Benefits of adaptive statistical iterative reconstruction and high definition compared with filtered back projection and standard definition multi detector row cardiac imaging with respect to radiation dose and diagnostic accuracy.

Abstract Aims: Assessment of the differences in diagnostic performance and radiation dose between Adaptive Statistical Iterative Reconstruction (ASIR) and High Definition (HD) CT coronary angiography (CTCA) compared with Filtered Back Projection (FBP) and Standard Definition (SD) CTCA using invasive coronary angiography as a reference standard. Methods: Data from 2069 consecutive patients undergoing CTCA was collected over a period of 2 years. A total of 30 patients were separately enrolled if they had a significant stenosis and underwent invasive coronary angiogram within 3 months. All 30 patients were scanned in high definition and then had 5 reconstructions performed using SD0%ASIR, SD50%ASIR, SD70%ASIR, HD50%ASIR and HD70% ASIR. Results: Median and total (including CACS) angiographic radiation dose for 2069 patients was 2.1 mSv and 2.7 mSv respectively. Determinants of radiation dose on multivariate regression analysis were scan voltage, tube current, padding, scan length and heart rate. The mean difference in adjusted angiographic radiation dose using ANCOVA between the ASIR cohort (n=624, mean 2.2 mSv) and FBP (n=572, mean 2.29 mSv) was 0.09 mSv (P 0.0008). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Area under the curve (AUC) values using Receiver Operator Characteristic (ROC) curves on an intention to diagnose analysis were highest for the reconstruction HD with 70% ASIR at 94%, 89%, 75%, 98% and 0.93 for a >50% obstructive stenosis threshold on a per artery basis; and 88%, 88%, 64%, 97% and 0.91 for a >70% stenosis on a per artery basis; 100%, 67%, 96%, 100% and 0.83 for a >50% stenosis on a per patient basis; and 95%, 67%, 87%, 86% and 0.81 for a >70% stenosis on a per patient basis. The greatest benefit for HD with 70% ASIR was in patient subgroups of CACS>200, BMI>25 and stented arteries with AUC values of 0.93, 0.89 and 0.83 respectively.Conclusions: ASIR resulted in a lower adjusted angiographic radiation dose than FBP although the reduction of 4.2% was less than that observed in other studies due to the tube current reduction with ASIR scans being smaller in our study. HD with 70% ASIR reconstruction demonstrated the most robust diagnostic performance with higher specificity, PPV and AUC values than all other reconstructions due to a lower false positive rate. These benefits were the most pronounced in patients with a CACS>200, BMI>25 and stented arteries