An MR examination usually requires various technically different acquisition methods (sequences), whereby the different tissues exhibit different signal intensities in a greyscale from black (no signal) to white (high signal). The sequences used in spondylarthropathy consist of:
Tl-weighted sequence which is appropriate with regard to anatomy because fatty tissue appears bright and fluid dark. Fatty tissue is present in the bone marrow and between muscles, which will therefore be clearly delineated on T1 images. Abnormal fatty deposition which can occur as a sequel after bone marrow inflammation, is well visualised. On the website T1-weighted images are generally marked with a black border.
STIR (Short Tau Inversion Recovery) sequence or a T2-weighted fat-suppressed sequence is suitable for the detection of active inflammation since tissue with high water content appear bright against a slightly variable dark background due to suppression of signals from fatty tissue. On the website STIR images are generally marked with a red border.
T1-weighted fat-suppressed (T1 FS) sequence is appropriate for visualising the articular cartilage and joint space, which appear bright compared to the osseous structures. This sequence is also used to delineate vessel containing (vascularised) inflammation after administration of MR contrast containing Gadolinium (Gd.). On the website post-contrast images are generally marked with a blue border and T1 FS images without contrast with the green border.
The images below show fat accumulation in bone marrow on T1-weighted image, erosion on T1 FS and signs of activity in the form of oedema on STIR and enhancement on T1 FS after administration of Gadolinium. The changes are marked with arrows.