BME 598/698 Seminar
Friday January 7th 8-9am
Blusson Spinal Cord Centre Lecture Hall
Presenter: Yuntao (Anthony) An
Supervisor: Dr. Gary S.Schajer
Title: Coarse Resolution CT scanning for Sawmill Logs Sorting and Grading
The successful running of a sawmill critically depends on its ability to recover the highest possible value from the log raw material. Substantial gains can be made by determining the internal structure of logs, such as knots, sapwood boundary and rot, and then processing the logs accordingly. Computed Tomography (CT) scanning provides an opportunity to reveal these internal features in logs and shows great promise as a practical real-time method for log sorting and grading. However, all modern CT machines are priced in the million dollars range, that is far beyond the affordability of most sawmills. Furthermore, there is no medical or industrial CT scanner that can meet sawmill’s extreme scanning speed and severe working environment requirements. Thus affordable and customized industrial CT application is of great need for sawmill industry.
This research is aimed at providing a real time in-line CT scanning solution for sawmill logs sorting and grading applications. The proposed approach is to use a medical cone-beam X-ray source with a large-area x-ray detector to form a stationary scanning system. Instead of meticulously rotating the source and detector at very high speed (the most challenging part which greatly limits the scanning speed for medical CT scanner), the log to be inspected is rotated and advanced in a spiral motion past the X-ray source and detector, and then coarse resolution CT reconstruction is achieved in real time to reveal the internal structure inside the log. Such approach greatly increases the scanning speed and opens the opportunity of less burdensome and more robust reconstruction.
To fulfill the purpose of this project, the author proposed a novel Scintillator-EMCCD (Electron-Multiplying CCD Camera) based detector design and assembled a prototype detector accordingly. The pilot testing results prove that the our detector achieved good-quality scanning at low light and high speed condition and satisfied the pre-set scanning requirements. Besides the detector design, a stepper-belt driven log carrier was built and set up. This carrier is capable of moving and rotating heavy log specimen simultaneously, thus advancing the log into the needed spiral motion. Except for the progress on physical setup of the CT scanner, a more detailed data acquisition scheme (sector boundary triggering) and more efficient data utilization method (hardware and software binning) were also proposed and analyzed. Research work also continued on further developing reconstruction models and proposing a practical approach to remove the adverse effect from rigid body motion during log transmission. The detailed research work and preliminary results will be demonstrated and discussed in this presentation.