| Popis: |
Twinkling artifact (TA) is a phenomenon that rapidly alternating color pixels behind a stationary strongly reflecting medium where a comet tail artifact is expected in Doppler mode. Although this phenomenon has a potential in clinical diagnosis for example early detection of microcalcification in dense breast, the occurrence mechanism has not been clarified yet. There have been several hypotheses for underlying mechanism of this phenomenon: surface roughness of calcification, phase jitter noise of the ultrasound machine, and oscillation of reflecting medium. In this study, in-vitro experiments were conducted, and the effects of the oscillating disturbance on a microcalcification embedded in soft tissue were investigated. A transparent poly (vinyl alcohol) hydro (PVA-H) gel with 7 wt% concentration and graphite power with 7 wt% concentration were used. Glass beads were embedded in the phantom. Each diameter is approximately 569 and 213 µm, respectively. All scanning were performed using a medical ultrasound machine (LOGIQ S8 pilot unit, GE Healthcare) with a linear array probe (ML6-15, GE Healthcare). The probe and the phantom were fixed in several ways for the purpose of determining the factor of the TA. As results, when the probe and the phantom were fixed with a stage and the stage was placed on the same table with the ultrasound machine, the twinkling artifact appeared, and stable Doppler shift components appeared in the peak values of the amplitude of successive I/Q signals. When the stage was isolated from the external disturbance including the US machine, the twinkling artifact and Doppler shift components were suppressed. Suppression of the twinkling artifact by control of oscillating environment demonstrated that the twinkling artifact generates from variability among the acoustic signals, not phase jitter or surface roughness of microcalcification. Furthermore, the variability was caused by acoustical oscillation with the speaker. |
