Quantitative imaging techniques for the assessment of osteoporosis and sarcopenia

Abstract

Bone and muscle are two deeply interconnected organs and a strong relationship between them exists in their development and maintenance. The peak of both bone and muscle mass is achieved in early adulthood, followed by a progressive decline after the age of 40. The increase in life expectancy in developed countries resulted in an increase of degenerative diseases affecting the musculoskeletal system. Osteoporosis and sarcopenia represent a major cause of morbidity and mortality in the elderly population and are associated with a significant increase in healthcare costs. Several imaging techniques are currently available for the non-invasive investigation of bone and muscle mass and quality. Conventional radiology, dual energy X-ray absorptiometry (DXA), computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound often play a complementary role in the study of osteoporosis and sarcopenia, depicting different aspects of the same pathology. This paper presents the different imaging modalities currently used for the investigation of bone and muscle mass and quality in osteoporosis and sarcopenia with special emphasis on the clinical applications and limitations of each technique and with the intent to provide interesting insights into recent advances in the field of conventional imaging, novel high-resolution techniques and fracture risk.

Keywords: Osteoporosis; absorptiometry; magnetic resonance imaging (MRI); multidetector computed tomography (CT); photon; sarcopenia.

Figure 1

“Picture frame” appearance of vertebral bodies on lateral lumbar spine view. As result of resorption processes, vertebral bodies show an overall increase in radiolucency and a thin and well-demarcated cortical rim.

Figure 2

Whole body DXA scan. The image on the left shows the standard ROIs used for regional body composition analysis: head (H), trunk (T), upper limbs (U), lower limbs (L), android (A) and gynoid (G) regions. The colored soft tissues map and the histograms (on the right) show the distribution of fat in different body segments (red areas: fat percentage >60%; yellow areas: fat percentage 25–60%; green areas: fat percentage <25%). DXA, dual energy X-ray absorptiometry; ROIs, regions of interest.

Figure 3

TBS printouts in a healthy control, on the left (BMD L1–L4 =0.929 g/cm²) vs. osteoporotic bone, on the right (BMD L1–L4 =0.799 g/cm²). Local TBS values are displayed on previously acquired DXA scan using a color scale: areas colored in green indicate a good microarchitecture, areas colored in red indicate a deteriorated microarchitecture. TBS, trabecular bone score; BMD, bone mineral density; DXA, dual energy X-ray absorptiometry.

Figure 4

Hip scan with hip geometry analysis. HAL is automatically traced throughout femoral neck from the lower base of the greater trochanter to the inner pelvic brim. The colored map on the right shows the different distribution of BMD values in different femoral regions (from blue to red—from high to low). HAL, hip axis length; BMD, bone mineral density.

Figure 5

VFA on lateral DXA scan. The placement of six vertebral points to determine vertebral heights is automated and the operator only needs to check for their correct positioning. VFA, vertebral fracture assessment; DXA, dual energy X-ray absorptiometry.

Figure 6

Morphometric analysis of DXA spine image with accompanying chart (on the top right). The magnified view (on the bottom right) illustrates moderate wedging of the T9 vertebral body. DXA, dual energy X-ray absorptiometry.