Objective:To explore the diagnostic reference level(DRL)of computed tomography(CT)based on size-specific dose estimate(SSDE)for child's head,and estimate the SSDE by using tube current time production.Methods:The CT data of head of 1259 pediatric patients who underwent CT examination in Children's Hospital of Nanjing Medical University from January 2023 to December 2023 were retrospectively collected.They were divided into six groups according to different ages:<6 months group,6 months to<1 year group,1 to<3 years group,3 to<6 years group,6 to<12 years group,and≥12 years group.Additionally,they were divided into five groups based on body size:<12.5 cm group,12.5 to<14 cm group,14 to<15 cm group,15 to<16 cm group,and≥16 cm group.The volume CT dose index(CTDIVOL),tube current time production(mAs),left and right diameter(LRD),area(AROI)and CT value(CTROI)of region of interest of different age groups were respectively measured and recorded.The water equivalent diameter(DW),conversion factor(f H16)and SSDE based on DW(SSDEDW)were calculated.The DRLs distribution based on age and body size was analyzed by statistic method,and the correlation between DW and mAs was analyzed by regression analysis,and a regression model between SSDEDW and mAs was further established.The intra-group correlation coefficient(ICC)was used to analyze the consistency.Results:In DRLs of various age groups,the CTDIVOL range and SSDEDW range were respectively(12.32 mGy-21.66 mGy)and(13.47 mGy to 17.83 mGy).In the DRL of various body size groups,the CTDIVOL range and SSDEDW range were(13.52 mGy-21.86 mGy)and(13.91 mGy-17.92 mGy).In different ages group of pediatric patients,the range of deviation rates of local DRL(LDRLs)value of radiation dose on head of CTDIVOL value to SSDEDW was-8.54%-21.48%.There were strong positive correlations between DW and mAs at 100 and 120 kVp(r=0.96,0.89,P<0.001),respectively.There was stronger consistency between the calculated value by using SSDEDW and actual measurement value by using sAs(ICC=0.98).Conclusion:SSDEDW can more accurately reflect radiation dose,and SSDEDW can be more quickly calculated to control the radiation dose by using the regression models between SSDEDW and mAs.

Objective:To explore the diagnostic reference level(DRL)of computed tomography(CT)based on size-specific dose estimate(SSDE)for child's head,and estimate the SSDE by using tube current time production.Methods:The CT data of head of 1259 pediatric patients who underwent CT examination in Children's Hospital of Nanjing Medical University from January 2023 to December 2023 were retrospectively collected.They were divided into six groups according to different ages:<6 months group,6 months to<1 year group,1 to<3 years group,3 to<6 years group,6 to<12 years group,and≥12 years group.Additionally,they were divided into five groups based on body size:<12.5 cm group,12.5 to<14 cm group,14 to<15 cm group,15 to<16 cm group,and≥16 cm group.The volume CT dose index(CTDIVOL),tube current time production(mAs),left and right diameter(LRD),area(AROI)and CT value(CTROI)of region of interest of different age groups were respectively measured and recorded.The water equivalent diameter(DW),conversion factor(f H16)and SSDE based on DW(SSDEDW)were calculated.The DRLs distribution based on age and body size was analyzed by statistic method,and the correlation between DW and mAs was analyzed by regression analysis,and a regression model between SSDEDW and mAs was further established.The intra-group correlation coefficient(ICC)was used to analyze the consistency.Results:In DRLs of various age groups,the CTDIVOL range and SSDEDW range were respectively(12.32 mGy-21.66 mGy)and(13.47 mGy to 17.83 mGy).In the DRL of various body size groups,the CTDIVOL range and SSDEDW range were(13.52 mGy-21.86 mGy)and(13.91 mGy-17.92 mGy).In different ages group of pediatric patients,the range of deviation rates of local DRL(LDRLs)value of radiation dose on head of CTDIVOL value to SSDEDW was-8.54%-21.48%.There were strong positive correlations between DW and mAs at 100 and 120 kVp(r=0.96,0.89,P<0.001),respectively.There was stronger consistency between the calculated value by using SSDEDW and actual measurement value by using sAs(ICC=0.98).Conclusion:SSDEDW can more accurately reflect radiation dose,and SSDEDW can be more quickly calculated to control the radiation dose by using the regression models between SSDEDW and mAs.

