engleski

Bone densitometric study using retroalveolar radiographs

Bone-mass measuring techniques are used to evaluate relationships between different regions of the sceleton, to distinguish the diseased from tne normal state, and to monitor bone- mass changes in the progress of disease or treatment. The radiographic picture is the easiest way to diagnose the bone condition, however, a minimum bone mass loss of 30%, and sometimes as much as 50-60% is needed before significant osteopenia can be detected radiographically. The aim of this study was to find out the most precise method for microdensitometry For this purpose, two retroalveolar radiographs (RR) of the same region of 10 patients were made, one after another. The Rtg machine (Siemens) was operated at 71 kV with a constant current of 16 mA/s and an exposure time of 16 sec. Images were recorded using the Kodak:, film for RRs. All films were processed together in an automatic processor. During the exposure, 6 steps copper stepwedge (SW) was attached to the bottom of the film (not to cover any bone structure of the mandible) to give a reference image on the radiographs. RRs were digitised by the Lynotype-Hell (8-bit, 300 DPI) transparent scanner. Grey levels (GL) of each step of SW were measured, as well as GLs of different regions of the interest (ROI). Optical densities (OD) were calculated: OD=-log Ii/255 for all GLs and were related to SW thickness (SWT). Different mathematical options were used to get the regression formu1a to express ODs in equivalent of SWT: linear, II degree polynomial function, III degree polynomial function and V degree polynomial function. After the statistical analysis it was concluded that the III degree polynomial function is precise enough to be used for such calculations.

microdensitometry; retroalveolar radiographs; osteopenia

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