[Impact of iterative reconstruction on shape reproducibility of three-dimensional computed tomography].

The purpose of this study was to evaluate the effect of an iterative reconstruction method (IR) on shape reproducibility in three-dimensional (3D) computed tomography images. We used an IR (sinogram-affirmed iterative reconstruction: SAFIRE) implemented in a 64-channel multi slice computed tomography system (Siemens, SOMATOM Definition AS). We scanned a simulated vessel phantom with 180-HU vessel contrast at various radiation doses and reconstructed axial images of filtered back projection (FBP) and SAFIRE. Then we reconstructed multi-planar reconstruction (MPR) and volume rendering (VR) images from the axial images. Roundness was evaluated from MPR images and vessel surface roughness was evaluated from pixel value profiles of a vessel in VR images and visual evaluation by radiological technologists. In comparison on equivalent dose, the roundness and roughness were improved with increase of SAFIRE strength level. However, in comparison on equivalent noise (standard deviation: SD) of axial images, SAFIRE strength levels of 2 to 5 were significantly inferior to FBP (p<0.05). SAFIRE strength of 1 with a dose reduction of 19% maintained the shape reproducibility in all evaluations. Therefore, it would be not appropriate to use the SD of axial image as index for the dose reduction rate determination of 3D-CT images.

Decreased abundance of urinary exosomal aquaporin-1 in renal ischemia-reperfusion injury.

Urinary exosomes, secreted into urine from renal epithelial cells, are known to contain many types of renal functional membrane proteins. Here, we studied whether renal ischemia-reperfusion (I/R) affects urinary exosomal aquaporin-1 (AQP1) excretion in rats subjected to renal I/R and patients who underwent renal transplantation. Immunoblotting studies demonstrated reduction of the urinary exosomal AQP1 level even at 6 h after renal I/R, and the level continued to be low over 96 h after I/R. Renal AQP1 mRNA and protein analyses revealed that the decreased excretion of urinary exosomal AQP1 is associated with renal AQP1 protein retention in the early phase and with a decreased expression level of renal AQP1 in the later phase of renal I/R injury. Decreased abundance of urinary exosomal AQP1 in a recipient patient was also observed at 48 h after renal allograft transplantation. No significant decrease in urinary exosomal AQP1 was observed in a rat model of nephropathy or in patients with proteinuria. Our studies suggest that the renal AQP1 expression level is possibly controlled by its urinary exosomal excretion and indicate that urinary exosomal AQP1 is a novel urinary biomarker for renal I/R injury.