In current magnetic resonance (MR) imaging systems, design choices are confronted with a trade-off between structured
(i.e. artifacts) and unstructured noise. The impact of both types of noise on perceived image quality, however, is so far
unknown, while this knowledge would be highly beneficial for further improvement of MR imaging systems. In this
paper, we investigate how ghosting artifacts (i.e. structured noise) and random noise, applied at the same energy level in
the distortion, affect the perceived quality of MR images. To this end, a perception experiment is conducted with human
observers rating the quality of a set of images, distorted with various levels of ghosting and noise. To also understand the
influence of professional expertise on the image quality assessment task, two groups of observers with different levels of
medical imaging experience participated in the experiment: one group contained fifteen clinical scientists or application
specialists, and the other group contained eighteen naïve observers. Experimental results indicate that experts and naïve
observers differently assess the quality of MR images degraded with ghosting/noise. Naïve observers consistently rate
images degraded with ghosting higher than images degraded with noise, independent of the energy level of the
distortion, and of the image content. For experts, the relative impact of ghosting and noise on perceived quality tends to
depend on the energy level of the distortion and on the image content, but overall the energy of the distortion is a
promising metric to predict perceived image quality.
A measure is proposed to express the conformance between any pair of greyvalue curves. This may be used to compare a greyvalue curve against a standard. Such a measure may be used to quantify and compare various causes of non-conformance.
The goal of our work is to noninvasively assess the abnormal contraction pattern of the heart in patients with hypertrophic obstructive cardiomyopathy, by means of Magnetic Resonance Imaging (MRI). To study the motion of the heart wall, the imaging plane is labelled a few milliseconds after the RÃ¢â‚¬â€wave with a grid pattern using the technique of Spatial Modulation of Magnetization (SPAMM). During systole several ECGÃ¢â‚¬â€triggered short and long axis views of the heart muscle are acquired with a conventional Fast Field Echo sequence. In a preliminary study of the normal left ventricle a clockwise twist of approximately 10 degrees at the base is found, increasing towards the apex, whereas patients with hypertrophic cardiomyopathy show a complex motion pattern, with a clockwise twist in the basal and counterclockwise twist in the apical segments.