Fig. 12From: Role of magnetic resonance imaging in the management of perianal Crohn’s diseaseCalculation of the magnetisation transfer ratio of a fistula. a Signal intensity on an oblique-transverse gradient-echo image encoded at 800 off-resonance radio frequency saturation. b Signal intensity on an oblique-transverse gradient-echo image without radio frequency saturation. The magnetisation transfer ratio (%) is = 1- (Msat image / Mnonsat image) × 100Back to article page