Ultra-high definition (8K UHD) endoscope: our first clinical success
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We have started clinical application of 8K ultra-high definition (UHD; 7680 × 4320 pixels) imaging technology, which is a 16-fold higher resolution than the current 2K high-definition (HD; 1920 × 1080 pixels) technology, to an endoscope for advanced laparoscopic surgery.
Based on preliminary testing experience and with subsequent technical and system improvements, we then proceeded to perform two cases of cholecystectomy and were able to achieve clinical success with an 8K UHD endoscopic system, which consisted of an 8K camera, a 30-degrees angled rigid endoscope with a lens adapter, a pair of 300-W xenon light sources, an 85-inch 8K LCD and an 8K video recorder. These experimental and clinical studies revealed the engineering and clinical feasibility of the 8K UHD endoscope, enabling us to have a positive outlook on its prospective use in clinical practice.
The 8K UHD endoscopy promises to open up new possibilities for intricate procedures including anastomoses of thin nerves and blood vessels as well as more confident surgical resections of a diversity of cancer tissues. 8K endoscopic imaging, compared to imaging by the current 2K imaging technology, is very likely to lead to major changes in the future of medical practice.
Keywords8K ultra-high definition (UHD) 4K ultra-high definition (UHD) Laparoscopic surgery Cholecystectomy
The present burgeoning of 8K ultra-high definition (UHD) imaging technology, ushering in an era of video with a 16-fold higher resolution (7680 × 4320 pixels, about 33 million pixels) than the current high-definition (HD, 1920 × 1080 pixels, about 2 million pixels) technology, is enabling the development of the next generation 8K broadcasting system (Sugawara et al. 2003, 2013; Yamashita et al. 2012; Shimamoto et al. 2014). In this context, there are heightening expectations in recent years for much important contributions of 8K UHD technology to innovative medical imaging in advanced image-guided diagnosis and treatment. Between HD and 8K UHD 4K UHD imaging technology (3840 × 2160 pixels, about 8 million pixels) is gradually progressed for medical use (International Telecommunication Union (ITU) 2012; Woo 2016; Maier et al. 2015), however, we started by developing an 8K UHD camera specifically designed for endoscopic use, and subsequently confirmed its capability of 8K imaging resolution in use coupled with a rigid endoscope. Based on preliminary testing experience and with subsequent technical and system improvements, we then proceeded to perform two cases of cholecystectomy and were able to achieve clinical success in the full employment of an 8K UHD endoscopic system for the first time in the world. These experimental and clinical studies revealed the mechanical and technical feasibility of the 8K UHD endoscope, enabling us to have a positive outlook on its prospective use in clinical practice. In this paper, we report on the outcome of our feasibility study of our current 8K UHD endoscopy, including its system configuration as well as the problems that need to be overcome before expanding its use in clinical practice.
System configuration of the 8K UHD endoscope
8K imaging resolution performance test
We tested the imaging resolution of our 8K camera head and the rigid endoscope in order to select the optimal lens adapter for 8K imaging using an ISO resolution chart for electronic still cameras. This resolution chart was prepared for the work of ISO TC42 WG18 and is based on ISO 12233. We captured images of the chart and visually counted the black and white lines on the display. At first, we observed the resolution of the display showing the output by the 8K camera itself with an AI Nikkor 50 mm f/1.2S lens (NIKON CORP.). Next we observed the resolutions of reproduction on the display when showing the output as an 8K UHD endoscope with the rigid endoscope with the lenses AF-S Micro NIKKOR 60 mm f/2.8G ED, AI Nikkor 50 mm f/1.2S or AI AF Nikkor 24 mm f/2.8D (NIKON CORP.).
Clinical cases of cholecystectomy
The first patient was a male in his seventies and visited Kyorin University Hospital with a complaint of biliary colic. The second patient was also a male in his seventies and visited Kyorin University Hospital with a complaint of abdominal pain and diagnosed with choledocholithiasis.
8K imaging resolution performance
The imaging resolution of the display showing the output by the 8K camera itself with AI Nikkor 50 mm f/1.2S (NIKON CORP.) was about 4000 line widths per picture height on the 8K display, which indicated an intrinsic performance of 8K. The resolutions of reproductions on the display when showing the output as an 8K UHD endoscope with the rigid endoscope were 2200 line widths per picture height with AF-S Micro NIKKOR 60 mm f/2.8G ED, 2600 lines with AI Nikkor 50 mm f/1.2S and 3600 lines with AI AF Nikkor 24 mm f/2.8D. With AI AF Nikkor 24 mm f/2.8D we could attain higher resolution but with a smaller field of view. For laparoscopic surgery, the field of view is required to be as large as possible. Therefore, with priority given to a greater field of view, in this study we selected AF-S Micro NIKKOR 60 mm f/2.8G ED as the lens adapter.
