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.
Absorptiometry, Photon ; Body Composition ; Consensus ; Magnetic Resonance Imaging ; Mortality ; Muscle, Skeletal ; Quality of Life ; Sarcopenia

Abdominal Muscles ; Adipose Tissue ; Artificial Intelligence ; Dataset ; Intra-Abdominal Fat ; Learning ; Muscle, Skeletal ; Muscles ; Sarcopenia ; Spine ; Subcutaneous Fat ; Tomography, X-Ray Computed

Purpose: We evaluated the association of body composition with long-term oncologic outcomes innon-metastatic rectal cancer patients. Materials and Methods: We included 1,384 patients with stage(y)0-III rectal cancer treated at Asan Medical Centerbetween January 2005 and December 2012. Body composition at diagnosis was measuredusing abdomino-pelvic computed tomography (CT). Sarcopenia, visceral obesity (VO), andsarcopenic obesity (SO) were defined using CT measured parameters such as skeletal muscleindex (total abdominal muscle area, TAMA), visceral fat area (VFA), and VFA/TAMA. Inflammatorystatus was defined as a neutrophil-lymphocyte ratio of ! 3. Obesity was categorizedby body mass index (! 25 kg/m2). Results: Among the 1,384 patients, 944 (68.2%) had sarcopenia and 307 (22.2%) had SO. The5-year overall survival (OS) rate was significantly lower in sarcopenic patients (no sarcopeniavs. sarcopenia; 84% vs. 78%, p=0.003) but the 5-year recurrence-free survival (RFS) ratewas not different (77.3% vs. 77.9% p=0.957). Patients with SO showed lower 5-year OS(79.1% vs. 75.5% p=0.02) but no difference in 5-year RFS (p=0.957). Sarcopenia, SO, VO,and obesity were not associated with RFS. However, obesity, SO, age, sex, inflammatorystatus, and tumor stage were confirmed as independent factors associated with OS on multivariateanalysis. In subgroup analysis, association of SO with OS was more prominent inpatients with (y)p stage 0-2 and no inflammatory status. Conclusion The presence of SO and a low body mass index at diagnosis are negatively associated withOS in non-metastatic rectal cancer patients.