Page 60 - Read Online

Bui et al. Vessel Plus 2021;6:31 https://dx.doi.org/10.20517/2574-1209.2021.97 Page 5 of 12

Another limitation of 3D printing is the processing time needed to produce a model, which is dependent on
the type of printer used, the complexity of the pathology, and the material used. Powder-based 3D printers
can take up to 3 h to finish printing a simple product [17,19,27] , but models for patients with complex pathology
[26]
can take around 7 days to complete . Materials that resemble cardiac myocardium have a higher cost but
take less time to produce a cardiac model, whereas less flexible materials have a lower cost but can take up
[25]
to 10 times longer to print . Hence, despite the benefits of patient-specific anatomy and usefulness in
determining surgical plans, long production times can lead to issues like high inpatient hospital bills and
psychological anxiety while patients await an appropriate surgical plan, making traditional imaging
techniques such as CT or MRI optimal diagnostic methods.

Despite the advancements in imaging technology, flaws can still be present, for example, due to the effect of
blood pooling, which results in the inability to fully capture structures like papillary muscles,
atrioventricular valves, and semilunar valves. This leads to the production of a 3D model that will be
difficult to analyze, diagnose, and plan an appropriate surgery for [19,30] . 3D printed cardiac models are also
unable to portray dynamic changes in the heart during cardiac cycles, which is imperative in understanding
[31]
the pathophysiology of patients with congenital heart diseases . Despite these limitations, some surgeons
still prefer 3D cardiac models because the benefits of surgical planning, improved patient communication,
and tactile experience of holding the heart can outweigh the costs in most situations.

Ethical issues regarding 3D printing
Despite the undeniable benefits of 3D printing in surgery, there still stand some ethical issues concerning
the use of 3D printing to produce patient-specific models. First of all, the use of samples from donors who
are not fully competent or who are coerced to give consent is unethical. Therefore, it is best to provide
detailed explanations about the risks, benefits, and expected outcomes to the donors and their legal
guardians . Currently, materials used for 3D printing can either be obtained synthetically (i.e.,
[32]
polyethylene glycol), from chemically modified natural products (i.e., gelatin methacrylate), or from non-
human animal sources. The use of bioink from non-human samples raises another ethical concern because
of its potential to cause zoonotic infection in humans. On the contrary, there are institutions and patients
that consider the use of human embryonic stem cells unethical. If regulation prevents certain cell lines from
[32]
being used, it could lead to 3D printing medical tourism in order to get access to these cell lines . In 2017,
the Food and Drug Administration (FDA) published a guidance on technical considerations for additive
manufacturing, an umbrella term of 3D printing. To protect patient’s privacy, it is advised that device
designers maintain proper care of a patient’s personally identifiable information and protected health
information. Regarding the strength of the final 3D printed model, the FDA recommends that materials
used to produce 3D implants should be noted, and the final product should be tested before surgical use.
For example, devices made from metal or ceramic are recommended to undergo mechanical testing if
[33]
structural inhomogeneity, microstructural voids, or incomplete isolation are detectable .
Virtual reality in surgery
VR offers a safe and flexible platform for surgeons to explore a computationally generated patient-specific
synthetic world. This includes assessing anatomical regions, generating surgical plans, and familiarizing
with procedures to minimize surgical risk [1,34,35] . The possibility to add haptic systems to provide tactile
feedback further enhances this experience [1,36] . Furthermore, VR provides physicians with unlimited training
opportunities that do not require any patients or cadavers. It can also be used as a form of assessment or a
trouble-shooting tool to investigate differing performances between surgeons without putting patients at
risk .
[37]