Oscillating gradient diffusion kurtosis imaging of normal and injured mouse brains

Recent advances in diffusion MRI employ multiple diffusion encoding schemes with varying diffusion direction, weighting, and diffusion time to investigate specific microstructural properties in biological tissues. In this study, we examined time‐dependent diffusion kurtosis contrast in adult mouse brains and in neonatal mouse brains after hypoxic–ischemic (HI) injury. In vivo diffusion kurtosis maps were acquired with a short diffusion time using an oscillating gradient spin echo (OGSE) sequence at 100 Hz and with a relatively long diffusion time (20 ms) using a pulsed gradient spin echo (PGSE) sequence. In the adult mouse brain, we found that the cortex and hippocampus showed larger differences between OGSE kurtosis and PGSE kurtosis than major white matter tracts. In neonatal mouse brains with unilateral HI injury, the OGSE kurtosis map overall provided stronger edema contrast than the PGSE kurtosis map, and the differences between OGSE and PGSE kurtosis measurements in the edema region reflected heterogeneity of injury. This is the first in vivo study that has demonstrated multi‐direction OGSE kurtosis contrasts in the mouse brain. Comparing PGSE and OGSE kurtosis measures may provide additional information on microstructural changes after ischemic stroke.     

Endogenous motion of liver correlates to the severity of portal hypertension

BACKGROUND Degree of portal hypertension(PH) is the most important prognostic factor for the decompensation of liver cirrhosis and death, therefore adequate care for patients with liver cirrhosis requires timely detection and evaluation of the presence of clinically significant PH(CSPH) and severe PH(SPH). As the most accurate method for the assessment of PH is an invasive direct measurement of hepatic venous pressure gradient(HVPG), the search for non-invasive methods to diagnose these conditions is actively ongoing.AIM To evaluate the feasibility of parameters of endogenously induced displacements and strain of liver to assess degree of PH.METHODS Of 36 patients with liver cirrhosis and measured HVPG were included in the casecontrol study. Endogenous motion of the liver was characterized by derived parameters of region average tissue displacement signal(dantero, dretro, d RMS) and results of endogenous tissue strain imaging using specific radiofrequency signal processing algorithm. Average endogenous strain μ and standard deviation σ of strain were assessed in the regions of interest(ROI)(1 cm × 1 cm and 2 cm × 2 cm in size) and different frequency subbands of endogenous motion(0-10 Hz and 10-20 Hz).RESULTS Four parameters showed statistically significant(P 0.05) correlation with HVPG measurement. The strongest correlation was obtained for the standard deviation of strain(estimated at 0-10 Hz and 2 cm × 2 cm ROI size). Three parameters showed statistically significant differences between patient groups with CSPH, but only dretro showed significant results in SPH analysis. According to ROC analysis area under the curve(AUC) of the σROI[0…10 Hz, 2 cm × 2 cm] parameter reached 0.71(P = 0.036) for the diagnosis of CSPH; with a cut-off value of 1.28 μm/cm providing 73% sensitivity and 70% specificity. AUC for the diagnosis of CSPH for μROI[0…10 Hz, 1 cm × 1 cm] was 0.78(P = 0.0024); with a cut-off value of 3.92 μm/cm providing 73% sensitivity and 80% specificity. Dretro parameter had an AUC of 0.86(P = 0.0001) for the diagnosis of CSPH and 0.84(P = 0.0001) for the diagnosis of SPH. A cut-off value of-132.34 μm yielded 100% sensitivity for both conditions, whereas specificity was 80% and 72% for CSPH and SPH respectively.CONCLUSION The parameters of endogenously induced displacements and strain of the liver correlated with HVPG and might be used for non-invasive diagnosis of PH.     

Segregation of sperm subpopulations in normozoospermic infertile men

Sperm function is essential for fertilization and embryogenesis yet semen contain a heterogeneous population of sperm. This study was designed to evaluate two different sperm populations separated by the density gradient method. Semen from 25 idiopathic normozoospermic infertile men was processed by double density gradient centrifugation and evaluated for sperm present in the 50% (upper) layer and the 90% (lower) layer for reactive oxygen species (ROS), sperm chromatin integrity, and morphology. The population of sperm in the 90% layer showed significantly lower ROS levels (22.90 (0.92, 85.32) vs. 382.03 (158.30, 1409.51) and lower DNA fragmentation index (DFI) (24.26 (22.54, 25.50) vs. 29.93 (28.48, 31.25) and higher number of sperm with normal morphology (55 (45.0, 60.0) vs. 32.5 (20, 40) compared to sperm in the 50% layer. However, in the original raw semen, sperm DFI (27.02 (26.19, 27.76)) and percentage high DNA stainability (% HDS) (3.1 (2.40, 3.78)) cells were significantly higher compared to the 90% layer population. Density gradient separation of the sperm subpopulation from the original semen favors the selection of sperm with genome integrity, low levels of ROS, and normal morphology. Therefore presence of pathological sperm in the semen may disrupt the function of normal spermatozoa, and hence the selection of the normal sperm subpopulation may be a better candidate for assisted conception. Further studies are required to evaluate the gradient separated sperm population in assisted reproductive techniques (ART).     

