The traditional imaging field of 400–500 mm is clearly too small for a comprehensive angiographic evaluation of the vascular system or for a comprehensive search for metastases. One option for extending the effective FOV is to perform imaging in a series of discrete steps, moving the scanner table between acquisitions so as to shift the position of the patient relative to the imaging field (Ho et al. 1998, 1999; Wang et al. 1998; Meaney et al. 1998; Ruehm et al. 2000a, 2000b, 2001; Leiner et al. 2000, 2004; Goyen et al. 2001; Busch et al. 2001; Huber et al. 2003). This technique, known as multistation imaging, allows step-by-step scanning of different body regions in the magnet’s isocenter, which is defined and limited by field homogeneity, gradient linearity, and RF signal excitation and readout. While the individual stations must meet the same requirements as in conventional MRI, the multistation technique extends the overall scope of the examination by enabling successive imaging of different parts of the patient’s body.

Multistation imaging requires a table moving relative to the isocenter of the magnet. The maximum table range directly determines the imaging range or how much of the patient’s body can be successively moved through the scanner’s effective FOV. The automatic patient tables of older scanners have a maximum range of less than 150 cm, which is sufficient for peripheral MRA of the pelvis and legs. For head-to-toe imaging, however, it is necessary to reposition the patient at least once between acquisitions: positioning the patient head-first for the first part of the examination and feet-first for the second part, or vice versa.

True whole-body MRI, the next step in the development, is no longer hampered by table range limitations and avoids the need for repositioning the patient during a full-body examination. Its technical implementation was made possible by important contributions from several independent study groups working in this field. The table range limitations were overcome by the advent of manually moved table platforms such as SKIP (Stepping Kinematic Imaging Platform, Magnetic Moments, Bloomfield, MI, USA) (Shetty et al. 2002) and AngioSURF (Angiographic System for Unlimited Rolling Field-of-views, MR-Innovation GmbH, Essen, Germany) (Ruehm et al. 2000a, b; Goyen et al. 2002; Winterer et al. 2003). These new platforms mark the beginning of true whole-body MRI, extending the range of motion to approx. 200 cm and enabling serial whole-body imaging in five or six stations. The problem of ensuring adequate signal readout over this extended imaging range was elegantly solved by using a stationary pair of RF coils in the isocenter of the magnet (Fig. 3.3). One coil of this pair is integrated in the patient table, contributing signal from the posterior body regions. The second coil, mounted on a coil glider, is height-adjustable and is held in position in the isocenter of the magnet by two flexible arms. This allows the coil to adjust to the body contour as the patient is being moved through the bore of the magnet for optimal signal readout from anterior body regions. The patient is positioned on an MR-compatible rolling table platform, allowing rapid and stepwise advancement of the patient through the main magnet and between the two stationary surface coils (Fig. 3.3). With this RF surface coil setup, an adequate SNR is achieved without the need for completely covering the patient’s body with surface coils. This technique has been widely used in clinical whole-body MRA (Shetty et al. 2002; Ruehm et al. 2000a, b; Goyen et al. 2002; Winterer et al. 2003; Quick et al. 2004; Herborn et al. 2004), in whole-body metastasis screening in oncologic patients (Lauenstein et al. 2002a, b; Lauenstein et al. 2004; Ghanem et al. 2004), and in MRI-based screening examinations (Ruehm et al. 2004; Goehde et al. 2005). The phased-array surface coil technology used is also suitable for performing parallel imaging to improve spatial resolution (Quick et al. 2004).

Newer generations of MRI scanners increasingly come equipped for whole-body imaging: an automatically moving table with a range of approx. 200 cm, comprehensive solutions for covering the patient’s body with a set of dedicated phased-array RF surface coils, and a large number of independent RF receiver channels to process the signals from these coils. With this equipment, it is possible to evenly cover the patient with highly sensitive RF surface coils from head to toe for optimal signal readout from all body regions. All vendors provide their most recent machines with a variety of phased-array RF surface coils for versatile applications in different body regions. Siemens (Healthcare Sector, Erlangen, Germany), for instance, offers an RF system called Tim (Total imaging matrix), which includes up to 76 coil elements and up to 32 readout channels for a table range of 185 cm (Fig. 3.4). Tim includes a variety of dedicated RF coils, which are optimized for individual body regions and integrated into a whole-body RF system. The individual coil elements can be flexible combined with a large number of RF receivers, allowing excellent exploitation of the potential SNR. Full body coverage with RF readout coils and a table range of approx. 200 cm are the basic hardware requirements for multistation imaging, that is, automatic movement of the table for discontinuous image acquisition at a discrete number of stations (Fig. 3.5).

In addition to the hardware developments outlined above, multistation imaging techniques would not have been possible without new software for a variety of new tasks: (1) rapid switching of RF coil elements between stations for selective signal readout by the coils at each given station; (2) acquisition of prescans (before the actual examination) to separately optimize and store parameters for each station related to tuning, shimming, specific absorption rate (SAR), and flip angle; determining these parameters before a whole-body scan is especially important in applications where the imaging window is small and timing is critical (e.g., contrast-enhanced MRA); and (3) capability for separately positioning and angling the image slab for each station and flexibly selecting spatial resolution (matrix, slice thickness). This flexibility is desirable to optimize parameters for the body part being imaged at each station and to make adjustments for differences in individual anatomy. With the new demands arising for the processing of whole-body MRI datasets, image postprocessing has also been taken from local to global. Manufacturers are increasingly offering postprocessing packages (e.g., composer tools) for virtually combining the images from the individual stations to create composite images for easier viewing and interpretation.