An international team of scientists led by the University of Adelaide and the University of Stuttgart has developed an optical coherence tomography (OCT) endoscope using micro 3D printing technology. The research team’s new probe manufacturing technology uses side-free-form micro-optics (less than 130μm in diameter) to directly 3D print single-mode fibers. The final microscopic imaging device is only 0.48mm in size, which is small enough to enter blood vessels and overcomes the resolution problem encountered by the prior art. The improved 3D images provided by the enhanced endoscopic camera can enable doctors to better understand the cause of heart disease, making it possible to prevent heart disease before it occurs.
Dr. Simon Schiller, head of the optical design and simulation team at the University of Stuttgart, said: “Until now, we have not been able to make such a small, high-quality endoscope so small. Using micro 3D printing, we can print too small to the naked eye. The invisible complex lens. The entire endoscope with a protective plastic shell is less than half a millimeter in diameter. It is great to work on these innovations and build them into such a useful project. When we put engineers and It’s amazing what we can do when clinicians are together.”
The researchers’ microscopic 3D printing device (pictured) is only 0.48mm in diameter. Picture from “Light: Science and Application” magazine.
For medical staff, fiber optic endoscopes have quickly become an important clinical tool that can provide real-time guidance during medical interventions. In particular, OCT endoscopy has been used in a large number of surgical cases. So far, it is estimated that 410,000 operations have been assisted in Australia alone. Nevertheless, despite its wide application, endoscopic technology is not yet perfect. Miniaturized high-resolution probes are still in high demand, which can not only image small and narrow luminal organs, but also minimize the discomfort of probe insertion during doctors’ operations. Generally, animals such as mice are also used as models of human diseases, and in order to make the most of such experiments, smaller solutions are needed.
Previous studies have also found that conventional probes cannot capture any images of structures deeper than 100 μm, which limits their potential life-saving applications in heart care. The main cause of heart disease is plaque, which is composed of fat, cholesterol and other substances deposited on the walls of blood vessels. “The University of Adelaide co-author and lecturer Li Jiawen explained. Preclinical and clinical diagnosis are increasingly dependent on visualizing vascular structures to better understand the disease. Miniature endoscopes are like miniature cameras that enable doctors to see How these plaques are formed and explore new ways to treat them.”
According to the researchers, because endoscopes often suffer from spherical aberration, low resolution or shallow depth of field, the current probe manufacturing technology is not sufficient. Moreover, although resolution and focal depth are usually traded off in existing probes, in small devices, their physical aperture is very small, and there is no appropriate compromise. In addition, in OCT imaging, the intravascular probe is deployed in a transparent catheter sheath to protect the patient from trauma during camera rotation.
Optically speaking, the cable cover can cause astigmatism in the camera, causing the camera to lose focus, and current manufacturing methods cannot alleviate this situation. Although previous methods focused on splicing existing fiber lenses, these methods cannot achieve the same resolution as traditional OCT imaging. To overcome these limitations, the research team set out to use two-photon polymerization technology to directly 3D print micro-optical devices with a diameter of 125 μm on a single-fiber compound.
The images captured using the research team’s endoscopic equipment showed a necrotic core of dead cells (pictured). Picture from “Light: Science and Application” magazine.
To make their add-on endoscope, the researchers spliced a coreless fiber with a length of 450μm into a single-mode fiber with a length of 20μcm, thus expanding the beam before it reaches the micro-optical camera. Then, the Nanoscribe two-photon lithography system was used to 3D print the beam shaping micro-optics directly to the far end of the material. The researchers’ production method was found to compensate for the astigmatism caused by the mandatory transparent catheter sheath. In addition, the optical fiber assembly is fixed in the thin-walled torque coil, so that the device can be accurately manipulated to the other end of the imaging probe.
In order to evaluate the performance of their ultra-thin OCT probe for scanning tissue samples, the research team tried to capture images within the newly removed human carotid artery. Although the blocked blood vessel showed severe stenosis, the team’s ultra-thin probe was able to pass through the blood vessel effortlessly and then be pulled back. In addition, the endoscopic camera can detect the necrotic core of dead cells, which is a key function for identifying high-risk plaques that may cause a heart attack.
Further OCT imaging tests were performed on the thoracic aorta of mice. The probe can capture images without any obvious rotation distortion, and successfully carried out 3D imaging in very small arteries, the smallest arteries are less than 0.5mm. The picture also shows thick, densely packed fat cells with a diameter of 15-25μm, which indicates that the 3D printed probe can identify microstructural features through in-situ imaging. As a result, the researchers believe that their experiments are sufficient to prove that their printed OCT equipment is an improvement on the endoscopes currently in use. The team believes that the success of their 3D printing method may lead to its adoption in a range of clinical applications. “In addition to the value of using imaging probes in small animals, this ultra-thin aberration correction probe can also safely enter fragile but inaccessible organs, achieve high-resolution cross-sectional imaging, and may lead to improved patient safety. Sex and improve health.”
Although the German/Australian research group’s approach is novel, many other research groups also use 3D printing to fight heart disease, although usually in the form of a polymer heart model. For example, the University of Kentucky (UK) School of Medicine is 3D printing customized heart models to help doctors and their patients. These replicas cost only $5 and are an accurate preoperative tool that can be precisely fitted to heart implants.
On the other hand, researchers at Stanford University School of Medicine are developing 3D printed cardiac catheter surgery equipment. Surgeons can use this product to map the electrical activity of the heart, so as to finally detect rhythm disturbances in the patient’s heartbeat.
Great Ormond Street Hospital (GOSH) is using 3D printed copies of children’s hearts to enable surgeons to better plan complex and critical heart operations. 3D printing models can bring faster and more effective surgery and faster recovery speed for patients.
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