Page 36 - Summer 2018

Quantitative Ultrasound and the Management of Osteoporosis
Quantitative ultrasound is a clinically validated, low-cost, portable, nonionizing alternative to traditional X-ray methods for managing osteoporosis.
Osteoporosis, Bone Structure, and X-ray
Diagnostic Methods
Do you know somebody who suffers from osteoporosis? There is a good chance that you do. An estimated 54 million adults in the United States are affected by osteoporosis or low bone mass (Wright et al., 2014). Osteoporosis, which means “porous bone,” is a systemic skeletal disease characterized by decreased bone den- sity and increased fracture risk. Globally, osteoporosis is responsible for 9 million fractures per year (Johnell and Kanis, 2006). Medical costs for the treatment of osteoporosis in the United States are projected to be $25 billion per year by 2025 (Burge et al., 2007).
Osteoporosis disproportionately affects postmenopausal women. After menopause, decreased estrogen levels disrupt the normal process of bone turnover in which spe- cialized cells called osteoclasts remove old bone tissue while other specialized cells called osteoblasts build new bone tissue. When osteoclast activity exceeds osteoblast activity, net bone loss occurs. Fortunately, drugs are available to treat this condition. It is estimated that 1 in 2 women and 1 in 4 men over the age of 50 will break a bone due to osteoporosis (National Osteoporosis Foundation, 2018).
Bones contain two main types of tissue (Figures 1 and 2). Cancellous bone (also called trabecular bone) is a lightweight, highly porous material located toward the inner regions of bones (Figure 1). Cortical bone is dense material that forms the outer shell (cortex) of bones. Both tissues consist of an organic phase (mainly col- lagen) and a mineral phase (mainly hydroxyapatite). The diagnosis of osteoporosis is often based on X-ray measurements of bone mineral density (BMD; Figure 2; see Table 1 for a list of abbreviations), which quantifies the concentration of hy- droxyapatite.
Email:
pascal.laugier@upmc.fr
Keith A. Wear
Address:
Food and Drug Administration 10903 New Hampshire Avenue Building 62, Room 2104 Silver Spring, Maryland 20993 USA
Email:
keith.wear@fda.hhs.gov
Brent K. Hoffmeister
Address:
Department of Physics Rhodes College 2000 North Parkway Memphis, Tennessee 38112 USA
Email:
hoffmeister@rhodes.edu
Pascal Laugier
Address:
Laboratoire d’Imagerie Biomédicale Sorbonne Université 15 rue de l’École de Médecine 75006 Paris France
34 | Acoustics Today | Summer 2018 | volume 14, issue 2
The most common diagnostic technique for osteoporosis is a two-dimensional technique called dual-energy X-ray absorptiometry (DXA). DXA measurements performed at the hip and spine, common locations for osteoporotic fractures, are considered the “gold-standard” method for diagnosing osteoporosis. However, DXA measurements at these central skeletal locations are inconvenient because they require large, whole body scanners. More portable options include periph- eral DXA (pDXA) and peripheral quantitative computed tomography (pQCT) systems, both of which perform X-ray BMD measurements at peripheral skeletal locations such as the leg or forearm. Another option is quantitative ultrasound (QUS).