Furthermore, the results of such a study could be helpful for patient care in the clinical setting by decreasing the use of US-FNAB for PCTNs on the basis of the high diagnostic efficacy of thyroid sonography for PCTN. A prospective study for sonographic diagnoses of PCTNs might be more accurate compared with a retrospective study that includes limited sonograms. However, to our knowledge, there has been no prospective study on the diagnostic efficacy of thyroid sonography for PCTN. 4, 7 Recently, Lee et al 7 reported that a predominantly solid component, an eccentrically placed solid component, and the presence of microcalcifications are associated with malignancy of PCTNs. Several sonographic features such as marked hypoechogenicity, an irregular margin, microcalcifications, and a taller than wide shape have been introduced as potential predictors for the presence of a thyroid malignancy in solid thyroid nodules however, to our knowledge, there are few studies on sonographic features as predictors of a diagnosis of cystic thyroid nodules. Thyroid sonography has been used as the major diagnostic technique for the evaluation of thyroid nodules. 5, 6 However, more recent studies have reported that the frequency of malignancy in cystic thyroid nodules is similar to that of solid nodules. 4 Some investigators have suggested that thyroid cysts can be considered benign lesions and managed conservatively. 1 – 7 Most cystic thyroid nodules showing a mixed echogenicity develop as a result of cystic degeneration of neoplastic or non-neoplastic nodules however, true thyroid cysts that have an epithelial lining are rare. With each reverberation the ultrasound pulse returning back to the probe is much weaker and it quickly fades.Abbreviations A eccentric configuration with acute angle B microcalcifications C macrolobulation D centripetal vascularity in pedicle FA follicular adenoma NH nodular hyperplasia NPV negative predictive value PCTN partially cystic thyroid nodule PPV positive predictive value PTC papillary thyroid carcinoma UA unavailable US-FNAB sonographically guided fine-needle aspiration biopsyĬystic thyroid nodules as detected by thyroid sonography and thyroid surgery are common. Some of the reverberating pulse is reflected back to the transducer but much more is reflected off in other directions. The ultrasound pulse is trapped between reflective surfaces that are not parallel. The reverberation focus is a tiny area of interstitial fibrous tissue or fluid with non parallel surfaces. Originating at the pleural surface is an echogenic vertical comet tail artefact. Sliding is seen as the two pleural surfaces move against each other through the respiratory cycle. How much ultrasound energy is lost – dissipated or attenuated, between each re-reflection.Ĭomet tail artefact is a short path reverberation artefact that weakens with each reverberation, resulting in a vertical echogenic artefact that rapidly fades as it continues in to the ultrasound image.The distance between the two reflective surfaces (long vs short path reverberation artefacts).The size of the two reflective surfaces.The appearance of the reverberation artefact depends on: This reverberation causes a repetitive artefact on the ultrasound image. Some of the pulse becomes caught between the two surfaces, bouncing forwards and backwards before returning in increments, between each reverberation, to the transducer. Not infrequently an ultrasound pulse encounters two parallel reflective surfaces lying perpendicular to its path. When this does not occur ultrasound artefacts are created. An ultrasound machine assumes a single pulse of ultrasound enters the tissues, is reflected off a structure, and returns directly to the transducer for interpretation.
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