title: Improved dead-time correction for PET scanners: application to small-animal PET.
abstract: Pile-up and dead-time are two main causes of nonlinearity in the response of a PET scanner as a function of activity in the field of view (FOV). For a given scanner and acquisition system, pile-up effects depend on the material and size of the object being imaged and on the distribution of activity inside and outside the FOV, because these factors change the singles-to-coincidences ratio (SCR). Thus, it is difficult to devise an accurate correction that would be valid for any acquisition. In this work, we demonstrate a linear relationship between SCR and effective dead-time, which measures the effects of both dead-time (losses) and pile-up (gains and losses). This relationship allows us to propose a simple method to accurately estimate dead-time and pile-up corrections using only two calibration acquisitions with, respectively, a high and low SCR. The method has been tested with simulations and experimental data for two different scanner geometries: a scanner with large area detectors and no pile-up rejection, and a scanner composed of two full rings of smaller detectors. Our results show that the SCR correction method is accurate within 7%, even for high activities in the FOV, and avoids the bias of the standard single-parameter method.
authors: Grupo de Física Nuclear, Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, CEI Moncloa, Spain.
authors: E
authors: E
authors: Vicente
authors: J L
authors: JL
authors: Herraiz
authors: S
authors: S
authors: España
authors: E
authors: E
authors: Herranz
authors: M
authors: M
authors: Desco
authors: J J
authors: JJ
authors: Vaquero
authors: J M
authors: JM
authors: Udías
mesh_terms: D000818:Animals; D016477:Artifacts; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D013997:Time Factors