Impact of gamma camera parameters on imaging performance, evaluated by receiver operating characteristics (ROC) analysis

Abstract

The relationship between gamma camera variables (total counts in image, collimator type, etc.) and diagnostic imaging performance was quantitatively investigated using receiver operating characteristic (ROC) curve analysis. A College of American Pathologists (CAP) liver phantom was used with a ⁹⁹Tc^m flood source to generate anterior and lateral liver images containing 'cold lesions'. These images were interpreted by four nuclear medicine physicians, and the areas under the corresponding ROC curves computed. These areas were taken as a quantitative estimate of the imaging performance of the system. The average area under the ROC curve for the four physicians reading the same 'standard' image six times was computed to be 66.8+or-5.8. Experiments were performed to show the effect on diagnostic performance of (i) increasing the total image counts from 200 k to 2000 k, (ii) varying the phantom-to-collimator separation from 0 to 8 cm and (iii) changing the collimator type. In all cases, data were generated which demonstrated the quantitative improvement (or deterioration) resulting from these changes. These data may be used in the design of clinical imaging protocols, for which choices have to be made for each gamma camera variable.