Create an 'en face' image from cross sectional or polar images

Hi all

I have cross multiple sectional images which I converted them into polar coordinate like this .

I want to convert this images into enface image like this

but I don't know how I can construct enface image like this . can anybody help me with some code or guide me how can create enface image from cross sectional or polar images

these images are taken from a paper

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0124192#authcontrib

here is the information about enface image

' First, we build an en face image from the entire cross-sectional images corresponding to a single pullback. From the cross-sectional images presented in polar coordinate (Fig 2(a)), we build an en face image as shown in Fig 2(c), where the height of the en face image is the number of A-lines in each cross-sectional image and the width is the number of all the cross-sectional images in a single pullback.'

the original image can be downloaded from following link

https://drive.google.com/open?id=1lBMTMt-yynULyJQqNQNmPrp9pGmmVmUP