Table 1.

Summary of windows for skin and AT imaging

Technique	Key points	Complexity	Advantages	Limitations
Footpad	Intact skin. Hair removal necessary to avoid autofluorescence.	Low	• Simple to perform. • Not invasive. • Longitudinal imaging through various days. • Saves animals (consistent with 3Rs).	• Autofluorescence if hair present. • Limited vascularization and imaging area.
Ear pinna	Intact skin. Hair removal necessary to avoid autofluorescence.	Low	• Simple to perform. • Not invasive. • Longitudinal imaging through various days. • Saves animals (consistent with 3Rs).	• Autofluorescence if hair present. • Limited vascularization and imaging area. • Rich in cartilage but poor in subcutaneous adipose tissue.
Tail	Intact skin. Hair removal necessary to avoid autofluorescence.	Low	• Simple to perform. • Not invasive. • Longitudinal imaging through various days. • Saves animals (consistent with 3Rs).	• Autofluorescence if hair present. • Poor in subcutaneous adipose tissue.
Dorsal skinfold chamber	Semi‐invasive. Requires the surgical implantation of a chamber, exposing a small skin area. The chamber remains in place and allows longitudinal imaging with recovery of the mouse.	High Important to cause as little damage as possible: the animal should survive surgery, implantation and multiple rounds of imaging.	• Longitudinal imaging through various days. • Reduces use of animals (3Rs). • Different vascular environment as that presented in more accessible skin sites.	• Could present postsurgical complications including infection and inflammation. • Chronic chamber may introduce artefacts. • Care should be taken to prevent pain.
Skin flap	Exposure of a large skin area by generating a skin flap that can be imaged through a simple window (e.g. a coverslip). It is invasive and terminal.	Medium to high   Important to cause as little damage as possible to avoid bleeding or artefacts during imaging	• Large imaging area. • Different vascular environment as that presented in more accessible skin sites.	• It is terminal. Possibility of ischaemia.
Skin flank	Relatively easy access. Exposure of a relatively large skin area.	Medium to high   Important to cause as little damage as possible to avoid bleeding or artefacts during imaging	• Large imaging area • Different vascular, nerve, and lymphatic environments as those presented in more accessible skin sites.	• In some modalities, it is terminal.
Abdominal window for AT access	Exposure of a large AT area that can be imaged through a simple window	Medium to high   Important to cause as little damage as possible to avoid bleeding or artefacts during imaging	• Large imaging area. • Away from heart (motion artefacts avoided).	• It is terminal.