컬러 도플러 초음파 영상에서의 트윙클링 허상

Abstract

Twinkling Artifact (TA) is an artifact which appears with random color changes in red and blue, even if there is no turbulence or a similar movement in the tissue. TA is often observed in renal stone, calcification, chronic pancreatitis accompanied with calcification, papilloma thyroid carcinoma, and calcinosis. The underlying mechanisms of TA have not been clearly understood, yet. In this study, the sources that is expected to cause TA was classified into target characteristics and machine settings, their effects on TA were experimentally tested using phantoms. In particular, this study proposed a new technique for enhancing TA contrast and evaluated its clinical potential. The present study is divided into three areas: (1) the effect of target characteristics, (2) the effect of color Doppler setting parameters, and (3) the TA contrast enhanced by mechanical impulse. First, this study examined the influence of various scatter characteristics of target on TA using tissue mimicking (TMM) phantoms under the same color Doppler settings. It was found that TA occurred more as the concentration and size scatterers were increased. Second, the effects of color Doppler settings on TA were assessed using a circular contrast targets, for the following eight setting parameters of PRF, frequency, WMF, ensemble, line density, smoothing, gain and CWP. TA was observed to be maximized when PRF, frequency, WMF and ensemble were low, line density, smoothing and CWP were high, and gain was mid. Third, this study found that TA increased rapidly at the moment when mechanical impulse was applied to the target. The increased TA induced by the impulse persisted longer when the impulse was stronger and the target contrast was high. This finding was verified to a patient with tiny renal stones which are hard to be seen on conventional ultrasonic images. In conclusion, the present study shows that TA is closely related to target characteristics and was affected by the color Doppler settings. The study suggested the use of a mechanical impulse to enhance TA and if such a 'Contrast Enhanced TA Mode' was implemented in an ultrasonic scanner. TA is expected to confirm microcalcification and fibrocystic lesion (i.e. early breast cancer, chronic infection, and tiny stone) which cannot be clearly identified with conventional ultrasonic images.