Performance evaluation of computed tomography systems: Summary of AAPM Task Group 233.

BACKGROUND: The rapid development and complexity of new x-ray computed tomography (CT) technologies and the need for evidence-based optimization of image quality with respect to radiation and contrast media dose call for an updated approach towards CT performance evaluation. AIMS: This report offers updated testing guidelines for testing CT systems with an enhanced focus on the operational performance including iterative reconstructions and automatic exposure control (AEC) techniques. MATERIALS AND METHODS: The report was developed based on a comprehensive review of best methods and practices in the scientific literature. The detailed methods include the assessment of 1) CT noise (magnitude, texture, nonuniformity, inhomogeneity), 2) resolution (task transfer function under varying conditions and its scalar reflections), 3) task-based performance (detectability, estimability), and 4) AEC performance (spatial, noise, and mA concordance of attenuation and exposure modulation). The methods include varying reconstruction and tube current modulation conditions, standardized testing protocols, and standardized quantities and metrology to facilitate tracking, benchmarking, and quantitative comparisons. RESULTS: The methods, implemented in cited publications, are robust to provide a representative reflection of CT system performance as used operationally in a clinical facility. The methods include recommendations for phantoms and phantom image analysis. DISCUSSION: In line with the current professional trajectory of the field toward quantitation and operational engagement, the stated methods offer quantitation that is more predictive of clinical performance than specification-based approaches. They can pave the way to approach performance testing of new CT systems not only in terms of acceptance testing (i.e., verifying a device meets predefined specifications), but also system commissioning (i.e., determining how the system can be used most effectively in clinical practice). CONCLUSION: We offer a set of common testing procedures that can be utilized towards the optimal clinical utilization of CT imaging devices, benchmarking across varying systems and times, and a basis to develop future performance-based criteria for CT imaging.

Y-90 microsphere therapy: prevention of adverse events.

OBJECTIVE: Thirty-three (33) events that were inconsistent with intended treatment for 471 Y-90 microsphere deliveries were analyzed from 2001 to 2007. METHOD: Each occurrence was categorized, based on root-cause analysis, as a device/product defect and/or operator error event. Events were further categorized, if there was an adverse outcome, as spill/leak, termination, recatheterization, dose deviation, and/or a regulatory medical event. RESULTS: Of 264 Y-90 Therasphere (MDS Nordion, Ottawa, Ontario, Canada) treatments, 15 events were reported (5.7%). Of 207 Y-90 SIR-Spheres (Sirtex, Wilmington, MA) treatments, 18 events were reported (8.7%). Twenty-five (25) of 33 events (76%) were device/product defects: 73% for Therasphere (11 of 15) and 78% for SIR-Spheres (14 of 18). There were 31 adverse outcomes associated with 33 events: 15 were leaks and/or spills, 9 resulted in termination of the dose administration, 3 resulted in recatheterization for dose compensation, 2 were dose deviations (doses differing from the prescribed between 10% and 20%), and 2 were reported as regulatory medical events. Fifty-five (55) corrective actions were taken: 39 (71%) were related to the manufacturer and 16 (29%) were hospital based. CONCLUSIONS: This process of analyzing each event and measuring our outcomes has been effective at minimizing adverse events and improving patient safety.