BACKGROUND

Single Photon Emission Computed Tomography (SPECT) imaging systems include a collimator in the path of radioisotope emitted by an object-under-study and a detector (e.g., a photomultiplier tube, or the like). The choice of collimator design can have an impact on the sensitivity and resolution of the SPECT system.

The collimator acts as the front-end of a gamma camera, and has a big impact on the signal-to-noise ration of the captured image. The collimator functions to spatially control the propagation direction (i.e., field-of-view) of the gamma rays reaching the detector—similar to a lens used in visible photon wavelengths. SPECT collimators are typically formed from radiation-absorbent material, where non-absorbed photons can reach the detector.

FIG. 1is a diagram of conventional SPECT scanner imaging system100. SPECT scanner system100includes gantry120to which two or more gamma cameras130a,130bare attached, although other numbers of gamma cameras can be used. Detector132in the gamma ray camera detects gamma photons140emitted by a radioisotope within the body of a patient145lying on a bed150. Collimator134is positioned between the emitted photon and the detector. Bed150is slidable along axis-of-motion A. At respective bed positions (i.e., imaging positions), a portion of the body of patient145is positioned between gamma cameras130a,130band an image of that body portion is captured.

Control processor110can execute instructions to control operation of the SPECT scanning system. Motion control/automation module112can control motors, servos, and encoders to cause gamma cameras130a,130bto rotate along gantry120, and to move bed150along an axis-of-motion (arrow A). Data acquisition/image processing module114can acquire projection data at defined imaging position points during the rotation of gamma cameras130a,130band/or the shifting of bed150. The acquired data can be stored in memory118. Imaging processing algorithms can manipulate the stored projection data to reconstruct a 3D image. The reconstructed 3D image can be displayed on an interactive display controlled by operator interface/display module116.

Conventional attempts to use commercially-available, off-the-shelf three-dimensional (“3D”) printers to produce the collimator patterns commonly used in SPECT have not achieved satisfactory results. Conventional 3D printing of collimators fails to meet the quality required for medical imaging (e.g., tolerances, uniformity, manufacturability, etc.).

There are significant challenges in making use of commercially-available, additive processes to produce medical-modality collimators on a 3D printer. One reason is that the required tolerances cannot be guaranteed using 3D printers' additive processes due to the high viscosity of the extruded filament print material, which is made even higher when imbedded with high-density and high-atomic number (“Z”) materials (required to increase the attenuation of ionizing radiation). Limitations controlling the position and speed of the extruding printhead relative to the flow of the extruded material also contribute to the challenges. Because of these factors, the conventional approach of producing stereolithography files (e.g., STL format) directly from 3D CAD files is not a viable solution. Further, conventional approaches to manufacturing collimators by 3D printing fail to yield devices that meet quality requirements of medical imaging (tolerances, uniformity, manufacturability, etc.) using off-the-shelf components.

In recent years, vendors of 3D printed collimators have been proposing green manufacturing processes (e.g., Pb-free and RoHS-compliant) that require special printing processes which require significant investment and add cost to the end products. None of these processes have been successfully produced in scale to replace current available lead collimators. The cost for these conventional 3D printed collimators is greater than existing lead collimators.

There is a need in the art to quickly, and accurately create medical-modality collimators by applying layered 3D printing techniques using information contained in a stereolithography file.

