3D Printing Assisted Collimator Design for Fan Beam-Based X-Ray Fluorescence Tomographic Imaging 📝

Author: Brett Bocian, Nesrin Dogan, John C. Ford, Alan Pollack, Ryder Marshall Schmidt, Junwei Shi, Jorge D Vega 👨‍🔬

Affiliation: University of Miami, University of Miami Sylvester Comprehensive Cancer Center 🌍

Abstract:

Purpose: X-ray fluorescence computed tomography (XFCT) is an emerging molecular imaging modality gaining attention in cancer theranostics with high-Z metal nanoparticles (MNPs). While XFCT has been demonstrated using single pencil X-ray beams and single-pixel detectors (SPD-XFCT), this method is time-consuming. A 2D pixelated array detector (PAD) enables faster imaging by simultaneously acquiring X-ray fluorescence photons and their spatial positions. This study presents a slit-beam collimator design for PAD-based XFCT.
Methods: A HEXITEC detector with 80 × 80 pixels, 250 μm pixel size, and 800 eV energy resolution at 60 keV was positioned 20.1 cm from the system isocenter, with the X-ray tube placed 33.9 cm away. Cerrobend was selected for collimator fabrication due to its low melting point and high X-ray attenuation, to form a 2 mm-thick vertical fan beam at the isocenter. A 3D model was designed in AutoCAD and 3D-printed with polycarbonate filament in Ultimaker Cura to create a 5 cm × 2 mm field size. The Cerrobend was molded to have a rectangular aperture with a copper insert. After cooling for 1-2 hours, the collimator was tested using EBT3 radiochromic film and a flat panel detector to verify beam size and uniformity.
Results: The 3D printing process achieved 0.2 mm precision. EBT3 film analysis indicated a field size of 4 cm × 2 mm at the isocenter. Flat panel detector measurements confirmed beam uniformity, with no leakage observed.
Conclusion: The 3D printing-based Cerrobend slit-beam collimator demonstrates its feasibility for fan-beam XFCT imaging. The high precision of 3D printing ensures accurate alignment of the collimator slit with the focal spot center of the X-ray tube. Most importantly, this adaptable design strategy can be applied to collimators of any shape or size, making it suitable for both preclinical and clinical imaging or irradiation research.