Figure 1: Our ultrasound computed tomography and scatter imaging setup [View Image]

The prototype system is shown in Figure 1. A plexiglass water-bath houses an ultrasound source transducer (speaker) and a detector transducer (microphone). The object to be imaged is placed in the center of the tank through the open top. A stepper motor unit with PC control moves the transducers around the object. The PC also captures voltage signals from the microphone (the data), applies signal processing to reduce noise in the data, and performs the mathematical reconstructions as programmed to produce ultrasound images.

Narrow Pulsed Incident Field: a Novel Approach

Figure 2: Incident Ultrasound Beam Width Profile [View Image]

• Our research utilizes a pulsed sound field that is both narrow (2-5 mm full-width/half-max) and longitudinally short (2.3mm long), as illustrated in Figure 2 and Figure 3.
• Hence we have a good knowledge of the incident field spectrum and we can localize it well in space and time.

Figure 3: Pulse [View Image]

Advantages over continuous-wave ultrasound (CWUS)

• simultaneous collection of multifrequency data
• CWUS has phase-shift ambiguity problems - phase of the detected sound wave may be off by a multiple of 2?
• pulsed CT reconstructions can determine both tissue densityand compressibility
• easier determination of ultrasound directivity patterns, since the primary sound energy origin can be pinpointed at any time