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Keywords:
Thyroid / Parathyroids, Ear / Nose / Throat, Oncology, Ultrasound, Diagnostic procedure, Biopsy, Tissue characterisation, Pathology
Authors:
B. Raghavan, D. Sundaram; Chennai/IN
DOI:
10.1594/ecr2015/B-0877
Purpose
AIM:
The aim of the study is to detect the impact of ARFI elastography on TIRADS categorization in risk stratification of thyroid nodules.
- To differentiate benign and malignant thyroid nodules by ARFI (VTQ and VTI images).
- To determine the impact of ARFI on TIRADS classification with cytology as gold standard.
BACK GROUND:
Only 5% of the incidentally detected thyroid nodules are malignant(1).
Based on ultrasound finding thyroid nodules can be grouped under 6 categories according to TIRADS(2)( Fig. 1 ).
Fig. 1: TIRADS classification
References: Horvath E et al . An ultrasonogram reporting system for thyroid nodules stratifying cancer risk for clinical management. J ClinEndocrinolMetab.2009 May; 94(5):1748-51.
FNAC or biopsy is warrented for nodules under categories 4A,
4B and 5.
But risk range of malignancy of nodules under TIRADS category 4 AND 5 is wide (5- 80%) hence the chance of unnecessary FNAC or biopsies is high.
Strain elastogrpahy is a qualitative method and has high intra and inter observer variation as the compression exerted the operator can vary.The soft tissue which deforms more is displayed as red or blue or green and the hard tissue which deforms less is displayed as blue or red.(3). Acoustic Radiation Force Impulse (ARFI) imaging is relatively newer elastogrphy technique in which the tissue in the ROI is mechanically excited by high intensity acoustic pulses(4)( Fig. 2 ).
Fig. 2: Principle of strain elastography and ARFI elatography demonstrated in a healthy volunteer. Bottom row shows ARFI elastography of a colloid nodule.
Advantages of ARFI over starin elastography:
- Unlike strain elastography ARFI is an operator independent technique.
- Gives uniform compression always.
- More reliable,
objective and reproducible technique.
- Tissue elasticity can be measured quantitatively(VTQ method) and qualitatively(VTI method) (5).