Evaluation of Perception based Image Quality Evaluator (PIQE) no-reference image quality score for 99mTc-MDP bone scan images

1415 Objectives: Research in nuclear medicine digital image processing requires processed images to be evaluated by nuclear medicine physicians (NMPs). However, it is difficult to get the time of NMPs for evaluating huge number of processed images. Perceptual image quality evaluator (PIQE score) is a no reference image quality evaluator. In this study, we have evaluated the performance of PIQE score for 99mTc-MDP bone scan images. Materials and Methods: Forty two 99mTc-MDP bone scan studies i.e. 84 images were restored using Richardson-Lucy algorithm. During the process of restoration, for each input image, 60 processed images were generated using different parameters of algorithm. Thus, the process generated 5124 images (61x84). For 5 studies (10 images), input and processed images were compared by a NMP to decide one combination of parameters that resulted in high quality processed image. Then for all 42 studies the image with the selected parameters was picked which yielded image series “A”. Based on PIQE score evaluator high quality images from each study were selected and image series “B” was formed. The quality of Image in series A and B were compared with corresponding input images by two NMPs. They were asked to score the quality of image by assigning one of the six numeric score with consensus (0, 1, 2, 3, 4 and 5), where score “0” is for very bad and annoying enhancement (the image quality is totally distorted), score “3” is for no noticeable enhancement (natural and similar to original image), score 5 is for significant enhancement without annoying distortions (looks natural across the overall image) and other values were selected according to the perceived image quality. Results: In 61.90% of the cases (52 out of 84 images) the high quality image selected based on PIQE score and high quality image selected based on NMPs evaluation were concordant. The difference in image quality score between two image series was equal 2 in only 5.97% of cases (5 out of 84 images). There were 28.57% images (24 images) in which the difference in image quality score was equal to 1. Visually, images in which the difference in image quality score was equal to 1; both images had appreciable enhancement with slight difference in degree of enhancement in some regions which was acceptable to NMPs. If we combine the images with same and acceptable difference of 1 in image quality score together, then overall 90.47% ( 76 out of 84) of the images selected based on PIQE score were acceptable to the NMPs. Conclusions: Our results demonstrate that although there is no replacement of visual image quality assessment made by NMPs however, PIQE score may be used during the initial part of the research as an image quality evaluator.