The primary aim of this study is to assess quantitative derived computed tomography (CT) body composition metrics in patients with Crohns Disease (CD) on standard and low dose abdomino-pelvic (AP) imaging and compare for significant differences, thus evaluate the possibility of an accurate, dose reduction technique and methodology of calculating analytic morphomics with inter-technique precision. While magnetic resonance imaging (MRI) is the gold standard cross-sectional modality for routine follow-up of CD particularly where small bowel disease is suspected or exists, CT remains a 1st-line modality...

A retrospective review of a prospectively generated database in patients with a known history of CD, >16 years of age presenting acutely and requiring urgent CT AP imaging between July 2017 and December 2018 were included. All included patients had CT AP imaging successively at both standard and low dose on the same presentation. Written informed consent was received from each patient for the additional low dose CT. All images were acquired on the same CT scanner, General Electric Discovery CT 750 HD scanner. See...

Demographics Forty-nine patients were included in the final analysis. Twenty-six patients were male (53%). The mean age was 42.6 years ±13.4. The mean BMI was 27.1 Kg/m2 ±5.9. Radiation Dose The mean effective dose reduction between the standard-dose and low-dose protocol was 76.5 % (See Figure 4 for summary table). [Fig 4] Inter-protocol Comparison of Analytic Morphomics A number of significant differences exist when comparing both the CSA and HU of various tissues.See Figure 5. [Fig 5] Degree of Agreement Mean CSA values were lower...

The altered acquisition and reconstruction parameters associated with lower dose CT AP technique results in significant difference in the quantitative data obtained using threshold-based segmental tools for body composition metrics when compared with standard dose CT AP. This difference presents a challenge on interpreting an apparent temporal change in morphomics when comparing imaging from different protocols. Caution should also be employed when describing myosteatosis on CT whilst neglecting acquisition parameters.

Desmond AN, O'Regan K, Curran C, McWilliams S, Fitzgerald T, Maher MM, Shanahan F. Crohn's disease: factors associated with exposure to high levels of diagnostic radiation. Gut. 2008 Nov;57(11):1524-9. doi: 10.1136/gut.2008.151415. Epub 2008 Apr 28. PMID: 18443021. Craig O, O'Neill S, O'Neill F, McLaughlin P, McGarrigle A, McWilliams S, O'Connor O, Desmond A, Walsh EK, Ryan M, Maher M, Shanahan F. Diagnostic accuracy of computed tomography using lower doses of radiation for patients with Crohn's disease. Clin Gastroenterol Hepatol. 2012 Aug;10(8):886-92. doi: 10.1016/j.cgh.2012.03.014. Epub 2012...

A. T. O'Mahony: Nothing to disclose J. Cosgrave: Nothing to disclose C. Crowley: Nothing to disclose J. O'Grady: Nothing to disclose O. O'Connor: Nothing to disclose M. A. Maher: Nothing to disclose