I'm not sure of you're application. CT and MR images both contain voxels so both can be used as 3-dimensional images. However they have very different contrasts. So, is your question: can you convert CT contrast to MRI contrast?
In terms of time saving, there are a number of MR techniques that can generate multiple contrasts within only a few minutes (e.g. syntheticMR/MAGiC/GoBrain etc), and MR techniques that can generate CT/bone contrast (e.g. zero TE), and unlike CT, MR does not produce radiation. Please be specific with your question.
CT and MRI both have different principal of working and complimentary to each other,but technically it is possible to convert by applying mathematical formulas.