## 3 Methodology  
### LIDC dataset  
The publicly available LIDC database (downloadable through the National Cancer Institute's Imaging Archive web site-[[http://ncia.nci.nih.gov/](http://ncia.nci.nih.gov/)]([http://ncia.nci.nih.gov/](http://ncia.nci.nih.gov/))) provides the image data, the radiologists' nodule outlines, and the radiologists' subjective ratings of nodule characteristics for this study. The LIDC database currently contains complete thoracic CT scans for 208 patients acquired over different periods of time and with various scanner models resulting in a wide range of values of the imaging acquisition parameters. For example, slice thickness ranges between 0.6 mm and 4.0 mm, reconstruction diameter ranges between 260 mm and 438 mm, exposure ranges between 3 ms and 6,329 ms, and the reconstruction kernel has one of the following values: B, B30f, B30s, B31f, B31s, B45f, BONE, C, D, FC01, or STANDARD. \begin{table}
\begin{tabular}{c c} \hline
**k-value (\%)** & **Strength of Agreement beyond Chance** \\ \hline \(<\)0 & Poor \\
0–0.2 & Slight \\
0.21–0.4 & Fair \\
0.41–0.6 & Moderate \\
0.61–0.8 & Substantial \\
0.81–1 & Almost perfect \\ \hline \end{tabular}
\end{table} 
Table 1: Kappa statistics interpretation scale. \begin{table}
\begin{tabular}{l l l} \hline
**Characteristic** & **Notes and References** & **Possible Scores** \\ \hline \hline \multicolumn{2}{l}{Calcification} & \multicolumn{1}{l}{Pattern of calcification present in the nodule} & 1. Popcorn \\  & & 2. Laminated \\  & & 3. Solid \\  & & 4. Non-central \\  & & 5. Central \\  & & 6. Absent \\ \hline \hline \multicolumn{2}{l}{Internal} & \multicolumn{1}{l}{Expected internal composition of the nodule} & 1. Soft Tissue \\ structure & & 2. Fluid \\  & & 3. Fat \\  & & 4. Air \\ \hline \multicolumn{2}{l}{Lobulation} & \multicolumn{1}{l}{Whether a lobular shape is apparent from the margin or not} & 1. Marked \\  & & 2.. \\  & & 3.. \\  & & 4.. \\  & & 5. None \\ \hline \multicolumn{2}{l}{Malignancy} & \multicolumn{1}{l}{Likelihood of malignancy of the nodule - Malignancy is associated with large nodule size} & 1. Highly Unlikely \\  & & 2.Moderately Unlikely \\  & & 3. Indeterminate \\  & & Most malignant nodules are non-calcified and have spiculated margins. & 4.Moderately \\  & & 3 Suspicious \\ \hline \multicolumn{2}{l}{Margin} & \multicolumn{1}{l}{How well defined the margins of the nodule are} & 1. Poorly Defined \\  & & 2.. \\  & & 3.. \\  & & 4.. \\  & & 5. Sharp \\ \hline \multicolumn{2}{l}{Sphericity} & \multicolumn{1}{l}{Dimensional shape of nodule in terms of its roundness} & 1. Linear \\  & & 2.. \\  & & 3. Ovoid \\  & & 4.. \\  & & 5. Round \\ \hline \multicolumn{2}{l}{Spiculation} & \multicolumn{1}{l}{Degree to which the nodule exhibits spicules, spike-like structures, along its border - Spiculated margin is an indication of malignancy} & 1. Marked \\  & & 2.. \\  & & margin is an indication of malignancy & 3.. \\  & & 4.. \\  & & 5. None \\ \hline \multicolumn{2}{l}{Subtlety} & \multicolumn{1}{l}{Difficulty in detection - Subtlety refers to the contrast between the lung nodule and its surrounding} & 1. Extremely Subtle \\  & & 2. Moderately Subtle \\  & & 3. Fairly Subtle \\  & & 4.Moderately Obvious \\  & & 5. Obvious \\ \hline \multicolumn{2}{l}{Texture} & \multicolumn{1}{l}{Internal density of the nodule - Texture plays an important role when attempting to segment a nodule, since part-solid and non-solid texture can increase the difficulty of defining the nodule boundary} & 1. Non-Solid \\  & & 2.. \\  & & 3. Part Solid/(Mixed) \\  & & 4.. \\  & & 5. Solid \\ \hline \end{tabular}
\end{table} 
Table 2: LIDC nodule characteristics with corresponding rating scale. The XML files accompanying the LIDC DICOM images contain the spatial locations of three types of lesions (nodules \(<3\) mm in maximum diameter, but only if not clearly benign; nodules \(>3\) mm but \(<\)30 mm regardless of presumed histology; and non-nodules \(>3\) mm) as marked by a panel of up to 4 LIDC radiologists.