Comparison of submillimetreswith millimetresslice thickness of lung 16 slice mdct in metastatic pulmonary nodule diagnosis

Background and Objective: The most common radiographic abnormalities related to lung metastasis are pulmonary nodules .The CT scan in most circumstances are the best modality for lung metastasis evaluation..In this study we aimed to investigate the diagnostic accuracy of lung CT scan with slice thickness less than 1 mm (0.625 mm) compared with the usual slice thickness for detection of tiny metastatic pulmonary nodules. Materials and Methods: This study was a diagnostic study performed on 110 patients with malignant diagnosis who were referred to the Radiology Department of Hospital. At first, following performance of routine CT scan with millimetres slice thickness (2mm ) from the patients’ lung, extra images were taken by sub millimetres slice thickness to assess either presence or not of nodules by two radiologists simultaneously. Data were analysed using Chi2, Fisher Extract, one way ANOVA, SPSS version 18 and Independent t statistical tests. In all cases, p < 0.05 was considered statistically significant. Results: Radiologists reported nodules in 40 (36.36%) of cases using millimetres slice thickness of the images and in the submillimetreslice thickness images, nodules were found in 58 (52.70%) cases (P=0.001). There were significant differences between images with different thickness in visibility, resolution and the number of nodules observation. Conclusion: With reducing thickness, pulmonary nodule detection is increased and the use of submillimetric slice thickness (0.625mm) in comparing to conventional millimetres slice thickness has a significant difference in detection, and the number of pulmonary nodules. Environmental factor as an independent factor non-related to the modality and the observer can be also effective.