The Clermont or DWI-MaRIA scoring system is used to assess ileocolonic Crohn disease activity on noncontrast MRI enterography. It is based on the earlier Magnetic Resonance Index of Activity (MaRIA) index, however, it does not require intravenous gadolinium by substituting relative contrast enhancement (RCE) with apparent diffusion coefficient (ADC) values in the equation.

The score can be obtained using the following formula ¹:

1.646 × bowel thickness (mm) − 1.321 × ADC + 5.613 × edema + 8.306 × ulceration + 5.039

The recommended cut-off values of the Clermont score are:

the ADC value of the bowel wall should be measured in the area of the highest DWI signal within the affected segment
the dimension of the ADC value should be x10^-3 mm²/s in the equation, while many MRI/PACS systems display it using other dimensions (e.g. x10^-6 mm²/s)
bowel wall hyperintensity (edema) is assessed by comparing the signal intensity of the bowel wall to the psoas muscle on T2-weighted sequences
it has been shown that the Clermont score has comparable performance to the MaRIA score ^2,3
since concerns have arisen regarding long-term effects of repeated intravenous gadolinium administrations this is a significant benefit by allowing the follow-up of disease activity using noncontrast imaging only