Fast Update Of Bitmap From Polar Coordinate Data?

I am producing a marine radar display in VB.Net and struggling to get the radar data to display quickly enough.The data is coming into my application from a callback from the radar maker's dll. Each dataset consists of an integer between 0 and 8191 denoting the angle from the datum (ship's head) that the dataset represents and a byte array with 480 elements containing data from ship's position (byte 0) to maximum range (byte 480). Each of these locations is a single byte, I want to set both red and green components of the relevant pixel in a 1000 x 1000 bitmap to this byte value. The dataset number increments round from 0 to 8191 as the radar scanner rotates.

My first approach was to use math.sin and math.cos to convert polar coordinates to cartesian coordinates, and then use setPixel to set the colour of the relevant pixels but this is far too slow.I'm now trying to use Boop Boops 'FastPix'

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Which looks like it should be much better, but I am wondering if there is a more efficient approach, for example cutting out the polar to cartesian conversion, or putting the data direct into a byte array?I am also running the radar picture processing code on a thread separate to the UI thread to keep the UI responsive - what is the best way to display the resultant bitmap onto the UI? I am currently using a delegate and putting the bitmap into a picturebox?