Recent Issues on Body Composition Imaging for Sarcopenia Evaluation

Abstract

Recently, sarcopenia has garnered renewed interest. Sarcopenia is a disease characterized by decreased skeletal muscle mass and strength/function, which can impair the quality of life and increase physical disability, adverse metabolic effects, and mortality. Imaging tools for evaluating and diagnosing sarcopenia have developed rapidly. Radiologists should be aware of sarcopenia and its clinical implications. We review current knowledge about sarcopenia, its pathophysiological impact, and advantages and disadvantages of methods for evaluation of sarcopenia focusing on body composition imaging modalities such as whole-body dual-energy X-ray absorptiometry, CT, and MRI. Controversial issues are discussed, including the lack of consensus and standardization of the disease definition, imaging modality, measurement methods, and diagnostic cutoff points.

Keywords: Body composition; Computed tomography; Dual-energy X-ray absorptiometry; Magnetic resonance imaging; Sarcopenia.

Fig. 1. Muscle as secretory organ.

Various myokines released through muscle contraction affecting anatomically distant organs, which could explain association between sedentary behavior and many chronic diseases. ANGPTL4 = angiopoietin-like 4, BAIBA = β-aminoisobutyric acid, BDNF = brain-derived neurotrophic factor, CSTB = cathepsin B, FAM5C = family with sequence similarity 5, FGF2 = fibroblast growth factor 2, FGF21 = fibroblast growth factor 21, FSTL1 = follistatin-related protein 1, IGF1 = insulin-like growth factor 1, SPARC = secreted protein acidic and rich in cysteine, IL-6 = interleukin-6, IL-7 = interleukin-7, IL-10 = interleukin-10, IL-15 = interleukin-15

Fig. 2. Sarcopenia cascade.

Various cause of sarcopenia entering vicious cycle, resulting in physical disability, falling, fracture, hospitalization, depression, poor quality of life, increased health care costs, adverse metabolic effects, and notably increased mortality.

Fig. 3. Dual-energy x-ray absorptiometry results for body composition in healthy 47-year-old male.

ASM is sum of lean muscle mass of both arms and legs. ASM is adjusted using height squared (ASM/ht²), weight (ASM/wt), or BMI (ASM/BMI). ASM = appendicular skeletal muscle, BMC = bone mineral content, BMI = body-mass index

Fig. 4. Body composition evaluation CT image with artificial intelligence segmentation technique.

In clinically acquired axial CT images at L3 vertebral body level TAMA, visceral fat area, subcutaneous fat area are segmented in 43-year-old male (A), and 55-year-old obese male (B). TAMA = total abdominal muscle area

Fig. 5. Sarcopenia evaluation with MRI.

In clinically acquired whole-body MRI of 55-year-old male patient (A), TAMA is segmented at L3 vertebral body level (B) and thigh muscle area is segmented at mid-thigh level (C).

Fig. 6. US images of thigh muscle.

In clinically acquired axial view US image of 30-year-old female patient (A), and sagittal panoramic view (B) provides both qualitative and quantitative information of thigh muscle. US = ultrasonography