Sdt Load Options

 

  
Figure 10: Sdt format options popup window

For loading an image set with sdt format, the options are shown in Figure 10. See Appendix A for a discussion on the sdt format. The following is a list of steps for specifying options for the loading of an image with sdt format:

1. The first step in loading a sdt image is to specify the spatial and temporal parameters. When the popup window comes up, the First Plane (10-1) and Last Plane (10-2) fields are set to the indices that yield the full spatial extent of the image volume. Thus the first plane is set to 0 and the last plane is set to the number of planes minus one. For stim files the temporal range is specified by the First Time (10-3) and Last Time (10-4) fields, and by default are set to yield the full temporal range. A subset of the data can be specified by modifying the planar and temporal range. As anat files are only 3D spatially, the last time field is not displayed, but the first time can be used to select a particular volume out of a 4D data set.
2. If it is desired to reduce high frequency 2D spatial noise, a LPF (Low Passs Filter) can be used by selecting a LPF choice (10-5). Then as each planar image is loaded, its inverse FFT is calculate. Then the resultant image is multiplied by the specified 2D filter, followed by a forward FFT. Examples of the LPF profiles are shown in Figure 9.

   The gaussian filter has a FWHM (Full Width - Half Maximum) equal to twice the radius specified in Radius field (10-6). The values, g(n), of the gaussian filter are given for one dimension in Equation 1 for a radius = r and an image width of N pixels.

   The values, s(n), of the sinusoidal filter are given for one dimension in Equation 2 for a radius = r (10-6) and an image width of N pixels.

   The values, h(n), of the hamming filter are given for one dimension in Equation 3 for a radius = r (10-6) and an image width of N pixels.

3. When loading stim image files, the Append (10-7) option is available. When this option is selected, the image volume(s) specified for loading are appended across time to the currently loaded stimulation set of image volumes. Note that the new image volumes to be appended must have the same spatial dimensions as those currently loaded.
4. Lastly, when all the options are set, press the Do It button (10-8) to invoke the loading process. See Section 7 for the procedure to display the images.