## 1 Introduction  
Radiation measurement and monitoring are some of the vital aspects of medical radiation. In this manner, the exposure of radiation to workers in radiology departments should be continuously monitored. This ensures that the workers' absorbed radiation doses are kept below the acceptable limits. Likewise, radiation applied during imaging and treatment procedures should be measured routinely to ensure the accuracy of doses delivered to the patients.  
Conventional methods in medical radiation measurement include ionization chambers, film badges, electronic dosimeters, and thermal luminescence diodes (TLDs). Current medical radiation measurement methods employ optical material for optically stimulated luminescence (OSL) [1; 2] and photonic devices such as photodiodes, photovoltaic sensors, phototransistors, lasers, and cameras (charge-coupled devices, CCDs/complementary metal-oxide-semiconductors, CMOSs). Photonic/optical devices are electronic components specifically utilized for emitting, detecting or manipulating light [3]. Photodiodes have been exploited for diagnostic radiology dosimetry [4; 5; 6; 7] as well as gamma radiation detection and measurement [8; 9; 10], phototransistors/MOSFETs for gamma-ray detection [11; 12] and radiation dosimetry [13; 14; 15], photovoltaic sensors for medical dosimetry [16; 17; 18], and CCD/CMOS cameras for Cerenkov luminescence imaging (CLI) in nuclear medicine [19; 20; 21], radiotherapy [22], and biomedical sciences [23; 24].  
However, the performance of current photonic devices implemented for radiation measurement deteriorates due to radiation-induced damage/defects [25; 26; 27; 28], leading to photonic device output degradation [29; 30; 31]. Although a light-emitting diode (LED) can detect electromagnetic (EM) radiation, a lot of research is focused on LED as a luminary--for instance, in phototherapy and photodynamic therapy (PDT) [32; 33]. There is limited research about the application of LEDs to the detection of EM radiation. Furthermore, LEDs could demonstrate better radiation hardness compared to other photonic devices such as photodiodes [34; 35]. This could imply that when used as radiation detectors, LEDs could withstand higher radiation doses without any degradation in output reading. LEDs are also flexible; they come in the form of surface mount devices (SMD) or chip on board (COB), and are five times cheaper than photodiodes [36].  
Connecting current across an LED terminal excites electrons situated in valence bands to conduction bands. During de-excitation, electrons lose their energy and fall back to the valence bands by emitting photons of light energy. To emit a specific color/wavelength, a combination of different elements and materials are used in the fabrication of LEDs.  
LEDs are semiconductor devices that consist of a PN junction in their active/sensitive layer [3; 37]. Whereas negative charges (electrons) are localized in the N region, positive charges (holes) are in the P region. When EM radiation is incident on a PN junction, electrons absorb packets of EM radiation (photons) and drift to recombine with the holes. Electron drift implies a quantifiable current that could be correlated to the EM radiation incident on the PN junction. In our study, a multimeter connected across the LED terminals displays this current in the form of voltage hence the term current-voltage (C-V) signal is used.  
LEDs of different colors are composed of distinct materials and elements. Because a particular wavelength range implies a specific color, in addition to the core PN junction component of the LED active region, phosphor layers are coated on sensitive areas to adjust the emission colors of LEDs [37]. Variation in LED structural components could hence imply a difference in the C-V response of LED strips to x-rays. Thus, our study was conducted to investigate the C-V response of five LED strips (emitting cold white, warm white, red, green and blue respectively) to low dose x-rays of the dosimetric ranges usually used in diagnostic radiology.