The sequence of a multiecho gradient recalled echo (GRE) T2*-weighted imaging (T2*WI) is a relatively new magnetic resonance imaging (MRI) technique. In contrast to T2 relaxation, which acquires a spin echo signal, T2*relaxation acquires a gradient echo signal. The sequence of a GRE T2*WI requires high uniformity of the magnetic field. GRE T2*WI can detect the smallest changes in uniformity in the magnetic field and can improve the rate of small lesion detection. In addition, the T2*value can indirectly reflect changes in tissue biochemical components. Moreover, it can be used for the early diagnosis and quantitative diagnosis of some diseases. This paper reviews the principles and clinical applications as well as the advantages and disadvantages of GRE T2*WI.

Magnetic resonance imaging for local complications of acute pancreatitis: A pictorial review

Impairment of adult neurogenesis in the hippocampus causes cognitive deficits; however, the underlying molecular mechanisms have not been fully elucidated. microRNAs (miRNAs) regulate neural stem cell (NSC) function. With the use of a transgenic mouse line with conditional ablation of the miR‐17‐92 cluster in nestin lineage NSCs, we tested the hypothesis that the miR‐17‐92 cluster regulates adult neurogenesis and cognitive function in vivo . Compared with wild‐type mice, ablation of the miR‐17‐92 cluster significantly reduced the number of proliferating NSCs and neuroblasts and neuronal differentiation in the dentate gyrus (DG) of the hippocampus and significantly impaired hippocampal‐dependent learning and memory, as assayed by social recognition memory, novel object recognition, and Morris water‐maze tests. Statistical analysis showed a highly significant correlation between newly generated neuroblasts in the DG and cognition deficits in miR‐17‐92 knockout (KO) mice. Western blot analysis showed that conditional KO of the miR‐17‐92 cluster significantly increased and reduced a cytoskeleton‐associated protein, Enigma homolog 1 (ENH1), and its downstream transcription factor, inhibitor of differentiation 1 (ID1), respectively, as well as increased phosphatase and tensin homolog gene. These proteins are related to neuronal differentiation. Our study demonstrates that the miR‐17‐92 cluster in NSCs is critical for cognitive and behavioral function and regulates neurogenesis and that the miR‐17‐92 cluster may target ENH1/ID1 signaling.—Pan, W. L., Chopp, M., Fan, B., Zhang, R., Wang, X., Hu, J., Zhang, X. M., Zhang, Z. G., Liu, X. S. Ablation of the microRNA‐17‐92 cluster in neural stem cells diminishes adult hippocampal neurogenesis and cognitive function. FASEB J. 33, 5257–5267 (2019). www.fasebj.org

Magnetic resonance imaging for acute pancreatitis