Automatic Channel Fault Detection and Diagnosis System for a Small Animal APD-Based Digital PET Scanner

Fault detection and diagnosis is critical to many applications in order to ensure proper operation and performance over time. Positron emission tomography (PET) systems that require regular calibrations by qualified scanner operators are good candidates for such continuous improvements. Furthermore, for scanners employing one-to-one coupling of crystals to photodetectors to achieve enhanced spatial resolution and contrast, the calibration task is even more daunting because of the large number of independent channels involved. To cope with the additional complexity of the calibration and quality control procedures of these scanners, an intelligent system (IS) was designed to perform fault detection and diagnosis (FDD) of malfunctioning channels. The IS can be broken down into four hierarchical modules: parameter extraction, diagnosis, channel fault detection and fault prioritization. Of these modules, parameter extraction and fault detection have previously been reported and this paper focuses on diagnosis, improved fault detection and fault prioritization. The status diagnosis module will diagnose all channels and propose an explanation of the reasons that lead to the diagnosis. The purpose of the fault prioritization module is to help the operator to zero in on the faults that need immediate attention. The FDD system was implemented on a LabPET avalanche photodiode (APD)-based digital PET scanner. Experiments demonstrated a FDD Sensitivity of 99.9% (with a 95% confidence interval (CI) of [99.6, 100.0]) for major faults. Globally, the balanced accuracy of the diagnosis for varying fault severities is 91%. This suggests the IS can greatly benefit the operators in their maintenance task.