Investigation On Radiation Dose And Study On Optimizing Scanning Parameters Of Multi-slice Spiral CT In Ningxia

Objective To investigate the current status of CT radiation dose of adults in Ningxia,and provide the basic data to establish the first diagnostic reference level of adult people CT scanning.Methods By stratified cluster sampling method to investigate the using status and the radiant status of various brands and different models CT scanners of different grade hospital in Ningxia,by interval sampling to obtain scanning parameters and radiant dose values for different scanning items of the surveyed unit each day.Collecting basic information include hospitals,CT scanner,scanning items,scanning types and patients,recording CT scanning parameters,CTDI_volol and DLP values,calculating effective dose values;The data were statistically analyzed by scanning items and compared with the DRL values recommended by other countries.Results Finally,there are 45 medical institutions in this study,including 10public tertiary A hospitals,5 public tertiary B hospitals,23 public secondary A hospitals,5 private hospitals and 2 physical examination centers.58 CT scanners from 6 manufacturers and 4,952 adult patients were investigated.The 75th percentile?P75?of CTDIvol,DLP,and patient E values of common scanning items are listed as follows:in skull scanning 65.7 mGy,860.4 mGy·cm,1.4 mSv;in neck scanning 29.2 mGy,490.0 mGy·cm,2.8 mSv,in neck enhanced scanning 36.9 mGy,954.4 mGy·cm,4.9 mSv;in chest scanning 11.5 mGy,382.06 mGy·cm,5.7 mSv,in chest enhanced scanning 45.8 mGy,1713.2 mGy·cm,25.0 mSv;in upper abdominal scanning 20.1 mGy,506.6 mGy·cm,7.8 mSv,in upper abdominal enhanced scanning 50.1 mGy,1434.2 mGy·cm,21.9 mSv;in abdominal-pelvic scanning 14.3 mGy,670.8 mGy·cm,10.3 mSv,in abdominal-pelvic enhanced scanning 48.0 mGy,2294.0 mGy·cm,35.1 mSv;in pelvic scanning 16.1 mGy,471.6 mGy·cm,6.8 mSv,in pelvic enhanced scanning 31.4 mGy,1138.8 mGy·cm,14.7 mSv.Conclusion The CT scanning radiation doses of skull,neck,chest and pelvis in Ningxia are lower than other countries or are not much different,but the abdominal scanning dose is significantly higher than other countries.It is high time to optimize the abdominal CT scanning protocol.Objective Taking CT urography?CTU?as an example,which is a multi-phase and high-frequency examination in abdominal CT,To compare the optimal parameters and radiation dose values of CT urography of patients with different body mass index,and explore the optimization of radiation dose control for abdominal CT scan.Methods Prospectively collected 133 patients who were required to undergo CT urography,according to three different CT urography scan types,the first type was conventional parameters scan?120 k Vp,CARE Dose4D?,the second was low k Vp scan?BMI ? 22.9: 80 k Vp,22.9 < BMI < 30: 100 k Vp,BMI ? 30:120 k Vp,CARE Dose4D?and last one was low m As scan?120 k Vp,40% reduction in m As on CARE Dose4D?.The noise,signal-to-noise ratio?SNR?and contrast-to-noise ratio?CNR?of all images were measured as objective evaluation indicators of image quality.The subjective evaluation of the images was performed by two radiologists who had been working for more than five years,using a double-blind method and a 5-point scale.The radiation dose values(CTDI_vol,DLP,E)of each group were recorded.Results Patients' effective dose decreased by 77.7% in 80 k Vp group and38.3% in 100 k Vp group,there was a statistical difference between groups?z=-3.330,-5.559,P<0.05?.There was a statistically significant difference in renal cortex noise,SNR,CNR and ureteral noise between the 80 k Vp scan and the routine scan?z=-3.705 ^-2.392,P<0.05?,but there was no significant difference in the ureteral SNR,CNR and renal pelvis noise,SNR,CNR?P >0.05?.There was a statistically significant difference in renal cortex noise and SNR between the100 k Vp scan group and the routine scan group?z=-5.096,-3.66,P<0.05?,but there was no statistical difference in renal cortex CNR,renal pelvis and ureteral noise,SNR,CNR?P >0.05?.The effective dose of low m As scan in the above three types patients decreased by 38.3%,32.0%,and 34.7%,respectively,and there was a statistical difference between them?P <0.05?.there was no significant difference in noise,SNR,and CNR between renal cortex,renal pelvis and ureter?P>0.05?besides ureteral CNR in 22.9 < BMI < 30 group?z=-2.587,P<0.05?.The subjective evaluation scores of all images were greater than 3 points.Conclusion In this study,the scan schemes for low k Vp and low m As used in patients with different body mass index can effectively reduce the radiation dose of patients and meet the requirements of clinical diagnosis.And the smaller the BMI,the greater the reduction.