The GAN generated pseudo-CT from NAC PET was registered to the corresponding non-contrast CT attenuation correction image using diffeomorphic (demons) non-rigid registration (Transform 1). The non-contrast CT AC was then registered rigidly to CT angiography image of the same patient (Transform 2). These two transforms (Transforms 1 and 2) were applied to AC PET image, registering PET to CT angiography automatically.
AC: attenuation corrected, CT: computed tomography, NAC: non-attenuation corrected, PET: positron emission tomography