Analysis of fractal dimensions of rat bones from film and digital images.
OBJECTIVE
(1) To compare the effect of two different intra-oral image receptors on estimates of fractal dimension; and (2) to determine the variations in fractal dimensions between the femur, tibia and humerus of the rat and between their proximal, middle and distal regions.


METHODS
The left femur, tibia and humerus from 24 4-6-month-old Sprague-Dawley rats were radiographed using intra-oral film and a charge-coupled device (CCD). Films were digitized at a pixel density comparable to the CCD using a flat-bed scanner. Square regions of interest were selected from proximal, middle, and distal regions of each bone. Fractal dimensions were estimated from the slope of regression lines fitted to plots of log power against log spatial frequency.


RESULTS
The fractal dimensions estimates from digitized films were significantly greater than those produced from the CCD (P=0.0008). Estimated fractal dimensions of three types of bone were not significantly different (P=0.0544); however, the three regions of bones were significantly different (P=0.0239). The fractal dimensions estimated from radiographs of the proximal and distal regions of the bones were lower than comparable estimates obtained from the middle region.


CONCLUSIONS
Different types of image receptors significantly affect estimates of fractal dimension. There was no difference in the fractal dimensions of the different bones but the three regions differed significantly.
Pornprasertsuk
S
S
Department of Diagnostic Sciences and General Dentistry, School of Dentistry, University of North Carolina at Chapel Hill, NC 27599-7450, USA.
Ludlow
J B
JB
Webber
R L
RL
Tyndall
D A
DA
Yamauchi
M
M
D000704:Analysis of Variance; D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D005269:Femur / Q000000981:diagnostic imaging; D017709:Fractals; D006811:Humerus / Q000000981:diagnostic imaging; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D011856:Radiographic Image Enhancement / Q000295:instrumentation; D019252:Radiography, Dental, Digital / Q000295:instrumentation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis; D015203:Reproducibility of Results; D013223:Statistics as Topic; D013977:Tibia / Q000000981:diagnostic imaging; D014962:X-Ray Film