The present chapter summarizes progress with optical methods that go beyond human vision. The focus is on two particular technologies: fluorescence molecular imaging and optoacoustic (photoacoustic) imaging. The rationale for the selection of these two methods is that in contrast to optical microscopy techniques, both fluorescence and optoacoustic imaging can achieve large fields of view, i.e., spanning several centimeters in two or three dimensions. Such fields of views relate better to human vision and can visualize large parts of tissue, a necessary premise for clinical detection. Conversely, optical microscopy methods only scan millimeter-sized dimensions or smaller. With such operational capacity, optical microscopy methods need to be guided by another visualization technique in order to scan a very specific area in tissue and typically only provide superficial measurements, i.e., information from depths that are of the order of 0.05-1 mm. This practice has generally limited their clinical applicability to some niche applications, such as optical coherence tomography of the retina. On the other hand, fluorescence molecular imaging and optoacoustic imaging emerge as more global optical imaging methods with wide applications in surgery, endoscopy, and non-invasive clinical imaging, as summarized in the following. The current progress in this field is based on a volume of recent review and other literature that highlights key advances achieved in technology and biomedical applications. Context and figures from references from the authors of this chapter have been used here, as it reflects our general view of the current status of the field.
Keywords: Biophotonics; Fluorescence imaging; Intraoperative imaging; Multispectral optoacoustic tomography; Optical imaging; Photoacoustic imaging; Surgical navigation.