RT and LT are NCCI (National Correct Coding Initiative) Claims Bundling Edit Override modifiers.
While you can use them routinely for informational purposes, they are only necessary in cases where your are trying to differentiate two procedures billed on the same claim from each other in cases where the lesser procedure is considered to be an inclusive component of the more comprehensive procedure if performed on the same side of the body. Modifier 59 can be used to indicate that the second procedure was distinct (because of the fact that it was performed on a different side of the body), but CPT instructs that -59 not be used if other more specific modifiers exist that better differentiate the services, and sometimes using RT and LT is appropriate instead of 59 on the lesser procedure.
If you are only billing one procedure code, attaching an anatomical modifier like RT or LT serves no claims processing purpose, as there is 0 chance that the procedure could be considered as bundled with another procedure billed. The claims processing computer system will ignore it. If it makes you feel better to include it, you can, but it would be the same as attaching Modifier 57 to a decision for surgery visit two weeks before the surgery--fine for informational purposes but not necessary for claims processing purposes.
Seth Canterbury, CPC, ACS-EM