الفهرس 
Anatomy of the Thyroid Gland
Arterial SupplyOnly 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
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by assessing the propagation of the US beam by a dedicated
software. The US elastogram was displayed over the Bmode 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.
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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 (F NA)
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.
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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