The THRESHOLD MASKING command allows masked and un-masked elements within the ROI to be defined automatically based on a user set logical criterion. The user selects one of two logical tests: i. greater than, ii. less than, and a threshold value. All data elements in the ROI which obey the test are set to be masked, and all those which fail are set to un-masked.
e.g. If we want all elements with a data value below 0.5 to be set to be masked, then the following program dialogue would be produced:
Fit sub-menu: ENTER COMMAND [INPUT PARAMETERS]:threshold INFO: This option allows masked-off elements with the ROI to be defined automatically depending on the data values. The user can set a threshold operation (<GREATER THAN> or <LESS THAN>) and a threshold level. All data values which CONFORM WITH the defined test will be set to be masked-off. All others will be set to be un-masked. LESS THAN COMPARISON [YES]: DECISION THRESHOLD DATA VALUE [1.0000]:0.5