Conclusion: There is nothing wrong with you studying medicine and working as a doctor, whilst taking precautions to avoid matters concerning which there are shar‘i reservations. In fact, studying medicine is a beneficial field of knowledge, by means of which one may benefit and help people.

Conclusion: if the scalp is injected with plasma, that does not invalidate the fast. That is in contrast to injection of blood via a vein, which takes the place of food and drink, so the fast is invalidated thereby.