HI, 

It is hard to predict exact cut off marks though. Its 40 perceentile for reserved category and 50 percentile for unreserved category. According to year neet PG 2017, the cut off ranks for radiodiagnosis was 681 in round 1 and 1177 in round 2. The lowedst score in radiodiagnosis in hte previous year was 1078 out of 1200.

In year 2018, the cut off percentile was 50, with 705 being minimum score out of 1500 for unreserved category and as for reserved category it was 618 out of 1500 with 32% cut off. This is followed in almost every state and seat approximation remains the same. 

hope it helps. Good Luck .