Conference Contribution Details
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Murphy KM, McLaughlin P,Watson B, Maher MM, O'Connor OJ
European Society of Gastrointestinal Radiology
Salzbur, Austria
Oral Presentation
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Purpose: Low dose CT protocols that employ pure iterative reconstructive techniques such as model based iterative reconstruction (MBIR) have recently been developed. We assess the ability of low dose images to maintain accurate tissue and lesion characterisation. Materials and Methods: Standard protocol (SP) and low dose modified protocol (MP) CTs were contemporaneously acquired in thirty-four Crohn’s disease patients referred for CT. The SP images were reconstructed using manufacturer recommendations (60%FBP, filtered back projection; & 40%ASiR, Adaptive Statistical iterative Reconstruction) (SP-ASiR40). The MP datasets were reconstructed in 4 ways (100%FBP; 40%ASiR; 70%ASiR; 100%MBIR). 3 observers measured tissue volumes using Hounsfield unit thresholds for fat, soft tissue and bone & contrast via Osirix (Ver 4.1.1) on each dataset. Data analysis was performed with SPSS. Results: Inter-observer agreement for tissue volume measurement was very strong for the 1530 datapoints (rs>0.9 for all comparisons). Tissue volume measurement on the MP-MBIR images was significantly superior to all other MP reconstructions and closely correlated with the ‘gold standard’ SP-ASiR40 images for all tissue types. The superiority of MP-MBIR was most marked in fat volume calculation where Bland-Altman plots showed closest correlation between SP-ASIR40 and MP-MBIR with the lowest average difference (336cm3) when compared with other MP reconstructions. Conclusion: Low dose CT images reconstructed with MBIR maintain accurate tissue and hence lesion characterisation that is superior to other reconstruction techniques when compared with conventional dose images.