Review of ultrasound elastography quality control and training test phantoms

While the rapid development of ultrasound elastography techniques in recent decades has sparked its prompt implementation in the clinical setting adding new diagnostic information to conventional imaging techniques, questions still remain as to its full potential and efficacy in the hospital environment. A limited number of technical studies have objectively assessed the full capabilities of the different elastography approaches, perhaps due, in part, to the scarcity of suitable tissue-mimicking materials (TMMs) and appropriately designed phantoms available. Few commercially available elastography phantoms possess the necessary test target characteristics or mechanical properties observed clinically, or indeed reflect the lesion-to-background elasticity ratio encountered during clinical scanning. Thus, while some phantoms may prove useful, they may not fully challenge the capabilities of the different elastography techniques, proving limited when it comes to quality control (QC) and/or training purposes. Although a variety of elastography TMMs, such as agar and gelatine dispersions, co-polymer in oil and poly(vinyl) alcohol cryogel, have been developed for specific research purposes, such work is yet to produce appropriately designed phantoms to adequately challenge the variety of current commercially available elastography applications. Accordingly, there is a clear need for the further development of elastography TMMs and phantoms to keep pace with the rapid developments in elastography technology, to ensure that the performance of these new diagnostic approaches are validated, and for clinical training purposes.