Table 1.

Description of published research clusters.

Cluster	Number of Papers	Central Paper/s	Imaging Mode	Connecting Theme	Data Source
1	36	[40,41]	CXR	Connected by the use of JSRT [40] and PLCO [41] datasets as a lung nodule dataset, along with a deep learning approach for image analysis and nodule classification.	JSRT PLCO
2	29	[42,43]	CT/CXR	Connected using local feature analysis, linear filtering, clustering techniques, and other non-deep learning techniques.	LIDC
3	24	[44]	CXR	Artificial intelligence and machine learning methods, including ANN, SVM, and KNN. Typically used the JSRT database.	JSRT
4	23	[45]	CXR	Rib/bone suppression and image enhancement techniques, including wavelet transform methods.	JSRT
5	17	[46,47]	CT	Use of deep learning and shape analysis to diagnose lung cancer from chest CT images.	Luna16
6	12	[48,49]	CXR	KNN classification of nodules as blobs. Used stratification of JSRT to train/calibrate schemes to reduce false positive detection by algorithms.	JSRT
7	12	[50]	CXR	A set of older papers using various techniques to detect nodules and reduce false-positive detections	Private Data JSRT