Kevin Murphy MBBCh, MRCS, Abstract Co-Author: Nothing to Disclose

Lee Crush MBBCh, FFR(RCSI), Abstract Co-Author: Nothing to Disclose

Patrick McLaughlin FFR(RCSI), Abstract Co-Author: Nothing to Disclose

Maria Twomey MBChB, FFR(RCSI), Presenter: Nothing to Disclose

Christopher Page, Abstract Co-Author: Nothing to Disclose

Iris Mildenberger, Abstract Co-Author: Nothing to Disclose

Niamh Moore, Abstract Co-Author: Nothing to Disclose

Jackie Bye BA, Abstract Co-Author: Employee, General Electric Company

Owen J. O'Connor MBBCh, Abstract Co-Author: Nothing to Disclose

Sean Edward McSweeney MD, Abstract Co-Author: Nothing to Disclose

Fergus Shanahan, Abstract Co-Author: Nothing to Disclose

Michael M. Maher MD, FRCR, Abstract Co-Author: Nothing to Disclose

We analyse the performance of pure model based iterative reconstruction (MBIR) in the setting of low dose CT Enterography (CTE).

44 Crohn’s patients (27 female) (38.5±12.98years) referred for CTE were included. Low dose modified-protocol (MP) and conventional-protocol (CP) CT datasets were contemporaneously acquired. CP-ASiR image formation used 40% adaptive statistical iterative reconstruction. MP data was reconstructed with 100%MBIR (MP-MBIR) and 40%ASiR (MP-ASiR). Image quality was assessed subjectively and objectively and at 6 levels. Clinical interpretation was undertaken independently by 2 blinded radiologists along with 2 non-blinded readers in consensus (‘gold-standard’).

A 74.7% average radiation dose reduction was seen - MP effective-dose (ED) 1.61±1.18mSv (size-specific-dose-estimate (SSDE) 2.47±1.21mGy); CP ED 6.05±2.84mSv (SSDE 9.25±2.9mGy). Image-quality assessment yielded 9372 datapoints. Objective noise in MP-MBIR images was superior (p<0.05) at 3/6 levels and comparable in the remainder. MP images were superior to CP-ASiR (p<0.05 in all cases) for subjective noise, spatial resolution, contrast resolution, streak artefact and diagnostic acceptability on coronal reconstructions. CP-ASiR axial diagnostic acceptability was superior (p=0.76). MP-MBIR clinical reads agreed more closely with gold-standard reads than CP-ASiR reads regarding bowel wall disease assessment (κ=0.589/0.700 Vs 0.583/0.564) for both readers whereas overall Crohn’s activity grade (κ=0.549/0.441 Vs 0.315/0.596) and detection of acute complications (κ=1.0/0.689 Vs 0.896/0.896) were comparable.

Low dose CTE with MBIR reconstruction, at a mean dose of 1.61 mSv, yields images that are superior or comparable to conventional images acquired at 3 times the radiation.

Pure iterative reconstruction is a valuable technology at improving low dose CT image quality, allowing considerable dose reductions at CT.

Murphy, K, Crush, L, McLaughlin, P, Twomey, M, Page, C, Mildenberger, I, Moore, N, Bye, J, O'Connor, O, McSweeney, S, Shanahan, F, Maher, M, Role of Model Based Iterative Reconstruction in CT Enterography.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017500.html