T2 gradient echo sequence

Figure 2.2.14 shows cross-sections of salmon acquired with a gradient echo sequence (TR = 30 ms, TE = 15 ms, slice thickness = 4 cm, image matrix = 128 x 128, total acquisition time = 3.84 s). For the female salmon, roe were clearly visualized as dark regions because the T2 is shorter than that of the surrounding tissues. For the male salmon, milt was observed instead of roe. However, the image intensity of the milt was similar to that of the surrounding tissues. 

For PI, basically all fast and strongly T2 w sequences can be used. In the early days of PI, measurements were performed using fast, T2 w gradient-echo sequences, particularly the fast low angle shot... 

Detection of Microbleeds. A second disadvantage of using CT rather than MR imaging for stroke assessment is the decreased sensitivity for detection of cerebral microbleeds compared with gradient-echo sequences. Microbleeds detected on T2 -weighted MR imaging, however, have been shown not to be a contraindication to thrombolysis [97]. 

Hermier, M., et al., MRI of acute post-ischemic cerebral hemorrhage in stroke patients diagnosis with T2 -weighted gradient-echo sequences. Neuroradiology, 2001. 43(10) p. 809-15. 

Fig. 3.6a-C. MDCT in portal venous phase (a) and MRI with a Tl-w 3D gradient-echo sequence after gadolinium-injection (b) and a T2 -w gradient-echo sequence after injection of the SPIO contrast agent ferucarbotran (c) in a male patient suffering from a colorectal carcinoma in whom atypical resection of a liver metastasis in the right lobe of the liver had been performed previously. Note the postoperative bilioma (marked by the asterisk). In the MDCT examination no further liver lesions can be detected, whereas the gadolinium-enhanced MRI faintly shows a hypervascular lesion arrow). The SPlO-enhanced MRI scan clearly depicts a newly developed metastasis with a high contrast between lesion and adjacent liver parenchyma...

Typically, 3D FT volume studies have been conducted with gradient echo sequences that could offer short acquisition time due to their short repetition time. Currently, 3D fast or turbo spin echo sequences can be applied clinically, and they offer pure T2-weighted volumetric images without susceptibility artifacts. Although fast or turbo spin echo sequences utilize... 

T2-weighted gradient-echo sequences with the steady-state free precession (SSFP) technique were initially usedby Wallner et al. (1991), Morimoto et al. (1992),HALL-CRAGGsetal. (1993), and IsmzAKiet al. (1993). Subsequently, other investigators have utilized two-dimensional (2D) and three-dimensional (3D) heavily T2-weighted fast spin-echo sequences... 

Fig. 2.9a,b. Multiple cavernomas. T2 -weighted gradient echo sequence. There are multiple cavernomas in both cerebral hemispheres and the cerebellum. The T2 sequence is particularly sensitive to hemosiderin... 

This BOLD MRI approach was discussed in detail in a recent review (Grenier et al. 2003). Using a multi-echo gradient-echo sequence, R2 maps can be obtained showing a higher R2 within the medulla (i.e., lower PO2) (Fig. 3.43). The BOLD technique does not measure pOj directly but allows intrarenal R2 (1/ T2 ) measurements that are dosely associated with the deoxyhemoglobin concentration. Therefore, absolute R2 values caimot be used in practice. 

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