Table 2. Detailed characteristic descriptions.

Characteristics	Malignancy	Margin	Texture	Calcification
Description	Likelihood of malignancy	If the nodule’s margin is clear	Internal texture of the nodule	Appearance of the calcification
Rating	1. Highly unlikely	1. Fuzzy margin	1. Non-solid	1. Popcorn
	2. Moderately unlikely	2. –	2. –	2. Laminated
	3. Indeterminate	3. –	3. Part solid	3. Solid
	4. Moderately suspicious	4. Clear margin	4. –	4. Non-central
	5. Highly suspicious	5. Sharp margin	5. Solid	5. Central
				6. Absent

We choose 4 nodule characteristics for the classification tasks. There were malignancy, margin, texture, and calcification. Scores for these 4 characteristics were binarized by their score meaning. The threshold was set as 4 for malignancy, margin, and texture characteristics. Label 0 represents the benign, fuzzy margin, and non-solid/partially solid internal density. Calcification was annotated by a rating of 1–6, with 6 indicating the “no calcification” pattern (label 1); all other ratings exhibited calcification (label 0).