Established paths and new avenues: a review of the main radiological techniques for investigating sarcopenia

Abstract

Sarcopenia is a clinical condition mainly affecting the elderly that can be associated in a long run with severe consequences like malnutrition and frailty. Considering the progressive ageing of the world population and the socio-economic impact of this disease, much effort is devoted and has to be further focused on an early and accurate diagnostic assessment of muscle loss. Currently, several radiological techniques can be applied for evaluating sarcopenia. If dual-energy X-ray absorptiometry (DXA) is still considered the main tool and it is even recommended as reference by the most current guidelines of the European working group on sarcopenia in older people (EWGSOP), the role of ultrasound (US), computed tomography (CT), peripheral quantitative CT (pQCT), and magnetic resonance imaging (MRI) should not be overlooked. Indeed, such techniques can provide robust qualitative and quantitative information. In particular, regarding MRI, the use of sequences like diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), magnetic resonance spectroscopy (MRS) and mapping that could provide further insights into the physiopathological features of sarcopenia, should be fostered. In an era pointing to the quantification and automatic evaluation of diseases, we call for future research extending the application of organ tailored protocols, taking advantage of the most recent technical developments.

Keywords: Sarcopenia; absorptiometry; computed tomography (CT); magnetic resonance (MR); radiology.

Figure 1

Axial CT scan of an 87-year-old female patient affected by cirrhosis and acute large bowel obstruction with signs of paravertebral muscles loss at level of L3 (yellow arrows in A). CT-based quantification of the muscle mass of the same patient using an open source software in (B) (3D slicer, www.slicer.org). CT, computed tomography.

Figure 2

US scan of the left gluteus muscle of a 72-year-old male patient, referring loss of muscle strength, showing high echogenicity of the muscle tissue (yellow arrows). US, ultrasound.

Figure 3

T1-weighted axial turbo spin echo of a 64-year-old male patient with chronic pulmonary disease well demonstrating muscle atrophy especially affecting the semimembranosus muscle on both sides (yellow arrows).

Figure 4

Axial in-phase (A), water-only (B), out of phase (C), and fat-only (D) Dixon images of a 64-year-old male patient with severe myositis, well demonstrating diffuse severe fatty conversion of the muscles of both thighs more severe in the posterior compartment (yellow arrows).

Figure 5

Axial T1-weighted turbo spin echo (A) and ADC map (B) of a 79-year-old male patient with metastatic colon cancer affected also by moderate atrophy of the paravertebral muscles at the L3 level (yellow arrows), especially on the left side. In agreement with the recent literature, which even proposed ADC values as biomarker of sarcopenia (70,71), in our patient, the left paravertebral muscles, which were more affected by atrophic changes, showed higher ADC values (red and yellow circles in B). ADC, apparent diffusion coefficient.