ACR TI-RADS Calculator for Thyroid Nodules
Enter the five ultrasound feature categories observed on imaging to score a thyroid nodule using the ACR Thyroid Imaging Reporting and Data System (TI-RADS). The calculator outputs the total point score, TI-RADS level (TR1 to TR5), estimated malignancy risk, and size-based recommendations for fine-needle aspiration (FNA) biopsy or follow-up surveillance. Results follow the 2017 Tessler et al. ACR white paper guidelines.
What is ACR TI-RADS?
The American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) is a standardized framework published in 2017 for assessing the malignancy risk of thyroid nodules detected on ultrasound. It assigns points to five sonographic features, composition, echogenicity, shape, margin, and echogenic foci, then uses the total to categorize the nodule from TR1 (benign) through TR5 (highly suspicious). The system was designed to provide consistent terminology and reduce unnecessary fine-needle aspiration (FNA) biopsies for clearly benign or low-risk nodules, a major problem with earlier, more aggressive guidelines.
How the scoring system works
Each of the five feature categories is scored independently. Composition scores 0 for purely cystic or spongiform nodules, 1 for mixed cystic and solid, and 2 for solid nodules. Echogenicity scores 0 for anechoic, 1 for hyperechoic or isoechoic, 2 for hypoechoic, and 3 for very hypoechoic (darker than strap muscles). Shape scores 0 if the nodule is wider than tall, and 3 if it is taller than wide, assessed in the transverse plane. Margin scores 0 for smooth or ill-defined borders, 2 for lobulated or irregular, and 3 for extrathyroidal extension. Echogenic foci scores 0 for none or large comet-tail artifacts, 1 for macrocalcifications, 2 for rim calcifications, and 3 for punctate echogenic foci (microcalcifications). Two important rules apply: first, a cystic or spongiform nodule is automatically TR1 and no other features are scored; second, echogenic foci are additive with the rest of the score.
FNA and follow-up thresholds explained
The ACR TI-RADS system intentionally uses higher size thresholds for FNA than many earlier guidelines, to avoid overdiagnosis of clinically insignificant microcarcinomas. TR3 nodules require FNA only at 2.5 cm or larger; follow-up ultrasound is recommended if they are 1.5 cm or larger at 1, 3, and 5 years. TR4 nodules call for FNA at 1.5 cm or larger and follow-up ultrasound at 1.0 cm or larger using a 1-, 2-, 3-, and 5-year schedule. TR5 nodules should be biopsied at 1.0 cm or larger; nodules between 0.5 and 1.0 cm warrant annual surveillance ultrasound for up to 5 years. Even TR5 nodules smaller than 0.5 cm do not require immediate action in most cases. Significant growth is defined as a 20% or greater increase in at least two dimensions with a minimum 2 mm increase, or a 50% or greater increase in volume.
Limitations and clinical context
ACR TI-RADS is validated for incidentally discovered thyroid nodules in adult patients. It is not intended for use in children or adolescents, patients with a prior or concurrent thyroid malignancy, previously biopsied nodules, or in the context of clinical features that independently raise concern (such as hoarseness, lymphadenopathy, or a family history of medullary thyroid cancer). The malignancy risk percentages are population estimates; individual patient risk factors, including radiation exposure history, family history, and biochemical findings, should inform the overall clinical assessment. FNA cytology results are interpreted using the Bethesda System and may lead to further surgical or molecular testing.
ACR TI-RADS Categories and Management Thresholds
| Level | Score | Description | Malignancy Risk | FNA Threshold | Follow-up Threshold |
|---|---|---|---|---|---|
| TR1 | 0 | Benign | <0.3% | No FNA | No follow-up |
| TR2 | 2 | Not suspicious | ~1.5% | No FNA | No follow-up |
| TR3 | 3 | Mildly suspicious | ~4.8% | 2.5 cm or larger | 1.5 cm or larger (1, 3, 5 yrs) |
| TR4 | 4-6 | Moderately suspicious | ~9.1% | 1.5 cm or larger | 1.0 cm or larger (1, 2, 3, 5 yrs) |
| TR5 | 7+ | Highly suspicious | ~35% | 1.0 cm or larger | 0.5 cm or larger (annual x 5 yrs) |
Based on the 2017 ACR TI-RADS white paper by Tessler et al. FNA and follow-up thresholds are based on maximum nodule dimension.
Frequently asked questions
What does TI-RADS stand for?
TI-RADS stands for Thyroid Imaging Reporting and Data System. The ACR (American College of Radiology) version, published in 2017, is one of several thyroid nodule risk-stratification systems but is among the most widely adopted in the United States because of its well-defined point-based scoring and clear management thresholds.
What is the difference between TR1 and TR5?
TR1 represents a benign nodule with a malignancy risk below 0.3%, typically a simple cyst or a spongiform nodule. TR5 represents a highly suspicious nodule with approximately 35% malignancy risk based on features such as solid composition, marked hypoechogenicity, a taller-than-wide shape, irregular margins, or punctate microcalcifications. The TI-RADS level directly informs whether FNA, surveillance, or no further workup is needed.
Does a high TI-RADS score mean the nodule is cancerous?
No. Even TR5 nodules have a malignancy rate of approximately 35%, meaning roughly two-thirds of them are benign on biopsy. TI-RADS is a risk stratification tool, not a diagnostic test. FNA cytology, and sometimes molecular testing or surgical pathology, is required to confirm or exclude malignancy.
Why does ACR TI-RADS use higher FNA thresholds than older guidelines?
Older systems such as the 2015 ATA guidelines sometimes recommended FNA for smaller or lower-risk nodules, leading to many unnecessary biopsies of nodules that turned out to be benign or clinically insignificant microcarcinomas. The ACR TI-RADS thresholds are deliberately conservative to reduce overdiagnosis and the patient harm that can come from overtreatment of indolent disease.
What happens after a positive FNA?
FNA cytology is reported using the Bethesda System, which assigns one of six categories from non-diagnostic to malignant. Bethesda III and IV results (indeterminate) may be followed up with repeat biopsy, molecular marker testing (such as Afirma or ThyroSeq), or diagnostic hemithyroidectomy depending on patient and nodule factors. Bethesda V and VI (suspicious or malignant) typically lead to surgical referral.
Can TI-RADS be used for nodules found on CT or MRI?
No. ACR TI-RADS was developed specifically for ultrasound-characterised nodules. Nodules incidentally discovered on CT or MRI require a dedicated thyroid ultrasound for proper characterisation and TI-RADS scoring. The ACR has separate guidance (the ACR Incidental Thyroid Nodule White Paper) for managing nodules found on cross-sectional imaging before ultrasound evaluation.
What does "spongiform" mean in the context of thyroid nodules?
A spongiform nodule is one composed of more than 50% tiny cystic spaces, giving it a sponge-like appearance on ultrasound. Like completely cystic nodules, spongiform nodules are automatically classified as TR1 under ACR TI-RADS because this appearance is essentially never associated with malignancy. No FNA or follow-up is required.
Sources
- Tessler FN et al. ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White Paper of the ACR TI-RADS Committee. J Am Coll Radiol. 2017.
- Middleton WD et al. Multi-institutional Analysis of Thyroid Nodule Risk Stratification Using the American College of Radiology Thyroid Imaging Reporting and Data System. AJR Am J Roentgenol. 2017.