Compressed sensing with signal averaging for improved sensitivity and motion artifact reduction in fluorine‐19 MRI

Fluorine‐19 (¹⁹F) MRI of injected perfluorocarbon emulsions (PFCs) allows for the non‐invasive quantification of inflammation and cell tracking, but suffers from a low signal‐to‐noise ratio and extended scan time. To address this limitation, we tested the hypotheses that a ¹⁹F MRI pulse sequence that combines a specific undersampling regime with signal averaging has both increased sensitivity and robustness against motion artifacts compared with a non‐averaged fully sampled pulse sequence, when both datasets are reconstructed with compressed sensing. As a proof of principle, numerical simulations and phantom experiments were performed on selected variable ranges to characterize the point spread function of undersampling patterns, as well as the vulnerability to noise of undersampling and reconstruction parameters with paired numbers of x signal averages and acceleration factor x (NAx ‐AFx ). The numerical simulations demonstrated that a probability density function that uses 25% of the samples to fully sample the k‐space central area allowed for an optimal balance between limited blurring and artifact incoherence. At all investigated noise levels, the Dice similarity coefficient (DSC) strongly depended on the regularization parameters and acceleration factor. In phantoms, the motion robustness of an NA8‐AF8 undersampling pattern versus NA1‐AF1 was evaluated with simulated and real motion patterns. Differences were assessed with the DSC, which was consistently higher for the NA8‐AF8 compared with the NA1‐AF1 strategy, for both simulated and real cyclic motion patterns (P < 0.001). Both strategies were validated in vivo in mice (n = 2) injected with perfluoropolyether. Here, the images displayed a sharper delineation of the liver with the NA8‐AF8 strategy than with the NA1‐AF1 strategy. In conclusion, we validated the hypotheses that in ¹⁹F MRI the combination of undersampling and averaging improves both the sensitivity and the robustness against motion artifacts.     

重组碱性成纤维细胞生长因子通过Notch1信号通路对糖尿病大鼠视网膜神经节细胞的保护作用

目的　探讨重组碱性成纤维细胞生长因子(recombinant basic fibroblast growth factor,rbFGF)通过Notch1信号通路对糖尿病大鼠视网膜神经节细胞(retinal ganglion cell，RGC)的保护作用。方法　雄性SD大鼠40只，随机分成对照组、糖尿病组、rbFGF组、rbFGF+DAPT组(DAPT为Notch1通路的特异性拮抗剂)，每组10只。后三组大鼠采用单次腹腔注射链脲佐菌素(streptozotocin,STZ) 诱导糖尿病模型。模型诱导成功后，rbFGF组给予rbFGF 10 μL(200 U)玻璃体内注射给药，rbFGF+DAPT组在给予rbFGF基础上加用DAPT(10 μmol·L^-1)。注射12周后，HE染色检测RGC密度，免疫组织化学染色检测神经元再生相关蛋白GAP-43、Notch1蛋白表达，Western blot检测GAP-43、Notch1蛋白及凋亡相关蛋白Caspase-3相对表达量。结果　与对照组RGC密度(433.49±6.02)个·mm^-2，GAP-43荧光强度(8.96±0.26)%、Notch1阳性率(45.04±0.46)%及Caspase-3 (27.91±0.63) %蛋白表达相比，糖尿病组RGC密度(328.35±6.43)mm^-2，Notch1荧光强度(31.66±0.40)%蛋白表达明显降低，GAP-43荧光强度(13.66±0.52)%、Caspase-3 (48.91±0.64)%蛋白表达明显增加(均为P<0.05)；而与糖尿病组相比，rbFGF组RGC密度(425.30±7.98)个·mm^-2，Notch1阳性率(41.76±0.62)% 及GAP-43荧光强度(33.05±0.37)%蛋白表达明显增加，Caspase-3 (28.86±0.71)%蛋白表达明显降低(均为P<0.05)；而rbFGF+DAPT组RGC密度(324.91±8.22)个·mm^-2，GAP-43荧光强度(14.27±0.64)%、Notch1阳性率(30.40±0.82)%及Caspase-3 (47.63±0.68)%蛋白表达均无明显变化(均为P>0.05)。结论　rbFGF可上调糖尿病状态下视网膜GAP-43蛋白表达，下调Caspase-3蛋白表达，进而提高RGC的存活，其机制可能与激活Notch1信号通路有关。     

基于SNP芯片研究PI3K/Akt/mTOR通路上自噬相关基因SNPs与胃癌的关联

目的： 探讨与胃癌发生相关的PI3K/Akt/mTOR通路上新的与自噬相关基因单核苷酸多态性位点（SNPs），为寻找有价值的胃癌发生相关的分子标志物提供新的依据。方法： 采用1：1配对病例-对照研究的方法。通过KEGG pathway网站和Gene Ontology、Ensemble数据库及HaploView、STRING、Cytoscape软件联合SNP芯片筛选目标SNPs，采用基质辅助激光解吸电离飞行时间质谱（MALDI-TOF-MS）对筛检出来的SNPs位点在来自福建省仙游县的622例胃癌患者和622例健康人群基因组中进行验证。结果： SNP芯片及生物信息学分析筛选出IRS1 rs10205233、PIK3CD rs3934934、PIK3R1 rs706711、PIK3R1 rs706714和AKT1 rs35285446为候选位点。扩大样本验证发现IRS1 rs10205233的多态性变异（C > T）显著降低了胃癌的发病风险[共显性模型、显性模型的OR（95% CI）分别为0.761（0.595，0.975）、0.764（0.601，0.973）]。进一步分层分析，该位点显性模型、隐形模型、共显性模型以及等位基因在贲门癌和非贲门癌人群中均未见统计学差异（P > 0.05）。并未见其他位点与患胃癌风险的关联有统计学意义。对PIK3R1基因2个位点（rs706711、rs706714）的单体型分析也未见统计学差异。结论： IRS1 rs10205233位点与福建省胃癌高发区仙游县的胃癌发生存在关联，T等位基因可能是胃癌发生的一个遗传保护因素。     

电针百会、腰奇穴对戊四氮致痫大鼠海马区脑电信号的影响

目的:通过研究电针百会、腰奇穴对戊四氮致痫大鼠脑电信号波幅、频率和功率谱密度的改变,探讨电针治疗戊四氮致痫大鼠的机制,为电针的抗痫作用提供理论依据。方法:将20只大鼠左右海马处植入电极,恢复7 d后进行戊四氮造模,造模成功的大鼠电针百会、腰奇穴治疗14 d。记录SD大鼠正常时、癫痫发作时、电针治疗时、电针治疗后脑电波信号,对截取的信号强度进行时域分析,傅里叶变换后进行频域分析。结果:电针百会、腰奇穴可以降低PTZ致痫大鼠发作期的波幅(P<0.01),升高被降低的Beta频段、Gamma频段主频率(P<0.01),降低各频段能量值(P<0.01),重新调整各波段的能量比重,使趋势接近正常大鼠。结论:电针百会、腰奇穴对戊四氮致痫大鼠的抗癫痫作用与兴奋GABA中间抑制性神经元的电生理活动有关。