1.  Doctors use the computer to examine the development of the patient.

2.  People who suffer these diseases must die in the not long future, during this period, the patients suffer great pain physically, they just support their lives by some medicine or artificial systems, they can't do anything, at this moment life is meaningless, what they want is to die early to release the pain Now, if the doctors use euthanasia to help the patient to die, it will be a really human thing.

3.  Fourth, the doctor should use a painless and human way to help the patient to die.

4.  Saving a dying patient is expensive because doctors must use advanced life-support system and expensive medicine to prolong patients' life artificially.