Can I still publish a paper in an IEEE transaction journal after uploading it to the arXiv? I read often that preprint servers such as arXiv are changing how we publish. However, no one in my area of medical imaging uses them and they are regarded in my lab with suspicion.

I currently have a finished manuscript that I am about to send to an IEEE transaction journal. I would like a preprint of this manuscript to be publicly available for several reasons. However, my supervisors are worried this might invalidate my ability to publish this manuscript. They don't want to take the risk that I do this wrong and can't publish.

So here is the simple question I never seem to see a simple answer to. Here is a finished manuscript, fully formatted for the journal I am going to submit it to, in PDF. Can I submit this  PDF as a pre-print to arXiv right now, or not? Will the publisher still consider publishing it? To play devil's advocate, why wouldn't IEEE say, this has already been published in the arXiv, it is no longer new work?

Edit: Here is what IEEE says: "Does IEEE consider an author posting her paper on preprint servers or on her company's web sites to be a form of prior publication, which may then disqualify the paper from further editorial consideration? No. IEEE policy allows an author to submit previously posted papers to IEEE publications for consideration as long as she is able to transfer copyright to IEEE, i.e., she had not transferred copyright to another party prior to submission."
Yes you can. If/when they accept the paper you need to perform the actions as described in:
From https://www.ieee.org/content/dam/ieee-org/ieee/web/org/pubs/author_version_faq.pdf

Can an author post his manuscript on a preprint server such as ArXiv?
Yes. The IEEE recognizes that many authors share their unpublished
manuscripts on public sites. Once manuscripts have been accepted for
publication by IEEE, an author is required to post an IEEE copyright
notice on his preprint. Upon publication, the author must replace the
preprint with either 1) the full citation to the IEEE work with
Digital Object Identifiers (DOI) or a link to the paper’s abstract in
IEEE Xplore, or 2) the accepted version only (not the IEEEpublished
version), including the IEEE copyright notice and full citation, with
a link to the final, published paper in IEEE Xplore

On the author center of IEEE it's restated here, that prior to publication one can share it on ArXiv
http://ieeeauthorcenter.ieee.org/publish-with-ieee/author-education-resources/guidelines-and-policies/policy-posting-your-article/

Prior to Submission to an IEEE Publication
Authors may post their article anywhere at any time, including on preprint servers such as arXiv.org.

Authors seem to get a lot of leeway from IEEE, including reuse of their previously submitted work in new works. Only thing is that your preprint must match the accepted version by IEEE. Not any rough draft or anything.