Nipple Temperatures in Breast Thermography
Objective: Since the advent of microbolometer infrared imagers that allow qualitative and quantitative nipple temperature assessment, peer-reviewed guidelines have stated that normal differential nipple temperatures should not exceed 1.0 °C. This study is designed to examine the validity of this and other nipple temperature measurements in a clinical breast thermography population. Methods: 211 women between 27 and 83 years of age underwent standard breast thermography. Images of 422 breasts were taken and analyzed. Average area temperatures were obtained for both the breasts and nipples. Besides analyzing the combined data from all subjects, three subsets of data with different Thermobiological (TH) evaluations and a subset of women with bilateral breast implants were analyzed. Results: Absolute breast temperature declined about 1°C from age 27 to 83. Nipple temperature was unaffected by age. A strong correlation was found between ipsilateral breast and nipple temperatures. Nipple temperatures were cooler than the breast in 93.8% of 422 samples. Nipple temperature increased relative to the breast temperature as the TH evaluation increased. Average right breast and nipple temperatures were warmer than the Left in all data sets. Nipple temperature difference tends to rise faster than breast temperature difference. As the TH evaluation increased, differential breast temperatures remained constant while nipple differentials increased. Women with breast implants were found to have the least variation in breast and nipple temperatures. Conclusions: Normal nipple temperature is less than breast temperature by an average of 1.1°C. A cutoff value for maximum nipple temperature difference is graphically confirmed to be 1.0 °C. Maximum breast temperature difference cutoff is 0.5°C, and a vector sum of these differences should be less than 1.5°C. Nipple temperatures are controlled by sympathetic neural tone and by local nitric oxide concentration. Lactiferous duct infection and intraductal tumors (DCIS) increase intraductal NO, which is directed up the duct to the nipple. Increased nipple temperature may signal the presence of breast pathology.
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