Importing images from PowerPoint and exporting as video

Hello guys!

I find myself in need of doing a video from a PowerPoint file. Here is the process:

#1. I export the slides from PowerPoint as PNG (tryed jpg and TIFF also)

#2. I make a new project as 720p ( as the images are 1280x720)

#3. I import the PNG slides(they all have just white background and text).

#4. I make a new sequance from clip(with one of the images selected)

#5 . I finish the project and export as H.264

The issue is that the exported video has small "stuff" around the text. See this image: http://prntscr.com/l5z9jo  , it's not 100% clear.

Can you please advice? I am kinda new to premiere, but i am pretty good with computers and stuff.

Thank you all!