Multiplanar reconstructed images

Fig. l.la-c. Surface rendering for fetal imaging, showing a 30-week-old fetus (a), volume-rendering methods for liver imaging (b) and multiplanar reconstruction of a focal nodular hyperplasia in the liver (c) (courtesy of ESAOTE)... 

The near isotropic imaging obtained by spiral CT allows not only the accurate evaluation of anatomic details on native images, but even the reconstruction of oblique planes (MPR, multiplanar reconstructions) (Ali et al. 1993 Hermans et al. 1995). MPRs are well known since the introduction of CT in the clinical practice. Initial applications of MPR to the study of the middle ear were carried out with conventional CT (Haas and Kahle 1988 Grevers et al. 1989), and such experiences addressed to MPR an effective integrative role in CT imaging of the middle ear. With the advent of spiral CT, MPRs have been made available for most users, and the frequency of their application in the clinical routine has increased. 

The CT should demonstrate the entire central airway system, i.e., a spiral data set should be obtained from the mouth to the segmental bronchi. In order to show potential postobstructive complications, the CT should be extended to the diaphragm. To allow appropriate postprocessing of the spiral data set obtained in transversal orientation, collimation should be 2-3 mm, the pitch factor should be 1.5-2, overlap index in reconstruction should be 30%-50%, and a low spatial algorithm should be used. Images should be displayed both at mediastinal and pulmonary window settings. Multiplanar reconstructions and three-dimensional reconstructions as well as virtual endoscopy can be obtained with the... 

The CT parameters will also impact the quality of the 2D, multiplanar and 3D reconstructed images. The details of scanner type, collimation, pitch, detector array for volume scanner, gantry rotation... 

Fig. 35.1. a Axial CT image and b coronal reconstruction of an 11 -year-old boy with Ollier s disease and multiple osteochondromas of the skeleton. A large osteochondroma is located at the left scapula (arrows). Note also a small osteochondroma the right scapula (small arrow). Due to the thin slices and the possibility of multiplanar reconstructions, the exact location can be determined for planning of surgery... 

To confirm the renal origin of the tumor in difficult cases (use sagittal or coronal MR sequences or multiplanar reconstructions of CT images, Fig. 24.25)... 

Multi-phasic multidetector CT allows, in a single examination, a comprehensive evaluation of potential liver donors and of graft recipients. 3D-CTA with maximum intensity projection, multiplanar reconstructions, shaded surface display, and volume rendering techniques has become a strong competitor for DSA. The new development of multislice CT (MSCT) allows scan times fast enough to image the liver during a pure arterial phase of contrast opacification. This offers the possibility of 3D CTA for a variety of clinical applications. 

For all multislice CT protocols, the reconstructed slice thickness for liver and pelvic scans should be 3-5 mm in all orientations. Thinner slices contain more noise and are less suitable for primary image interpretation. Thin slices are mostly acquired to generate multiplanar reformations with a comparable spatial resolution. 

For examinations on a multislice scanner, thin slices should be used to compute high-quality multiplanar reformations. However, for interpretation of the source images, the reconstruction slice thickness should not be less than 3-5 mm, regardless of the slice orientation. 

Diederichs et al. (1996) applied a variant of MPR, called multiplanar volume reconstruction (MPVR), to the study of the middle ear after high-resolution computed tomography performed with a reduced dose. The aim of the study was to reduce image noise and at the same time increase the partial volume averaging to balance this effect the tentative attempt failed for visualization of little bony structures, and, for example, the stapes was not visualized. 

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