Subjective quality and depth assessment in stereoscopic viewing of volume-rendered medical images

No study to-date explored the relationship between perceived image quality (IQ) and perceived depth (DP) in stereoscopic medical images. However, this is crucial to design objective quality metrics suitable for stereoscopic medical images. This study examined this relationship using volume-rendered stereoscopic medical images for both dual-and single-view distortions. The reference image was modified to simulate common alterations occurring during the image acquisition stage or at the display side: added white Gaussian noise, Gaussian filtering, changes in luminance, brightness and contrast. We followed a double stimulus five-point quality scale methodology to conduct subjective tests with eight non-expert human observers. The results suggested that DP was very robust to luminance, contrast and brightness alterations and insensitive to noise distortions until standard deviation sigma=20 and crosstalk rates of 7%. In contrast, IQ seemed sensitive to all distortions. Finally, for both DP and IQ, the Friedman test indicated that the quality scores for dual-view distortions were significantly worse than scores for single-view distortions for multiple blur levels and crosstalk impairments. No differences were found for most levels of brightness, contrast and noise distortions. So, DP and IQ didn't react equivalently to identical impairments, and both depended whether dual-or single-view distortions were applied