The computed tomography (CT) number within the region of interest (ROI) was used as a parameter to assess lung density in patients with congestive heart failure. Thirty-eight patients with valvular heart disease (VHD) and 34 patients with ischemic heart disease (IHD) were studied. Based on the New York Heart Association (NYHA) classification, 24 VHD patients were in class I or II (VHD I-II) and the other 14 were in NYHA class III or IV (VHD III-IV). Eighteen patients with IHD were in NYHA class I or II (IHD I-II) and 16 were in class III or IV (IHD III-IV). The CT number was measured bilaterally at the upper, middle and lower levels of the chest and compared with the corresponding values in 21 normal subjects (Group N). In a preliminary study on Group N, the CT numbers were insensitive to the size of the ROI, but were closely related to its location.
In clinical applications, the mean values of the CT numbers in all six lung fields increased in the order of IHD I-II, to VHD I-II, IHD III-IV and VHD III-IV. Except for patients in IHD I-II, they were significantly larger than in Group N. The relationship between the CT number and the systolic and mean pulmonary arterial pressures and the pulmonary capillary wedge pressure were evaluated in 36 patients. Significant correlations were obtained in all six lung fields (r=0.65-0.78, p<0.001). The results suggest that measurement of lung density by CT is useful for the quantitative evaluation of the severity of disease in patients with congestive heart failure.