TwinTree Insert

20-07 Speeding up Clinial Imaging

n the 1980s, Continental Europe started to contribute intensively to MR imag­ing. Rapid imaging originated in European laboratories.

Jürgen Hennig (Figure 20-46), together with A. Nauerth and Hartmut Friedburg, from the University of Freiburg in Germany introduced RARE (Rapid Acquisition with Relaxation En­han­ce­ment) imaging in 1986 [⇒ Hennig 1986]. This technique is probably better known under the commercial names of 'fast' or 'turbo' spin-echo (Figure 20-47).

Figure 20-46: Jürgen Hennig

Figure 20-47:
First page of Hennig's article about RARE imaging (submitted in 1985, published in 1986).

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 …"

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-scientific reasons, was very rapidly adopted com­mer­ci­al­ly. The FLASH se­quen­ce was developed at Max-Planck-In­sti­tu­te, Göttingen, by Axel Haase (Figure 20-48), Jens Frahm (Figure 20-49), Dieter Matthaei, Wolfgang Hä­ni­cke, and Dietmar K. Merboldt [⇒ Haase 1986].

Figure 20-48: Axel Haase

Figure 20-49: Jens Frahm

The inclusion of Hennig's RARE into the clinical imaging protocols was slower, and Mansfield's echo-planar imaging (EPI) took even more time to find its way into cli­ni­cal imaging — for technical reasons.

Figure 20-50: Richard A. Jones

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 (Figure 20-50) [⇒ Jones 1993].

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 [⇒ Sodickson 1997].

Figure 20-51: Klaas Prüssmann

Figure 20-52: Markus Wei­ger

In 1999 Klaas Prüssmann (Figure 20-51) and Markus Wei­ger (Figure 20-52) intro­duced SENSE and thus of­fer­ed a more gen­eral solution [⇒ Pruessmann 1999]. Algorithms of the GRAPPA type, introduced a year later by Mark A. Griswold [⇒ Griswold 2002], work better than the SENSE type for abdominal and thoracic or for echo planar imaging.