Table 3.

Optical methods employed to study IA drug pharmacokinetics.

Method	Depth	Advantage	Disadvantage
Diffuse reflectance spectroscopy	1-2 mm	(i) Insensitive to scattering changes (ii) Low cost (iii) High spectral resolution	(i) Recovery of relative absorption (ii) Low spatial resolution
Diffuse optical tomography	up to ~4 cm	3D reconstruction of absolute optical pharmacokinetics (OP)	(i) Expensive (ii) Bulky (iii) Low spectral resolution
Frequency domain photon migration	up to ~4 cm	Recovery of absolute OP	(i) Low spectral resolution (ii) Expensive (iii) Low spatial resolution (iv) Not suitable for small geometries
Diffuse optical spectroscopic imaging	up to ~4 cm	(i) 3D reconstruction of absolute OP (ii) High spectral resolution	(i) Expensive (ii) Not suitable for small geometries
Spatial frequency domain imaging	up to ~1 cm	(i) Noncontact (ii) High spatial resolution (iii) Depth sensitivity	(i) Long acquisition times (ii) Expensive (commercial)
Multispectral imaging	up to ~1 cm	(i) Low cost (ii) High spatiotemporal acquisition rate	(i) Relative absorption values (ii) Susceptible to scattering effects (iii) No depth resolution