In surgery of the first case, since the brightness of the laparoscopic view was insufficient with only a 300-W xenon light source, we utilized the backup 2K rigid endoscope with a 300-W xenon light source as a second light source for illumination. In addition to achieving nearly the standard brightness of the laparoscopic image, we also increased the gain by 9 dB.
We succeeded in completing the two cases of cholecystectomy within the standard surgical time without switching to the standard 2K rigid endoscopic system. From the first and second patients, several gallstones with maximum dimensions of 18 mm and of 5 mm, respectively, were removed. Both patients left the hospital on the fourth postoperative day with the standard prognosis of Kyorin University Hospital.
With sufficient illumination, laparoscopic images with quite high resolution could be viewed
8K laparoscopic images were excellent in reproducing the appearances of solidity and reality
Vessels on the multilayer membrane around the bile duct and the gallbladder could be clearly recognized
Viewing of 8K laparoscopic images caused less eye strain.
Without sufficient illumination, the darkness and low quality of color reproduction of the images made laparoscopic surgery impossible
The large size of the 8K camera head interfered with the surgical field
The weight of the heavy 8K camera head made it difficult to hold in position even by two laparoscopists.
We achieved clinical success in the performance of 8K endoscopic cholecystectomy. In the experimental and clinical studies using our custom-built 8K endoscopic system, we were able to demonstrate the technological feasibility and clinical utility of the 8K UHD endoscope. 8K endoscopic imaging, compared to imaging by 2K imaging technology, is likely to lead to major changes in future medical practice in terms of the following viewpoints. First, 8K imaging displays true-to-life images of high reality that is able to reproduce the sense of looking onto the original field of view. Second, the 8K UHD endoscope enables reproduction with high resolution corresponding to super visual acuity (around 4.3) with pin-sharp, non-blurred images that make it possible to distinguish diverse tissue architectures which otherwise appear similar to each other and are easily confused. Notably, the spatial resolution was substantially higher in both the central and pericentral areas. This was noted in all areas of the display (85-inch) even near the periphery. Third, a particularly interesting point is that the 8K UHD endoscope with a built-in digital zoom function can be positioned to stay high up close to the abdominal wall of the intraperitoneal cavity, presenting a bird’s eye view of the operative field. This means that the tip of the endoscope does not need to come close to the organs and/or tissues undergoing surgery. Such positioning of the tip of the endoscope is expected to be effective in preventing the surgical devices and the endoscope from clashing into each other, allowing the surgeon more room to easily perform surgical maneuvers.
In conclusion, the 8K UHD endoscopy promises to open up new possibilities for intricate procedures including anastomoses of thin nerves and blood vessels as well as more confident surgical resections of a diversity of cancer tissues. As a result of the experimental and clinical studies using our custom-built 8K UHD endoscope, we have demonstrated the mechanical and engineering feasibility of the 8K UHD endoscope and its clinical utility. 8K endoscopic imaging, compared to imaging by the current 2K imaging technology, is very likely to lead to major changes in the future of medical practice.
HY is a corresponding author of this article, and in charge of optimal combination of a rigid endoscope, a lens adapter and an 8K UHD camera head, collection and assembly of the clinical cases, drafting of this article, and critical revision of this article for important intellectual content. HA is in charge of the planning and setting of the clinical cases. She operated the 8K UHD endoscope during cholecystectomy. KT is in charge of construction of the 8K UHD endoscopic system, collection and assembly of the 8K imaging resolution performance test, and adjustment of imaging performance of the 8K UHD endoscope during clinical cases. TM is in charge of final approval of the clinical cases, surgical operation of cholecystectomy and results of clinical evaluation. TC is a principal investigator of this study and in charge of final approval of the article. All authors read and approved the final manuscript.
Apart of this work was supported by Health and Labour Sciences Research Grants (H24-Area-Norm-007).
The authors declare that they have no competing interests.
Ethics approval and consent to participate
This feasibility study was performed with the approval of the ethics committee of Kyorin University Hospital (reference number: 597) and we obtained informed consent from the two patients before surgery.
Toshio Chiba received research funding from Health and Labour Sciences Research Grants. A part of this work was supported by Health and Labour Sciences Research Grants (H24-Area-Norm-007).
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