[Lung Imaging Reporting and Data System (Lung-RADS) in Radiology: Strengths, Weaknesses and Improvement]

Abstract

In 2019, the American College of Radiology announced Lung CT Screening Reporting & Data System (Lung-RADS) 1.1 to reduce lung cancer false positivity compared to that of Lung-RADS 1.0 for effective national lung cancer screening, and in December 2022, announced the new Lung-RADS 1.1, Lung-RADS^® 2022 improvement. The Lung-RADS^® 2022 measures the nodule size to the first decimal place compared to that of the Lung-RADS 1.0, to category 2 until the juxtapleural nodule size is < 10 mm, increases the size criterion of the ground glass nodule to 30 mm in category 2, and changes categories 4B and 4X to extremely suspicious. The category was divided according to the airway nodules location and shape or wall thickness of atypical pulmonary cysts. Herein, to help radiologists understand the Lung-RADS^® 2022, this review will describe its advantages, disadvantages, and future improvements.

Fig. 1. A 68-year-old male with a 30-pack-year smoking history with perifissural lymph node. There is a 7 mm triangular solid nodule (arrow) near the right major fissure on low-dose chest CT. It is category 3 in Lung RADS 1.0, but downgraded to category 2 in Lung RADS 1.1. and Lung-RADS^® 2022.

Lung-RADS = Lung CT Screening Reporting & Data System

Fig. 2. A 57-year-old male with a 32-pack-year smoking history with perifissural lymph node.

A. There is a 20 mm lobular, ellipsoidal solid nodule (arrow) near the left major fissure on low-dose chest CT. In Lung RADS 1.1, it is considered category 4A. B. After one year, a follow-up low-dose chest CT shows no change in this perifissural lymph node (arrow) near the left major fissure. It is category 2 in Lung RADS 1.1. and Lung-RADS^® 2022 and assigned to follow-up low-dose chest CT. Lung-RADS = Lung CT Screening Reporting & Data System

Fig. 3. A 60-year-old male with a 30-pack-year smoking history classified as category 4A in Lung RADS 1.1. and Lung-RADS^® 2022.

A, B. If measured two-dimensionally, the nodule of the right lower lobe (A, arrow) is 8.2 mm, and the addition of the volumetric measurement (B) is 283.7 mm³ (arrow), all of which are category 4A. Lung-RADS = Lung CT Screening Reporting & Data System

Fig. 4. A 62-year-old male with a 30-pack-year smoking history with inflammatory nodule at follow-up CT.

A. There is a 9 mm sized cavitary nodule with spiculated margin (arrow) in right upper lobe. In Lung RADS 1.1 and Lung-RADS^® 2022, it is considered as category 4X and 4A, respectively. B. After one month, on non-enhanced chest CT, the nodule size in the right upper lobe (arrow) reduced from 9 mm to 7 mm, and the nodule border changed from spiculated margin to irregular margin. C. No FDG uptake was noted on the nodule in the right upper lobe on ¹⁸F-FDG PET/CT. Video-assisted thoracic surgery was performed on the right upper lobe nodule, and the pathologic result was high grade glandular hyperplasia. FDG = fluorodeoxyglucose, Lung-RADS = Lung CT Screening Reporting & Data System

Fig. 5. A 71-year-old male with a 40-pack-year smoking history diagnosed with lung cancer within a year.

A. In low-dose chest CT, the subcarnial lymph node (arrow) had a short diameter of 6 mm; therefore, it was category 1. B. After 10 months, a follow-up chest CT with enhancement was performed for chronic cough, and the subcarinal lymph node (arrow) increased to 3 cm and was diagnosed with metastatic neuroendocrine carcinoma.

Fig. 6. A 62-year-old male with a 42-pack-year smoking history classified as category 3 in Lung RADS 1.1 and Lung-RADS^® 2022.

A. If measured two-dimensionally, there is a solid nodule with an irregular margin of 7.1 mm in right lower lobe. In Lung RADS 1.1 and Lung-RADS^® 2022, it is categorized as Lung-RADS 3. B. If measured three-dimensionally, the same solid nodule is measured at 8.7 mm. In Lung RADS 1.1 and Lung-RADS^® 2022, it is considered as category 4A. Consequently, the Lung-RADS for this nodule and false positive increased. Lung-RADS = Lung CT Screening Reporting & Data System

Fig. 7. Verification of variation in three-dimensional measurement of nodule in Lung-RADS 1.1 and Lung-RADS^® 2022 using two different softwares.

A. The left upper lobe nodule on low-dose chest CT is 5.5 mm in diameter and 90 mm³ in volume if measured using software, which is category 2. B. If the same left upper lobe nodule is measured using another software, it is 5.6 mm in diameter and 91.8 mm³ in volume, which is category 2. In monitoring the same nodule measurement using two different softwares, there is a slight difference in the diameter and volume, but the category is the same. Lung-RADS = Lung CT Screening Reporting & Data System A B

Fig. 8. A 72-year-old male with a 40-pack-year smoking history with atypical pulmonary cyst.

A. In the initial low-dose chest CT, 6 mm sized nodules and thin-walled cyst with 2 mm sized mural nodule (arrow) are present in the right upper lobe. Lung-RADS 1.1 does not provide a criterion on methods to measure the size of the cyst nodule, but the overall size of the nodule, including cyst, is 6 mm, which can be considered category 2. However, in Lung-RADS^® 2022, this atypical pulmonary cyst can be considered category 3. B. After one year, if a follow-up examination was performed with low-dose chest CT, the cystic nodule in right upper lobe increased to 12.2 mm, and the thin walled cyst changed to the thickened irregular walled cavity with inner nodules (arrow). In Lung-RADS 1.1, it is considered as category 4X. However, the growing atypical pulmonary cyst can be considered as category 4B in Lung-RADS^® 2022. Lung-RADS = Lung CT Screening Reporting & Data System

Fig. 9. A 62-year-old male with a 30-pack-year smoking history and a subpleural nodule.

A. In the initial low-dose chest CT, there is a 6 mm round nodule (arrow) in the right lower lobe. In Lung-RADS 1.1, it is considered as category 3. However, the solid nodule can be considered as category 2 in Lung-RADS^® 2022. B. After two years, the size of the right lower lobe nodule (arrow) reduced to 5 mm in follow-up low-dose chest CT, and its shape changed from round to circular. Lung-RADS = Lung CT Screening Reporting & Data System