MRI Sequences

Brain imaging is required to distinguish between primary intracerebral hemorrhage and cerebral infarction since this distinction cannot be made reliably on clinical criteria alone (Hawkins et al. 1995). Recent developments in brain imaging, in particular new MRI sequences, and to a lesser extent CT techniques, have enabled visualization of the pathophysiological processes involved in brain infarction. These new techniques are being developed to select patients suitable for thrombolytic treatment beyond the three-hour time window (Ch. 21) and may in the future enable targeting of treatments such as neuroprotection. 

Recent advances in new MRI sequences that allow further characterization of ischemia have led to increased interest in using gradient-echo (GRE) MRI to detect hemorrhage (Ch. 10). This would avoid having to perform two imaging modalities in acute stroke, CT followed by MRI, in patients in whom further characterization of pathophysiology is necessary, for instance to determine selection for thrombolysis. 

Sibon, 1., et al., Inter- and intraobserver reliability of five MRI sequences in the evaluation of the final volume of cerebral infarct. J Magn Reson Imaging, 2009. 29(6) p. 1280-4. 

Fig. 5.1 Diffusion Weighted (left panel) and Perfusion Weighted (right panel) MRI sequences of acute ischemic stroke. Lighter grey area on the perfusion MRI is laiger than the diffusion restriction area suggesting the presence of hypoperfused but salvageable tissue...

Table 12.2. MRI sequences recommended for imaging of vaginal cancer...

Oppelt A, Graumann R, Barfiiss H, Fischer H, Hertl W, Schajor W (1986) A new fast MRI sequence. Electromed 3 15-18... 

Pech M, Spors B, Wieners G, Warschewske G, Beck A, Cho C et al (2004) Comparison of different MRI sequences with and without application of Gd-BOPTA as follow-up after LITT. Rofo 176(4) 550-555... 

FIGURE 8 Focused ultrasound treatment of breast fibroadenoma. Left the breast is positioned on a water-filled pillow which provides acoustic coupling between the breast tissue and the transducer. (The transducer is positioned within the MR table.) The focal planes are positioned within the tumor. Right the outline of the tumor target is defined by the dashed line. The colored area represents temperature rise at the focai point measured by temperature-sensitive MRI sequences. 

Assessing transfusion iron overload with precision for possible toxic evaluations and its treatment with chelation therapy requires reliable monitoring end points and procedures. Liver iron content is an important variable for such monitoring that may also be measured using standardised MRI sequences. A study compared liver iron content of 68 patients obtained using gradient-echo sequences and mean liver proton transverse relaxation acquired with spin-echo sequences. The authors suggested that a difference in results from the two techniques may lead to a difference in chelation decisions in patients [122 ]. 

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