TOASTPLUSPLUS.ORG

We can see that the sensitivity regions spread out widely inside the tissue, which means that each measurement contains little spatial information. Furthermore, the regions are distorted by the included object, so the region probed by a measurement itself depends on the distribution of optical parameters! This has a profound effect on the solution of the imaging problem, because if we want to backproject boundary measurements into the tissue, we need to know the shape of the PMDFs and hence the solution of the problem we want to solve. This demonstrates the nonlinearity of the imaging problem in ODT. In general, it can only be solved by an iterative approach, where the estimates of the PMDFs are updated along with the estimates of the optical parameters.