Background and Aim: Non-invasive imaging techniques such as 99mTc-Sestamibi (MIBI) thyroid scanning and US Elastography are widely utilized in the evaluation of thyroid nodule. However, the outcomes of these diagnostic tests are inconsistent; the goal of our study was to compare the accuracy of US Elastography and 99mTc-MIBI in distinguishing between malignant and benign thyroid nodules in patients with a cytological diagnosis of follicular neoplasm.
Patients and Methods: Twenty-one patients with thyroid nodules underwent US-elastography by an experienced radiologist to obtain the Elastography score (ES) and the strain ratio (SR). 99mTc-Pertechnetate scintigraphy and dual phase MIBI SPECT/CT scanning were also done. Tracer uptake in MIBI images were visually graded as; no, faint, iso-, and intense uptake. Additionally, the pattern of tracer washout—decreased, unchanged, or increased uptake in the delayed images as compared to the early images was used. As the gold standard, radiologic follow-up and histopathology were utilized.
Results: The majority of nodules (16/21) were TI-RADS IV, while the remaining five were TI-RADS III. Elastography showed that the majority of benign nodules (87.5%, 14/16 patients) had a score of 3, with one nodule in each category for score 2 and score 4, while malignant nodules had two with a score of 3, two with a score 4, and one with a score 5, yielding 60% sensitivity, 93.8% specificity, and 85.7% accuracy (P=0.008).The mean SR value for the benign nodules was insignificantly lower than that of the malignant ones (3.1±1.9 versus 4.5±3.2, P= 0.236). With an AUC of 0.619 (95%- CI: 0.294-0.944 and P=.433), the optimal SR cutoff value for detecting malignancy was set at 0.82, yielding 100% sensitivity and 93.8% specificity. The number of malignant and benign nodules was found to be 5 and 16, respectively. Most nodules were hypo-functioning in nature. With a 100 % NPV, delayed MIBI image scoring outperformed the early one. Despite having the same sensitivity (80%), the washout pattern in delayed SPECT/CT scans had a significantly higher specificity, accuracy, NPV, and PPV (P=0.003) than that in the delayed planar ones (P=0.003).
Conclusion: In cases of thyroid nodules with a cytological diagnosis of follicular neoplasm; SR yields considerably higher sensitivity and specificity than the Elastography score. Additionally, the use of SPECT/CT strengthens the diagnostic accuracy of the late MIBI scans. The results of MIBI readings proved superior to those of Elastography scores.
Keywords: US Elastography, SR, Sestamibi, MIBI washout, semiquantitative parameters, thyroid