Abstract
The potential of ultrasound aided investigation of breast tumors remains unexhausted if it is limited to the conventional B-mode imaging, due to its qualitative nature, its examiner dependence and its irreproducibility. There is a need to standardize the examination itself and to reconstruct such parameters quantitatively which possess histological relevance for the differentiation of the breast tissue types. Two such acoustic parameters are speed of sound and acoustic attenuation. Even though the concept of reconstructing the two parameters is about as old as the morphological ultrasound itself, the former could not make its way into the clinical environment for some practical reasons. One of the major impediments has been a fully custom designed solution that was good enough for the initial experiments but failed to achieve the technical ripeness necessary for a broader clinical use owing to its complexity. The approach presented here is envisaged as an add-on for a conventional ultrasound system, comprising a mechanical applicator to standardize and automate the measurement, a control software to synchronize the mechanical applicator with the ultrasound system and finally a reconstruction algorithm to extract the two acoustic parameters from the B-scan data, thus taking advantage of the sophisticated design of the commercial ultrasound systems. The applicator consists principally of a mounting to hold a commercial ultrasound transducer array of a standard ultrasound system looking into a metallic reflector fixed on the opposite side of the object. The assembly resides in a water tank in such a way that the organ may hang in water between the two fixtures the ultrasound array and the metallic reflector. The RF data of a B-scan through the organ is acquired via an interface between the ultrasound system and an external PC. The presence of the metallic reflector makes it possible not only to estimate a time of flight of the ultrasonic pulse through the organ but also the acoustic attenuation profiles from the acquired RF data through the organ, provided a reference B-scan is taken for a fluid with a known speed of sound and a known attenuation at the given measurement conditions. Water was used as such a fluid in the system presented here. The two parameters are then reconstructed with a spatial resolution from a number of such profiles measured from different angular positions of the applicator.