Imaging of visceral adipose tissue: an emerging diagnostic tool and therapeutic target

Several lines of evidence support the contention that excess visceral fat plays a significant role in the development of an unfavourable metabolic and cardiovascular risk profile. Hence, estimation of visceral adipose tissue (VAT), that is, the fat surrounding the internal organs, might be important for cardiovascular risk stratification. Classically, anthropometric measures have been employed to assess body fat distribution for risk assessment. But more recently, imaging methods for visceral fat quantitation have become a focus of attention particularly in a clinical research setting. Several imaging methods have evolved for estimation of VAT mass. Among these, magnetic resonance imaging (MRI) is fairly well established, but ultrasound and magnetic resonance spectroscopy (MRS) are also emerging as useful methods for quantitation of VAT and fat tissue content in vivo. Ultrasound is the most cost-effective and a convenient imaging tool whereas MRS is still in its infancy but it is highly promising because of its high sensitivity and specificity. There is a compelling need to quantify VAT not only for diagnostic purposes, but also for therapeutic interventions with weight reduction drugs or pharmaceuticals targeted to with adipose tissue. For example, changes in regional fat distribution can be used to estimate drugs effectiveness and their mechanism of action. Therefore, in this review I shall present briefly latest and main imaging techniques to detect the visceral adiposity, including the new ultrasound measurements of different visceral adipose tissue compartments. Some visceral adipose tissues which are not traditionally assessed, such as intraperitoneal, mediastinal and the relatively small depots, such as epicardial adipose tissue have also been recently studied and are now proposed as new markers of visceral adiposity.