Table 1. Calculated signal-to-noise ratio data from examined filters according to artificial Gaussian noise (standard deviation (SD)) in synthetic images.

Image/filter	Gaussian noise
	SD = 10	SD = 20	SD = 30	SD = 40
Unprocessed	2.22	1.36	1.09	0.94
Gauss 3 × 3/0.4	6.88	4.16	3.3	2.83
Gauss 5 × 5/0.4	11.31	6.87	5.38	4.62
Mean 3 × 3	6.67	4.03	2.91	2.73
Mean 5 × 5	11.13	6.76	5.33	4.56
Median 3 × 3	5.84	2.81	1.9	1.46
Median 5 × 5	10.18	4.7	3.01	2.19