Selective Photothermolysis
Pronunciation: foh-toh-THER-moh-LY-sis
The theoretical principle underpinning laser and light-based treatments, whereby specific chromophores in the skin are targeted by a laser wavelength that they absorb preferentially, generating heat that destroys the target while sparing surrounding tissue.
Full Definition
Proposed by Anderson and Parrish in 1983, selective photothermolysis rests on three conditions: the wavelength used must be preferentially absorbed by the target chromophore (e.g., melanin, oxyhaemoglobin, water); the pulse duration must be shorter than or equal to the thermal relaxation time of the target; and the fluence (energy density) must be sufficient to achieve therapeutic injury. The principle explains why different wavelengths are used for different targets—585 nm for vascular lesions, 755 nm for hair with dark melanin, 2,940 nm for water in ablative resurfacing. In editorial contexts, the term should never be abbreviated to 'SPhT' or similar; it should be written in full or referred to as the 'principle of selective photothermolysis'. Editors reviewing scientific papers on laser dermatology must recognise this as a foundational concept and flag any inaccurate summary of its conditions.
Usage
Usage note: Do not abbreviate. Distinguish from photodynamic therapy (PDT), which involves a photosensitising agent and is not based on the same chromophore-targeting principle.
In Context
- "The introduction incorrectly stated that selective photothermolysis requires only wavelength matching; the editor queried this, noting the pulse duration criterion was omitted." — Peer-reviewed journal manuscript
- "A sound understanding of selective photothermolysis is essential for editing laser parameter tables in clinical protocols." — Clinical laser protocol