3D printing has many different applications in medicine. We already showed you one example of use in IKEM, a specialized hospital in Prague, where they use 3D printed model organs for preoperative briefings. Here, in the University Hospital in Olomouc, Czech Republic, they use 3D printing to test their radiology equipment (various types of x-ray machines, CTs, SPECT/CT, PET/CTs), using custom made printed objects of various sizes and shapes: so-called phantoms.
University Hospital Olomouc is one of the biggest hospitals in the Czech Republic, providing a wide spectrum of health care for both children and adults. The vast complex is comprising more than 50 buildings with 3500 employees. In 2018, medical physicists from the Department of Medical Physics and Radiation Protection started to use 3D printed phantoms for ionizing radiation-based imaging modalities. Creating own phantoms instead of purchasing them means a substantial saving of time, allows for a custom design tailored to actual experimental needs and also has the potential to save thousands of EUR. The commercially available phantoms are somewhat limited in their size and shape diversity, while in Olomouc they wanted to create specific custom models, necessary for thorough tuning of their hi-tech machines.
The main challenge was the proper material choice. At first, a special material mix of PETG and glass fiber was used, but later they switched to a regular ABS, which has proven to have the right characteristics for a modest price. Besides other things, the density of both PETG and ABS is similar to water, which means it behaves roughly the same as human tissue, as far as gamma rays and X-rays are concerned.
Fillable models are processed using PrusaSlicer software and printed with a single layer setting with no infill. For better impermeability, the prints are treated with XTC-3D epoxide coating. Such models have, according to the existing experience, the same durability as commercially available phantoms and can be used repeatedly for a very long time. For the calibration itself, the models are filled either with a iodine contrast solution for CT or radioactive solution for SPECT or PET and is usually placed in a larger, liquid-filled container (either original one or 3D printed as well), which simulates the human body (scattering of x or gamma rays and/or radioactive background) for the testing purposes.
“With phantoms printed on Original Prusa 3D printers, we can test our scanners more easily. We often need custom shapes and 3D printing is perfect for that,” comments Ing. Jaroslav Ptáček, Ph.D., Head of the Department of Medical Physics and Radiation Protection. “Also, we are much more flexible and efficient than with official procurement procedures. We value the durability of 3D prints hardened with XTC-3D, which can be used repeatedly and frequently.”