X2CT-FLOW: Reconstruction of multiple volumetric chest computed tomography images with different likelihoods from a uni- or biplanar chest X-ray image using a flow-based generative model

We propose X2CT-FLOW for the reconstruction of volumetric chest computed tomography (CT) images from uni- or biplanar digitally reconstructed radiographs (DRRs) or chest X-ray (CXR) images on the basis of a flow-based deep generative (FDG) model. With the adoption of X2CT-FLOW, all the reconstructed volumetric chest CT images satisfy the condition that each of those projected onto each plane coincides with each input DRR or CXR image. Moreover, X2CT-FLOW can reconstruct multiple volumetric chest CT images with different likelihoods. The volumetric chest CT images reconstructed from biplanar DRRs showed good agreement with ground truth images in terms of the structural similarity index (0.931 on average). Moreover, we show that X2CT-FLOW can actually reconstruct such multiple volumetric chest CT images from DRRs. Finally, we demonstrate that X2CT-FLOW can reconstruct multiple volumetric chest CT images from a real uniplanar CXR image.