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Objective To investigate the image quality,radiation dose and iodine intake of CT pulmonary angiography (CTPA) in patients using low tube voltage (100 kVp) combination of different noise indexes (NI) and low concentration contrast agent.Methods A total of 80 patients with suspected pulmonary embolism (PE) and other pulmonary diseases who had undergone CTPA were divided into four groups (A,B,C and D),with 20 patients in each group.Group A underwent 120 kVp CT scan protocol in combination with NI=25 and 370 mg iodine/ml contrast agent,while groups B,C and D underwent 100 kVp CT scan protocol in combination with NI=30,35,40,and 320 mg iodine/ml contrast agent,respectively.All images were restructured using 60％ adaptive statistical iterative algorithm 2.0.Objective image quality evaluation included CT values of pulmonary artery,noise values of pulmonary artery,signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).Subjective image evaluation used a 5-point scoring method and was conducted by two independent radiologists.The CT dose index of volume (CTDIvol),dose-length product (DLP) and iodine intake was recorded,and the mean value was calculated.The DLP was converted to the effective dose (ED).Analysis of Variance or Kruskal-Wallis test was used to evaluate the differences among the four groups in terms of image quality,radiation dose and iodine intake.Results There was a significant difference in CT values of pulmonary artery among the groups A,B,C and D (P＜0.05),and the CT values of pulmonary artery of group A was the lowest.There was no significant differences in noises of pulmonary artery,SNR,CNR and subjective indexes scores among the groups A,B,C and D (P＞0.05).There was a significant difference in iodine intake among the groups A,B,C and D,iodine intake of the group A was the highest,iodine intake of the group D was the lowest.The iodine intake of groups B,C and D decreased by 12.4％ (42/340),13.2％ (45/340) and 15.0％ (51/340) relative to group A,respectively.There was a significant difference in radiation dose among the groups A,B,C and D,The CTDIvol,DLP and ED of group D decreased by 45.3％ (3.9/8.6),48.6％ (120/247) and 48.3％ (2.02/4.18) relative to group A,respectively (P＜0.01).Conclusion Low tube voltage combination with high NI value and low concentration contrast agent can more effectively reduce the radiation dose and iodine intake for CTPA while maintaining diagnostic image quality.
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Objective To investigate the effect of different noise index (NI) combined with iterative recombination on the image quality and radiation dose of CT scan in patients with different body mass index (BMI). Method One hundred and sixty patients who had a liver CT enhanced scan were divided into group A (18 kg/m2≤BMI<24 kg/m2 ) and group B (24 kg/m2≤BMI<31 kg/m2) according to BMI, and each group had 80 patients. The two groups were randomly divided into 4 subgroups which NI value was 11, 13, 15 and 17 respectively. All images were restructured with 50% adaptive statistical iterative reconstruction. Subjective evaluation, objective evaluation [signal noise ratio (SNR) and contrast noise ratio (CNR)] and the effective dose of each group were recorded and calculated after the scan. ANOVA and Kruskal-Wallis test were used to evaluated the difference of imaging quality and radiation dose. Results In group A, the SNR, CNR and the subjective score of the later arterial phase images showed a statistical difference between NI=17 group and other subgroups (P<0.05), while there was no statistical differences among the other three subgroups during three CT enhanced phase. The average ED of NI=15, 17 group were decreased by 57.56%(2.17/3.77) and 61.54% (2.32/3.77) compared with NI=11 group, respectively. In group B, the SNR, CNR and the subjective image scores of the later arterial phase showed a significant difference between NI=15 and NI=11, 13 group (P<0.05). There was a statistically difference of image quality in group NI=17 compared with the other three subgroups in the later arterial phase, portal venous phase and equilibrium phase (P<0.05). The average ED of NI= 13, 15 group was decreased by 26.41% (1.69/6.40) and 45.31%(2.90/6.40) compared with NI=11 group, respectively. Conclusion Upon maintaining diagnostic imaging quality, setting different NI according to BMI and applying the iterative reconstruction algorithm can effectively reduce the radiation dose of liver CT enhanced scanning.