MRI evaluation of fatty liver in day to day practice: Quantitative and qualitative methods

Intracellular fat accumulation is a common feature of liver disease. Steatosis is the histological hallmark of non-alcoholic fatty liver disease (NAFLD) but also may occur with alcohol abuse, viral hepatitis, HIV and genetic lipodystrophies, and chemotherapy. This condition is common in the Western population and is typically associated with obesity and the metabolic syndrome. Early diagnosis and early treatment of NAFLD are important to prevent the development of end-stage liver disease and cancer. In addition, liver fat is a risk factor for postoperative complications after liver resection and transplantation. MRI has become a primary modality to assess hepatic steatosis, both qualitatively and quantitatively. In this article we discuss various MRI methods for evaluation of hepatic steatosis.     

低场MR二维快速扰相梯度回波序列在颅脑检查中的应用

目的观察快速扰相梯度回波(2D FSPGR)在颅脑低场MR检查中的应用价值.方法随机对70例颅脑用翻转角(FA)为70°的2D FSPGR(2D FSPGR 70°)获得T1加权图像,与常规自旋回波(SE)T1WI作对照,比较轴向图像的成像速度、血管显示、清晰度、增强效果、灰白质对比等方面,计算相关的质量控制参数,包括信噪比(SNR)、对比度(C)及对比噪声比(CNR).结果2D FSPGR 70°的图像具有成像快速、血管显示为高信号、增强效果佳等特点.2D FSPGR与SET1WI的SNR、C及CNR分别为81.98、0.116、6.58和87.15、0.117、7.18,二者基本相当.结论2D FSPGR 70°在颅脑低场MR检查中具有许多SE T1WI无法比拟的优势,可以代替SE T1WI或作为T1加权的优先替补序列.     

Urinary clearance of albumin is critically determined by its tertiary structure

The excretion of serum albumin in the urine is considered the net result of renal glomerular filtration and tubular uptake. During routine experiments, we observed that a batch of tritium-labeled albumin yielded anomalous results, being excreted in the urine of isolated perfused kidneys at 10 times the rate of normal tritiated albumin. This anomalous albumin, when simultaneously studied with normal carbon 14-labeled albumin, exhibited 10 times greater excretion than normal [(14)C]albumin. Anomalous albumin could not be reversed to normal albumin by means of conditioning with blood. In vivo clearances of anomalous albumin could not be quantitated because anomalous albumin is degraded during circulation. Anomalous albumin appeared to have the same molecular size (as determined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, capillary electrophoresis, and gel chromatography) and isoelectric-point profile (2-dimensional electrophresis) as normal albumin. Normal albumin could be transformed to anomalous albumin with alkali/heat treatment. Reverse-phase high-pressure liquid chromatography analysis of fragments from tryptic digests of anomalous albumin, alkali/heat-treated albumin, and normal albumin suggest that anomalous albumin and alkali/heat-treated albumin have altered tertiary structure, possibly as a result of denaturation and disulfide exchange. These studies show that the tertiary structure of albumin, beyond simple size and charge, is a critical determinant for albumin processing by the kidney and suggest that a specific albumin-recognition event by the kidneys is critical to normal renal handling of albumin.     

冠状动脉CT血管造影管腔内衰减梯度的研究进展

冠状动脉CT血管造影（CCTA）广泛应用于冠状动脉疾病的诊断,但CCTA只能提供冠状动脉的解剖学信息,在分析冠状动脉功能性狭窄方面存在不足。随着CCTA一些新技术的发展,使得CCTA可同时提供冠状动脉的解剖学和功能学信息。本文对CCTA的管腔内衰减梯度（TAG）进行综述。     

Value of contrast enhanced spoiled gradient (SPGR) MR and MIP MR imaging in diagnosis of peri-anal fistula

Purpose

To assess the value of the combination of contrast enhanced T1 spoiled gradient (SPGR) MR and maximum intensity projection (MIP) MR imaging in the complete pre-operative evaluation of peri-anal fistula.

Patients and methods

This prospective study contained 28 patients with clinical diagnosis of peri-anal fistula, they were performed MRI using the following sequences in both axial and coronal planes: Pre contrast T2FSE, T1FSE and Post contrast SPGR. MIP reformated images were done using the SPGR sequence. Fistulas were classified according to Parks (6) classification, they were evaluated regarding site, type, extensions, complications and diagnostic accuracy of each sequence. Our findings were correlated with operative findings.

Results

Fourteen patients had inter-sphincteric fistulas (50%), 8 patients had trans-sphincteric fistulas (28.6%) and 6 patients had supra-sphincteric fistulas (21.4%). Simple non branching tracts were found in 22 patients, branching tracts in 6 patients, abscess cavity in 5 patients, horseshoe extension in 4 patients. Overall diagnostic accuracy of post contrast T1 SPGR was 97.3% and MIP MR imaging was 100%. Post contrast T1 SPGR accurately evaluated all patients but missed one faint horseshoe extension and other fine para anal branches. MIP imaging accurately evaluated all the extensions and ramifications but was poor in depth orientation.

Conclusion

MRI is a reliable diagnostic modality in the evaluation of peri-anal fistulas. Post contrast T1 SPGR sequence with its high resolution images and excellent anatomical orientation provides almost all the necessary details for accurate evaluation. Although MIP images lack depth orientation their high sensitivity, rotational 2D and 3D capabilities exquisitely depict all the fine ramifications and extensions. The combination of both provides complete evaluation and highest possible diagnostic accuracy aiding successful surgical interventions, aiming to reduce complications and recurrences.