Fig. 4

Detection of small lesions using different correction methods. Region 1: a spherical region of radius 5 with CBF of 75 mL/100 g/min, region 2: a 3 × 3 × 3 cubic region with CBF of 45 mL/100 g/min, region 3: a 2 × 2 × 2 cubic region with CBF of 75 mL/100 g/min. From left to right: no correction, LR, sEM, and sEM-LR methods. From top to bottom: different levels of Gaussian noise, with a standard deviation of 5, 10 and 15, respectively