What is 3D printing? Rapid prototyping, additive manufacturing, or 3D printing all refer to technologies that fabricate objects quickly and inexpensively. These processes can take a 3D computer design and transform it into physical form by depositing material layer by layer. Originally intended for preliminary prototypes, the latest 3D printing technology can produce end products that deliver quality and specifications even better than traditional manufacturing processes. There are many different 3D printing technologies, including fused filament fabrication, stereolithography, polymer inkjet, paper inkjet, and many more. These technologies provide an extraordinary range and flexibility for transforming ideas into physical reality.

Why 3D printing in medical imaging? Given the amazing capabilities of 3D printing, it is no surprise that the medical imaging field has embraced these technologies. Already many hospitals are adopting 3D printing to design patient-specific surgical plans and implants, resulting in measurable clinical impact in terms of improved quality and safety. Even more exciting possibilities have emerged in medical imaging research. At the 2017 SPIE Medical Imaging conference, a workshop entitled “3D Printing in Medical Imaging” showcased some of these new research topics, including anthropomorphic breast phantoms for varying imaging modalities, specialized imaging instruments, and even living tissue samples. 3D printing can translate virtual designs and medical imaging data alike into the real world.

In this issue: this special section aims to highlight some of the applications of 3D printing in medical imaging. In particular, the issue has five informative papers. Gerbl et al. in their paper titled “Characterization of office laser printers for 3-D printing of soft tissue CT phantoms” showcase how commonplace office hardware can be repurposed to create realistic imaging phantoms.

Shepard et al. in “Initial evaluation of three-dimensionally printed patient-specific coronary phantoms for CT-FFR software validation” use polymer inkjetting to create functional phantoms that mimic the physiological flow and pressure conditions of actual patients.

In “Three-dimensionally-printed anthropomorphic physical phantom for mammography and digital breast tomosynthesis with custom materials, lesions, and uniform quality control region,” Rossman et al. “hack” polymer inkjetting to create bespoke breast phantoms with characteristics that cannot be achieved by any commercial phantom making techniques.

Nouls et al., in their paper titled “Three-dimensional printing applications in small-animal MRI,” draw upon both filament fabrication and selective laser sintering to create a myriad of MR-compatible parts and instruments customized for five separate preclinical studies.

Finally, Samei et al. in their paper titled “Design and fabrication of heterogeneous lung nodule phantoms for assessing the accuracy and variability of measured texture radiomics features in CT” use polymer inkjetting to create lesions that can provide ground truth for radiomics measurements. This demonstrates the potential for 3D printing to address issues in a way that cannot be done with in vivo patient data.

What is next? Beyond the topics above, 3D printing covers a wide range of topics. They include advances in technology and material science related to printing:

The technology as applied to basic and translational research can cover a wide range of areas:

Finally, in clinical practice, 3D printing objects are paving their way into multiple uses:

We encourage the readers of this special issue to ponder and tackle these relevant topics. We hope papers corresponding to these topics will be published in future issues of JMI. And the results will hopefully lead to a measurable impact on the reach of medical imaging to advance medicine and associated techniques.