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3D Printed Medical Models May Assist in Better Monitoring of Ventricular Devices & Blood Flow

In ‘Innovative Modeling Techniques and 3D Printing in Patients with Left Ventricular Assist Devices: A Bridge from Bench to Clinical Practice,’ US researchers examine new techniques for better monitoring of left ventricular assist devices (LVAD) and troubleshooting alarms. The need is there due to altered flow dynamics caused by LVADs, which have been a developing technology for the last 30 years.

The authors examine new development methods that are not yet in use clinically but may have significant bearing in the future as they are able to improve treatment of cardiac patients who may have low cardiac output or even be in end-stage heart failure. As LVADs offer a ‘bridge’ to transplants or further therapy, some models may cause issues such as:

  • High thrombosis
  • Valve failure rates
  • Flow augmentation
  • Bleeding complications
  • Stroke

Even with superior design, issues may arise due to how the LVAD is placed in the body. Here, the researchers look further into techniques predicting LVAD flow. Not only can these techniques lead to better troubleshooting, but also better surgical planning, often with the help of 3D printed guides.

Computational fluid dynamics are used to create LVAD prototypes as well as test them:

 

The workflow for computational fluid dynamics (CFD) analysis in a patient with LVAD.

“Prior to running a computer simulation, the accurate 3D geometry of the object needs to be defined, usually from cardiac CT or 3D echocardiography,” state the researchers. “The physical characteristics of the fluid, in this case blood, and the surrounding boundaries are defined. In these computer simulations, blood is assumed to act as an ideal fluid.”

“The quantity of blood flow through the ‘inlet’ (the left ventricle) and the ‘outlet’ (the aorta) can be derived from cardiac catheterization or echocardiography. These geometric and boundary conditions are inputs to a computer simulation that essentially functions as a virtual flow lab. The information can then be used to generate information on shear stress, heat dissipation, and wall pressure. Models for hemolysis and platelet activation can also be generated to test a device for hemocompatibility.”

CFD simulations with varying outflow cannula angles relative to the aortic arch and variations in absolute pressure (in Pascals) and distribution on the aortic arch and great vessels.

Fluid structure interaction (FSI) allows researchers to examine fluid flow around a ‘deformable structure,’ with CFD simulations allowing assessment of the following hemodynamic parameters:

  • Pressure
  • Velocity
  • Wall shear stress
  • Displacement

Simulations allow researchers to observe disturbed flow, which may be in connection to issues with atherosclerosis and thrombogenesis. The authors point out that most CFD studies are deficient in the specific patient geometry required, along with long-term outcomes.

“CFD can prove to be a useful technique that could potentially be used clinically for LVAD implant planning, surveillance and troubleshooting of complications of patient with LVAD,” state the researchers. “Assessment of adverse fluid characteristics in relation to adverse long-term clinical outcomes may provide important insight into surgical implant techniques.”

In particle image velocimetry (PIV), researchers look at rapid sequential imaging for computing velocity vectors as well as fluid dynamics. PIV modeling involves setting up:

  • A transparent phantom organ
  • Laser
  • Camera
  • Seeding particles
  • Image processing software

The authors see potential for PIV in understanding LVAD placement and fluid dynamics.

3D printed models are also being used now so that researchers can understand more about heart disease. They may be helpful in surgical planning, as well helping in the placement of ventricular assist devices (VADs). Heart models have also helped with virtual implantations, along with VADS in children too. The researchers point out that 3D printed heart models do improve anatomical positioning and surgical techniques, they are inferior to continuous flow pump simulation. They recommend better simulation models with either CFD or PIV modeling.

“As 3D printing technology evolves, there is hope to develop patient-specific models that replicate the anatomic and physiological features to be used in LVAD surgical planning,” conclude the researchers.

“In the long run, improved fluid dynamics may help improve implant techniques and lessen the burden of significant adverse events.”

An example of a flow circulatory flow loop with LVAD connected to compliance chambers and flow meters

Because there are so many heart conditions affecting so many around the world—and they can be deadly—researchers are constantly looking for better ways to treat patients. With 3D printed models and devices, patient-specific care is much more accessible, meaning that medical professionals have an easier time diagnosing heart conditions, treating them, and explaining what is going on to not only patients, but their families too. Medical students also have much more expanded training mechanisms with advanced 3D printed heart models and surgical guides.

[Source / Images: Innovative Modeling Techniques and 3D Printing in Patients with Left Ventricular Assist Devices: A Bridge from Bench to Clinical Practice]

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Natural Plant-Derived Resins Used to Make Antibacterial 3D Printing Filament

Hospital-acquired infections are a growing problem everywhere. The CDC calls them a “major, yet preventable threat to patient safety,” and the key to preventing them lies in keeping bacteria from spreading in a setting where bacteria is rampant. As 3D printing becomes more and more prevalent in the medical field, it is vital to make sure that 3D printed implants and tools do not play a role in spreading disease. Certain companies have been working on creating antibacterial 3D printing filament, and a group of researchers has conducted a study on bioactive filaments with antimicrobial and antifungal properties. You can access the paper, entitled Bioactive Potential of 3D-Printed Oleo-Gum-Resin Disks: B. papyrifera , C.myrrha , and S. benzoin Loading Nanooxides—TiO2 , P25, Cu2O, and MoO3, here.

The researchers point out that bacteria have managed to develop resistance to many antibiotics, but that there are many natural antibiotics to which resistance has not yet been developed. They extracted oleo-gum-resins from benzoin, myrrha, and olibanum plants and combined some of them with 10% of metal nano oxide particles. 3D printer filament was created from the resins and metals, then 3D printed into disks which were subject to a number of tests.

