Abstract:
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Purpose: Computerized radiographic texture analysis (RTA) is currently being
investigated as a measure of bone structure and a diagnostic predictor of
osteoporosis. In this study, we assess the physical image quality indices of a
bone densitometry system as well as its ability to yield images useful for RTA.
Methods and Materials: The bone densitometry system investigated was the
GE/Lunar PIXI, which uses dual-energy subtraction to measure bone mineral
density (BMD) and provides 512 x 512 digital images of the heel or forearm (0.2
mm pixels). We compared the physical imaging properties (contrast, resolution
and noise) of the PIXI to those of a Fuji computed radiography (CR) system (0.1
mm pixels). Contrast was measured using a series of uniform exposure images,
presampling modulation transfer functions (MTF) were measured using an edge
method, and noise power spectra (NPS) were calculated using a two-dimensional
Fourier analysis method. We also analyzed texture features of heel images from
24 subjects who had both CR and PIXI exams taken. The Fourier-based texture
features characterized the magnitude, frequency content and orientation of the
trabecular bone pattern.
Results: The slope of the characteristic curve of the BMD system was found to
be position dependent, across the image, although this dependence was
substantially reduced by use of the sustem's clinical-settings corrections. An
MTF value of 0.5 was found at 0.5 cycles/mm for the PIXI system compared to the
same value at 1.4 cycles/mm for the CR system. Unlike the CR system, the NPS of
PIXI was found not to be directionally dependent and did not drop off at higher
frequencies. There was correlation for the first moment features between the
two modalities with r=0.61 (p-value=0.001) for first moment of the power
spectrum (FMP) and r=0.50 (p-value=0.01) for minimum FMP. Root-mean-square
(RMS) showed little correlation with r=0.22 (p-value=0.3).
Conclusion: Initial results indicate that a bone densitometry system is a
promising means of performing computerized RTA. A more extensive patient study
is warranted to determine the suitability of RTA in osteoporosis assessment. (M.L.G.,
M.D.C. are shareholders in R2 Technology, Inc. (Sunnyvale, CA).)
Questions about this event email: jwilkie@uchicago.edu
Wilkie, J,
Comparison of Image Quality and RTA between a Bone Densitometry System and CR. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3102949.html