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Objective To compare the image quality and radiation dose of CTA of the kidney in patients using routine CT and the spectral imaging combination of different scanning protocols with the adaptive statistical iterative reconstruction 2.0 algorithm (ASIR 2.0). Methods A total of 90 patients who had undergone a CTA of the kidney were divided into three groups (A, B and C), with 30 patients in each group. Group A underwent a routine CT examination, and the scan parameters are:120 kVp, 30 to 650 mA, rotation time 0.5 s/r, scan FOV 50 cm × 50 cm;while groups B and C underwent spectral imaging protocol 1 and 2, the scan parameters of spectral imaging protocol 1 and 2 are:rapid dual kVp (80-140 kVp) switching in 0.25 ms, 375 mA and 360 mA, rotation time 0.7 s/r and 0.6 s/r, scan FOV 36 cm × 36 cm and 32 cm × 32 cm, respectively. All images were reconstructured using ASIR 2.0. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated when the kidney CTA was completed. Each subjective image evaluation used a 5-point scoring method and was conducted by two independent radiologists. The CT dose index (CTDIvol) and dose-length product (DLP) were recorded, and the mean value was calculated. The DLP was converted to the effective dose (ED). All data were compared with Kruskal-Wallis test and one-way ANOVA. Results The energy level of 49 to 56 keV was found to provide the best CNR for displaying CTA of the kidney. There were significant differences in CT values, noise, SNR, CNR and subjective score between groups B, C and A (P0.05). There were significant differences in ED among groups A, B and C (P<0.05), and the ED of groups A, B and C were (8.2±1.2), (5.2± 0.9) and (4.4 ± 0.7) mSv, respectively. Conclusion Spectral imaging with different scanning protocols can more effectively reduce the radiation dose than the routine CT scan mode for a kidney CTA while still maintaining diagnostic image quality, and protocol 2 of spectral imaging in our study is recommended.
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Objective To investigate the feasibility of automatic spectral imaging protocol selection (ASIS) and adaptive statiatical iterative reconstruction (ASiR) technique to reduce radiation dose and dose of contrast agent.Methods Sixtyfour patients underwent routine abdominal examination were randomly divided into two groups.The test group used ASIS technique,with 30％ ASiR and 50％ ASiR reconstruction algorithm.The control group used 120 kVp tube voltage,FBP reconstruction method.The noise of liver,pancreas,sacrospinal muscle,CNR of liver and pancreas,subjective image score in arterial phase and portal venous phase were compared between the image of 70 keV+30％ ASIR and control group.CNR of abdominal aorta and its branchs,CNR of portal vein,and subjective image score were statistically analyzed between im age 55 keV+50％ ASiR and control group in the arterial phase and portal venous phase.Results Compared with control group,CT dose index volume for arterial phase and portal venous phase in test group decreased by 23.68％,23.57％ and dose length product decreased by 25.61％,18.45 ％,total contrast injection decreased 16.86 ％,the noise of liver,pancreas and sacrospinal muscle in 70 keV+30％ ASiR were lower than those of control group in abdominal arterial and portal phase (all P＜0.05).CNR of abdominal aorta,superior mesenteric artery,celiac axis and score in 55 keV+50％ ASiR were higher than those of control group in abdominal arterial phase (all P＜0.05),CNR of portal vein and score in portal phase had no statistically difference (all P＞ 0.05).Conclusion Combining of ASIS and ASiR including 70 keV + 30％ ASiR and 55 keV+50％ ASiR,images are superior to that of the conventional 120 kVp+FBP scan mode for abdominal CT image and vessel image quality,which can reduce the radiation dose and the dose of contrast agent.
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Objective To investigate the best weighting of adaptive statistical iterative reconstruction (ASIR) algorithm and optimized low-dose scanning parameters in thoracic aorta CT angiography(CTA).Methods Totally 120 patients with the body mass index (BMI) of 19-24 were randomly divided into 6 groups.All patients underwent thoracic aorta CTA with a GE Discovery CT 750 HD scanner (ranging from 290-330 mm).The default parameters (100 kV,240 mAs) were applied in Group 1.Reconstructions were performed with different weightings of ASIR (10％-100％ with 10％),and the signal to noise ratio (S/N) and contrast to noise ratio (C/N) of images were calculated.The images of series were evaluated by 2 independent radiologists with 5-point-scale and lastly the best weighting were revealed.Then the mAs in Group 2-6 were defined as 210,180,150,120 and 90 with the kilovoltage 100.The CTDIvoland DLP in every scan series were recorded and the effective dose (E) was calculated.The S/N and C/N were calculated and the image quality was assessed by two radiologists.Results The best weighing of ASIR was 60％ at the 100 kV,240 mAs.Under 60％ of ASIR and 100 kV,the scores of image quality from 240 mAs to 90 mAs were(4.78 ±0.30)-(3.15 ±0.23).The CTDIvol and DLP were 12.64-4.41 mGy and 331.81-128.27 mGy,and the E was 4.98-1.92 mSv.The image qualities among Group 1-5 were nor significantly different (F =5.365,P ＞ 0.05),but the CTDIvol and DLP of Group 5 were reduced by 37.0％ and 36.9％,respectively compared with Group 1.Conclusions In thoracic aorta CT Angiography,the best weighting of ASIR is 60％,and 120 mAs is the best mAs with 100 kV in patients with BMI 19-24.