Objective To explore the application values of fixed tube current based on head circumference(HC)in children's head CT examinations.Methods A total of 573 children's head CT imaging data were collected retrospectively,the tube current and HC were recorded.Pearson's correlation analysis was used to determine the relationship of tube current with HC,counted the median tube current values of each group based on HC and used them as the prefixed tube current.Seventy-two children were prospectively collected.According to the random number table method,the children were divided into the control group and the experimental group,with 35 cases in the control group and 37 cases in the experimental group.The control group used automatic exposure control(AEC)technology for tube current,while the experimental group used the median value of tube current corresponding to HC group-ing.The difference in radiation doses and image qualities between the two groups was compared.Results Pearson analysis of 573 retrospec-tive cases showed that the correlation between HC and tube current was considerably strong(r=0.95,P＜0.001).The median tube current values of each group based on HC were 70-130 mAs.There were statistically significant differences in CTDIvol.16 and SSDEDW based on water equivalent diameter(DW)between the two groups(t=-11.27,2.81,P＜0.05).Compared with the control group,CTDIvol.16 and SSDEDW in the experimental group decreased by 10.83％and 12.59％respectively.There were no statistically signifi-cant differences in signal-to-noise ratio(SNR)between the two groups(t=-1.26,P＞0.05)and there were also no statistically significant differences in the subjective evaluation of images(Z=-0.45,P＞0.05).Conclusion Measuring children's HC before examination and setting the fixed tube current corresponding to HC grouping can reduce radiation doses while maintaining image qualities.

Objective:To analyze the influence on radiation dose and image quality of children neck CT with anterior flexion of cervical spine using self-made sponge pad with DoseRight technique.Methods:A total of 125 children aged 1-5 years who underwent neck CT examination were consecutively collected prospectively. The patients were divided into control group and test group with computer random number method . The control group was supine on the scanning bed and fixed in the CT skull stent. The test group was supine on the scanning bed with a self-made sponge cushion under the neck to extend the head and droop the shoulder. The data was acquired with Philips Brilliance iCT and CTDI VOL was obtained from the dose report. SSDE ED and SSDE WD were calculated seperately.The image quality by measuring the noise value and signal-to-noise ratio of the paravertebral muscle area at the middle level of the third cervical vertebra and thyroid area. Subjective evaluation of image quality by 5-point scoring systemwas performed. Results:The noise values of paravertebral muscles and thyroid regions in the test group were lower than those in the control group( t=-6.93, -7.41, P<0.05), and the signal-to-noise ratios were higher than those in the control group ( t=5.74, 6.14, P<0.05). The subjective score of the test group (4.32±0.70) was better than that of the control group (3.70±0.66), and the difference was statistically significant ( Z=-4.27, P<0.05). The jaw-pharynx angle and the number of vertebra displayed of the test group were higher than those of the control group ( t=4.94, 5.09, P<0.05). CTDI VOL, and in the control group were 22.1%, 26.0% and 27.1% higher than those in the test group ( t=6.17, 5.11, 4.35, P<0.01). Conclusions: is more accurate to indicate the CT radiation dose of children. The self-made sponge pad keeping the cervical spine in anterior flexion can reduce radiation dose and improve image quality.

Objective: To confirm the effect of the relative position between upper limbs and cervicothoracic vertebrae on image quality and radiation dose while performing airway CT examination of children with airway foreign bodies. Methods: One hundred and three children, aged from 1 to 48 months were enrolled prospectively and divided into 3 groups according to the position of upper limbs.In group A, the upper limbs were raised beside the cervical vertebra, in group B, the upper limbs were placed beside the thoracic vertebra, and in group C, the upper limbs were raised about 45 degrees with sponge pads and placed beside the chest. Data were acquired by Philips 128iCT, and CT dose index (CTDI_vol) and dose-length product (DLP) were recorded and compared among three groups. The image qualities were evaluated subjectively and objectively. Results: Subjective score of cervical image quality in group B (4.33±0.72) and group C (4.19±0.63) were higher than that in group A (3.71±0.66), and the difference was statistically significant (Z=-3.19、-2.61, P<0.05). Subjective score of chest image quality in group A (4.21±0.47) was higher than that in group B (3.71±0.39) and group C (3.92±0.42), and group C was higher than that in group B, the difference was statistically significant (Z= -1.71, -2.08, P<0.05). The difference of DLP in group B (57.7±6.8) mGy·cm was higher than that in group A (51.6±7.6) mGy·cm and group C (51.3±6.3) mGy·cm, the difference was statistically significant (P<0.05), and there was no significant difference between group A and group C (P>0.05). Conclusions Raising upper limbs 45 degrees and placing them beside the chest will improve the CT image quality of airway and reduce the radiation dose.