Digital Tongue Figure Tongue Color Standardization Method

1 ObjectiveTo investigate ancient TCM study on the lateral and the bottom of tongue. Relevant records were selected from monographs written in and before Qing dynasty. In this paper, we are trying to solve present problems in analyzing digital tongue images. For example: if the tongue is covered by coating and the tongue color can not be seen, can we use the color of the lateral and the bottom of the tongue as a substitute? How to deal with the light reflected from the lingual surface when photographing the lateral tongue? How to transform relevant data of digital tongue images into non-digital color space? How to extract tongue color from digital tongue images and show it? Form the aspects mentioned above, we studied the standardization of the tongue color based on the theory and method of color science.2 Methods2.1 Theoretical researchMedical works written in and before Qing dynasty were reviewed; descriptions about the lateral and the bottom of the tongue were selected; methods used by ancient doctors to find the tongue color under fully covered coating were collected. From the aspect of modern anatomy, the relationship between lingual structure and color of the lingual surface, of the lateral and bottom of tongue were studied.2.2. Experimental research2.2.1 255 cases digital photographs of the lingual surface, the lateral and the bottom of the tongue were taken. Data on the tongue color of different portions of the lateral and the bottom of the tongue were collected. By calculating the chromatic aberration of different portions of the tongue, we tried to find out the distribution regularity of the tongue color.2.2.2 With mathematical technique, typical tongue colors were abstracted from several kinds of tongue color including pale tongue, combined pale and amphi-purple tongue, combined pale and amphi-dark tongue, red tongue, combined red and amphi-purple tongue, combined red and amphi-dark tongue. Then they were transformed into the Musell color system in which the distribution characters of these tongue colors were observed.2.2.3 Based on methods of computer programming, a program was designed for extracting tongue color data from tongue pictures and displaying the corresponding color block on computer screen.3.Results:3.1 Theoretical research3.1.1 Ancient TCM doctors considered the lateral tongue as an important part of the tongue body. Records of relationship between the lateral tongue and the spleen meridian appeared in Renzhai Zhizhi Fanglun written by Yang Shiying in song dynasty. When treating swollen tongue the ancient TCM doctors also pricked the lateral tongue to cause blood oozing. However the relationship between the lateral tongue and the tongue color had not been mentioned in ancient times.3.1.2 In ancient medical books not only the physiological structures like the vessels below the tongue, mucus under the tongue were recorded but also the pathological phenomena were described such as abnormity of the vessels below the tongue, tongue bleeding and tongue carbuncle. The tongue color was recorded in several ancient medical books; however these records were based on surgical therapy, conditions of the bottom of tongue and the state of the whole body was not connected.3.1.3 Dealing with thick coating through which the tongue color can not be seen, the method of scrapping the coating off to see the tongue color was discussed in Shanhan Guanshe xinfa written by Shen douhuan in Qing dynasty. After that many medical books recorded similar methods which suggested that ancient TCM doctors had looked for skills of observing tongue color under fully covered coating3.1.4 From the aspect of anatomy, the colors of the lateral tongue above and below horizontal ridgeline are the same because the muscles are the same and the mucus are similar. They have the anatomy basis of showing the same color.3.1.5 We marked different parts of the tongue body and ask the patient to stick out the tongue in different ways, we found that the portion above the horizontal ridgeline of the lateral tongue is the ordinary site we observe the tongue color when the tongue is horizontally stuck.3.2 Experimental research3.2.1 Comparing the tongue color of different portions of the lateral we found only the color of the middle part of the portion above and below the horizontal ridgeline of the lateral tongue are the same. Except that the difference among the color of other portions are significant.3.2.2 Comparing tongue color of different portions of the bottom, we found the distribution of color in the bottom of the tongue is complicated and no obvious regularity was discovered though the color is similar to the middle part of the portion above the horizontal ridgeline of the lateral tongue.3.2.3 We transformed the tongue color of the lateral portions from the CIELAB color space into the LCH color space and compared their characters. We found red is the main color of tip, the lightness of the root is lower than other parts of the tongue and there are statistic significance. The color of the middle portion of the lateral tongue is well-distributed3.2.4 Transforming the color of pale tongue, red tongue and their combination with other colors into the Musell color system we found the distribution of the color mentioned above is regular and it is easier to observe the characters of different tongue color in the Musell color system.3.2.5 A software was designed for extracting and displaying tongue color. It can extract tongue color data from tongue pictures and display the corresponding color block on computer screen.4 Conclusions4.1Theoretical researchAncient TCM doctors considered the lateral and the bottom of the tongue as important parts of the tongue body. But in clinical work, these two parts were mainly used for blood pricking, not for observing the tongue color as the lingual surface. Now, the anatomy structure of the tongue body suggested that the lateral tongue can be used for observing tongue color and worth further study. Meanwhile study color of the bottom of the tongue from multiple aspects can provide more methods for promoting the standardization of tongue color.4.2 Experimental research4.2.1 If the bottom was covered by thick coating and can not be seen, the middle part of the portion below the horizontal ridgeline of the lateral tongue can be used for color observation. In this way accurate tongue color can be obtained without interference of the coating4.2.2 Of the bottom of the tongue, the tip has similar color as the lingual surface although there are statistic differences between their colors. Study on the color of this part can probably suggest some regularity4.2.3 Transforming tongue color into the Musell color system, we can see the distribution of tongue color better. We proposed that research of the tongue color should be done in both digital color space and non-digital color space which is better for the standardization of tongue color.4.2.4 Computer system for extracting and displaying tongue color was created. We proposed that making standard electronic color card is an important step to the standardization of tongue color.