The Study Of Advanced Iterative Reconstruction Technique On Radiation Dose Reduction With Coronary Computed Tomography Angiography

Part oneThe application value of iterative reconstruction in low-dose prospectivecoronary computed tomography angiography.【Objective】To investigate the combination value of BMI-adapted prospective cardiaccomputed tomography angiography and iterative reconstruction technique.【Methods】ninety one consecutive patients underwent prospectively triggered coronary CTA forsuspected or known coronary artery disease (CAD). Patients with heart rate above70bpsbefore the scan despite β-blocker administration and with arrhythmia were excluded. FromMarch to May2012,91patients underwent coronary artery CTA using a conventionalprotocol (120kv,200mAs), Filter Back Projection was used in this group and served asgroup A. From May to July2012, based on the Body Mass Index (BMI) of the examinedpatients underwent coronary CTA, current tube voltage and tube current was80-100kvand100-150mAs (BMI≤25kg/m2：80kv，150mAs；25kg/m2＜BMI≤28kg/m2：100kv，100mAs；BMI＞28kg/m2：100kv，150mAs). FBP (group B)and iDose(group C) were bothused in this group Image quality, noise, volume CT dose index (CTDIvo1) and effectivedose(ED) in the two groups were measured.【Result】Patients examined usingconventional protocol exhibited the highest radiation exposure (3.07±0.50mSv), while lowdose group was much lower(0.96±0.40mSv,radiation saving69%).Overall image qualitywas much lower in group B(3.94±0.71) compared to group A(4.71±0.63) andC(4.57±0.71)(p<0.05),while group A and group C exhibit similar overall imagequality.SNR and CNR were similar in group A and C(p>0.05); while SNR and CNR ingroup B were much lower than group A and C(p<0.05for all).【Conclusion】 Using thecombination of BMI-adapted low dose and iDose, image quality can be maintained withsimultaneous radiation savings of～69%(dose of～1mSv).Part twoLow contrast dose and low tube voltage in prospective cardiac computedtomography angiography【Objective】 To evaluate the effect on image quality of a low contrast and radiation doseprotocol for cardiac computed tomography (CT) using a low tube voltage, the iterativereconstruction algorithm, and a256-row CT scanner.【Methods】85consecutive patients underwent coronary CTA on a256-slice MDCT. The control group (Group A, n=44) werescanned using the conventional tube output (120kVp,200mAs, contrast volume:68ml)and reconstructed using FBP. Low tube voltage(100kvp or80kvp) and low contrastvolume(40or50ml) were implied into41cases, FBP, iDose-4and iDose-6were all usedin this protocol,these groups were marked as group B,C,D，respectively（BMI≤25kg/m2：80kv，200mAs， contrast volume:40ml； BMI>25kg/m2：100kv，200mAs,contrastvolume:50ml）. Image quality，noise，volume CT dose index(CTDIvo1) and effectivedose(ED)in these groups were measured.【Result】The ED and contrast dose in low dosegroup was53%and32%lower than in conventional group(1.46±0.53vs3.09±0.59(mSv),46.11±4.94vs68(ml), p<0.05). Significant differences in SNR and CNR wereobserved between group D and group A, there was no significant difference in image scorebetween group D and A.There were no significant difference in image score,CNR and SNRbetween group A with group C. On the other hand, significant differences in SNR or CNRand image quality between group B and group A.【Conclusion】 The low tube voltagescan and iterative reconstruction algorithm can dramatically decrease the radiation doseand contrast dose with adequate image quality at cardiac CT using a256-row CT scanner.Part threeThe Value of Advanced Iterative Reconstruction and low tube current inretrospective Cardiac Computed Tomography Angiography with low-dose【Objective】To investigate the value of iterative reconstruction in retrospective cardiaccomputed tomography angiography.【Methods】74consecutive patients underwentcoronary CTA on a256-slice MDCT.Conventional dose(120KV，800mAs)was implied into32cases,FBP was implied in this group and was served as group A;Both iDose andFBP(Filter Back Projection)were used in the residual42cases under the condition ofremaining the tube voltage and decreasing the tube current.600mAs was used in20cases(group B),400mAs was used in22cases(group C).400mAs+FBP，600mAs+FBP,800mAs+FBP，400mAs+iDose,600mAs+iDose were marked as A to Egroups.Image quality，noise，volume CT dose index(CTDIvo1)，and effective dose(ED)inthe two groups were measured.【Result】The respective image scores of group A-E were1.84±0.41,1.62±0.43,1.56±0.40,1.54±0.50,1.42±0.43,the Contrast Signal to Noise ratiowas10.38±2.43,13.16±4.49,14.5±5.01,13.19±3.00,15.05±5.34,the Signal to noise ratiowas12.95±3.21,15.52±3.4,17.52±5.07,17.63±4.22,19.46±5.51, group A had lower CNR or SNR and higher image score compared to group B and C（p<0.05）,while there was nosignificant difference between group D or E and group C(P>0.05).The respectivelyeffective doses of400mAs、600mAs、800mAs were（5.27±0.52）mSv，(6.87±0.98)mSv,(8.31±0.83)mSv,the effective dose of400mAs was reduced by36%(P<0.05)【.Conclusion】Combining tube current reducing protocol and iDose could notonly reduce radiation dose，but also meet the demand of diagnosis.