Only 14 pages are availabe for public view
Thyroid cancer accounts for approximately 1% of all cancer cases (Lin et al., 2012).
Differentiated thyroid cancer is generally characterized by long term survival, good prognosis and low aggressiveness. Distant metastases is relatively rare with incidence ranging from 4- 27% (Bertagna et al., 2012).
Most people diagnosed with thyroid cancer have a total thyroidectomy followed by radio-active iodine ablation. After treatment has finished patients will have regular check-ups. At some visits, patients may have blood tests, US, CT, MRI and scans (Hamed et al., 2014).
The thyroglobulin (Tg) is primarily used as a tumor marker to evaluate the effectiveness of treatment for thyroid cancer and to monitor for recurrence. (Razfar et al., 2013).
I-131 whole body scan (WBS) had been at the center of recurrent thyroid cancer detection; it detects iodine-avid cancers & is ineffective in undifferentiated tumors. One distinct advantage of I-131 WBS over other imaging modalities is its ability to identify distant metastasis. Similar to Tg, I-131 becomes more sensitive after thyroid suppression withdrawal & thyrotropin stimulation (Razfar et al., 2013).
The differentiated thyroid cancer cells after total thyroidectomy & radioiodine ablation may undergo a process of transformation thus losing some or all their ability to take up & retain 131-iodine, but they still retain the ability to absorb FDG (Razfar et al., 2013).
The role of F-18 FDG PET/CT in differentiated thyroid cancer (DTC) is well established, particularly in patients presenting with elevated thyroglobulin (Tg) levels and negative radioactive iodine whole body scan (WBS ). The uptake of F-18 FDG is related to tumor size, thyroid capsule invasion and histological variants with a poor prognosis (Mosci et al., 2013).
Combination between positron emission tomography (PET) and computed tomography (CT) allow anatomic, functional & molecular information. The advantages of this combined technique over PET alone have become obvious. There is increasing evidence to suggest that PET/CT adds complementary information in staging, re-staging and follow-up in post-thyroidectomy patients, leading to changes in management plans (Kim et al., 2010).
The sensitivity of using FDG PET/CT in the detection of cancer thyroid is very high and more accurate than the other imaging modalities as it is capable of differentiating among tumors, scars, fibrosis and necrosis (Leboulleux et al., 2015).
Also PET/CT images from survey of the body could reveal abnormal areas of uptake indicating the spread of the thyroid cancer to lymph nodes, lungs, bones or central nervous system (Muresan et al., 2010).
The fusion of the metabolic and morphologic information in PET/CT was able to increase the diagnostic accuracy, reduces pitfalls and changes therapeutic strategies in a considerable number of patients (Lind & Kohlfurst., 2014).
Studies on the value of 18F-FDG PET for DTC have concentrated on patients in whom radioiodine scintigraphy is negative associated with an increase of TG level. It has been shown that 18F-FDG PET is the most accurate method in this situation (Giammarile, 2015).