Phantom experiment and clinical utility of quantitative shear wave elastography for differentiating thyroid nodules

Abstract

Recently ultRasonogRaphy equipment has remarkably improved. High-resolution ultrasonography excels in the detection of thyroid lesions, and it is an essential tool for diagnosing thyroid diseases. The present of specific features on B-mode sonography, evaluation of blood flow with Doppler sonography, and the strain ratio measured by strain elastography (SE) provide predictions of tissue characteristics to a certain degree. However, ultrasonography remains suboptimal for diagnosing thyroid diseases [1,2].The novel technology of shear wave elastography (SWE), also known as virtual touch quantification For phantom study, we measured the shear wave velocities (SWVs) of the four spheres of 2-and 1-cm diameters with varying hardness. For clinical study, the SWVs of normal thyroid glands and thyroid nodules, that were classified as benign or malignant according to either cytological or pathological findings, were measured. The SWVs of each thyroid patient were compared with that of a normal thyroid and each other. In phantom study, the SWVs for the 2-cm spheres correlated with the hardness of the targets, whereas the values for the 1-cm spheres did not. In clinical study, 112 nodules identified in 167 patients and 94 normal thyroid glands were analyzed according to the criteria for the study. The nodules included 84 benign nodules, and 28 papillary carcinoma. The mean SWVs of each group were 1.64 ± 0.47 m/s for normal thyroid, 1.88 ± 0.62 m/s for benign nodules and 2.67 ± 0.76 m/s for papillary carcinoma. The SWVs of papillary carcinoma were significantly higher than those of benign nodules (P < 0.001). The area under the ROC curve was 0.809 with a cutoff value of 2.01 m/s. The sensitivity and specificity were 85.7% and 62.0% respectively. Results showed that SWE provides new information on tumor characteristics, such as hardness and larger nodules tended to provide stable measurements.

Ultrasound elastography in thyroid disease

“…Thus, small nodules are not accurately measured using ARFI because the ROI will contain not only the nodule, but also the surrounding thyroid tissue and the values of velocity measured for that nodule will not be real. On the other hand, Fukuhara et al showed that the measurements of the velocity in nodules smaller than 20 mm in diameter are not stable [92].…”

Intra- and inter-observer variation and accuracy using different shear wave elastography methods to assess circumscribed objects – a phantom study.

“…Fukuhara et al acknowledge in their study that when objects exhibit small diameters, measurements of SWV parameters are unstable. They interpret the phenomena of this depreciation as being accounted for by the US waves of the push pulse, which were reflected and refracted at the boundaries of the objects, thus resulting in the irregular production of shear waves [15,34]. Such factors in the border area of the phantom object may be responsible for the high relative error of US shear wave elastography measurements when adapting the ROI directly to the shape of the object ("best fitted").…”

“…Hence, the measurement procedure in the second part of the study was repeated five times for each target type, with the stiffness value defined as the mean of the five measurements for each ROI diameter (diameters: 40, 38, 36, 34,32,30,28,26,24,22,20,18,16,14,12,10,8,6, 4 and 2 mm).…”

Acoustic radiation force impulse imaging (ARFI) for differentiation of benign and malignant thyroid nodules—A meta-analysis

“…Finally, there were 16 studies meeting inclusion criteria in our meta-analysis [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Table 1 presents the main characteristics of the studies.…”