Table 2 Description of magnetic resonance imaging variables

MCs

Signal changes in the vertebral bone marrow that extend from the endplate. Excluded are changes separated from the endplate, abutting the endplate with a smaller base than height, or extending through the endplate (Schmorl’s hernias).

MC type

MC type 1 is hypointense on T1- and hyperintense on T2-weigted images. Type 2 is hyperintense on T1 and hyper- or isointense on T2. Type 3 is hypointense on T1 and T2. Borderline type 1 vs 2 with near isointense T1 signal is rated as type 2.

MC-ADC

Highest mean ADC value in a 41.8 mm² ROI in the vertebral body marrow at the endplate with MC on T1/T2. The ROI is placed in the most intense MC related region on the ADC map. If the MC region has uniform intensity on the ADC map, the ROI is placed in the MC area with largest height on T1/T2. ADC is not measured for MCs with height < 10% of vertebral body height or diameter ≤ 5 mm. A ROI of only 41.8 mm² (diameter 7 mm) is used to accommodate small MCs.

CSF-ADC

Mean ADC value in the CSF in a 41.8 mm² ROI at the level of the MC affected vertebral unit, measured in the midsagittal image, or the next image left or right, avoiding non-CSF structures (like nerve roots seen on T1/T2). CSF-ADC is measured in an area with uniform intensity and no pulsation artefacts, behind the lower half of the cranial vertebra of the vertebral unit (e.g., behind L3 if the MC is superior or inferior to the L3/L4 disc) if possible, and otherwise behind the caudal vertebra of the unit or at the next vertebral unit caudally or cranially.

Body-ADC

Mean ADC value in a 94 mm² ROI in normal (on T1/T2) vertebral body marrow near the MC. The ROI is placed close to the endplate in the central anteroposterior third of the normal opposite part (caudally or cranially) of the vertebral body with the MC. If the opposite part is not normal, and always when the MC is in S1, the ROI is placed in the nearest vertebra above, in its caudal part if possible, and otherwise in its cranial part. The measurement is first considered in the midsagittal image and then, if necessary, considered in the next image (left or right) before a new location may be considered. The larger 94 mm² ROI is used to average more pixels without including the central vertebral vein in the ROI.

MC-ADC-ratio

Calculated as MC-ADC / Body-ADC

MC-ADC%

Calculated as (MC-ADC – Body-ADC) × 100% / (CSF-ADC – Body-ADC)