Table 1. Characteristics of Eight Spherical Synthetic Nodules.

Nodule Types	Diameter (mm)	Reference Volume (mm3)	Density (HU)
PSNs
Outer GGO portion	20/9*	3807.1	−650
	20/7*	4009.2
	20/5*	4123.3
	20/3*	4174.7
Inner solid portion	3	14.1	50
	5	65.5
	7	179.6
	9	381.7
Solid nodules			50
	3	14.1
	5	65.5
	7	179.6
	9	381.7

^*Whole nodule diameter/diameter of each inner solid portion. GGO = ground-glass opacity, PSN = part-solid nodule