2012 Proceedings - International Tissue Elasticity Conference

013 SHEAR WAVE VELOCITY DISCRIMINATION OF INFLAMED FROM FIBROTIC BOWEL
SEGMENTS IN A CROHN’S DISEASE ANIMAL MODEL.
Jonathan R Dillman 1 , Ryan W Stidham. 1 , Peter DR Higgins 1 , David S Moons 1 , Laura A Johnson 1 ,
Jonathan M Rubin 1 .
1 University of Michigan, Ann Arbor, MI, USA
Background: Crohn’s Disease is a relapsing and remitting form of transmural inflammatory bowel
disease that affects the gastrointestinal tract of both children and adults. Deposition of fibrosis within the
bowel wall as response to inflammation occurs unpredictably in some Crohn’s disease patients with
resultant stricture formation and bowel obstruction. Presently, no diagnostic test can confirm the degree
of fibrosis relative to inflammation in a reliable, non–invasive manner.
Aims: To determine if acoustic radiation force impulse (ARFI) elastography–derived bowel wall shear wave
velocity (SWV) can distinguish inflamed from fibrotic intestine in a Crohn’s disease animal model.
Methods: Appropriate University Committee on the Use and Care of Animals approval was obtained. An
acute inflammation Crohn’s disease model was produced by treating Lewis rats with a single
trinitrobenzenesulfonic acid (TNBS) enema, with imaging performed two days later (n=8). Colonic fibrosis
in Lewis rats was achieved by administering repeated TNBS enemas over four weeks, with imaging
performed seven days later to allow resolution of acute inflammation (n=8). Nine transcutaneous bowel
wall SWV measurements (Virtual Touch IQ/Acuson S3000 ultrasound system; Siemens Medical
Solutions, USA) were obtained from the rectosigmoid colon region in all rats without and with applied
strain. Mean bowel wall SWVs without and with applied strain were compared between animal cohorts.
Receiver operating characteristic curves were created to assess diagnostic performance. Three rats were
excluded from analysis due to demise.
Results: Mean bowel wall SWVs were significantly higher for fibrotic versus acute inflammation cohort
rats at 0% (3.42±1.12 vs. 2.30±0.51m/s; p=0.047) and 30% (6.27±2.20 vs. 3.61±0.87m/s; p=0.021)
applied strain. Both acute inflammation and fibrotic cohort rats demonstrated linear increases in mean
SWVs with increasing applied strain with no overlap in the 95% confidence intervals. The mean slopes
(0.054±0.029 vs. 0.114±0.044; p=0.016) and y–intercepts (2.07±0.32 vs. 3.33±1.14; p=0.023) were
significantly different. The c–statistic of SWV for differentiating fibrotic from inflamed bowel was 0.764.
Conclusion: Bowel wall SWV distinguishes fibrotic from inflamed intestine in a Crohn’s disease animal
model. This finding could have a major impact in the diagnosis and treatment of strictures in Crohn’s
disease where fibrotic strictures can only be treated surgically, while inflammatory strictures are treated
medically. In addition, the linearity of the slopes in the shear wave vs. applied strain model would remove
pre–loading effects up to at least 30% applied strains, which could significantly impact measurement
variations that may exist due to different operator pre–loads.
Acknowledgement: This study was funded in part and equipment was provided by Siemens Medical Solutions.
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