Multiplanar Reformation

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Orthographic MPR reconstruction of a CT image
Oblique MPR reconstruction of a CT image
Curved MPR reconstruction of a CT image

The multiplanar reformatting (also abbreviated as MPR) is a method of two-dimensional image reconstruction, which u. a. is used in computed tomography (CT), nuclear medicine , but also in magnetic resonance imaging (MRT).

In CT as well as in SPECT , the image reconstruction algorithm always generates transverse sections from the raw data . In the first generation of devices, this was the only possible form of image display.

With the MPR, frontal , sagittal , oblique or curved sections are calculated and displayed from these transversal sections in order to help the viewer with the anatomical orientation. Oblique cuts are helpful, for example, in cardiac imaging (four-chamber view, short-axis cuts), curve-shaped reconstructions along structures that run in multiple bends to show vessels (such as the coronary arteries ) or the ureters.

In order to obtain high-quality MPR reconstructions, the image data for the CT should be recorded overlapping with a small slice thickness. In addition, a small slice thickness should be selected to avoid step artifacts during image reconstruction. The image noise can be reduced by adding several layers. The availability of isotropic voxels resulted in a diagnostic gain for many questions. Isotropic voxels have the same spatial resolution in all three spatial directions, so that no distortions whatsoever are discernible with an oblique MPR reconstruction. Isotropic voxels are calculated by a computer tomograph when a suitable recording and reconstruction protocol is selected; If you record with a high pitch , oblique reconstructions in the Z-direction are displayed blurred.

In magnetic resonance imaging, isotropic voxels are often not available; In the case of recordings made in layers, the resolution in the image plane is far higher than perpendicular to it and instead of MPRs, additional recordings are added for each image plane to be displayed. In contrast to CT, PET and SPECT, the original data are therefore often already available in the form of sagittal or coronal sections, so that these representations do not have to be calculated.

For some years now, special 3D recording sequences have also been used in MRT that can generate high-resolution isotropic image voxels and thus allow artifact-free MPR display.

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