Direct reconstruction of anatomical change in low-dose lung nodule surveillance.

In sequential imaging studies, there exists rich information from past studies that can be used in prior-image-based reconstruction (PIBR) as a form of improved regularization to yield higher-quality images in subsequent studies. PIBR methods, such as reconstruction of difference (RoD), have demonstrated great improvements in the image quality of subsequent anatomy reconstruction even when CT data are acquired at very low-exposure settings. However, to effectively use information from past studies, two major elements are required: (1) registration, usually deformable, must be applied between the current and prior scans.