Micro-CT is used with pinecones for tree breeding studies to confirm when pollination and fertilization occurred and to assess seed viability. We chose to demonstrate the option of continuous rotation imaging for extremely quick scans, from about one hour to a matter of minutes. This approach can be used for qualitative viewing for faster and lower-cost applications while somewhat lengthier quantitative analysis can be done when more data is required.
Continuous Rotation X-Ray Microscopy Imaging
With the fast readout times provided by its high-speed flat panel CMOS detector, the SkyScan 1273 desktop micro-CT allows for rapid scans at reduced resolution using a continuous rotation during the imaging process rather than a step and shoot mode. Traditional micro-CT image collection follows the step and shoot method where the sample rotates a fraction of a degree (specified by the user), pauses in place, projection images are acquired, and then the process repeats until the scan is complete. Continuous rotation imaging, present only on our SkyScan 1273 instrument, instead rotates the sample constantly while acquiring all projection image data necessary to reconstruct the sample.
With no rotational pauses during image acquisition, continuous rotation imaging can provide a drastic time savings in imaging samples. Naturally, if we increase acquisition speed significantly there must also be a tradeoff. In this case, the tradeoff arises in both pixel resolution and dataset noise. For most samples, pixel resolution will be halved but time savings can exceed 90%. Continuous rotation imaging is most suitable for lower density samples where a general overview dataset is desired in place of a larger, more resolved dataset. Continuous rotation imaging works well to screen samples on a broad scale to look for defects or features of note prior to imaging a second time under higher resolution conditions.
For the large pinecone (~X inches in height) inspected in this study, continuous rotation imaging at 100um voxel size required 3 minutes of acquisition time to compile the dataset. Meanwhile, a step and shoot acquisition at a similar resolution required about 45 minutes. Thus, the continuous rotation imaging represents a 93% reduction in scan time. In inspecting the results from both imaging modes, we see minimal differences between the datasets present in DataViewer (Figure 2). Both the continuous rotation data and the step and shoot data have similar levels of artifacts and noise while features are sharp in both cases.
Moving to a volumetric rendering in CTVox, we again see that both datasets are nearly indistinguishable from one another (Figure 3).
Continuous rotation imaging using the SkyScan 1273 provides users with the flexibility to greatly increase sample throughput for overview imaging and screening with only minimal effect on resolution. In comparing the continuous rotation imaging mode with the standard step and shoot imaging mode under the same imaging conditions, the samples are nearly indistinguishable except for the total acquisition time required. We hope you found this Image of the Month informative and encourage you to subscribe to our newsletter and social media channels in preparation for the continuation of our image of the month series next month.
These scans were completed on our desktop SkyScan 1273 system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon 2.1 and visualization of 2D and 3D results were completed using DataViewer and CTVox.
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