Reducing the radiation dose with the adaptive statistical iterative reconstruction technique for chest CT in adults: a parameter study / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography (CT) examination. This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis. This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.</p><p><b>METHODS</b>Seventy-two adult patients were examined by Gemstone Spectral CT. They were randomly divided into six groups. We set up a different value of noise index (NI) when evaluating each group every other number from 13.0 to 23.0. The original images were acquired with a slice of 5 mm thickness. For each group, several image series were reconstructed using different levels of adaptive statistical iterative reconstruction (ASIR) (30%, 50%, and 70%). We got a total of 18 image sequences of different combinations of NI and ASIR percentage. On one hand, quantitative indicators, such as CT value and standard deviation (SD), were assessed at the region of interest. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The volume CT dose index (CTDI) and dose length product (DLP) were recorded. On the other hand, two radiologists with ≥ 5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.</p><p><b>RESULTS</b>The different combinations of noise index and ASIR were assessed. There was no significant difference in CT values among the 18 image sequences. The SD value was reduced with the noise index's reduction or ASIR's increase. There was a trend towards gradually lower SNR and CNR with an NI increase. The CTDI and DLP were diminishing as the NI increased. The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.</p><p><b>CONCLUSIONS</b>Increasing NI can reduce radiation dose. With the premise of maintaining the same image quality, using a suitable percentage of ASIR can increase the value of NI. To assure image quality, we concluded that when the NI was set at 17.0 and ASIR was 50%, the image quality could be optimal for not only satisfying the requirements of clinical diagnosis, but also achieving the purpose of low-dose scanning.</p>

The influencing factors and methodological evaluation on tigecycline susceptibility testing methods for Acinetobacter baumannii and Klebsiella pneumoniae / 中华检验医学杂志

Objective To investigate the factors affecting the susceptibility of tigecycline and assess the testing methods.Methods The 116 isolates of Acinetobacter baumanaii and Klebsiella pneumoniae were collected in 13 hospitals from January to December,2010,to evaluate the effects on the tigecycline susceptibility of the overnight medium,medium brand and lot number,respectively.The 56 isolates of Acinetobacter baumannii and the 47 isolates of Klebsiella pneumoniae were selected randomly according to the MIC distribution proportion in 2010 and 2012.The broth microdilution was taken as the reference method to evaluate the effects of the agar dilution,disk diffusion,MIC Test Strip (MTS) and Vitek2 (GN16) on the susceptibility of tigecycline.Results The essential agreement (EA) of Acinetobacter baumannii and Klebsiella pneumoniae is 89.7％ (52/58)and 87.9％ (51/58) using overnight medium and fresh medium respectively.Both EA and categorical agreement (CA) of the different brands (BBL and Oxoid) and lot numbers are 100％ using agar dilution.According to the FDA break point criteria,the CA/EA is 77.7％ (80/103)/99.0％ (102/103),87.4％ (90/103)/98.1％ (101/103),64.1％ (66/103)/76.7％ (79/103) using agar dilution,MTS,Vitek (GN16) with respect to broth microdilution.The CA is 79.6％ (82/ 103,S≥14 mm,R≤10 mm),69.9％ (72/103,S≥ 16 mm,R≤ 12 mm),34.0％ (35/103,S≥19 mm,R≤14 mm)using disk diffusion method compared with broth microdilution (FDA break point criteria).Conclusions The susceptibility of tigecycline must be tested using fresh medium.The medium brands and lot numbers used in this test have no effects on the tigecycline susceptibility to Acinetobacter baumannii and Klebsiella pneumoniae.There exist the better correlations on MIC using agar dilution and MTS than the disk diffusion and Vitek(GN16) compared with broth microdilution.It is expected that the consistency can be improved by adjusting the break point of disk diffusion.