Screening and early diagnosis of osteoporosis through X-ray and ultrasound based techniques

Abstract

Effective prevention and management of osteoporosis would require suitable methods for population screenings and early diagnosis. Current clinically-available diagnostic methods are mainly based on the use of either X-rays or ultrasound (US). All X-ray based methods provide a measure of bone mineral density (BMD), but it has been demonstrated that other structural aspects of the bone are important in determining fracture risk, such as mechanical features and elastic properties, which cannot be assessed using densitometric techniques. Among the most commonly used techniques, dual X-ray absorptiometry (DXA) is considered the current "gold standard" for osteoporosis diagnosis and fracture risk prediction. Unfortunately, as other X-ray based techniques, DXA has specific limitations (e.g., use of ionizing radiation, large size of the equipment, high costs, limited availability) that hinder its application for population screenings and primary care diagnosis. This has resulted in an increasing interest in developing reliable pre-screening tools for osteoporosis such as quantitative ultrasound (QUS) scanners, which do not involve ionizing radiation exposure and represent a cheaper solution exploiting portable and widely available devices. Furthermore, the usefulness of QUS techniques in fracture risk prediction has been proven and, with the last developments, they are also becoming a more and more reliable approach for assessing bone quality. However, the US assessment of osteoporosis is currently used only as a pre-screening tool, requiring a subsequent diagnosis confirmation by means of a DXA evaluation. Here we illustrate the state of art in the early diagnosis of this "silent disease" and show up recent advances for its prevention and improved management through early diagnosis.

Keywords: Bone mineral density; Diagnosis of osteoporosis; Peripheral sites; Quantitative ultrasound; Screening techniques; X-ray based methods.

Figure 1

Bone densitometry scan (dual X-ray absorptiometry). Schematic representation of X-rays source and detector system in dual X-ray absorptiometry device. Adapted from Drugs.com[94].

Figure 2

Dual X-ray absorptiometry examination on reference sites. A: Dual X-ray absorptiometry (DXA) scan of the femoral neck; B: DXA examination of the lumbar spine with analysis of the vertebral bodies (L1-L4); C: A graphic curve of T-score values normalized for age. The green area of the panel indicates normal T- score values (≥ -1.0), the yellow one indicates osteopenia (< -1.0 but > -2.5) and the red area indicates osteoporosis (≤ 2.5). BMD: Bone mineral density.

Figure 3

Quantitative ultrasound method. A: Ultrasound beam through a bone tissue of phalanx (transmission way) in a typical quantitative ultrasound measurement (section view); B: Ultrasound pulse.

Figure 4

A new ultrasound-based methodology. A: Ultrasound (US) scan of lumbar spine; B: Physical principles of the ultrasound technique based on the reflection of US waves; C: Selection of the target bone interface and automatic detection of the region of interest for diagnostic evaluations and medical report provided with BMD, T-score and Z-score values. BMD: Bone mineral density.

Figure 5

Available systems for osteoporosis diagnosis on main anatomical reference sites. US: Ultrasound.