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GE Phoenix Vtome x S

GE Phoenix Vtomexs

Introduction 
 
Our Computed Tomography (CT) Laboratory has been developed with the intent of doing non-destructive, 3D imaging and analyses of both rare and delicate samples of varying size and physical properties. Another aim has been to digitally collect samples for metrology and collaborative purposes due to the ease of file sharing and digital processing. For examples of the type of work we use the CT scanner and its resources for, we are currently developing a YouTube channel to display some of our scans and to give users an example of attainable results. A link will be provided here and on the MIF home page once the channel is up and running
 
Usage and User Responsibilities
 
For use of our CT scanner, please first refer to the Laboratory User Policy on our website, before contacting MIF staff for its use. For reservation of the CT scanner, please refer to our Instrumentation Schedule. In addition, please refer to “MIF GE VTOMEX CT Scanner” on the calendar when looking for open days.
 
          Scan Data
The MIF currently houses a limited storage space that only allows the lab to hold on to scan data for a 30-day period. Within this 30-day period users are required to retrieve their data and delete it from MIF servers. In many instances, this can be done on the same day that the user scans specimens. However, in other instances the user is required to schedule a “data reconstruction and retrieval” day in which they process and transfer data on to their or their departments storage device(s). For further details, contact MIF Staff
 
Technical Overview and Description
 
GE phoenix v|tome|x s240 System Overview
 
The 2010 GE phoenix v|tome|x s240 system is composed of two x-ray tubes, a high-resolution amorphous silicon detector and GE phoenix datos acquisition and reconstruction software. Scan data is reconstructed by the implementation of 4 PC’s which are interconnected to function as a computational cluster. The reconstructed data is then compiled on a HP z800 workstation. For post-processing and analysis of reconstructed-scan data, the lab currently utilizes Volume Graphics VG Studio Max 2.1 on the aforementioned HP z800 as well as a Dell Precision T7500. Both of these workstations have been optimized to process large files through computationally rigorous algorithms such as high-resolution CT data requires.
 
GE phoenix v|tome|x s240 System Technical Description
 
For technical details regarding our CT system, we have broken the system down in to sub-systems below with details pertaining to both x-ray tubes as well as the detector. The two x-ray tubes are used interchangeably to meet sample based and research requirements. The same detector is used for both x-ray tubes.  These sub-systems are all GE manufactured products and can be viewed on their web-page.
 
Nano-Focus High Resolution X-Ray Tube: The nano-focus, 180kv x-ray tube produces a transmission type signal with interchangeable molybdenum and tungsten targets. This tube is employed when scanning small or low x-ray attenuating samples. It is able to produce a focal spot of 200nm through the use of specialized modi. A tungsten target is used for most samples requiring this tube’s resolution potential, however for those of low-attenuating contrast and the need for sub-10 micrometer resolution, the molybdenum target is employed for improved scan quality. With ideal settings, the resultant CT data is capable under optimal sample conditions of yielding sub-micrometer voxel resolution.
 
Micro-Focus High Energy X-Ray Tube: The micro-focus, 240kv x-ray tube emits a reflected signal off of a tungsten target. This tube is employed when CT-ing large or high x-ray attenuating samples. Due to the high yield of x-rays generated by a reflective signal rather than a transmitted signal, the reflected signal’s high-energetic nature is able to supply the radiation needed to penetrate high attenuating material. In addition, the high yield of x-rays produces a strong signal transmitted through the sample for cleaner data collection. Commonly, this x-ray tube is used when a voxel size greater than 15 micrometers is sufficient for a sample or when metal deposits, high attenuating material or other artifact causing, absorptive material is commonplace in the sample.
 
DXR250RT Real Time Detector: This amorphous silicone flat-panel detector is composed of a 1024x1024 pixel array at 200 micrometer pixel pitch with 14-bit capable detection. The active area of detection is 8 in. x 8 in. (20.62 cm. x 20.62 cm.) with the capability of doubling its wide dimension through the enabling of the tiling function. Exposure rates (termed “detector timing” in our set-up) can be adjusted to suit saturation needs at multiple intervals ranging from 33ms to 5s. For large specimens, a multiple scan project can be enabled to cover specimens unable to fit entirely within the 8 in. (20.62 cm.) height of the detector face.  The 14-bit detection allows for x-ray positive images written in a 16-bit .tiff format, which corresponds to over 65,000 gray-levels for an enhanced dynamic range of x-ray images.
 

For more information or clarification of the details provided please contact us at either jthostenson@amnh.org or mhill@amnh.org.