Hello aspirant!
Hope you are doing well!

Bsc. Nuclear medicine technology is a 3 year undergraduate course, which teaches about diagnosis and treatment of diseases in patients using radioactive medicines.
It is based upon chemical, physical, applied anatomy facts.
It is different from ct scans, tomography etc.

Here is the first year syllabus of this course:-
Human anatomy
Physiology
Basics of computer

It has a high scope in coming future.

Now, Bsc. Radiology is also a 3 year undergraduate exam which is based upon Ct scans, Mri, tomography, xrays etc. .

Subjects in Radiology
Principles of Medical Imaging

Medical Biochemistry

Radiographic Technique

Para- clinic Training

Human Anatomy

Radiation Physics

It is also a huge scope career in India and abroad also.

So now, you should decide based on your interests .
As both are high salary and high scope courses.

Hope this helps you
All the best