Usefulness of a No-Reference Metric for Evaluation of Images in Nuclear Medicine -A Comparative Study with Visual Assessment

Abstract

Purpose The normalized mean square error (NMSE) method is widely used to evaluate images in nuclear medicine. However, its use in clinical practice requires creating target images over a long time, which is difficult. It also requires standard images and reference teacher data that can be used at facilities worldwide because methods and doses in nuclear medicine imaging are yet to be standardized. This study examined the validity of perception-based image quality evaluator (PIQE), a no-reference metric that does not require a target image for image evaluation in nuclear medicine.Methods The Hoffman brain phantom with 18F-fluoro-2-deoxy-D-glucose (FDG) was imaged and evaluated on slices in which the frontal and temporal lobes, bilateral lateral ventricles, and basal ganglia were drawn. Sixteen images with different pixel numbers and acquisition times were created and evaluated from the same slice. For the images obtained, visual evaluation criteria were developed for two endpoints: separation of white and gray matter boundaries, and uniformity of accumulation. Five evaluators assessed all the images using a paired comparison method, and then scored and ranked them. The images were also physically evaluated by the PIQE and a natural image quality evaluator (NIQE). The rankings obtained from the visual and physical evaluations were statistically compared.Results Based on Spearman's test of significance, visual evaluation rankings showed a strong correlation with those obtained with PIQE (rs = 0.9559, p < 0.0001) and no correlation with those obtained with NIQE (rs = 0.2324 and p = 0.3865).Conclusions Evaluation of images by PIQE is as effective as visual evaluation.