what subject i should take in 11th fir radiology including optional subject ?
For Radiology you must have a science background i.e., Physics Chemistry and Biology is must. Now if you want to keep options open for Engineering then you can keep Mathematics. Although Maths is now not compulsory for Engineering but for entrance you will need it so its better to keep in your curriculum. If you want to supplement then you can put anything in the place of Mathematics.
I hope my answer helps. All the very best for your future endeavors!