Table 1.

Advantages and disadvantages of the main imaging tools for the assessment of body composition and mass/fat assessment

Technique	Strengths	Weak points	Measurements
DXA	• Fast acquisition • Widely available • Accurate and reproducible • Validated cut-off values • Minimal irradiation • Cheap	• Different results varying the densitometer brands • Dependent by hydration status • Bidimensional data	• Appendicular lean mass (ALM) •Appendicular lean mass index (ALMI)
CT	• Fast acquisition • Widely available • Accurate and reproducible • High spatial resolution	• Non-negligible irradiation • Cut-off values are still not used in clinical practice • Expensive • Time-consuming segmentation process	• CSA indexed by height2 (SMI) • Attenuation values
MRI	• Accurate and reproducible • No irradiation • High contrast resolution • Capability to identify muscle oedema and fat infiltration • Promising advanced sequences	• Long acquisition time • No validated cut-off values for sarcopenia • Expensive • Lower availability • Long post-processing of advanced sequences	• CSA indexed by height2 (SMI) • Fat content on DIXON • Experimental measurements of advanced sequences (ADC, FA, T2 relaxation time..)
US	• Fast acquisition • Widely available • No irradiation exposure • Cheap • Real-time imaging	• Scarcely reproducible • Poor accuracy • No validated cut-off values for sarcopenia	• CSA indexed by height2 (SMI) • Muscle thickness and echogenicity