Current imaging techniques for thyroid nodules and thyroid cancer

Thyroid cancer incidence has risen, and incidental nodules are common, especially in middle‑aged women. About 5–15% of nodules are malignant. Most differentiated thyroid cancers are indolent with favorable prognosis, but cervical lymph node metastasis can complicate surgery. Accurate diagnosis and evaluation are critical. This review proposes scenario‑based imaging selection.

Imaging Techniques

Main modalities: ultrasound, CT, PET‑CT, spectral CT, and MRI. Ultrasound uses high‑frequency sound waves; CT uses X‑ray computed tomography; PET‑CT combines FDG metabolic imaging with anatomy; spectral CT uses dual‑energy or multi‑energy data; MRI uses magnetic fields and radiofrequency pulses. Advanced ultrasound includes elastography, superb microvascular imaging (SMI), shear‑wave elastography (SWE), and contrast‑enhanced ultrasound (CEUS). Radiomics extracts quantitative image information.

Diagnostic Ultrasound

Ultrasound is the preferred initial examination. Diagnosis is based on morphology, margins, echogenicity, and calcifications, with TI‑RADS for risk stratification. SMI improves microvascular visualization; SWE assesses stiffness; CEUS evaluates perfusion. Advantages: real‑time, no radiation, low cost, high resolution, biopsy guidance. Limitations: operator dependence, poor visualization in retrosternal or obese patients, subjective interpretation.

CT

CT provides high spatial and density resolution and clearly shows cervical lymph nodes, retrosternal lesions, and calcifications. It evaluates lesion location, size, margins, calcification, enhancement, lymph node metastasis, and distant spread. Malignant nodules may be lobulated with irregular density, poor margins, or capsular discontinuity. CT is valuable for surgical planning, especially with retrosternal extension or invasion. Limitations: ionizing radiation, contrast reactions, interference with thyroid function, lower sensitivity for microcalcifications than ultrasound.

PET‑CT

PET‑CT is an adjunct for selected cytologically indeterminate nodules, not routine initial evaluation. Increased FDG uptake usually indicates higher malignancy risk. It is useful in high‑risk differentiated thyroid cancer for suspected recurrence or metastasis, especially with elevated thyroglobulin but negative radioiodine imaging. It can also identify sonographically suspicious, scintigraphically hypofunctional nodules. Limitations: high cost, high radiation dose, false positives from thyroiditis.

Spectral CT

Spectral CT generates iodine maps, virtual monoenergetic images, and spectral curves. It may reduce radiation dose, additional acquisitions, artifacts, and improve lesion conspicuity. Because thyroid tissue is iodine‑rich, iodine content decreases with follicular epithelial damage. Arterial‑phase iodine images may help diagnose nodules. Limitations: equipment not widely available, protocols need standardization, complex post‑processing.

MRI

MRI provides superior soft tissue contrast and multi‑planar imaging without ionizing radiation. Most malignant nodules show signal similar to or lower than normal thyroid on T1‑weighted images and high signal on T2‑weighted images. MRI clearly shows relationships with nerves and vessels and is valuable for invasion, residual disease, or recurrence. Functional sequences add tissue characterization. Limitations: long scan time, high cost, insensitivity to calcifications, restrictions with some implants or claustrophobia.

Optimal Clinical Scenarios

Ultrasound is best for initial screening, TI‑RADS risk stratification, FNA guidance, and follow‑up. CT is indicated for preoperative assessment of confirmed or suspected malignant nodules, especially with retrosternal goiter, extensive lymph node metastasis, or invasion of trachea, esophagus, or major vessels. PET‑CT is recommended for staging and restaging high‑risk thyroid cancer, especially with elevated thyroglobulin and negative iodine scans. Spectral CT may provide adjunctive quantitative information for selected nodules. MRI may be considered when iodinated contrast‑enhanced CT is unsuitable, especially for soft‑tissue invasion or postoperative residual/recurrent disease.

Comparison and Selection Strategies

Initial screening and risk assessment: ultrasound with TI‑RADS. Preoperative assessment and staging: contrast‑enhanced CT when high‑risk features or local invasion are suspected; MRI as alternative or supplement. Recurrence and metastasis monitoring: FDG PET‑CT when thyroglobulin is elevated but radioiodine imaging is negative. In difficult cases, spectral CT iodine maps or MRI functional sequences can be combined. Radiomics and AI may improve differential diagnosis and prognosis. Final strategy should be individualized.

Future Directions

Focus on standardized multimodal imaging, quantitative functional imaging, radiomics, and validated AI‑assisted approaches.

Limitations

Narrative review without predefined search strategy or structured quality assessment. Selection and interpretation may be biased; evidence levels not graded. No meta‑analysis or pooled analysis. Future systematic reviews are needed.

Conclusions

Ultrasound is primary for initial screening and TI‑RADS risk stratification. CT or MRI may be used for preoperative anatomical evaluation and local invasion. Spectral CT may provide adjunctive quantitative information for selected nodules, but routine use requires validation. FDG PET‑CT is reserved mainly for selected high‑risk, recurrent, metastatic, or radioiodine‑negative differentiated thyroid cancer.

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https://www.xiahepublishing.com/2835-3315/CSP-2026-00036

The study was recently published in the Cancer Screening and Prevention.

Cancer Screening and Prevention (CSP) publishes high-quality research and review articles related to cancer screening and prevention. It aims to provide a platform for studies that develop innovative and creative strategies and precise models for screening, early detection, and prevention of various cancers. Studies on the integration of precision cancer prevention multiomics where cancer screening, early detection and prevention regimens can precisely reflect the risk of cancer from dissected genomic and environmental parameters are particularly welcome.

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