유사 흉막 삼출액의 CT Density측정에 관한 연구

초록

Computed tomography(CT) can differentiate much smaller differences in density than conventional techniques. This capability prompted early attempts to use quantitative CT data to separate disease process, and it has a potential use in assessing density of intrathoracic fluids. In patients with pleural effusion, thoracentesis may not always be desirable because of risk factors, thus noninvasive method for examining pleural fluid and its specific gravity would be useful. Interest remains in direct use of CT No as source of diagnostic data, but CT No are greatly inflenced by various factors, relates to machine itself and relates to the object. So, Authors observed relationship between specific gravity of pleural fluid analogs and CT No, other factors influencing CT No and also applicability of CT No as direct diagnostic data in clinical setting. The results are as follows: 1. A good correlation was found between specific gravity of pleural fluid and CT No in vitro, but not in vivo. 2. CT No of smaller diameter of specimens were always higher than CT No of larger diameter of specimens in experimental study and decreased accuracy of the CT No 3. CT No of lesions in 27cm field of view was higher than 53cm field of view about 9.7 HU in experimental study, and with 27cm field of view, the CT density values overestimate the physical density values. 4. For a decrease of slice thickness of 8mm to 2mm, a increase CT No was noted in experimental study and clinical applications. 5. Increasing CT No of surrounding medium in chest phantom resulted in a decrease in CT No of lesions. 6. The value which was 11.6 HU added to CT No of exudate in vivo study was same as CT No in vitro study, and a good correlation was found between specific gravity and corrected value. It is unlikely that the specific gravity of pleural fluid is differentiated by CT densitometry. But in clinical setting with current scanner, CT can differentiate exudate from transudate in pleural fluid.