Virtual Touch Tissue Imaging on Acoustic Radiation Force Impulse Elastography

Abstract

Objectives- Acoustic radiation force impulse elastography is a newly developed ultrasound elasticity imaging technique that included both Virtual Touch tissue quantification and Virtual Touch tissue imaging (VTI; Siemens Medical Solutions, Mountain View, CA). This study aimed to evaluate the usefulness of VTI in differentiating malignant from benign thyroid nodules. Methods- This study included 192 consecutive patients with thyroid nodules (n = 219) who underwent surgery for compressive symptoms or suspicion of malignancy. Tissue stiffness on VTI elastography was scored from 1 (soft) to 6 (hard). The VTI scores between malignant and benign thyroid nodules were compared. The intraobserver and interobserver agreement for VTI elastography was also assessed. Results- On VTI elastography: score 1 was found in 84 nodules (all benign); score 2 in 37 nodules (3 papillary carcinomas and 34 benign nodules); score 3 in 25 nodules (1 medullary carcinoma, 6 papillary carcinomas, and 18 benign nodules); score 4 in 53 nodules (50 papillary carcinomas and 3 benign nodules); score 5 in 17 nodules (14 papillary carcinomas and 3 benign nodules); and score 6 in 3 nodules (all papillary carcinomas). A VTI elasticity score of 4 or greater was highly predictive of malignancy (P< .01), and the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 87.0% (67 of 77), 95.8% (136 of 142), 91.8% (67 of 73), 93.1% (136 of 146), and 92.7% (203 of 219), respectively. The κ values were 0.69 for intraobserver agreement and 0.85 for interobserver agreement. Conclusions- Virtual Touch tissue elasticity imaging has great potential as an adjunctive tool combined with conventional sonography for differential diagnosis between benign and malignant thyroid nodules.

Acoustic Radiation Force Impulse Imaging: A New Tool for the Diagnosis of Papillary Thyroid Microcarcinoma

“…As the real-time elastography (RTE) displayed over the B-mode image in a color scale that ranges from red (for soft components) to blue (for hard components), VTI reflects the change of elasticity in a gray-scale image from bright (for soft components) to dark (for hard components). A VTI elastography image score standard had been developed in the previous study to evaluate the elasticity of lesion compared with the surrounding tissue [9]. The present study showed that VES 3 or less was highly suggestive of benign thyroid nodule whereas VES 4 or greater was highly suggestive of malignant thyroid nodule.…”

“…The FOV is adjusted to include the whole lesion (approximately occupying 70% of the whole FOV) and some surrounding thyroid tissue (approximately occupying 20–30% of the whole FOV). The VTI images of the thyroid lesions were thereafter scored according to Xu's scoring system [9]: VTI elasticity score (VES) 1, the nodule is displayed predominantly in bright (dark portion, 0–20%); VES 2, the nodule is displayed predominantly in bright with few dark portion (dark portion, 20–40%); VES 3, the nodule is displayed equally in dark and bright (dark portion, 40–60%); VES 4, the nodule is displayed predominantly in dark with a few bright spots (dark portion, 60–80%); VES 5, the nodule is displayed almost completely in dark (dark portion, >80%); VES 6, the nodule is displayed completely in dark without bright spots (dark portion, 100%).…”

“…The diagnosis of PTMCs was relatively difficult compared with the carcinoma >1 cm. Some recent studies showed that acoustic radiation force impulse (ARFI) elastography was useful for the differentiation between benign and malignant thyroid nodules [9–11]. However, there is no study on the usefulness of ARFI on the diagnosis of PTMC till now.…”

A Risk Model for Predicting Central Lymph Node Metastasis of Papillary Thyroid Microcarcinoma Including Conventional Ultrasound and Acoustic Radiation Force Impulse Elastography

“…The scale ranges from white, showing areas of greatest strain (ie, softest component), to black, showing no strain (ie, hardest component). Based on the Xu's VTI grading method, 26,28–30 VTI elastography images were divided into 6 grades according to the proportion of blackness and whiteness shown in the lesion, in which higher grade of VTI elastography corresponds to harder tissue. Then, the nodules area ratio was calculated using both VTI and B-mode images.…”

“…The former is denoted with qualitative virtual touch tissue imaging (VTI) whereas the latter is denoted with quantitative virtual touch tissue quantification (VTQ). 25–30 In comparison with conventional US strain elastography techniques, ARFI is more operator-independent and reproducible. 28–32 To our knowledge, no studies have been carried out to investigate the association between ARFI elastography findings and prognostic factors in patients with PTMC.…”