ABSTRACT
In order to be useful, these parameters have to be effi ciently visualized and preferably quantifi ed. For this, there are some requirements on the images obtained. This includes intrinsic image quality, with a suffi cient temporal and spatial resolution, and appropriate tools for processing the data. With regard to spatial resolution, one would prefer this to be as high as possible in order to be able to detect the smallest anatomical details. However, in some cases, for example when evaluating cardiac function, it might be suffi cient to have a resolution, which is just enough for detecting clinically relevant information. In terms of myocardial function, a resolution cell about the order of magnitude of 1 cm3 seems appropriate as smaller disease is not likely to be clinically relevant. However, it is important that this resolution is obtained everywhere within the myocardium. Even if that is possible, this fi gure is clearly not good enough when trying to evaluate the morphology of the valve and valvular apparatus and chordae. In this case, a submillimeter resolution
would be more appropriate. This implies that there is no one unique defi nition for the required spatial resolution; it depends on the specifi c purpose of the information. Similar considerations can be made with regard to the temporal resolution. Because, in the cardiac cycle, there are some very fast events, especially during the isovolumic periods, a very high temporal resolution is needed if these are to be studied. This means that typically a temporal resolution of over 200 Hz is required. Given some of the intrinsic limitations in the processing of some derived parameters (like deformation), a frame rate of 200-300 Hz is thus desirable for quantifi cation of myocardial motion and deformation. For visual interpretation of wall motion, 30 Hz would be suffi - cient as the human visual system is not able to discriminate faster moving images. However, higher frame rates enable to display the images in slow motion, thus enabling a better evaluation of events.
