Evaluation of solitary thyriod cold nodules wioth technetium-99m ses-amibi and thalium -201

الملخص EN

This is a prospective study, including 54 patients with solitary cold thyroid nodules detected on the standard technetium-99m pertechnetate scintigraphy in the period between September 1999 and February 2001.

All patients underwent thyroid ultrasonography, triple-phase thyroid scan with Technetium-99m pertechnetate (99mTc), Tech-netium-99m sestamibi (99mTc-MIBI) and thallium-201 (201TI) followed by fine needle aspiration cytology (FNAC).

All patients, except those with thyroiditis, were subjected to surgery for histopathologically diagnosis.

Quantitative analysis was performed by drawing a region of interest (ROI) over the nodule and contralateral normal thyroid tissue.

The lesion to normal thyroid (L / N) uptake ratio on early (ER) and late image (LR) were calculated.

Based on histopathologically examination, there were 19 patients (35 %) with well differentiated carcinoma and 35 patients (65 %) with benign lesions.

The mean uptake L / N ratios for benign and malignant thyroid nodules were 1.25 ± 0.47 and 1.56 ± 0.24 in the early 99mTc-MIBI scan ; 0.99 ± 0.18 and 2.38 ± 0.71 in the late 99mTc-MIBI scan.

There was no statistical difference between the mean early L / N uptake ratio of benign versus malignant thyroid lesions using 99mTc-MIBI (p = 0.073).

On the other hand, there was a statistically significant difference between the mean late L / N uptake ratios of benign versus malignant thyroid nodules using 99mTc-MIBI (p = 0.001).

Also, there was no significant difference in the mean early L/N uptake ratios for thallium-201 scan between benign (1.29 ± 0.41) and malignant nodules (1.35 ± 0.17) (p = 0.133).

A significant difference in the late thallium scan between the mean uptake ratio in benign (1.06 ± 0.12) and malignant nodules (1.74 ± 0.31) was noted (p = 0.01).

To determine the threshold levels to differentiate between benign and malignant nodules, a receiver operating characteristic (ROC) analysis was applied.

The mean uptake ratios of 1.31 and 1.48 for early and late 99mTc-MIBI scans and 1.23 and 1.34 for early and late 201TI scans were selected, respectively.

Based on these threshold values, the sensitivity and specificity of early 99mTc-MIBI scan were 84.2 % and 83.3%, whereas they were 89.5 % and 90 % for late 99mTc-MIBI.

A lower sensitivity and specificity for early thallium-201 scan of 78.9 %, and 66.7 % and 84.2 % and 86.7 % for late thallium-201 were found.

In conclusion, LR for 99mTc-MIBI and 201TI studies was superior to ER in differentiating malignant thyroid nodules.

Also, LR of 99mTc-MIBI was more sensitive than that of 201TI scan in diagnosis of benign versus malignant thyroid nodules.