الفهرس 
Acknowledgement
Thyroid Gland Embryology and AnatomyOnly 14 pages are availabe for public view
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Abstract
Thyroid cancer accounts for approximately 2% of all cancers diagnosed worldwide and 95% of all endocrine cancers.
Of these tumors, there are thyroid carcinomas, which divided into follicular cell-derived thyroid carcinomas including (PTC, FTC, PDTC and ATC), which account for the majority of thyroid malignancies and Para follicular C cell-derived thyroid carcinoma (MTC), which accounts for a small proportion of thyroid malignancies.
PTC and FTC are collectively classified as DTC, and accounts for at least 94% of thyroid carcinoma.
Since the overall recurrence rate for these tumors approaches 20%, and up to 10% of recurrences may occur after 20 years, long-term follow-up of the patient is required after thyroidectomy.
This follow up includes 131I WBS which has been considered the main stay for evaluating the patients thyroidectomized for DTC in addition to Tg serum level assay and conventional radiological procedures.
However, due to the limited resolution of planar acquisitions together with the background activity in RI images, small lesions may be missed (false-negative results).
On the other hand, the presence of numerous areas of physiologic uptake not always easily differentiable from pathologic uptake can give false-positive results.
The recent application of new technology that combines functional and anatomic SPECT/CT images had overcome the above drawbacks; as it allows precise anatomic localization and characterization of RI foci, in addition to CT benefits.
This has been obviously noted in our study, as the planar imaging revealed false negative in 6.9% and false positive results in 12.7% of the total studies.
The incremental diagnostic value of SPECT–CT over planar imaging was obtained for 44% of patients.
Additional imaging studies were avoided in 23.4% of patients; and avoidance of unnecessary RI treatment was permitted 25.5% of patients with follow up studies
The risk stratification has been modified by SPECT/CT in 40% of the post surgical group.