In-plane resolution

In routine clinical imaging the thickness of a sHce is approximately 3 mm and the in-plane resolution approximately 0.8 mm for a 20-cm FOV,... 

D image is extracted from individual points along the spectral range (2.4-5 ppm). Three series of images are shown within each series the chemical shift separation between images is 0.065 ppm. This complete data set took approximately 27 h to acquire—as a 128 x 128 data array with in-plane resolution of 140 pm x 140 pm for an image slice thickness of 1mm. 

Fig. 19. 2-D MR image of an oscillating chemical reaction occurring within a bed of diameter 15 mm packed with 1-mm-diameter glass beads. In-plane resolution was 195 pm x 195 pm, and the image slice thickness was 1 mm. A single image was acquired in 1 s. Chemical waves are imaged as a result of the...

CE-MRA also allows repetitive measurements to follow the passage of contrast bolus. Reduction in the number of slices and of in-plane resolution admits sequential measurements with a temporal resolution ofless than 1 s (Krings and Hans 2004). In combination with high resolution measurements, thus dynamic processes in arteriovenous shunts or for instance in steal phenomena can be studied (Fig. 5.7). 

Instead of polarized noble gases, thermally polarized NMR microimaging was used to study of liquid and gas flow in monolithic catalysts. Two-dimensional spatial maps of flow velocity distributions for acetylene, propane, and butane flowing along the transport channels of shaped monolithic alumina catalysts were obtained at 7 T by NMR, with true in-plane resolution of 400 xm and reasonable detection times. The flow maps reveal the highly nonuniform spatial distribution of shear rates within the monolith channels of square cross-section, the kind of information essential for evaluation and improvement of the efficiency of mass transfer in shaped catalysts. The water flow imaging, for comparison, demonstrates the transformation of a transient flow pattern observed closer to the inflow edge of a monolith into a fully developed one further downstream. 

An example of the current state of the art is the HP xenon lung image in a rat shown in Fig. 19, which illustrates an impressive level of detail. The in-plane resolution of the 3D image is 0.39 x 0.39 mm, with a field of view of 5 cm. A 100 mL xenon/oxygen bolus was delivered over the course of 80 breaths, and the image was acquired using a radial projection encoding sequence. 

Fig. 19. In vivo MRI of rat lung space following respiration of a gas mixture containing 80% enriched laser-polarized Xe with a polarization of 8% and acquired at 2T. The in-plane resolution was 0.39 mm. (Courtesy of Bastiaan Driehuys and G. Allan Johnson of the Duke Center for In Vivo Microscopy, an NCRR National Resource (P41 05959).)...

In Figure 6.1 three data volumes are depicted with different voxel size a) isotropically sampled image at low resolution b) anisotropically sampled image with in-plane resolution higher than resolution between consecutive slices and c) isotropically sampled image at high resolution. 

MSCT data sets allow reconstruction of a continuous slab of 0.5-mm slices with 20% overlap. In such a slab, resolution along the z-axis (or slice-to-slice resolution) is about twice as high as in-plane resolution of axial images. For most applications, 1 mm slices with 0.8 mm increment are sufficient. The latter has two advantages the amount of data to be stored and transferred is reduced by half, and image noise is also reduced because more raw data are averaged. For those reconstructions a softer reconstruction kernel, e.g., body filter should be used to limit the image noise. 

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