Update app.py

app.py

@@ -410,8 +410,8 @@ class DicomAnalyzer:
             phantom_sizes = ['(7mm)', '(6.5mm)', '(6mm)', '(5.5mm)', '(5mm)', 
                            '(4.5mm)', '(4mm)', '(3.5mm)', '(3mm)', '(2.5mm)']
             for i, size in enumerate(phantom_sizes):
-                ws.cell(row=row_pairs[i][0]-1, column=1, value=size)
-                cell.font = red_font
+                header_cell = ws.cell(row=row_pairs[i][0]-1, column=1, value=size)
+                header_cell.font = red_font
 
             # Process results
             result_idx = 0