Step-and-shoot respiratory or cardiac gated images are readily available from many Cone beam geometry microCT scanners on the market today. While admittedly the simplest method to acquire multiphase image data, step-and-shoot scan methods can spend upwards of 50% of the scan time simply accelerating and decelerating gantry equipment. A free-running acquisition mode, on the other hand, accelerates the gantry only at the beginning and end of the scan, so less time is wasted. One downside of this free-running mode, however, is that acquired raw image data needs to be sorted according to phase prior to image reconstruction, and there's little or no guarantee that images will be acquired at precisely the correct phase at all. Based on recently published methods, we've been experimenting with a post-scan retrospective gating method implemented on the GE Locus Ultra preclinical scanner, and the image above demonstrates an example result: 10 phases were reconstructed automatically using our GPU reconstruction engine, running on our custom workstation. The total scan acquisition time was 50 seconds, during which time the CT scanner made 10 full rotations. The total reconstruction time was 86 seconds. While our initial goal is to produce a turn-key third-party solution for the Ultra scanner, there's no reason why this can't be extended to other hardware platforms - we'll be investigating other scanners, which don't currently have such gating options, in the upcoming months.
Today we turn our attention to the GE Locus Ultra platform in our continuing set of posts on GPU reconstruction: Integrating a faster GPU reconstruction engine into the GE Locus Ultra requires more careful consideration than some other CT scanners because of the system's complexity and the need for end-to-end integration. Without this, the scanner cannot maintain it's incredible scan workflow. Keeping this in mind, we've sought out a solution that improves not only the raw reconstruction speed, but the data access rate to the operator console too. We've blended the original 32-bit-only console software with a 64-bit host computer that runs GPU reconstructions as well as a 64-bit MicroView for visualization purposes. The workflow is almost indistinguishable from the original, but is faster in almost all aspects, since data is no longer situated on a remote computer, but rather at the operator's console computer. See the video below for an introduction to the work we're doing in this area.
Another GPU reconstruction progress update day: See below two line profiles drawn through an aluminum stack phantom, imaged on a CT-120 microCT scanner. A typical "cupping" artifact, caused by beam hardening, is clearly visible in the left-hand, uncorrected image. The right image demonstrates the advantage of the basic beam hardening correction algorithm integrated into our GPU reconstruction engine.
Click on the image to see a larger version.
Our efforts to integrate our GPU reconstruction engine into different CT scanner platforms continue: see below a video showing the installation process for the Parallax Innovations GPU engine on an eXplore CT-120 console computer. The total install time is about 2 minutes, not including the download of the software. We recommend upgrading to NVidia driver version 295.49, since this driver provides the aforementioned Fermi architecture support such as on the GTX 680 and 690 GPU adapters.
And here's a video comparing CPU vs. GPU CT engines on the same machine:
As before, if you're interested in helping to test this release, don't hesitate to contact us.
We've posted a YouTube video that some of our readers might find interesting: it's a video showing a side-by-side comparison of CPU vs. GPU for CT conebeam reconstruction - the GPU engine here, is the one that Parallax Innovations has developed. We compare it against a conventional CPU-based multiprocessor CT FDK reconstruction engine found in GE Locus products.
The astute reader will realize that perhaps what is really news here is that this reconstruction engine can now be integrated into existing scanning workflow on the Locus and Locus SP platforms. Drop us a note if you are interested in beta testing this software on 32-bit or 64-bit Windows platforms.