Methods for reconstructing an image can include, inter alia, (i) reconstructing a contrast-enhanced output CT image from a nonenhanced input CT image, (ii) reconstructing a nonenhanced output CT image from a contrast-enhanced CT image, (iii) reconstructing a dual-energy, contrast-enhanced output CT image from a single-energy, contrast-enhanced CT image, and/or (iv) reconstructing a full-dose, contrast-enhanced CT image from a low-dose, contrast-enhanced CT image.