Influence of region of interest and bone size on calcaneal BMD: implications for the accuracy of quantitative ultrasound assessments at the calcaneus

Influence of region of interest and bone size on calcaneal BMD: implications for the accuracy of quantitative ultrasound assessments at the calcaneus

S Cheng, PhD ¹^,2 C F Njeh, PhD, CPhys ¹ B Fan, MD ¹ X Cheng, MD, PhD ¹ D Hans, PhD ¹ L Wang, MD ¹ T Fuerst, PhD ¹ and H K Genant, MD ¹

¹Osteoporosis and Arthritis Research Group, Department of Radiology, University of California, San Francisco, 350 Parnassus Avenue, San Francisco, CA 94134-1349, USA and ²Department of Health Sciences, University of Jyväskylä, Finland

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Figure 1. Examples of the original images from dual energy X-ray absorptiometry scans used for bone mineral density determination, demonstrating the effect of foot size on the region of interest (ROI). The ring indicates the position of the manufacturer's ROI (ROI_M). The upper images (a,b) show a large foot (29 cm) and the lower images (c,d) show a small foot (22.5 cm). (a,c) The ROI_M of the Sahara, with a diameter of 19 mm, which was the same size as the transducer. (b,d) The ROI_M of the Achilles+, with a diameter of 25 mm, the same size as the transducer.

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Figure 2. (a) The location of the manufacturer's region of interest (ROI_M) and the anatomical region of interest ROI_A where bone mineral density was analysed, where R1 represents ROI_M and R2 represents ROI_A. The upper image shows the ROIs determined using the Sahara device and the lower image are the ROIs determined using the Achilles+ device. (b) An example of how the true dimension has been calculated for each subject. True calcaneal length=measured calcaneal length x (true ring diameter/measured diameter).

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Figure 3. The quantitative ultrasound results of individual subjects measured both with the Sahara ( ${square}$ ) and the Achilles+ ( ${blacksquare}$ ). The broken vertical line (–.–) indicates the mean value obtained with the Sahara and the dotted vertical line (....) indicates the mean value obtained with Achilles+. The horizontal line links the same person measured with both devices. BUA, broadband ultrasound attenuation; SOS, speed of sound; QUI, quantitative ultrasound index; SI, stiffness index.

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Figure 4. Areal bone mineral density (BMD) between the manufacturer's region of interest (ROI_m) and the anatomical region of interest (ROI_a) for (a) the Sahara and (b) the Achilles+. The dots represent individual values and the lines link measurements on the same person.

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Figure 5. Volumetric BMD between the manufacturer's region of interest (ROI_m) and the anatomical region of interest (ROI_a) for (a) the Sahara and (b) the Achilles+. The dots represent individual values and the lines link values for the same person.