الفهرس 
Anatomy of the Thyroid GlandOnly 14 pages are availabe for public view
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Abstract
Thyroid nodules are very common and are found in 4% to 8% of adults by palpation, 41% by ultrasound, and 50% by pathologic examination at autopsy. Most nodules are benign, with less than 5% of them being malignant.
Cytological examination of material obtained by fine needle aspiration (FNA), due to its high sensitivity and specificity, is the best single test for differentiating malignant from benign thyroid lesions. Yet, a substantial proportion of nodules are not correctly diagnosed before surgical treatment, and histological examination is required.
Sonography has many favourable features, such as detection of non palpable nodules, estimation of nodule size/goiter volume, and guidance for fine needle biopsy (FNB). High-resolution ultrasound is very sensitive in detection of thyroid nodules, enabling differentiation of solid and liquid lesions.
Ultrasound features indicative of malignant nodule include the presence of irregular margins, marked hypoechogenicity, microcalcifications, taller than wide nodule and intranodular vascularity. Although the strongest independent factor related to malignancy was the absence of surrounding halo sign.
The principle of USE is to acquire two ultrasonographic images (before and after tissue compression by the probe), and to track tissue displacement by assessing the propagation of the US beam by a dedicated software. The US elastogram was displayed over the B-mode image in a color scale that ranged from red, for components with greatest elastic strain (i.e. softer components), to blue for those with no strain (i.e. harder components).
The purpose of this study was to evaluate indeterminate thyroid nodules by US elastography.
In this study, 30 cases were included. The cases were subjected to complete U/S, Colour Doppler examination, and US elastography the results were compared to U/S guided FNAC.
Strain elastography involves two kinds of elasticity assessments; realtime visual scoring of colour within and around the nodule and calculation of strain ratio between two regions of interests, within the nodule and within the surrounding. The likelihood of malignancy increases with the increase in strain ratio.
When using the best cut off value of strain colour code 3, we found that elasticity imaging is significantly higher in malignant nodules than in benign nodules and normal thyroid tissue with sensitivity and specificity were 91% and 72% respectively.
On the off line processed elastograms a strain index higher than 1.6 was shown to be an independent predictor of thyroid malignancy with sensitivity and specificity were 89% and 70% respectively.
While using combined US findings -mainly halo sign and margin irregularity- and elastography strain ratio and/or starin colour, statistically significant results are obtained.
The major limitations of our study were:
Selection of indeterminate nodules among the cases of multinodular goiters which represents up to 40% of the referred cases in daily practice.
Quality and subjective variability in the freehand compression data.
Relatively long post processing time for thyroid stiffness index calculation
Low reliability on a narrow scale of available cases such as the result of only one nodule taken colour code 5 and proved as papillary thyroid cancer. So, further studies with a wider scale of patients should be considered.
Indeterminate and nondiagnostic patterns represent the main limitation of fine needle aspiration (FNA) cytology of thyroid nodules.
The newly developed real-time ultrasound elastography (USE) has been previously applied to differentiate malignant from benign lesions.
US-elastography is a promising technique that when combined with other US suspicious signs, it can help to predict thyroid nodules that are likely to be malignant.
We generally found that ultrasound elastography is an easy, non invasive and rapid technique that can be routinely used in thyroid US scans to select cases for FNAC, and decrease the number of unnecessary biopsies, and consequently decrease the hazards and costs.
Cases with ES of 4 and 5 are considered to be highly suspicious for malignancy and other US criteria of malignancy should be looked for to support the diagnosis e.g pattern of vascularity and cervical lymph nodes infiltration.
Hence we advice to consider cases with ES 1 and 2 as benign, in absence of sonographic criteria of indeterminate lesions, requiring follow up, to consider cases with ES 3 as equivocal, should at least undergo cytological analysis and cases with ES 4 and 5 as highly suspicious cases for malignancy to work up.
FNAC should be recommended in all cases of score 3 where malignancy cannot be excluded using ultrasound elastography criteria only.
Further studies are necessary before being able to conclude about the place of elastography in thyroid nodules evaluation, versus fine-needle aspiration cytology (FNAC), the gold standard. However in current time, elastography could reduce FNAC or at least allow selecting nodules or nodular zones for aspiration.