• K Suga, K Yasuhiko, H Iwanaga, O Tokuda, and N Matsunaga.
• Department of Radiology, St. Hill Hospital, Ube, Yamaguchi, Japan. sugar@sthill-hp.or.jp
• Acta Radiol. 2009 Jan 1; 50 (1): 34-41.

BackgroundThe functional mechanism of lung mosaic computed tomography attenuation (MCA) in pulmonary vascular disease (PVD) and obstructive airway disease (OAD) has not yet been fully clarified.PurposeTo clarify the mechanism of MCA in these diseases by assessing the relationship between regional lung function and CT attenuation change at MCA sites with the use of automated deep-inspiratory breath-hold (DIBrH) perfusion single-photon emission computed tomography (SPECT)-CT fusion images and non-breath-hold Technegas SPECT.Material And MethodsSubjects were 42 PVD patients (31 pulmonary thromboembolism, four primary/two secondary pulmonary hypertension, and five Takayasu arteritis), 12 OAD patients (five acute asthma, four obliterative bronchiolitis, and three bronchiectasis), and 12 normal controls, all of whom had MCA on DIBrH CT. The relationship between regional lung function and CT attenuation change at the lung slices with MCA was assessed using DIBrH perfusion SPECT-CT fusion images and non-breath-hold Technegas SPECT. The severity of perfusion defects with or without MCA was quantified by regions-of-interest analysis.ResultsOn DIBrH CT and perfusion SPECT, in contrast to no noticeable CT attenuation abnormality and fairly uniform perfusion in controls, 60 MCA and 274 perfusion defects in PVD patients, and 18 MCA and 61 defects in OAD patients were identified, with a total of 77 ventilation defects on Technegas SPECT in all patients. SPECT-CT correlation showed that, throughout the 78 MCA sites of all patients, lung perfusion was persistently decreased at low CT attenuation and preserved at intervening high CT attenuation, while lung ventilation was poorly correlated with CT attenuation change. The radioactivity ratios of reduced perfusion and the intervening preserved perfusion at the 78 perfusion defects with MCA were significantly lower than those at the remaining 257 defects without MCA (P<0.0001).ConclusionAlthough further validation is required, our results indicate that heterogeneous pulmonary arterial perfusion may be a dominant mechanism of MCA in PVD and OAD.

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