Non-invasive imaging techniques allow a quick and easy in vivo examination of the skin with different penetration depths and resolution depending on the applied technology. Established methods such as dermoscopy and high-resolution sonography of the skin have been an integral part of everyday life for decades. Additionally, new emerging techniques such as optical coherence tomography (OCT), reflectance confocal microscopy (RCM), and line-field confocal OCT (LC-OCT) have entered clinical practice. Multiphoton tomography and optoacoustic imaging are also considered promising new methods. RCM and LC-OCT can also be used ex vivo on freshly excised tissue, for example in Moh's surgery margin assessment. The data generated by all imaging methods is ideal for the application of AI-based algorithms to increase diagnostic accuracy and support experienced users. All mentioned methods have preferred indications depending on their strengths and limitations, both in skin tumor diagnostics and in inflammatory, infectious and parasitic dermatoses. The following guideline provides an overview of the various devices and techniques, explains how each method works and provides the current study situation with indications and limitations of each procedure.
