Table 1. When the angle between the drill and vertical axis is less than or equal to 10°.

Drill radius (mm)	2	2.5	3	3.5	4
Numbers of checked cylinders	25	16	9	9	4
Whether found cylinder that drilling is available	✓	✓	✓	✓	✓
Average Hounsfield value	718.9	784.4	780.4	552.1	553.9
Time complexity	39.7	22.6	11.2	10.4	9.3