Spatial registration without interpolation for uniform display of longitudinal images on clinical PACS systems

Spatial alignment of longitudinal images has been shown to improve the ability of radiologists to evaluate anatomical changes over time. However, although automated alignment using image registration algorithms is routinely performed in research applications, it is not as common within clinical workflows, partly due to limitations in the capabilities of many PACS viewing systems, as well as concerns regarding modification of the original image data. In this work, we propose an approach to integrate spatial registration into radiology workflows without altering the original pixel intensities of the acquired data. Baseline images and follow-up images are received from the PACS, co-registered within a standard reference space, and sent back to the PACS as a separate study. A key advantage of our approach is that the pixel data is not interpolated or modified in any way. The alignment of images is specified solely through modification of DICOM tags, allowing multiplanar reformation features of the PACS viewer to perform the spatial transformations. By leaving the imaging data intact, artifacts that may result from multiple transformations or oscillating interpolating functions are minimized. We demonstrate the use of this approach on magnetic resonance images of the brain, although the framework is applicable to any type of three-dimensional radiological imaging.