Effect of Increasing Diffusion Gradient Direction Number on Diffusion Tensor Imaging Fiber Tracking in the Human Brain

OBJECTIVE: To assess the effects of varying the number of diffusion gradient directions (NDGDs) on diffusion tensor fiber tracking (FT) in human brain white matter using tract characteristics. MATERIALS AND METHODS: Twelve normal volunteers underwent diffusion tensor imaging (DTI) scanning with NDGDs of 6, 11, 15, 21, and 31 orientations. Three fiber tract groups, including the splenium of the corpus callosum (CC), the entire CC, and the full brain tract, were reconstructed by deterministic DTI-FT. Tract architecture was first qualitatively evaluated by visual observation. Six quantitative tract characteristics, including the number of fibers (NF), average length (AL), fractional anisotropy (FA), relative anisotropy (RA), mean diffusivity (MD), and volume ratio (VR) were measured for the splenium of the CC at the tract branch level, for the entire CC at tract level, and for the full brain tract at the whole brain level. Visual results and those of NF, AL, FA, RA, MD, and VR were compared among the five different NDGDs. RESULTS: The DTI-FT with NDGD of 11, 15, 21, and 31 orientations gave better tracking results compared with NDGD of 6 after the visual evaluation. NF, FA, RA, MD, and VR values with NDGD of six were significantly greater (smallest p = 0.001 to largest p = 0.042) than those with four other NDGDs (11, 15, 21, or 31 orientations), whereas AL measured with NDGD of six was significantly smaller (smallest p = 0.001 to largest p = 0.041) than with four other NDGDs (11, 15, 21, or 31 orientations). No significant differences were observed in the results among the four NDGD groups of 11, 15, 21, and 31 directions (smallest p = 0.059 to largest p = 1.000). CONCLUSION: The main fiber tracts were detected with NDGD of six orientations; however, the use of larger NDGD (> or = 11 orientations) could provide improved tract characteristics at the expense of longer scanning time.

The detection of glomeruar charge-barrier in children with nephrotic syndrome by the clearance method / 中华肾脏病杂志

Objective To observed the alteration of the glomerular charge-barrier (GCB) in children with idiopathic nephrotic syndrome(INS) and relationship between GCB and severity of proteinuria. Mothods The clearance ratios of pancreatic to salivary isoamylase(CPAM/CSAM) were detected in 21 cases with INS and 29 healthy controls by use of a selective inbibitor, then use the clearance ration to show the CCB. Results The ratio of CPAM/CSAM in the cases with massive proteinuria was mean 1. 18 (range 0.82 - l .54), in the cases with no-massive proteinuria was mean 2.06(1 .22 - 3. 14), in healthy controls was 3 .33 (l. 18 - 6.54). There was a significant difference in ratios CPAM/CSAM between three groups. As all cases with INS, the ratio was very significantly negatively correlated with 24-hour urine protein quantity, but not correlated when 24 hour proteinuria was in excess of 50 mg/kg. Conclusion GCB of the cases with INS is reduced, and of the cases with massive proteinuria almost dissappeared.