Wolf Schweitzer: “3D Printing is Helping to Develop Forensic Devices”


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Post mortem examinations are widely used to determine the cause of death, yet traditional autopsy has changed little in the past century, consisting of external examination and evisceration, dissection of the major organs with identification of macroscopic pathologies and injuries. A few years ago, and in a quest to advance the field of forensic medicine, a team of scientists at the University of Zurich, Switzerland, has been serially developing automated tools and technologies to improve results, reduce costs, and time during autopsies. By combining new technologies, like 3D imaging, scanning, and printing to generate virtual autopsy tools, into what has eventually become a household name in forensics a venture known as the Virtopsy project, or just virtopsy, they are changing the paradigm of forensics.

As part of the Virtopsy project, scientists have come up with creative ways to help the field of forensics, with ideas ranging from a modified automotive robotic arm with tools called Virtobot, to non-invasively discovering injuries present on the skin surface of a body, along with 3D true color representations of surface injuries and 3D scaled models of entire crime scenes and events. One device, in particular, caught our attention, a post mortem computed tomography angiography or PMCTA kit, made using 3D printing and parts that can be found at your local hardware store. The team posted online all of the files and part specifications so that anyone who wants to recreate the PMCTA can do it, for a total cost of just $120. But first, to understand what the device really does, 3DPrint.com asked Wolf Schweitzer, a forensic pathologist at the University of Zurich and part of the team behind the 3D printed PMCTA, why the device is so important and how disruptive technologies can aid experts to achieve better autopsies.

Production of Very Affordable PMCTA-kits. Left: 3D printing in progress; Middle: finished print batches; Right: kits in process of being packed

Why is the PMCTA important in forensic medicine?

A post-mortem CT is relevant in forensic pathology to examine the body, particularly for the consequences of violence or trauma. The findings add insight and help prepare autopsies so they can be performed faster and with a better focus on what we are looking for. Autopsy diagnosis is often very specific, yet performing it is tedious and time-consuming. For example, a few years ago it took seven hours of careful dissection to find the source of fatal hemorrhage in a body. These types of cases would greatly benefit from a PMCTA. Via an external pump, the vessels of the body are filled with a contrast substance that appears opaque on the computed tomography (CT). Knowledge of the normal anatomy of blood vessels allows examiners to identify certain possible or potential leaks. This means that while using PMCTA, vascular injuries, leaks or other pathologies can be examined. Once they are found, they may be documented or the results may be given to the pathologist who then narrows down the search for the actual autopsy dissection.

Why did you design a low-cost PMCTA for anyone to use?

Resulting PMCTA with a view of the whole body showing contrasted vessels and organs

Specialized commercial devices can be costly and require dedicated and expensive additional installations such as oil separators, consumables, and maintenance. A top of the line PMCTA-pump can easily be worth $80,000, while materials cost around $1,000 per single case or examination. Additionally, users need to install an oil separator to avoid their oil-based contrast agent to leak or get drained into the sewer. While some privileged forensic medicine institutes may find that acceptable, we wondered whether that type of technology was really necessary. So that is why we decided to custom design and 3D print our own immersion pump to be used as a forensic PMCTA and fill in the rest of the materials list with parts from a hardware store, for just $120. The whole idea of providing very affordable PMCTA technology became evident during our Virtopsy courses, for 15 years, specialists and trainees from around the world came to Zurich to attend our courses, and one frequently voiced concern was about the PMCTA, how problematic the oil was to the environment, and how expensive the materials where, so we listened and began evaluating better options.

In the paper Very economical immersion pump feasibility for postmortem CT angiography (that has Schweitzer as co-author) our team at the Department of Forensic Medicine and Imaging concluded that more widespread and systematic implementation of PMCTA demands affordable equipment for facilities with tight budgets. This is why we uploaded everything anyone needs to develop their own PMCTA (the printable 3D models went up as STL-files) online at virtopsy.com.

How did 3D printing become part of the solution?

Unlike clinical medicine, forensics get lower, more restricted public budgets, motivating us even further to use more affordable means of production, design, and materials. Plus, we often do not need anti-allergic or extensively sterilized catheters or solutions. This means that we can design, 3D print prototypes and test them in one or two days, then revise the design and keep re-iterating until the 3D models (and their 3D printed instances) are ok. Once the 3D printed PLA models are enough for routine work, we use them. We really wanted to get the actual design process first, since having the ability to design hardware prototypes using CAD software is useful anywhere custom parts are needed.

What 3D printers did you use?

For the 3D printing process, we used a MakerBot Replicator 2 (originally built to print ABS, but tweaked to print with PLA) and a MakerBot Replicator+ (fifth generation). PLA feeding was a problem, as the Makerbot printers appeared to have trouble pulling the PLA into the nozzle where it is melted for printing. To work around that, we decided to built PLA-roll mounts with ball joint bearings using available 3D models of Thingiverse. We used 3D printing to get the models’ shape right.

Still, 3D printing spare parts and new add-ons does not end with the PMCTA, the team has also identified a few other applications for 3D printing. For example, they are currently investigating whether it is possible to print skeletal parts (skull and lung bones) to perform bio-mechanical crash or impact tests on 3D printed materials, and verify if they fracture in a similar way as natural bone.

Is there access to technology for forensic medicine? 

Forensic medicine is usually run as a government or state service to examine violent, suspicious, sudden and unclear deaths. Like most scientists and doctors, we are interested in new technologies and love developing and creating new ideas, yet funding is a big factor, as well as structural restrictions or opportunities for research and development of technological advances.

Technologies are not necessarily expensive, anyone can discover free or affordable software and courses and forensic medicine is often embedded in a university or hospital setting so we are really not alone in this mission. Originally, we started with post-mortem CT scanning, using already installed hospital or veterinarian CT scanners (rather than having our own), so we made friends with experts in other departments. We also worked with other engineers, researchers, and specialists, such as Claudio Gygax from 3D-EDU GmbH, who provided technical support and advice. I come from a creative tech household, so building stuff was what everyone else was doing anyway. It is really important to recognize what is missing from an apparently abundant world, to “see” the technical void, to recognize the applied advantage in filling empty space with (initially at least) plastic, and once that is identified, the rest is usually fairly straight forward. This requires teamwork to ignite creative thought and innovation.

Forensic pathology is full of inquisitive and interesting people that go forward to adopt all kinds of useful technologies (without having to spend a lot of money on it). In the end, it really is the investigative mind that makes a difference and there are absolutely wonderful ideas out there to develop even further.

Wolf Schweitzer

[Images: Virtopsy project, University of Zurich and Wolf Schweitzer]

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