RA Technique

The OsteoGram uses the Radiographic Absorptiometry (RA) method to measure bone mineral density (BMD). Sites of measurements are the middle phalangeal bones of the 2^nd(index), 3^rd(middle) and 4^th(ring) fingers. CompuMed has developed the OsteoGram to implement the RA technique at the highest precision possible, in addition it has automated the analysis process.

• Using standard x-ray equipment, two Posterior-Anterior (PA) views of the left hand fingers are taken on one 8"x10" film with an aluminum alloy reference wedge in each exposure
• The developed film is scanned at high resolution, or in the case of a digital system, the image is imported. The two exposures are automatically cropped to be exported to the analysis software
• Elements of interest (the three middle phalangeal bones and the aluminum wedge) are automatically identified and their contours highlighted
• X-ray related variations, soft tissue absorption and small errors in subject positioning are corrected
• For each phalange, the aluminum wedge is referenced to measure bone mass in every pixel inside the automatically detected contour. Then, one average bone mass is calculated per bone
• For each phalange, bone volume is calculated from bone contour and bone length by superimposing the cylindrically shaped one-pixel-thick cross sections
• BMD is calculated in arbitrary units for the three bones in each exposure (six total)
• BMD results are cross-checked between the two exposures. Variations in BMD results higher than the precision error would invoke an error message (to verify the validity of the scanned x-ray and re-take the x-ray if necessary)
• The overall average BMD index is considered, normative databases are referenced to calculate t-score and z-score