MRIcro can view medical images such as magnetic resonance imaging (MRI) and computerized tomography (CT/CAT) scans. It can show 2D slices, 3D slices as well as graphs for 4D data (for example, changes over time observed on functional MRI scans). It loads images in NIfTI, NRRD, Philips PAR, Bio-Rad Pic, ITK MetaImage, AFNI BRIK, Freesurfer MGH, and DICOM formats (for images saved as 2D slices, you may want to first convert them to 3D volumes using a free tool like dcm2nii). The web site includes sample images including photographs of a head from the visible human project. These samples provide an intuitive way to learn about brain anatomy.

What’s New

Version 1.6

Minor bug fixes and interface changes. This version can view any bitmap image natively supported by the OS, which is handy for viewing 3D TIFF images (a popular format for 3D Microscopy).

Ratings and Reviews

2.9 out of 5
10 Ratings

10 Ratings

Critical user ,

Inconsistent File Loading and Other Problems

I can view MRI and CT files in the DICOM format using Graphicconverter (a common image program) but I wanted the power of a medical application to switch through the images and organize them instead of seeing them one file at a time. MRIcro seems to be part of an open source effort for scientific use and my impression is that it still needs a lot of development. I tired opening a common DICOM file from the File>Open menu and it showed the files greyed-out and not all of the files so I couldn’t open them. Next I selected a DICOM file in the finder and used drag-and-drop onto the MRIcro icon and it opened a dialog box telling me to convert the file using “dcm2nii” which is also mentioned in the product overview on this page. It turns out that dcm2nii is part of the full MRIcro package and isn’t on the App Store so I had to download the software again, but from their site. I opened dcm2nii and it is a unix utility with a typical Unix interface. For my limited use it’s not worth learning to use this utility and I’m not sure if I will produce accurate results (some website talk about inverted images and other problems with versions of this utility.)
Finally, I selected a DICOM image in the finder and right-clicked and selected “Open With…” and selected MRIcro and it worked. I viewed a couple of images and I wasn’t sure if the white dots scattered in the background were real parts of the image or an artifact from MRIcro.

In summary, this may be a useful tool if you put in some effort but for use as a casual image viewer I will look elsewhere.

jkenney ,

It worked for what I needed!

First I should say I am not in the medicial profession, I’m just nosy about my own MRI that I had done. I was struggling to find an app I trusted to download (things not available in the app store scare me) and I knew I had DICOM, but I didn’t really know which file was the one for this app. I first tried to open the DICOM file among others to no success, however I looked on their website and they had a beta version available to convert DICOM to something that would work. So I downloaded that but still couldn’t open/convert the dicom file. However I had a folder called DICOM and within that I tried to convert the subfolders and it worked. It wasn’t super clear, but was able to figure out that in each image if you select the view that is actually in focus (axial,sag, or coronal) and then you can scroll through the slices. Sometimes it worked with the arrows, but sometimes I had to scroll with my mouse. Either way, I was able to see my views fairly clearly. I spent WAY too much time on this little weekend project and would still be working if I hadn’t found this software - so I’m glad for that. Imagine how easy it will be if you actually know what you are doing!!

BassaBoy ,

Did not work

The program started up but, could not load any file. Try all the file that was on my MRI disk and all failed to open. These files are meant to be open on a PC runing windows not mac.


Christopher Rorden
387.7 KB

OS X 10.7 or later, 64-bit processor



Age Rating


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.