Under the national TB programme, for a PHC to be called a PHC-R, requisite is:

Microscopy Facilities are available at all Primary health centres (PHC). Those Primary health centres (PHC) with additional Radiology facility were called PHC-R (R for Radiology) under the national tuberculsis (TB) programme. Ref: Park's Textbook of Preventive and Socaial Medicine By K.Park, 18th Edition, Page 335.