Horos and OsiriX are the top two medical image viewers for Apple computers. However, the two products have different functionalities and work very differently in many respects. If you're looking for an alternative to your medical image viewing software, or are just interested in what's out there, here's what you need to know about the differences between the two.
Open-Source vs. Closed-Source
Horos is totally free and open-source software (FOSS), which means that its source code is available to anyone who wants to peruse it. This is especially valuable and relevant for people who might want to access or contribute to the source code, such as plugin developers, scientists and academic researchers.
What's more, the Horos software is issued under the GNU Lesser General Public License (GPL), which enables users to add their own plugins to Horos and to establish legal protections for their code.
By contrast, OsiriX started as an open-source project, but is no longer truly open-source. Instead, the software is now available as a freeware application, known as OsiriX Lite, and as a paid version with full functionality known as OsiriX MD, which costs $699.
In March 2015, OsiriX version 6.5 was released under a new closed-source license, which upset many people in the open-source community. Many of these OsiriX users have since gone on to use Horos and participate in the Horos Project.
32-bit vs. 64-bit
If you expect to deal with a large number of images while using your medical imaging software, you'll probably need to worry about the difference between 32-bit and 64-bit software. Essentially, 64-bit computers are able to store and fetch much more data simultaneously than 32-bit computers, which is especially important when working with large files like medical images.
Horos comes ready for use on 64-bit computers, which gives you a lot more computing power and makes the product more robust. On the other hand, OsiriX Lite only comes in a 32-bit version. If you want 64-bit functionality with OsiriX, you'll have to pay for it. The 64-bit version of the software can be up to 4.4 times faster than the 32-bit version.
OsiriX Lite and Horos are not FDA-approved or CE IIa Labeled. However, the paid version of OsiriX is FDA-approved. This likely only comes into play in cases where FDA approval for diagnosis is necessary.
Unlike OsiriX Lite, Horos is able to edit DICOM imaging metadata for a particular study. This can be very helpful if you need to make changes or correct the name of a patient or an institution. Again, if you want this functionality in OsiriX, you'll need to purchase OsiriX MD.
Another Horos feature is the ability to connect Horos to as many medical imaging devices and systems as you'd like. OsiriX Lite limits you to only a few connections at once.
Finally, OsiriX Lite contains a lot of image overlays or watermarks that read "not for medical usage," which can be annoying or even prohibitive when you want to share an imaging study with other people. This negatively impacts the application's clinical use.
What Do You Need?
Features such as built-in 64-bit support, metadata editing and multiple connections are invaluable for people who prefer Horos over OsiriX. If you need access to some of these features and want to support an open-source project, then Horos will be the smarter and more cost-efficient choice.
However, if you need to use a medical image viewer in an environment with a strict level of compliance requiring FDA-certification and you're able to bear the cost, then OsiriX MD or an approved cloud-based medical image viewer, such as the one offered by Purview, is more likely the right choice for you.