Ultrasound (US) is acoustic energy that interacts with human tissues, thus, producing bioeffects that may be hazardous, especially in sensitive organs (i.e., brain, eye, heart, lung, and digestive tract) and embryos/fetuses. Two basic mechanisms of US interaction with biological systems have been identified: thermal and non-thermal. As a result, thermal and mechanical indexes have been developed to provide a means of assessing the potential for biological effects from exposure to diagnostic US. The main aims of this paper were to describe the models and assumptions used to estimate the “safety” of acoustic outputs and indices and to summarize the current state of knowledge about US-induced effects on living systems deriving from in vitro models and in vivo experiments on animals. This review work has made it possible to highlight the limits associated with the use of the estimated safety values of thermal and mechanical indices relating above all to the use of new US technologies, such as contrast-enhanced ultrasound (CEUS) and acoustic radiation force impulse (ARFI) shear wave elastography (SWE). US for diagnostic and research purposes has been officially declared safe, and no harmful biological effects in humans have yet been demonstrated with new imaging modalities; however, physicians should be adequately informed on the potential risks of biological effects. US exposure, according to the ALARA (As Low As Reasonably Achievable) principle, should be as low as reasonably possible.

The respiratory system may be involved in all systemic vasculitides, although with a variable frequency. Aim of our review is to describe radiographics and high-resolution computed tomography (HRCT) findings of pulmonary vasculitides and to correlate radiological findings with pathological results. Lung disease is a common feature of antineutrophil cytoplasmic autoantibody (ANCA)-associated small-vessels vasculitides, including Granulomatosis with polyangiitis (Wegener's), Eosinophilic granulomatosis with polyangiitis (Churg-Strauss) and Microscopic Polyangiitis. Pulmonary involvement is less frequent in immune complexmediated small-vessels vasculitides, such as Behçet's disease and Goodpasture's Syndrome. Pulmonary involvement associated to large-vessels (Gigantocellular arteritis and Takayasu's disease) or medium-vessels (Nodose Polyarteritis and Kawasaki's disease) vasculitides is extremely rare. The present review describes the main clinical and radiological features of pulmonary vasculitides with maj...