Figure 2.

Image-data mappings. An image (a) consisting of some explicit values, is organized according to the coordinate system $\mathcal{I}$. (b) Through the transformation effected by the forward model operator $M$, one determines (c) the photoacoustic data in coordinate system $\mathcal{D}$. In practice, one acquires the data and (d) seeks to reconstruct the corresponding image through the action of some reconstruction operator $R$. Iterative schemes are often favored for the reconstruction process, and so $R$ is implicitly dependent on the operator $M$. Figure created using a combination of MATLAB and Microsoft PowerPoint.