@ Sushma ma'am, there are several research papers available in public domain opting the same representation, and I also do believe that there is no problem writing this , i.e. if someone follows any method and as per the requirement (sample type/ conditions, etc.) they alter the original described method with slight modifications, than it can be written.
Looking forward to see further expert views/suggestions on this.
I think, in my opinion, that adding the sentence «…. with some modifications » is correct, provided that the said modifications will be slight (changing one or two parameters) and do not completly modify or alterate the structure of the original protocol, otherwise it will be a new protocol.