Calculating the Measurements of Objects

Digitome is capable of accurate measurement down to the order of microns given a small focal spot size and low pixel depth for a digital image plate, typical conditions for high-resolution digital radiographs. This video demonstrates how Digitome measures objects in an exam; the objects used have well-known sizes to test the software’s accuracy.

The first sample object is a wooden block with two screws and a nail. The screws have been drilled into the block on the same face about half an inch apart. The nail has been placed into the block at the center of an adjacent face of the block so that it is orthogonal to and in between the screws. The most interesting aspects of this composite are its screw threads, which have different densities. One of the screws has about 24 threads/inch while the other has about 32 threads/inch (manufacturer’s quantities, McMaster Carr). With Digitome, we are able to discern the thread patterns and measure about 24 threads/inch and 32 threads/inch, respectively.

The second object is made of two ruby spheres used in fiber-optic cables placed in contact with each other on a flat plane. The spheres in fiber-optic cables must be accurately made to precisely transmit information throughout the cable. Thus, the two spheres have been made with an uncertainty in diameter only the level of microns. Digitome effectively measures a diameter that has only a 1.29% error compared to the manufacturer value.

In contrast to Computed Axial Tomography exams, Digitome exams do not have to interpolate between slices and therefore (theoretically) contain all of the object information in one exam. So accurate measurements made in the software can be used to measure any aspect of an object that is detectable through x-ray imaging.

These measurements were carried out with a tungsten x-ray source with a spot size of 0.5 mm and an amorphous silicon digital image plate with a pixel depth of 127 microns.