Evaluation On The Effect Of Flash Mode Of Dual Source Computed Tomography In Children With Post-infectious Bronchiolitis Obliterans

PARTⅠFeasibility study on application of low tube voltage using Flash mode of DSCT in pediatric chest CT scanObjectiveTo evaluate the impact of three different tube voltages on image quality and radiation dosage in pediatric chest examination with Flash mode (subsecond high-pitch scan mode, HPM=3.0) of dual-source computed tomography (DSCT) and to analyze the feasibility of the low-voltage CT scan.MethodsThis was a prospective analysis. A total of93patients undergoing chest scans with Flash mode of DSCT were enrolled in this study and divided into three groups equally according to different tube voltages (group1:80kV,34cases; group2:100kV,29cases; group3:120kV,30cases). The image quality was evaluated by two radiologists using4-point scores independently. Image attenuation and noise were measured. Signal-to-noise-ratio (SNR) and effective dose were calculated. The effective mAs, CTDlvol and DLP were recorded and to use SPSS Statistics18.0statistical software for data processing and analysis. ResultsThe average image quality score of the three groups was (3.12±0.640),(3.69±0.471) and (3.80±0.407). The average SNR was (4.25±0.945),(5.46±1.790) and (5.88±1.665). There was significant difference in score and SNR between group1and2, group1and3(P<0.05). There was no difference between group2and3(P>0.05). The average CTDlvol was (1.05±0.056) mGv,(2.14±0.306) mGv and (2.63±0.697)mGv. The average ED was (0.69±0.086) mSv,(1.36±0.250) mSv and (1.84±0.808)mSv. There was significant difference in CTDlvol and ED among three groups(P<0.05).ConclusionThe Flash mode of DSCT under100kV has comprehensive advantages in reducing radiation dose while ensuring high image quality, and is of great clinical application value in the pediatric chest CT scan, especially in the observation of fine structures, such as small airways, interstitial tissues, and so on.PARTⅡAnalysis on radiological image of Flash mode using DSCT and pathogenesis in children with post-infectious bronchiolitis obliteransObjectiveTo analysis radiological image of Flash mode using DSCT in children with post-infectious bronchiolitis obliterans (PIBO) and re-investigate its pathogenesis.MethodsA total of65patients with clinical confirmation of PIBO were included in this study. All patients (55boys,12girls; mean age:18months, range:4months-4years) were examined by a dual source CT system in a Flash mode (subsecond high-pitch scan mode, HPM=3.0). Scan parameters were as follows:100kV tube voltage, tube current with automatic tube current adjustment technology (Care dose4D on), pitch=3.0,128x0.6mm slice acquisition,0.28seconds gantry rotation time. The gonads of all children were protected with lead aprons. None of the patients was sedated for the CT examination and no breathing instructions were given. We analyzed the imaging findings, including frequency, distribution and the changes of lung markings(vascular).ResultsThe frequency of main signs included:bronchial wall thickening in64cases (98.46%), bronchiectasis in20cases (30.77%), air trapping in65cases (100%), mucus plugging in42cases (64.62%), bronchiolectasis in21cases (32.31%), accompanied with inflammation in54cases (83.08%); and there were three changes of lung markings in air trapping areas:attenuation in38cases (58.46%), normal in20cases (30.77%) and slightly increased in7cases (10.77%). Distribution:bronchial wall thickening occurred in all lung segments in57cases (87.69%), and the lower lobe was the most commonly occurred part; bronchiectasis most commonly occurred in the posterior basal segment of the left lower lobe (14/65,21.54%); air trapping occurred in12or more lung segments in53cases (81.54%), in all lung segments in44cases (67.69%), and like mucus plugging, the posterior basal segment of the left lower lobe was their most commonly occurred part, which were in65cases (100%) and32cases (49.23%).ConclusionThe Flash mode of DSCT can show abnormal radiological features and their distribution in children with PIBO more precisely, and the diffuse distribution of these abnormal images suggest that the immune system may be involved in the formation of PIBO in children.