Figure 3b. CT scans from a 7-year longitudinal study in a 33-year-old persistent current smoker (7.5 pack-years at T0; 16.0 pack-years at T1). (a) Transverse thin-section CT scan targeted to the right lung at T0 shows faint parenchymal micronodules (arrowheads) in the upper lung zone. (b) Transverse thin-section CT scan obtained at the same level as in a at T1 shows numerous nodular areas of increased attenuation (arrowheads), some depicted with a patent centrilobular distribution and more prominent septal lines.