Looks like version 1.3 was just released (July 30th)
From the OsiriX site:

“OsiriX is an image processing software dedicated to DICOM images produced by medical equipment (MRI, CT, PET, PET-CT, …) and confocal microscopy (LSM and BioRAD-PIC format). It can also read many other file formats: TIFF (8,16, 32 bits), JPEG, PDF, AVI, MPEG and Quicktime. It is fully compliant with the DICOM standard for image comunication and image file formats. OsiriX is able to receive images transferred by DICOM communication protocol from any PACS or medical imaging modality (STORE SCP – Service Class Provider, STORE SCU – Service Class User, and Query/Retrieve) .

OsiriX has been specifically designed for navigation and visualization of multimodality and multidimensional images: 2D Viewer, 3D Viewer, 4D Viewer (3D series with temporal dimension, for example: Cardiac-CT) and 5D Viewer (3D series with temporal and functional dimensions, for example: Cardiac-PET-CT). The 3D Viewer offers all modern rendering modes: Multiplanar reconstruction (MPR), Surface Rendering, Volume Rendering and Maximum Intensity Projection (MIP). All these modes support 4D data and are able to produce image fusion between two different series (for example: PET-CT).

Osirix is at the same time a DICOM PACS workstation for medical imaging and an image processing software for medical research (radiology and nuclear imaging), functional imaging, 3D imaging, confocal microscopy and molecular imaging.

Osirix supports a complete plug-ins architecture that allows you to expand the capabilities of OsiriX for your personal needs! This plug-in architecture gives you access to the powerfull Cocoa framework with an easy object-oriented and dynamic language: Objective-C.”

I am not endorsing this product, nor affliated with it in anyway.