This chapter is available as free (personal) off-print from the new book version.
20-07 Speeding up Clinial Imaging
In the 1980s, Continental Europe started to contribute intensively to MR imaging. Rapid imaging originated in European laboratories.
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Jürgen Hennig (Figure 20-37), together with A. Nauerth and Hartmut Friedburg, from the University of Freiburg introduced RARE (Rapid Acquisition with Relaxation Enhancement) imaging in 1986 [⇒ Hennig]. This technique is probably better known under the commercial names of fast or turbo spin-echo (Figure 20-38). Figure 20-37: Jürgen Hennig. |
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Figure 20-38: |
The beginning of the article summarizes the problem to be solved:
"Conventional imaging techniques used in MRI take several minutes for a multiple and/or multiecho 256×256 image. The use of these time-consuming methods causes several problems in routine clinical work. These well known problems include patient discomfort and positioning …"
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At about the same time, FLASH (fast low angle shot) appeared, opening the way to similar gradient-echo sequences. FLASH had a completely different approach and, for non-scientifically reasons, was very rapidly adopted commercially. Figure 20-39: Axel Haase |
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The FLASH sequence was developed at Max-Planck-Institute, Göttingen, by Axel Haase (Figure 20-39), Jens Frahm (Figure 20-40), Dieter Matthaei, Wolfgang Hänicke, and Dietmar K. Merboldt [⇒ Haase]. Figure 20-40: Jens Frahm. |
The inclusion of Hennig's RARE into the clinical imaging protocols was slower, and Mansfield's echo-planar imaging (EPI) – for technical reasons – took even more time to find its way into clinical imaging.
Acquiring images faster and with better quality remained one of the main goals in MR research. New ideas and distinct concepts were developed, for instance k-space substitution as proposed by Richard A. Jones [⇒ Jones].
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A combination of dedicated hardware and specific software led to parallel imaging which can reduce imaging time considerably. A first technique was described by Sodickson and Manning but it required a particular coil configuration. Figure 20-41: Klaas Pruessmann. |
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In 1999 Klaas Pruessmann (Figure 20-41) and Markus Weiger (Figure 20-42) introduced SENSE and thus offered a more general solution [⇒ Pruessmann]. Figure 20-42: Markus Weiger. |
Algorithms of the GRAPPA type, introduced a year later by Mark A. Griswold [⇒ Griswold], work better than the SENSE type for abdominal and thoracic or for echo planar imaging.
