Résumé
Objective To investigate the effect of CareDose 4D combined with Care kV on CT pulmonary ground glass nodule ( GGN) with respect to quality and radiation dose. Methods The thoracic model containing 6 GGN was performed by using 7 low-dose schemes. The CareDose 4D + Care kV was adopted in scheme 1. In schemes 2, 3 and 4, the tube voltage was 120 kV, and the tube current 30, 20 and 10 mAs respectively. In schemes 5, 6 and 7, the tube voltage was 100 kV, and the tube current was 30, 20 and 10 mAs, respectively. The image quality [ CT value, contrast noise ratio ( CNR) , noise value (SD) and subjective score] and effective dose (E) were compared. Results There was no statistically significant difference in CT value of GGN among different schemes (P>0. 05). The SD of scheme 1 was higher than those of schemes 2, 3 and 5, but lower than those f scheme 7, while the CNR of scheme 1 was lower than those of schemes 2, 3 and 5, but higher than that of scheme 7 ( t=13. 020, 9. 560, 8. 120,-5. 720, -7. 849, -5. 192, -4. 130, 1. 361,P<0. 05). SD and CNR of scheme 1 were not significantly different from those of scheme 4 and 6 ( P>0. 05) . The subjective scores of each GGN of schemes 1, 2, 3, 5 and 6 was over 3 points, but and the subjective scores of one GGN of each of schemes 4 and 7 were below 3 points. The value E of the scheme 1 was reduced by 63. 0％, 44. 4％, 38. 8％, and 9. 1％, compared with the schemes 2, 3, 5 and 6, respectively. Conclusions CareDose 4D combined with Care kV in low-dose lung CT scan can ensure the image quality of GGN and reduce the radiation dose effectively.
Résumé
Objective To explore the influence of iterative algorithm on image quality in ultralow-dose CT scan of lung.Methods The thoracic model was scanned using different parameter combinations.The tube voltage was chose with 80,100 kV in ultra-low dose group and the mAs was selected by 10,15,20,25 and 30 mAs.The control group selected the parameters of 120 kV,30 mAs.All the images were reconstructed with filtered back projection (FBP group) and iterative algorithm (IR group).The image noise and effective dose (E) were compared.Results When tube current and voltage were constant,the image noise of IR group was lower than that of FBP group,and the difference was statistically significant (t =1.102-8.070,P＜0.05).When the tube current was constant,the image noise of the 80 kV with FBP group was higher than that of 100 kV with FBP group,and the image noise of the 80 kV with IR group was lower than the 100 kV with FBP group(t =-8.639-7.841,P＜0.05).Compared with the conventional low-dose with FBP group,the image noise of each ultra-low-dose with FBP group was significantly increased,and the image noise of (80 kV,10 mAs),(80 kV,15 mAs),(80 kV,20 mAs) with IR group was significantly increased,and the image noise of (100 kV,15 mAs),(100 kV,20 mAs),(100 kV,25 mAs),(100 kV,30 mAs) with IR group was significantly reduced (t=-8.140-23.028,P＜0.05).There was no significant difference in image noise between the groups of (80 kV,25 mAs),(80 kV,30 mAs),(100 kV,10 mAs) with IR and the group of conventional low dose with FBP (P＞0.05).Compared with the conventional low dose group,the E of the groups of (80 kV,25 mAs),(80kV,30mAs),(100kV,10 mAs),(100kV,15mAs),(100kV,20mAs),(100kV,25 mAs),(100 kV,30 mAs) was decreased by 75.9％,71.0％,79.8％,70.4％,60.3％,50.2％,40.0％,respectively.Conclusions The image quality of the ultra-low dose protocol (100 kV,10mAs) with iterative algorithm is similar to that of the conventional low dose with FBP group,and the radiation dose could be significantly reduced.
Résumé
Objective To explore application of automatic tube current modulation combined with iterative reconstruction in CT scanning ( non-enhanced and enhanced) of neck. Methods A total of 80 patients with CT scanning of neck were randomly divided into test group(n=40, automatic tube current modulation, iterative reconstruction ) and control group ( n = 40, 200 mAs, filtered-back-projection reconstruction ) . Subjective scores and objective evaluation of two groups were evaluated. Evaluation included image noise ( SD ) of thyroid gland, trapezius muscle, sternocleidomastoid muscle, submandibular gland, lateral pterygoid muscle and brain tissue. Effective dose ( E ) was compared. Results The E of non-enhanced and enhanced scanning in test group was lower than that of control group with the statistically significant difference(t = -2. 451, -2. 451, P <0. 05). The subjective scores of non-enhanced and enhanced scanning in test group were higher than those of control group with the statistically significant difference (Z = - 1.969, - 2.056, P < 0.05), while SD of thyroid gland, trapezius muscle, sternocleidomastoid muscle, submandibular gland in test group were lower than that of control group with the statistically significant difference ( t =2. 400,2. 516,2. 120,2. 411,4. 134,4. 674, 2. 711,2. 892, P<0. 05). There were no significant differences in SD of lateral pterygoid muscle, brain tissue of non-enhanced and enhanced scanning between two groups (P>0. 05). Conclusions Automatic tube current modulation combined with iterative reconstruction in CT scanning of neck could improve image quality, and reduce effectively radiation dose.