volumetric images of chromophore heating. To evaluate the accuracy of PTT for blood vessel imaging, we used a computational model to simulate an object vessel at various depths and calculate resultant infrared emission frame sequences after pulsed laser excitation. We then applied an inversion algorithm to obtain three-dimensional PTT images, which were then compared with the respective modeled objects. We found that PTT can determine accurately vessel depth, but lateral and longitudinal spatial resolution degrade considerably with increasing depth. To improve the performance of PTT, we propose a simple technique to estimate the actual vessel diameter using an empirically determined, depth resolved linespread function.