# Application of Visual Radiographic Analysis of Quality Grade of Table Eggs
## 1 Introduction  
The structure of eggs mainly constitutes the shell, yolk, albumen, and air cell [1]. Currently, the quality of eggs on the market is graded according to the US Department of Agriculture based on the appearance and internal characteristics of the eggs. Using the standards for the interior quality of chicken eggs by camdling, with the air chamber, egg albumin, egg yolk, and spots as the basis of grading, the four grades applied are AA, A, B, and inedible [2]. The quality of eggs also varies with storage time and the way of raising the laying hens [3]. The European Union established the Welfare of Laying Hens Directive in 1999. Eggs are graded as 0-Organic, 1-Free Range, 2-Barn, and 3-Caged. Different housing systems have impacts on egg production performance [4, 5] and the health of hens [5, 6] leading to the egg qualities. This information is printed on the outer packaging of the eggshell, and makes a difference in the quality and market pricing [7]. The analysis of egg quality is mostly based on physical measurements, such as grading the interior quality by candling, calculation from a Haugh unit conversion, shell thicknessmeasurement, shell strength measurement, yolk and albumen egg quality measurement, and spectrum analysis. Egg quality inspection by candling is tedious and subjective and is not a scientific way to ensure egg quality. In studies related to the nondestructive detection of egg quality, near-infrared spectroscopy (NIR) has been one of the fastest-developing spectral analysis techniques since the 1990s. With a fast analysis speed and high efficiency, it is widely used in non-destructive detection and analysis. It is commonly used for quality control of agricultural products such as meat, fruits, and vegetables. [PERSON] et al. suggested that visible/near infrared reflectance (VIS/NIR) transmission spectroscopy is a good tool for evaluating the freshness and protein pH of eggs and can be used as a non-destructive detection method for predicting the Haugh unit (HU), albumen pH, and storage days. The authors indicated that the wavelengths of VIS and NIR range from 411 to 1729 nm [8]. [PERSON] et al. combined Raman technology with chemometrics to predict the freshness of eggs by scanning the top, waist, and bottom of the shell surfaces. Their study showed that the Raman spectrum of the shell surface is strongly correlated to its freshness. Furthermore, the model using the top of the eggs was determined to be the best [9]. [PERSON] et al. used a non-destructive ultrasonic method to create an evaluation model for the prediction of egg freshness. It can predict the Haugh unit, albumen thickness, air cell height, and storage time by calculating the ultrasonic phase velocity in the egg, and it was observed that the amplitude of the main peak of the ultrasonic signals increases with an increase in the days of storage. Furthermore, there is a significant difference between the average phase velocity obtained at different times [10]. Using the principle of radiography, by controlling the basic exposure controlling factors of kVp and mAs to produce ionizing radiation X-rays of different intensities, imaging is conducted based on the linear attenuation coefficients of different substances and the absorption intensity of the ionizing radiation [11]. Over time, the radiography technique has evolved from traditional film radiography to the current era of digital high-resolution X-ray imaging [12,13]. The receiving method of the radiation signals has also developed from traditional gray-scale film imaging to a multi-layer photometric interpretation of monochrome gray-scale imaging established through a globally standardized format under the Digital Imaging and Communications in Medicine (DICOM) standard [14,15]. The analysis of X-ray images has also evolved from intuitive visual diagnosis to the analysis of gray-scale image data using the region of interest (ROI) and threshold [16,17].