"Using" or "by using"? [duplicate]
Solution 1:
No, not necessarily.
That is, inserting by makes the PET/CT technology crucial to the demonstration and the feasibility of the approach.
Not using by means that the technology used is incidental, and the focus is on the approach being shown to be feasible.
Without more context it's impossible to say what the intended import of the sentence is and whether by would actually be better or not. And that means that this question is Not A Real Question.