There is provided a color image sensor including a sensing array and a processing unit. Low-voltage CMOS components are housed in the first active areas. The processing includes: determining an approximate location of the knee; using the determined the location to define a volume of interest; segmenting the femur in the defined volume of interest; and determining a bottom point on the femur portion on a right side and a left side of the segmented femur in an axial and a coronal slice to determine the two lines. The mounting assembly is movable in the MD direction while the BL position is fixed.