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A method for determining skeletal lengths from DXA images.

Chinappen-Horsley U, Blake GM, Fogelman I, Spector TD - BMC Musculoskelet Disord (2007)

Bottom Line: Two methods, linear pixel count (LPC) and reticule and ruler (RET) were used to measure skeletal sizes on DXA images and compared with real clinical measures from 20 subjects and 20 x-rays of the femur and tibia taken in 2003.Although both methods were highly correlated, the LPC inter- and intra-observer error was lower at 1.6% compared to that of RET at 2.3%.This new phenotype will be useful for osteoporosis research for individuals or large-scale epidemiological or genetic studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: King's College London, St Thomas' Hospital Campus, Twin Research & Genetic Epidemiology Unit, Lambeth Palace Road, London, SE1 7EH, UK. usha.chinappen@kcl.ac.uk

ABSTRACT

Background: Skeletal ratios and bone lengths are widely used in anthropology and forensic pathology and hip axis length is a useful predictor of fracture. The aim of this study was to show that skeletal ratios, such as length of femur to height, could be accurately measured from a DXA (dual energy X-ray absorptiometry) image.

Methods: 90 normal Caucasian females, 18-80 years old, with whole body DXA data were used as subjects. Two methods, linear pixel count (LPC) and reticule and ruler (RET) were used to measure skeletal sizes on DXA images and compared with real clinical measures from 20 subjects and 20 x-rays of the femur and tibia taken in 2003.

Results: Although both methods were highly correlated, the LPC inter- and intra-observer error was lower at 1.6% compared to that of RET at 2.3%. Both methods correlated positively with real clinical measures, with LPC having a marginally stronger correlation coefficient (r2 = 0.94; r2 = 0.84; average r2 = 0.89) than RET (r2 = 0.86; r2 = 0.84; average r2 = 0.85) with X-rays and real measures respectively. Also, the time taken to use LPC was half that of RET at 5 minutes per scan.

Conclusion: Skeletal ratios can be accurately and precisely measured from DXA total body scan images. The LPC method is easy to use and relatively rapid. This new phenotype will be useful for osteoporosis research for individuals or large-scale epidemiological or genetic studies.

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Related in: MedlinePlus

A bar graph of RMS SD against region of measurement for LPC (no. of lines) and RET (mm) methods.
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Figure 3: A bar graph of RMS SD against region of measurement for LPC (no. of lines) and RET (mm) methods.

Mentions: Fifty females were used to test observer error. When the coefficient of variation (CV) was calculated for long-term precision and intra-observer error using both methods (Figure 2), mean CV% for LPC (1.6%) was lower than RET (2.3%). Although units of measurement were different in each method, comparison of these true measures using the root mean square standard deviation (RMS SD) shown in Figure 3 indicates that deviation for the LPC and RET were similar for the same sites, except for the tibia where the LPC was higher than all other measures. For RET, 1 mm was equivalent to approximately 2.06 cm and for LPC, 1 line was equivalent to approximately 1.3 cm.


A method for determining skeletal lengths from DXA images.

Chinappen-Horsley U, Blake GM, Fogelman I, Spector TD - BMC Musculoskelet Disord (2007)

A bar graph of RMS SD against region of measurement for LPC (no. of lines) and RET (mm) methods.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211289&req=5

Figure 3: A bar graph of RMS SD against region of measurement for LPC (no. of lines) and RET (mm) methods.
Mentions: Fifty females were used to test observer error. When the coefficient of variation (CV) was calculated for long-term precision and intra-observer error using both methods (Figure 2), mean CV% for LPC (1.6%) was lower than RET (2.3%). Although units of measurement were different in each method, comparison of these true measures using the root mean square standard deviation (RMS SD) shown in Figure 3 indicates that deviation for the LPC and RET were similar for the same sites, except for the tibia where the LPC was higher than all other measures. For RET, 1 mm was equivalent to approximately 2.06 cm and for LPC, 1 line was equivalent to approximately 1.3 cm.

Bottom Line: Two methods, linear pixel count (LPC) and reticule and ruler (RET) were used to measure skeletal sizes on DXA images and compared with real clinical measures from 20 subjects and 20 x-rays of the femur and tibia taken in 2003.Although both methods were highly correlated, the LPC inter- and intra-observer error was lower at 1.6% compared to that of RET at 2.3%.This new phenotype will be useful for osteoporosis research for individuals or large-scale epidemiological or genetic studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: King's College London, St Thomas' Hospital Campus, Twin Research & Genetic Epidemiology Unit, Lambeth Palace Road, London, SE1 7EH, UK. usha.chinappen@kcl.ac.uk

ABSTRACT

Background: Skeletal ratios and bone lengths are widely used in anthropology and forensic pathology and hip axis length is a useful predictor of fracture. The aim of this study was to show that skeletal ratios, such as length of femur to height, could be accurately measured from a DXA (dual energy X-ray absorptiometry) image.

Methods: 90 normal Caucasian females, 18-80 years old, with whole body DXA data were used as subjects. Two methods, linear pixel count (LPC) and reticule and ruler (RET) were used to measure skeletal sizes on DXA images and compared with real clinical measures from 20 subjects and 20 x-rays of the femur and tibia taken in 2003.

Results: Although both methods were highly correlated, the LPC inter- and intra-observer error was lower at 1.6% compared to that of RET at 2.3%. Both methods correlated positively with real clinical measures, with LPC having a marginally stronger correlation coefficient (r2 = 0.94; r2 = 0.84; average r2 = 0.89) than RET (r2 = 0.86; r2 = 0.84; average r2 = 0.85) with X-rays and real measures respectively. Also, the time taken to use LPC was half that of RET at 5 minutes per scan.

Conclusion: Skeletal ratios can be accurately and precisely measured from DXA total body scan images. The LPC method is easy to use and relatively rapid. This new phenotype will be useful for osteoporosis research for individuals or large-scale epidemiological or genetic studies.

Show MeSH
Related in: MedlinePlus