Application Of Low Dose CT Urography In Children With Flash Dual Source CT

BackgroundPediatric surgical diseases constitute a great proportion of pediatric urinary system diseases in children, such as congenital malformations, hydronephrosis.When urinary tracts are filled with iodine contrast agent in the secretory phase of CT urography, the tracts show high-density, with the surrounding soft tissue low-density to form a good contrast, which provides the basis for the application of the low-dose CTU. Today, CT technology has entered the low-dose era. How to reduce the X-ray dose as far as possible under the premie of ensuring the diagnostic image quality is important content and direction in the current CT clinical research. In terms of reducing the radiation dose people have tried many techniques, such as automatic tube current regulation technology in scanning step, the iterative reconstruction technique in image reconstruction.ObjectiveTo explore the practical application of low-dose CT urography (CTU) in children with Flash dual-source CT.Methods30children ((?)15Kg) suspected hydronephrosis or urinary malformation via USG screening all undertook Flash Mode low dose CTU examination of second-generation dual source computed tomography.Post contrast parenchymal and excretory phase scannings were done with preset procotol of70kV tube voltage,tube current with automatic tube current adjustment technology (Care dose4D), adaptive dynamic tube current (40-60mAs),pitch=3.0,128x0.6mm slice acquisition,0.28seconds gantry rotation time.Scaning time,the volume CT dose index(CTDIvol),the overall dose-length product (DLP)of both the parenchymal and secretory phase dose were recorded and analysed in every case.The effective dose (ED) of each patient was calculated out. The raw data of each case was reconstructed by traditional filtered back projection (FBP) and five different level sinogram affirmed iterativere construction (SAFIRE) respectively.The mean CT value, noise, signal to noise ratio(SNR), contrast to noise ratio(CNR), image quality score of the different level reconstruction images at the same slice were analyzed by using statistic method. The accordance rate of imaging diagnosis between FBP images and SAFIRE-3images was analyzed. Analyze the accordance rate of imaging diagnosis between imaging diagnosis of SAFIRE-3, FBP reconstructed images and postoperative diagnosis,follow-up results.ResultsScanning time with FlashCTU sequence is in the range of0.62-0.82s,(重复了) is in the range of0.62-0.82s,the volume CT dose index(CTDIvol) is in the range of0.43-0.54mGy,the actual dose (DLP) of the total2phase scanning is in the range of20-34mGy*cm, the effective dose (ED) is in the range of0.60-0.68mSv. SNR and CNR values of SAFIRE images were higher than those of FBP. There were positive linear correlation between CNR and iterative reconstruction. SAFIRE-3images have the best quality of the five level iterative reconstruction(4.03±0.33). The accordance rate of imaging diagnosis between FBP images and SAFIRE-3images was100%. The accordance rate of imaging diagnosis between imaging diagnosis of SAFIRE-3,FBP reconstructed images and postoperative diagnosis,follow-up results was100%.ConclusionsLow-dose protocols of Flash dual-source CT can be applied to children CTU scanning, which can not only reduce the scan time, but also can meet the clinical diagnostic requirements.In children’s CTU application, low dose strategy should be recommended in clinical use. In addition, optimization of the scan protocols is possible.