“Due to their intrinsic properties, disks containing resins in pure state mostly prevent surface-associated growth; meanwhile, disks loaded with 10% oxides prevent planktonic growth of microorganisms in the susceptibility assay,” the researchers explain. “The microscopy analysis showed that part of nanoparticles was encapsulated by the biopolymeric matrix of resins, in most cases remaining disorderly dispersed over the surface of resins. Thermal analysis shows that plant resins have peculiar characteristics, with a thermal behavior similar to commercial available semicrystalline polymers, although their structure consists of a mix of organic compoundsThe disks 3D printed from the natural materials, in most cases, inhibited the growth of the clinical pathogens being studied, and when nano oxide particles were added, the materials were even more effective.

Whats more these materials behaved just like some polymers do. The resins,

showed thermal behavior inherent to semicrystalline polymers such as polyester and polyurea; at some point, the molecules disposed in amorphous matrix obtain enough freedom of motion to spontaneously rearrange themselves into crystalline forms. This transition from amor-phous solid to crystalline solid was evidenced by distinct exothermic peaks, as the temperature increases to 500∘C samples, eventually reaching its melting point.

In short this is a promising study. Polymeric behavior from these Oleo-Gum-Resin may make it easy to process them just as many other 3D printing materials. Furthermore, as 3D printing is being increasingly used to create things such as surgical instruments, surgical guides and implants, special consideration should be given to the materials that are used to 3D print these tools. Of course, all surgical instruments and implants are made to be sterile before being used, but what if they could be made from materials that actively prevented infection? There’s a big difference between tools that are free of pathogens and those that actively repel pathogens. Surgeries could be made safer and recoveries quicker, without the complications and extended hospital stays that happen when infections are acquired. 3D printing surgical tools from these materials will not eliminate all hospital-acquired infections; there are a number of causes for these diseases that go beyond surgeries themselves and threaten anyone who has to stay in a hospital. But if the use of these materials could cut down even a little bit on surgical complications, that would be progress.

Authors of the paper include Diogo José Horst, Sergio Mazurek Tebcerhani, Evaldo Toniolo Kubaski, and Rogério de Almeida Vieira.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below. 

 

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Using Patient-Specific 3D Printed Surgical Guides for Total Knee Replacement

While surgery has always, ultimately, been about the patient, it hasn’t always been patient-centered. Historically, patients have not had an easy time of understanding exactly what their surgery entails and have often been treated as if they were ancillary to the surgical problem presented. This can’t all be blamed on uncaring medical staff, as most people involved in medicine do care and care profoundly. Instead, it has largely been a result of resources and standing custom. Surgical procedures are complicated and difficult to understand, hence the reason why experts are the ones who address them, and the pressure and stress involved in going into a procedure largely blind has made it difficult for surgeons to relax and broaden their focus to include the patient beyond the problem.

3D technology is making great contributions to medicine, from aiding in research to assisting in the preparation of students to practice medicine to producing the tools necessary to perform better operations. It is being integrated into the surgical theater and changing the face of surgery as we know it. One of the ways it is doing this is through the provision of a greatly improved ability to plan for the procedure. 3D technology not only allows the medical team a sneak preview, 3D printing can create models of the particular areas to be addressed and allow surgeons to study them in advance. This helps minimize surprises and therefore reduces the stress on both the patient and the medical staff.

The staff at Orthoparc in the Netherlands has figured out another way to help create and deliver the best in patient centered care. Using 3D technology, they have developed a method of patient-centered total knee replacement that allows a patient to walk in, in the morning, and walk out that same day. Such a possibility requires a highly interconnected team of specialists working together to ensure that not only does the patient get the knee replacement they need, but their psychological, nutritional, and whole health needs are met as well.

Dr. Saskia Boekhorst

One component of this is the integration of 3D printed, patient-specific surgical guides that take the uncertainty out of the procedure itself. These surgical guides are produced using data gathered about an individual patient’s knee and are fabricated in-house on a 3D printer. When placed upon the patient during surgery, they guide the surgeon to exactly where cuts need to be made in relationship to where the knee is resting. Dr. Saskia Boekhorst is an orthopedic surgeon at Orthoparc, and she described the impact these guides have had in her experience:

“I’m a big fan of the patient-specific knee guides because this technology allows me to place the components of the knee arthroplasty exactly in the right axis of the leg in all dimensions. The first one hundred cases I’ve double checked by manual measurements, because it was a different approach and I am very careful. But after seeing very nice and consistent results, I became convinced.”

This increase in precision means that the surgery is more exactly what the patient needs and reduces the risk of unnecessary or erroneous incisions. The surgical guides also make the surgery less invasive, removing the need to drill into the femur canal as in traditional knee replacement surgery procedures. They also help decrease the amount of time the patient has to spend in surgery, as Dr. Boekhorst explained:

“The positioning and alignment are already done by me within an interactive planning software in which I can rotate the knee in all directions and see how the prosthesis could be placed for a particular patient. You will never be able to see this in all these dimensions and directions with a real patient because of soft tissue.”

All of this adds up to mean that there is less anesthesia necessary and less powerful post surgery painkillers required. Not only does that reduce the risks associated with such powerful medicines but allows the patient to be more fully cognizant and mentally focused on an increased timeline, something which is necessary for the implementation of a physical therapy regimen.

It’s not just good for the patients, it also makes sense for the surgical team in terms of reducing stress and ensuring they are better prepared for the operation. In addition, using these guides means that fewer surgical tools need to be prepped and sterilized as the knee guides come in a comprehensive ‘knee in the box’ package that includes all the necessary instrumentation and two sizes of preselected implants to treat a single patient. This means less overhead and a reduction in logistics cost, something which allows the medical practice to reinvest its resources elsewhere, such as in its staff and patients.

What do you think of this news? Let us know your thoughts; join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source/Images: Materialise]