For several years ISIS/SurgiMedia has been offering a full range of 4K-compatible video management solutions, but what is 4K really ? and what is his actual contribution to an operating room, an endoscopy room or an interventional room?
The 4K label : if HD is known to be the acronym for High Definition, 4K is not an acronym but corresponds to a digital image format whose definition width is close to 4000 pixels (light points), so 4000 = 4K !
Resolution and format : this image resolution is more precisely 3840 horizontal and 2160 vertical pixels and is also known as UHD (Ultra High Definition). Without taking into account the 4K DCI format (mainly used in the world of cinema). The resolution (Full) HD is 1920 x 1080 (by analogy it would be 2K HD), the resolution 4K UHD being 3840 x2160, it is therefore 4 times higher, the remaining 16/9th display format.
Color rendering : If, for 4K displays, resolution is often the important data, this is not the only one. The color 'rendering' or color 'depth' is also a major parameter. Each light point (pixel) is composed of three ‘sub-pixels’, one red (R), one green (G) and one blue (B), each of which can be coded to 8 or 10 bits, resulting in an encoding (or depth) of 16.8 million (8 bits) or one billion (10 bits) of color.
Unfortunately, the human eye does not perceive all these shades of color and, in order to gain (yet) color perception, specific encoding has been developed for 4K and 8K resolutions by combining 10 or 12 bits square pixel encoding with a new, wider color space : Rec. 2020 (or BT.2020).
What is the actual surgical intake of 4K ? : As with HD more than 15 years ago, the ‘4K’ mainly disrupted endoscopic surgery because the increased quality (4x) of the surgical image now made it possible to use much larger display monitors and, in the opinion of surgeons, a “striking” vision with (at least for some) a feeling of immersion in the image. The sharpness and fineness of the display provides a “3D effect” that improves the differentiation of organs and tissues allowing decision facilitation for surgical planes. The color rendering, also significantly improved, allows to better differentiate the malignant tissues from the healthy ones and, thus, facilitate resections or biopsies.
For “open” surgery, nothing that can replace the surgeon’s direct vision of the surgical field, the contribution of 4K vision from a camera is especially predominant for the rest of the surgical team, the instrumentalists, anesthesiologists or scrub nurses who can follow the progress of the procedure on a monitor with the best possible image quality.
Another medico-surgical area where 4K has been used for many years without even really being aware of it is in interventional or hybrid rooms. Indeed, the need to display several sources of information simultaneously on the same (large) screen, with the best possible definition for each of the sources, quickly forced manufacturers to choose ‘large’ 8 million pixel tiles.
Apart from these display systems were actually 3840 x 2160 (=8.3 MP) resolution monitors, it was just exactly 4K !
Caution ! There is, however, an important technical limitation that must always be borne in mind when wishing to transmit and display 4Ksources: indeed, as for the adage “a chain is as solid as its weakest link”, ensure that each of the “links” (video sources, connectors, cables, boosters, encoders, switches, decoders, monitors, etc.) between the source and the display have the best compatibility characteristics with the 4K signal to be transmitted.