| Cat. | Descriptor | Key findings | Management | Malignancy |
|---|---|---|---|---|
| 0 | Incomplete | Part/all of lungs not evaluable, awaiting prior CT, or suspected infection/inflammation | Compare to prior CT, additional imaging, and/or 1–3 mo LDCT | n/a |
| 1 | Negative | No nodules, or nodule with benign (complete/central/popcorn/ring) calcification or fat | Annual LDCT (12 mo) | < 1% |
| 2 | Benign | Solid < 6 mm (new < 4 mm); part-solid < 6 mm total; GGN < 30 mm; juxtapleural < 10 mm | Annual LDCT (12 mo) | < 1% |
| 3 | Probably benign | Solid ≥ 6–< 8 mm (new 4–< 6); part-solid ≥ 6 mm total w/ solid < 6 mm; GGN ≥ 30 mm | 6-month LDCT | 1–2% |
| 4A | Suspicious | Solid ≥ 8–< 15 mm (new 6–< 8); part-solid solid comp. ≥ 6–< 8 mm; segmental airway (baseline) | 3-month LDCT; PET/CT if ≥ 8 mm solid | 5–15% |
| 4B | Very suspicious | Solid ≥ 15 mm (new/growing ≥ 8); part-solid solid comp. ≥ 8 mm; slow-growth over serial exams | Diagnostic CT, PET/CT, ± tissue sampling | > 15% |
| 4X | Very suspicious + | Category 3/4 nodule with extra features increasing suspicion (spiculation, nodal/metastatic disease, GGN doubling) | As for 4B | > 15% |
| S | Modifier | Significant/potentially significant finding unrelated to lung cancer (added to category 0–4) | Per ACR Incidental Findings | — |
This tool implements ACR Lung-RADS® v2022 rules. Final classification and management must be made by a qualified radiologist using the full imaging study and clinical context.
What Is the Lung-RADS® v2022 Calculator?
This Lung-RADS calculator is a free, instant tool that assigns the correct Lung-RADS® version 2022 assessment category to a pulmonary nodule detected on low-dose CT (LDCT) lung cancer screening. Enter the nodule type, its relationship to prior exams, and its mean diameter, and the calculator returns the Lung-RADS category, the recommended management, and the estimated probability of malignancy in real time.
Lung-RADS (Lung Imaging Reporting and Data System) was developed by the American College of Radiology (ACR) to standardize the reporting and management of screening chest CT examinations. Version 2022, released in November 2022, is the current edition and replaces Lung-RADS v1.1. It reduces variability between readers, improves communication with referring clinicians, and links each category to a specific, evidence-based follow-up recommendation.
How to Use This Lung-RADS Calculator
- Select the dominant finding – the nodule with the highest degree of suspicion (each exam is coded by its most concerning nodule).
- Choose the timepoint – baseline screen, a new nodule, a growing nodule (> 1.5 mm increase within 12 months), or a stable/slowly growing nodule.
- Enter the mean diameter – the average of the long and short axis, measured to one decimal point on lung windows. For part-solid nodules, also enter the solid-component diameter.
- Add any modifiers – features that increase suspicion for lung cancer (category 4X) or a significant non-lung finding (S modifier).
The result, with its colour-coded category and management recommendation, updates automatically as you complete each field.
Size Thresholds by Nodule Type
Solid nodules
- Category 2: < 6 mm at baseline, or new < 4 mm.
- Category 3: ≥ 6 to < 8 mm at baseline, or new 4 to < 6 mm.
- Category 4A: ≥ 8 to < 15 mm at baseline, new 6 to < 8 mm, or growing < 8 mm.
- Category 4B: ≥ 15 mm at baseline, or new/growing ≥ 8 mm.
Part-solid nodules
- Category 2: < 6 mm total mean diameter at baseline.
- Category 3: ≥ 6 mm total with solid component < 6 mm at baseline, or new < 6 mm total.
- Category 4A: solid component ≥ 6 to < 8 mm at baseline, or new/growing solid component < 4 mm.
- Category 4B: solid component ≥ 8 mm at baseline, or new/growing solid component ≥ 4 mm.
Non-solid (ground-glass) nodules
- Category 2: < 30 mm at baseline, new, or growing; or ≥ 30 mm that is stable or slowly growing.
- Category 3: ≥ 30 mm at baseline or new.
Key Changes in Lung-RADS v2022
- Ground-glass nodules: non-solid nodules < 30 mm are now classified as category 2, reducing unnecessary follow-up.
- Slow-growing nodules: a solid or part-solid nodule that grows over multiple screening exams without crossing the 1.5 mm/12-month threshold is suspicious and classified as category 4B.
- Atypical pulmonary cysts and airway (endobronchial) nodules now have explicit classification criteria.
- Juxtapleural nodules: solid, smoothly marginated, oval/lentiform/triangular nodules < 10 mm are category 2.
- Growth definition is clarified as an increase in mean diameter of > 1.5 mm within a 12-month interval.
How to Measure a Nodule for Lung-RADS
To calculate the mean nodule diameter, measure both the long and short axis to one decimal point in millimetres and report the average to one decimal point. The long and short axis may be measured in any plane to reflect the true size of the nodule. For part-solid nodules, measure both the total nodule and the solid component. When volumetry is used, report volumes to the nearest whole cubic millimetre.
The S and 4X Modifiers
Category 4X applies to a category 3 or 4 nodule with additional imaging features that increase suspicion for lung cancer, such as spiculation, lymphadenopathy, frank metastatic disease, or a ground-glass nodule that doubles in size within one year. The S modifier can be added to any category (0–4) to flag a clinically significant or potentially significant finding unrelated to lung cancer, managed according to ACR Incidental Findings recommendations.
Frequently Asked Questions
What does a positive Lung-RADS screen mean?
For practice-audit purposes, a negative screen is defined as Lung-RADS category 1 or 2, and a positive screen as category 3 or 4. A negative screen does not guarantee that an individual is free of lung cancer.
How is Lung-RADS growth defined?
Growth is an increase in mean diameter of more than 1.5 mm within a 12-month interval. A nodule that crosses into a higher size category should be re-classified by size even if it does not formally meet the growth definition.
When does follow-up timing start?
The timing of follow-up imaging is measured from the date of the exam being interpreted – for example, a category 2 recommendation for a 12-month screening LDCT is counted from the current exam.
Is this Lung-RADS calculator a substitute for clinical judgement?
No. This calculator is an educational aid. The final Lung-RADS classification and management decision must be made by a qualified radiologist using the complete imaging study and the patient’s clinical context.
Improve Content And Help Your Colleagues!
Found an error in the post? Please let us know using our contact page and we will update it with due credits!
If you wish to contribute radiological images for this case (or any other article on the website), you can submit them here and you will be duly credited: Submit radiology case
About the Author
Dr. Amar Udare, MD, DNB
Dr. Udare holds an MBBS and MD degree, and his expertise lies in the field of radiology. He has authored multiple peer-reviewed publications, contributing significantly to the medical field. His works can be accessed on PubMed and Google Scholar.
In addition to his academic and professional achievements, Dr. Udare is an avid reader and enjoys exploring the latest advancements in medical technology. His commitment to making complex medical knowledge accessible to patients and the general public aligns with our mission at RadioGyan.com.
For any further questions or clarifications, feel free to reach out to Dr. Udare via the contact form.