A needle could easily be inserted each time and there should be no need to walk around with a needle piercing her body all the time. MRIs can be claustrophobic. One patient said he fell asleep while he lay in the white plastic tube. How he could snooze with a noise like a pneumatic drill going on, shows how good his mental powers were. Sometimes ultrasound is used although without care this can press on a sensitive liver or spleen.
Some tests are helpful to the patient, others aid the doctors' research.
There is a difference. You might want to help in research but remember you have the right to say no, and have the right to ask for less intrusive monitoring. Gauchers disease causes enough pain without any additional discomfort inflicted which could be avoided. Gauchers News March 1996.