Independent variable

Assignment method

Pathological type

0 = non-leukemia; 1 = leukemia

Complication

0 = NO; 1 = YES

Number of puncturing times

0 = 1 times; 1 ≥ 1 times

Positioning method

0 = ECG positioning; 1 = chest radiography positioning

Maintenance frequency

0 ≥ 1 (times/week); 1 = 0 (times/week)

Maintenance place

0 = in-hospital maintenance; 1 = out-of-hospital maintenance