How can I construct 3D images from X-ray files .bmp format. ?

The x-ray source is located at (0, 0, 450mm), which means it is 450mm above the center of the detector. During the data collection, both the x-ray source and detector are driven by a C-arm so that the source and detector rotate from 0° to 180° with an interval of 12°. There is no relative movement between the x-ray source and detector. One 2D x-ray projection is captured at each position, thus a total of 16 projections are obtained. The object (i.e., the fingers and other supporting structures), is placed along the rotational axis that is 100mm above the detector. The dimensions of the object in Y and Z directions are assumed to be <30mm. There is no movement of the object during the data collection. The 2D projections have 980 x 980 pixels corresponding to a detector area with a diameter of 150mm. The projections are given in BMP format.

Answer 1

[Image Analyst]

Describing how filtered back projection works to reconstruct a volumetric images from projection images is beyond the scope of Answers. There are textbooks on that, but the math is pretty complicated. Involves radon transforms, etc. I mean Hounsfield literally got a Nobel Prize for inventing it. Not to say that you can't do it, but I can't say much other than to search the web for text books and algorithms and articles. The basic algorithms shouldn't be too hard to find, though the best ones are proprietary to the CT instrument manufacturers.