ABSTRACT
Objective To investigate the image quality and radiation dose of 640-slice CT coronary arteriography(CTCA) with adaptive iterative dose reduction three-dimensional (AIDR3D)reconstrucction algoritym.Methods 640-slice CTCA with auto-matic exposure was performed on 84 consecutive patients.The original image data were reconstructed with AIDR3D and the filtered back-projection (FBP)algorithms at the image postprocessing workstation.Two experienced radiologists without knowing clinical information and reconstruction algorithms independently measured and calculated the image noise,signal-to-noise ratio and contrast-to-noise ratio with AIDR3D and FBP reconstruction algorithms.The qualitative image quality was assessed by using the 4-point scale.The radiation dose was calculated based on dose-length product exported on CT scanner.The quantitative and qualitative im-age quality with two kinds of reconstruction algorithm was analyzed statistically.Results The CTCA image noise was (27.20± 4.40)HU with AIDR3D and (60.00±12.40)HU with FBP,which with AIDR3D was decreased by 46.10% than that with FBP;the signal-to-noise ratio was 21.10 ± 5.10 with AIDR3D and 11.40 ± 2.80 with FBP,which with AIDR3D was increased by 84.70% than that with FBP;the contrast-to-noise ratio was 24.70±5.10 with AIDR3D and 13.50±3.20 with FBP,which with AIDR3D was raised by 82.20% than that with FBP,the differences in 3 indexes between the two kinds of reconstruction algorithm were statistically significant(P < 0.05 ).The CTCA qualitative image quality scores of proximal,middle and distal parts with AIDR3D were (3.90±0.30),(3.70±0.50)and (3.60±0.60)respectively,which all were higher than (2.60±0.60),(2.30± 0.60)and (2.10±0.70)with FBP respectively,the differences in 3 items between 2 kinds of algorithm had statistical significance (P <0.05).The total segments which could be used to diagnose the CTCA images with AIDR3D and FBP algorithms were 1 216 segments (96.50%)and 504 segments (40.00%),respectively,the difference had statistical significance(P <0.05).The mean ef-fective radiation dose was (2.10±1.00)mSv.Conclusion 640-slice CTCA with AIDR3D reconstruction algorithm not only signifi-cantly reduces the image noise than the conventional FBP algorithm,improves the quantitative and qualitative image quality,but also decreases the effective radiation dose.
ABSTRACT
Objective To analyze retrospectively the impact of different heart rates on image quality and radiation dose of coronary angiography using 640-slice dynamic volume CT.Methods A total of 461 patients with suspected coronary artery disease or referred to health check underwent coronary angiography with 640-slice dynamic volume CT.Two groups were created according to their heart rates:Group A had heart rate < 65 beats per minute (n=337)and Group B had heart rate between 65 to 122 beats per minute (n=124).Image quality was assessed by analyzing the 1 5 segments of the main coronary branches using 3-grade scale (grade I-good,grade Ⅱ-acceptable,grade Ⅲ-poor).Effective radiation dose was also evaluated.Results Patients in both A group and B group performed successful CT coronary angiography with a total of 6 91 5 coronary segments.Among them,coronary segments that could be evaluated reliably accounted for 94.5% (6 535/6 91 5)while 5.5% (380/6 91 5)were too small (≤1.5 mm)to be assessed. For the image quality,Group A and Group B had grade I in 90.5% (305/337)vs 74.2% (92 /124),grade Ⅱ in 9.5% (32/337)vs 21.0% (26 / 124)and grade Ⅲ in 0 % (0 / 337 )vs 4.8% (6 / 124),respectively.Image quality was significantly different be-tween Group A and Group B (P <0.001).In addition,32 patients (9.5%)in Group A had slight cardiac motion artifacts but with-out affecting image quality,whereas 26 patients (21.0%)in Group B had higher degree of cardiac motion artifacts thus graded as grade Ⅱ.Stair-step artifacts were not found in all patients.The effective radiation dose was higher in Group B than in Group A by 32.05%(7.91±0.34 mSv vs 5.99±0.17 mSv).Conclusion Coronary angiography using 640-slice dynamic volume CT can guarantee excellent image quality when heart rate < 65 beats per minute.Although the image quality would decrease in some extent it is still diagnostic when heart rate is between 65 to 122(include 65 and 122)beats per minute.