The Usefulness of Contrast-Enhanced Ultrasound to Evaluate Small Solid Thyroid Nodules Compared to TI-RADS

• Clin Thyroidol 2021;33:114–116.
• Background
  • Thyroid nodules are very common and frequently incidentally detected with the increasing use of imaging
  • The primary concern is how to identify those with suspicious features in order to avoid unnecessary diagnostic exams like fine-needle aspiration biopsy (FNAB) and overtreatment
  • Even though the Thyroid Imaging Reporting and Data System (TI-RADS):
    • Created by the American College of Radiologists:
      • Is widely accepted as an easy and useful tool to avoid unnecessary FNAB and close follow-up it still suffers from some biases, including experience and heterogeneity among sonographers
  • Contrast-enhanced ultrasound (CEUS) is a novel technology:
    • That can help differentiate between benign and malignant thyroid nodules
  • TI-RADS does not recommend FNAB for nodules up to 1 cm:
    • Even though such nodules have mild, moderate, or high (TI-RADS 3, 4, and 5, respectively) sonographic risk for malignancy
  • However, CEUS represents a new tool in the evaluation of thyroid nodules
  • The aim of this study was to compare the use of CEUS versus conventional ultrasound (as TI-RADS) in the risk stratification of thyroid nodules
• Methods
  • In this study, 185 solid thyroid nodules between 0.5 and 1 cm in 154 patients were evaluated by conventional ultrasound and CEUS at the same time and by the same investigator
  • In conventional ultrasound, each target nodule was scored based on the components of:
    • Echogenicity, shape, edge, and strong echogenic focus, according to the 2017 edition of ACR TI-RADS in order to ascertain a TI-RADS classification
  • Qualitative indicators of CEUS analysis in the targeted thyroid nodules included:
    • Enhancement intensity, patterns of enhancement, internal homogeneity, the presence of perfusion defect, clearness of boundary, morphology, and size at enhance‐ ment peak
  • The CEUS characteristics of benign and malignant thyroid nodules with the significant differential diagnosis were scored, and the total scores of each thyroid nodule were calculated
• Results
  • Of 185 thyroid nodules, the diagnosis was confirmed in 133 by surgical pathology, with 90 nodules (67.67%) showing papillary thyroid cancer (PTC) and 43 (32.33%) having benign results
  • In 52 thyroid nodules, cytology from the FNAB showed PTC in 11 nodules (21.15%) and nonmalignancy in 41 (78.85%)
  • Overall, there were 101 malignant thyroid nodules
  • When comparing the risk assessment scores:
    • CEUS outperformed TI-RADS using conventional ultrasound for benign diseases, but this was not the case in malignant nodules
  • Comparing the diagnostic performance between TI-RADS TR5 nodules and CEUS nodules that scored 5 points:
    • Sensitivity was 90.10% versus 86.13%, specificity 55.95% versus 89.29%, accuracy 74.59% versus 87.57%, positive predictive value 72.22% versus 90.63%, negative predictive value 82.46% versus 84.27%, and the area under the receiver-operating-characteristic curve 0.738 (95% CI, 0.663–0813) versus 0.916 (95% CI, 0.871– 0.961).
• Conclusions
  • This study found that CEUS:
    • When evaluating small solid thyroid nodules, had higher diagnostic performance and a higher specificity than TI-RADS using conventional ultrasound
    • CEUS may be a valuable imaging tool to select patients with thyroid nodules for FNAB or surgery
  • Conventional ultrasound is currently the initial diagnostic tool for the risk stratification of thyroid nodules
  • To increase the diagnostic confidence and avoid unnecessary FNABs, many societies have proposed systems to stratify malignancy risks by ultrasound and guide physicians in when to perform FNAB:
    • One of the most popular and practical methods is TI-RADS
  • However, how to accurately differentiate malignant from benign nodules remains a significant challenge in many situations:
    • Since at least a half of all biopsied nodules are benign and up one third of FNABs are inconclusive
  • The new imaging method of CEUS can show tumor perfusion and vascular distribution after intravenous injection of a microbubble contrast agent:
    • Since vascular structures in the nodule differ from those of normal tissues
• The specific characteristics of CEUS, like enhancement intensity, patterns of enhancement, and internal homogeneity, seem to be valuable in determining which nodules should undergo an FNAB and which may be kept under observation
• In this study evaluating small nodules:
  • CEUS had significantly higher performance than TI-RADS in differentiating malignant from benign nodules:
    • Suggesting that CEUS qualitative analysis could be more effective in excluding malignant nodules and avoiding unnecessary biopsies
  • The use of CEUS in clinical practice has some crucial limitations, including the:
    • Cost of the exam, especially if the patient has more than one nodule to be analyzed:
      • Each nodule requires injection of a contrast agent
    • In addition, the small numbers of radiologists trained to perform this imaging study, as well as the absence of well-estab‐ lished criteria and consensus regarding the patterns of enhancement and classification of thyroid nodules, make its broad use in clinical practice controversial at present

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