Fig. 2

Axial enhanced CT at baseline examination showing ROI delineation and deep ulcer measurement. (A-C) CT images in a 42-year-old woman with esophageal cancer. A CT image showed an esophageal mass with a deep ulcer in the right wall. B The same CT image showed the measurement of the depth of deep ulcer (red line) at 10 mm, residual esophageal wall (green line) at 7 mm and the thickness of adjacent wall to ulcer (yellow line) at 17 mm in the ulcer layer. The ratio of ulcer depth to adjacent tumor thickness of 58.8% and tumor thickness of 17 mm could predict fistula formation after treatment. C The esophageal fistula occurred in the region of the deep ulcer after three chemotherapy cycles and radiotherapy. D-F CT images in a 50-year-old man with esophageal cancer. D CT image showed an esophageal mass with a thickness of 15 mm. E The highest (red circle; 119 HU) and lowest enhancement (blue circle; 20 HU) zones, the ratio of minimum to maximum enhanced CT value of 16.8% and a tumor thickness of 15 mm could predict fistula formation after treatment. F Esophageal fistula occurred in the region of the lowest zone after three chemotherapy cycles and radiotherapy