Program Information
Determination of LDRBT Prostate Seed Location Using An Endorectal X-Ray Sensor
J Steiner*, K Matthews , G Jia , Louisiana State University, Baton Rouge, LA
Presentations
SA-B-BRA|B-3 (Saturday, March 18, 2017) 10:30 AM - 12:30 PM Room: Ballroom A|B
Purpose: To develop a new method to determine the location and orientation of LDRBT prostate seed implants using an endorectal x-ray sensor.
Methods: Simulated and physical male pelvic phantoms were created to investigate imaging of ¹²⁵I LDRBT prostate seed implants using an endorectal x-ray sensor. Parallel tomosynthesis scanning was performed with source-to-axis distance 96.5 cm, axis-to-detector distance 1.5 cm, arc angle -20° to 20°, and detector size (2.6 x 3.6) cm² with 0.002 cm pixels. 27 seeds were simulated in a (2 cm)³ volume using MATLAB©. Physical phantoms were implanted with 10 seeds in plastic/Styrofoam in a 1.5 cm diameter x 1 cm depth volume and 35 seeds in Agar in a (4 cm)³ volume. Images of the phantoms were collected in 2 degree increments using computed projection imaging (simulated phantom) and a GE Proteus XR/a unit and XDR x-ray sensor (physical phantoms). The resultant planar images were reconstructed using IDL™ to provide seed locations and orientations using geometrical and morphological operators to track and differentiate seeds.
Results: In both the simulation and physical phantoms, seed center points, azimuthal angles, and elevational angles were determined in relation to the x-ray sensor. In the simulated phantom, the mean distance from known to calculated seed position was 0.46 ± 0.11 mm and the mean angular variation from known to calculated seed orientation for both azimuthal and elevational angles was 15.1° ± 9.7°. In the physical phantoms, qualitative comparisons overlaying reconstructed images on planar images showed good agreement.
Conclusion: A digital endorectal x-ray sensor can be used to localize center points, azimuthal angles, and elevational angles of LDRBT prostate seed implants. This information is expected to provide improvements in post-implant dosimetry by incorporating seed geometry and seed dose anisotropy into a 3D dose calculation.
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