Gland dimensions are usually enlarged,
with global gland volume above normality,
6 to 15 cm3 .
In many cases,
patients with GD are diagnosed and,
when presenting large goiters,sometimes plunging,
causing compression/deviation of adjacent structures such as trachea,
esophagus and vascular structures,
leading todyspnea and dysphagia,
aesthetic discomfort to the patient.
Normal gland has an echogenicity characteristic in ultrasound,
easily distinguishable from adjacent muscular structures.
The thyroid gland ecogenicity is due to its follicular structure: the interface among thyroid cells and colloid produces high acoustic impedancy,
causing high frequency sound waves to be reflected back to the probe .
Resulting greater ecogenicity relative to the neck muscles and bigger or equal to the submandibular glands.
GD change the normal anatomic gland structure including diffuse heterogeneity and hypoechogenicity.
hypoechogenicity is a result of hypervascularity and hypercellularity .
Vitti et al.  proved that in a study group including 105 patients,
70% of GD patients showed low thyroid gland echogenicity.
This pattern is related to the TSH-receptor antibody (TRAb) higher positive frequency and hyperthyroidism recurrence.
In this study,
we observed a statistical significant progressive reduction of thyroid volume after radioiodine therapy.
Color Doppler evaluation is GD ultrasonography diagnosis’ next step,
and probably the most important.
Before GD treatment or effective therapy,
there is a diffuse increase of the parenchyma vascularization,
known as “thyroid inferno”,
a term first used to describe this phenomenon in Ralls et al.  publication,
The thyroid gland vascularization correlates to the underlying functional status,
decreases with the disease under control and can rise again in cases of recurrence.
observed that GD vascularity decrease occurred in parallel to the biochemistry remission and disease control,
ratifying that thyroid US Doppler has the potential to monitor therapy response in patients with GD,
as well as distinguish GD patients from Hashimoto thyroiditis,
with similar B-mode pattern,
without the use of expensive laboratory assays -  in their studies.
In spectral analysis,
Macedo’s study et al. ,
with US Doppler reference values in 84 healthy subjects without iodine deficiency,
the normal SPV obtained was 24.80 cm/s and 25.85 cm/s in the superior thyroid arteries and 20.92 cm/s and 21.50 cm/s in the inferior thyroid arteries.
The inferior thyroid arteries from the tireocervical trunk while the superior ones comes from the external carotid arteries; for this reason is believed that the inferior thyroid arteries are less susceptible to hemodynamic changes. Donkol et al.  considered the systolic peak velocity 40.0 cm/s in the inferior thyroid artery as higher and suggestive to GD,
while most authors consider the velocity value above 50.0 cm/s for patients with this disease,
values above 100.0 cm/s can be reached and not treated or not responsive to treatment  .
In our experience,
a cut off 50.0 cm/s velocity is considered to GD diagnosis measurement in the inferior thyroid arteries,
and we verify that patients responded to the treatment,
presenting SPV reduction,
while the parenchyma vascularity,
although showing a significative reduction,
remains increased when compared to the normal gland.
In non-treated patients or non-responsive to the treatment no SPV decreasing is noted,
so then US Doppler entitles is an excellent patient management method.
Thyroid arteries SPV method has become accurate and reliable,
with excellent reproducibility     in modern advanced technology.
Varsamidis et al.
(19) and Liu et al.
(20 ) demonstrated descrease in peak systolic velocity (PSV ) in patients with Graves disease after successful treatment .
the VPS in the inferior thyroid artery averaged was 81.3 cm/s and after treatment were reduced to 28.9 cm / s.
We observed a significant reduction of thyroid volume and velocity flow of the inferior thyroid arteries,
demonstrating that ultrasound duplex-Doppler of the thyroid gland is an available and efficient method in the follow up of patients with Graves disease after radioiodine therapy.