Table 1.

Registration frameworks considered for msLevelCheck. Framework notation for n_k over a number of stages (S) is denoted in { } brackets, with ‘All’ denoting all vertebrae within the radiographic field of view. For example, {All, 5, 3, 1} denotes a four-stage framework in which the registration is computed for all vertebrae (as in the basic LevelCheck algorithm), followed by 5, 3, and finally each (1) single vertebrae. Performance of each framework is shown in figure 6.

Framework	1	2	3	4	5	6	7
S	2	2	2	3	3	4	6
nk	{All, 1}	{All, 2}	{All, 3}	{All, 3, 1}	{All, 4, 1}	{All, 5, 3, 1}	{All, 5, 4, 3, 2, 1}