Ultrasound Evaluation of Crohn's Disease

The investigators will study the efficacy of ultrasound shear wave elastography and
vascularity imaging for Crohn's Disease (CD) evaluation. Literature evidences demonstrate
that bowel stiffness is correlated with fibrosis, while bowel vascularity and perfusion is
correlated with inflammation. Therefore, the investigators expect the combination of shear
wave elastography and vascularity imaging can increase the sensitivity and specificity of CD
evaluation.

Ultrasound is safe, cost-effective, and widely accessible, thus provides an attractive
alternative to the clinical standard Computed Tomography (CT), risks of radiation)) and
Magnetic Resonance Imaging (MRI), more expensive and limited accessibility)).

Because ultrasound may not be able to image bowel loops deep in the body, its main role is
for follow-up after initial screening by CT or MRI, especially for terminal ileum, which is
easily accessible by ultrasound and the most frequently affected bowel segment for CD.

Inclusion Criteria:

- Crohn's disease patients with involvement of terminal ileum (thickness > 3mm).

- Scheduled to start new medical therapy (change of medicine or dosage).

- Clinically indicated contrast enhanced Magnetic Resonance Enterography (MRE) at
baseline and 6 months.

Exclusion Criteria:

- Patients with change of medicine or going to surgery over the 6-months follow-up
period.

- Patients with unreliable ultrasound images due to conditions such as large body
habitus or poor ultrasound imaging window.

- Adults lacking capacity to consent.

- Vulnerable subjects such as prisoners.

- Pregnant women and nursing mothers.

- Patients with known or suspected right-to-left, bi-directional, or transient
right-to-left cardiac shunts.

- Patients with history of hypersensitivity allergic reactions to ultrasound contrast
agents.