“…Developed in its modern form by Dougherty in the 1970's [17], PDT is currently clinically employed in dermatology (e.g., for actinic keratinosis), ophthalmology (e.g., for age-related macular degeneration) or oncology (e.g., for skin, retina, bladder, gastronintestinal, prostate, lung, head and neck cancers). However, as reported by Zhang et al in a recent review [18], clinical development of PDT remains somewhat limited because of various challenges, ranging from photosensitizer formulation, light dosimetry, to planning and monitoring the treatment [15,[18][19][20][21][22]. Some of these points have been recently reviewed: ideal photosensitizers [23], challenges in formulating photosensitizers, and choosing the right light dosimetry [24], as well as monitoring the treatment response [25].…”