Preoperative Characterization of Thyroid Nodule with Cytological Reading of Follicular Neoplasm Using 99mTc-MIBI Scanning and Ultrasound Elastography

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.