50 carries the same defintion as RT, LT. 50 is a procedure that is defined as unilateral being perfomed on a defined bilateral body part or organ. two sides of the same foot is not bilateral. the foot is a unlateral body part that has both a left and a right. If you do only the right foot the you use the code with RT if you do both then it is bilateral.
RT, LT are modifiers for when you do the left side only or right side only of a defined bilateral body part or organ.
If your xray is different sides of the same foot then this changes the view and you change how many view you bill, not use a 50.