# Feasibility of Magneto-Encephulography Scan under Color-Tailored Illumination
## 2 Experimental  
The LUME-20R lamp has 20 LEDs grouped into four colored clusters, with each cluster made of five LEDs. These four colored clusters are red, green, blue, and amber. A four 10-bit pulse width modulation channel controls the fluxes generated by each group of LEDs [6]. The LUME-20R lamp uses LEDs from LUMILEDS LUXEON Rebel family with peak wavelength 452 nm (B), 523 nm (G) InGaN LEDs, InGaN-based phosphor converted amber LED at 589 nm, and direct-emission AlGaInP LED at 637 nm (R) [6]. The lamp can be controlled by setting specific values of hue, saturation, and brightness (or value) (HSV) presented as a color cone (see details on conversion of the color coordinates in Appendix A). Hue is the term which defines a dimension of color, with specific wavelength, while brightness defines the lightness or darkness of the color, and saturation defines the intensity of the color [11]. The HSV is widely used in computer graphics and printing applications. Hue denotes the angular dimension starting from red at 0\({}^{\circ}\) and passing through green at 120\({}^{\circ}\), blue at 240\({}^{\circ}\), and back to red at 360\({}^{\circ}\). The brightness (or value) evolves along the axis of color cone, with 0 representing black, and white has the value of 1. The radial dimension of the cone is saturation, which gives a pure color at 1 (at the outside edge of the color cone) and \(S\) = 0 at the center of cone (on its axis).  
The aim of this project is to control the LUME-20R LED (Ledigma Ltd., Vilnius, Lithuania) bulb from outside the EM-shielded room (Figure 1). The main reason to select this bulb is that it has a capability to change lighting parameters quantitatively and qualitatively, such as CSI and CFI. This LUME-20R LED bulb can be controlled only via Bluetooth. However, the Bluetooth communication is not applicable due to the bulb being located inside the EMshielded room. Therefore, it requires a wired method to communicate and to control the bulb from the outside-shielded MEG room. Figure 1 shows a block diagram of the organization of the devices used in this study (Figure 2).  
Protocol. The MEG scanner is very sensitive to magnetic fields. Therefore, to verify the impact of the four-color LED lamp (LUME-20R) and its control software on the MEG scanner, an initial test was conducted with the help of a MEG expert team. At this stage, eight different combinations of MEG scanner data were measured over a minute period. Those combinations were used to test the changed condition of MEG operation and the reference. The main tests were the following combinations: (1) empty the MEG scanner itself, (2) have the MEG scanner have a person inside (a normal operation), (3) put a person inside the MEG scanner with a candle light, (4) MEG scanner with a candle light (5), and MEG scanner with primary color lights at a time (RGB+Amber); values obtained were 1500 K (candle light), 3500 K (halogen), and 6500 K (daylight).  
The person has to sit in the MEG scanner to measure brain magnetic fields during the session, with different (in color) lighting conditions defined by the LED lamp (Figure 1).  
Figure 1: A magneto-encephalography (MEG) brain scanning experiment carried out with four-color RGBA (amber is added) illumination; the Elekta/Neuromag 306 channel MEG system was used. Different illumination was defined as: saturation, preferential, natural, and dulling [6], which were selected by RBGA mixture from the CIE 1931 chromaticity diagram; the preferential illumination was patented. The LUME-20R lamp was used in this study; its control via USB connection and the user interface were developed in this project (see details in Figure 2). Photo: C.W. in MEG scanner and W.W. setting MEG up.  
Figure 2: LUME-20R Bluetooth connection (**a**) and wire connection for USB communication (**b**).