1. Fundamentals of Light and Laser Technology

The way a laser interacts with tissue underpins its diagnostic value. Diagnostic lasers typically operate at low power to avoid damage while maximizing data acquisition through optical signals.

Common interaction mechanisms include:

• Elastic scattering: Light bounces off tissue without a change in energy, used in techniques like diffuse optical imaging.
• Inelastic scattering (Raman effect): Light loses or gains energy, revealing molecular composition—useful in Raman spectroscopy.
• Fluorescence: Light excites tissue molecules, which emit secondary light. This is harnessed in Laser-Induced Fluorescence (LIF) to identify abnormal metabolic activity.
• Interference: Used in Optical Coherence Tomography (OCT) to reconstruct internal structures based on reflected wave phase shifts (Barsom et al., 2016).

Understanding these interactions allows researchers and clinicians to design non-invasive diagnostic tools that can detect diseases such as cancer, macular degeneration, and cardiovascular conditions without needing to cut into tissue or extract samples.