Figure 1.

Construction of dictionary of temporal basis functions from a specified tracer kinetic model (a). Based on a physiological range of kinetic parameters and an arterial input function (AIF), a library of concentration vs time profiles is generated (b). A subset of the profiles in the library is highlighted in red. Using k‐SVD, the library is then reduced to a smaller set of temporal basis functions in a dictionary (c). The basis functions generated with the extended Tofts‐Kety model is shown in (c). The basis functions themselves are not representative of kinetic model profile, and hence can be nonpositive. Instead, the linear combination of them is designed to mimic any profile in (b). Approximate MATLAB computational times respectively for generating the library (~400 000 profiles) and learning the dictionary were 11.5 min and 3.5 h. [Color figure can be viewed at http://www.wileyonlinelibrary.com]