AbstractID: 7173 Title: Effect of Radiographic Exposure on Texture Features Extracted from Bone
Densitometry Images
Bone structure is an important component that determines bone strength
and therefore fracture risk. Recent bone densitometers may have
adequate spatial resolution to characterize bone structure by
performing texture analysis on the acquired images. In this study we
investigate the effect of exposure on texture features.
A PIXI (GE Medical Systems) peripheral densitometer with 0.2 mm pixel
size was used to image the heel of an Alderson Phantom
Patient. Multiple scans were performed using the default protocol.
Additionally, images were acquired with up to 2.5 times the default
relative exposure. Regions of interest (ROIs), 64x64 pixels in size,
were selected for calculation of the texture features. The ROIs
encompassed approximately the same region from which the BMD was
calculated. The texture analysis included Fourier-based features such
as RMS variation and first moment of the power spectrum. The ROIs
were analyzed individually and by averaging their Fourier transforms
prior to calculation of the features. Averaging in the
spatial-frequency domain avoids problems that might occur due to a
slight shift of the heel between scans.
The first moment decreased by 23% with the doubling of the mAs and by
13% with the averaging of the Fourier transforms of ROIs from two
scans. These decreases are expected due to the corresponding decrease
in quantum mottle with increasing exposure. The difference in the
decrease of the first moment between the two methods may be due to
system characteristics that affect different noise components in the
image.
MLG, shareholder R2 Technology