Mosaic attenuation

Figure 2 (A) A 36-year-old female with subacute HP. HRCT scan shows bilateral poorly defined centrilobular nodules and ground-glass opacities. (B) A 43-year-old female with subacute HP. HRCT illustrates ground-glass opacities and areas of decreased attenuation (mosaic pattern). Abbreviations HP, h3fpersensitivity pneumonitis HRCT, high-resolution computed tomography.

Fig. 26.22. Chronic hypersensitivity pneumonitis in a 52-year-old man, related to mold exposure. Axial CT image shows patchy ground-glass opacities with associated centrilob-ular nodules (inset magnified view of centrilobular nodules). Also note mild subpleural reticular opacities (black arrowheads) indicating fibrosis, and subtle mosaic attenuation (white arrowhead)...

Fig. 3.1.3a,b. Thin-section computed tomography images obtained on inspiration (a) and expiration (b) in a 52-year-old farm worker. There is a suggestion of a mosaic attenuation pattern on the inspiratory image, but the appearances are far more striking on the expiratory image, with focal areas of air-trapping... 

Among the advanced HCC tumors, the typical expansive type of HCC is a sharply demarcated lesion that may be unifocal or multifocal, lypical features of expansive type HCC include tumor capsule and internal mosaic architecture. Most expansive HCC lesions have a well-developed fibrous capsule. The fibrous capsule is demonstrated by CT as a hypoattenuating rim which enhances in the delayed phase (Karahan et al. 2003 Ros et al. 1990). Internal mosaic architecture is characterized by components separated by thin fibrous septa. The different components may show various attenuation indexes on CT images, particularly if areas of well-differentiated tumor with different degrees of fatty metamorphosis are present. Internal septa show delayed enhancement, similar to that of the fibrous capsule (Fig. 13.9) (Yoshikawa et al. 1992). The infiltrative type HCC is characterized by an irregular and indistinct tumor-nontumor boundary. This type is demonstrated as a mainly uneven hypodense area with unclear mar-... 

Fig. 13.9a-d. Hepatocellular carcinoma with internal mosaic architecture, intratu-moral septa and areas of necrosis. Spiral CT images obtained in the baseline (a), arterial phase (b), portal venous (c) and delayed phase (d) images. Different components of the tumor show various degrees of attenuation. Internal fibrous septa are depicted as they enhance in the portal venous phase... 

Histologically, there is a predominantly constrictive bronchiolitis with destruction and narrowing of the bronchiolar lumen by fibrous tissue. This association suggests an immunologic mechanism that includes bronchial epithelial injury. High-resolution CT findings include areas of decreased attenuation and vascularity (mosaic perfusion), air... 

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