**7.1 MRI protocol**

The ankle tendons are visualized as low signal intensity structures in all MR sequences. The T1WI sequences are used to evaluate the anatomy and the T2W sequences are used to assess abnormal increase in fluid, usually related to tendon pathology [33]. Axial images are used to evaluate morphologic features of the tendons and synovial sheath distention, longitudinal splits, fluid within the tendon sheath, and adjacent soft tissue abnormalities, if any. For evaluating the Achilles tendon, sagittal images prove most useful. Sagittal images also assess the proximal-to-distal extent of tendon pathologies. Oblique coronal or short axis images at the level of the mid- and forefoot are best for assessment of the tendons distal to the ankle [33, 34].

When the normal tendons form an angle of approximately 55° with the main magnetic vector, it produces increased signal intensity within the tendons. This phenomenon is called the magic angle, more commonly in sequences with echo times less than 20 msec (T1WI, PD or GRE). This effect is particularly common with ankle tendons because of their curvatures around the ankle joint [33, 34].

For general purposes, an ankle MRI should include at least the following: axial T1WI or PD sequences and fat-suppressed T2WI, coronal T1WI or fat-suppressed T2WI and IR sagittal images [34].
