Comparative Study of Image Quality in Time-Correlated Single-Photon Counting Computed Tomography

Computed tomography (CT) is widely used in medical imaging to reconstruct a 3-D image of a patient. To limit the radiation dose applied to patients, researches focus on reducing the statistical noise or increasing the contrast in the image. Recently, time-correlated single-photon counting (TCSPC) CT—also known as time-of-flight (TOF) CT—has been proposed to reduce scatter contribution to images and its negative effects on image quality. This technique uses the TOF information of X-ray photons to sort out scattered and ballistic photons without energy measurement. This article compares simulated images quality obtained from different CT scanner implementations (fan-beam, cone-beam with and without anti-scatter grids, and TCSPC). The contrast-to-noise ratio (CNR), the scattered-to-primary ratio (SPR), the inaccuracy of the computed attenuation value, and the cup artifact magnitude are used as comparison metrics to study the overall sensitivity of the different scanner implementations to scatter contribution. Using timing jitters of 200, 100, and 50 ps, the simulations demonstrate that the TCSPC implementation improves the CNR, accuracy, and cup artifact levels of the reconstructed images, when compared to a cone-beam CT, by reducing its scatter contribution. A 10-ps timing jitter on the measured time of flight leads to an image quality similar to fan-beam CT.