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Figure 4b. CT scans from a 5-year longitudinal study in a 31-year-old persistent current smoker (15.0 pack-years at T0; 21.0 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. Arrows points to subpleural emphysematous area. (b) Transverse thin-section CT scan obtained at the same level as a at T1 shows replacement of the micronodular pattern (arrowheads) observed in a in the peripheral part of the anterior segment by small areas of hypoattenuation indicative of emphysematous changes, also observed in the central part of the lung. No change in the subpleural emphysematous area (arrow) is seen.