Region of Interest (ROI) Analysis Using MATLAB and EMMA
editThere are existing packages at the MNI for performing ROI analysis, the foremost of which is roi. However, none of these was designed to work explicitly with MATLAB. Since much analysis is currently being done within the MATLAB environment, a ROI package was developed for MATLAB. The package consists of the following MATLAB functions:
- drawboxroi - Draw a simple box ROI on a figure
- drawpolyroi - Draw a general polygonal ROI on a figure
- drawroi - Draws a given ROI on a given figure
- getroi - Get the normalized vertices of a ROI
- makeroimask - Create a mask from a set of ROIs
- transferroi - Copies ROIs from one figure to another
Use of this package is reasonably straight forward. The following short example demonstrates the use of the ROI package for creating a mask to be applied to PET images:
>> h=openimage('kunl1_avg.mnc')
>> PET=getimages(h,8);
>> closeimage(h);
>> h=openimage('kunl1_mrirsl_21.mnc');
>> MRI=getimages(h,8);
>> viewimage(MRI);
>> drawpolyroi;
Click on the vertices of the ROI...
Click outside the figure to quit
>> mask=makeroimask(1,2,[128 128]);
>> figure
>> viewimage(mask.*PET);
In this example, we load a PET image and an MRI image (which have been registered to each other and resampled so that slice 8 of one corresponds to slice 8 of the other). The MRI slice is displayed, and the drawpolyroi function is called to create an ROI. Once the ROI has been drawn, a 128x128 mask is created, and this is applied to the PET image.
This same technique could be applied for the creation of any number of ROIs on a single slice, and then all of the ROIs could be included in a single mask.