Diffusionstomografi

Diffusionstomografi, commonly referred to as diffuse optical tomography (DOT), is a medical imaging method that reconstructs images of tissue optical properties from measurements of diffusely scattered light. It relies on the diffusion approximation to the radiative transport equation to describe how near-infrared light propagates through highly scattering biological tissue. By placing light sources and detectors around a region of interest and collecting measurements at multiple wavelengths, DOT solves an inverse problem to estimate spatial maps of the absorption coefficient (μa) and the reduced scattering coefficient (μ's). Changes in μa at near-infrared wavelengths are related to concentrations of chromophores such as oxyhemoglobin and deoxyhemoglobin, enabling functional imaging of tissue hemodynamics.

In practice, DOT uses tomographic reconstruction algorithms, such as finite element or finite difference methods, with regularization to cope with the ill-posed nature of the problem. Multi-wavelength data can separate chromophore contributions; sometimes dynamic measurements yield functional information.

Applications include functional brain imaging in infants and adults, breast cancer imaging and assessment, monitoring of muscle metabolism and peripheral oxygenation, and small-animal imaging. DOT is non-invasive and uses non-ionizing light, and is relatively inexpensive and portable compared to MRI or CT, but it trades off spatial resolution, typically delivering centimeter-scale resolution and shallow depth sensitivity, with results influenced by tissue heterogeneity and model accuracy.

Emerging variants include time-domain and frequency-domain DOT, and combination with other modalities such as MRI or ultrasound to improve spatial localization.