FUDAN UNIVERSITY SHANGHAI CANCER CENTER Nature contrast in film Four principal densities are recognized on plain X-ray films 4 1.air/gas black R 2. fat dark grey 3, soft tissue/water light gray 4. bone white ⑨复旦大学上海医学院肿痼学糸FUDAN UNIVERSITY SHANGHAI CANCER CENTER 复旦大学上海医学院肿瘤学系 Nature contrast in film Four principal densities are recognized on plain X-ray films 1.air/gas black 2.fat dark grey 3.soft tissue/water light gray 4.bone white