Program Information
No-Motion X-Ray Digital Electron Beam Tomosynthesis with Respiratory Motion Tracking
D Boyd1*, M Weil2 , S Song1 , V Ziskin1 , A Ely1 , N Kim1 , E Seppi1 , L Partain1 , (1) TeleSecurity Sciences, Las Vegas, NV, (2) Sirius Medicine LLC, Half Moon Bay, California
Presentations
TH-AB-205-7 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 205
Purpose: Demonstrate no-motion low-mAs kV x-ray digital electron beam tomosynthesis system, capable of tracking lung cancer lesions with respiratory motion, as a subsystem attached to MV linac treatment systems at moderate costs with minimal disruption of standard clinical treatments.
Methods: A TumoTrak™ “U” shaped vacuum chamber was constructed with 19 tungsten anodes, spread uniformly over 3 sides of a 30 cm x 30 cm square, each attached to a cylindrical copper heat sink cooled by flowing water. A beam from an electron gun was steered and focused onto each of the 19 anodes in a predetermined sequence by a series of dipole, quadrupole and solenoid magnets. The projection image was captured by a Varex PaxScan 4030X, an amorphous Si, TFT-switched digital flat panel x-ray imager with 0.194 mm pixels laid out in 1576 rows by 2048 columns. Several phantoms were imaged, including an anthropomorphic chest phantom with 3 separate small simulated lung cancer lesions.
Results: An 80kVp and <60 mA electron beam was focused to sequentially dwell on each focal spot for 7 ms, for <0.4 mAs exposures that totaled <8 mAs for all 19 focal spots (i.e., no gantry motion). The resulting 19 projection images were reconstructed using SIRT-type reconstruction regularized by total variation (TV). At beam’s-eye-view, the images approached the quality of a 3D cone beam CT slices reconstructed (FDK) from 661 projection images spread uniformly with a 60 s 360° of gantry rotation at 120 kVp and 264 mAs total x-ray exposure.
Conclusion: X-ray tomosynthesis tracking of lung tumors at 2-4 fps rates is possible at 30-60 fps projection image acquisition rates, when both the “U” shaped x-ray tube and the commercial flat panel imager (enabled by 2x2 and 4x4 pixel binning), both become operational at 30-60 fps rates in the near future.
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