Utilization of X-rays in the medical field is one way to improve public health. X-rays are one of the applications of radiation for radio diagnostics. X-ray examination using X-rays can provide information about the human body without the need for surgery. In the use of radiation technology it is realized that in addition to its use for radio diagnostics, X-rays harm the environment and living things around them, especially radiation workers. The impact that can result in cancer due to the accumulation of radiation dose exposure received by the body exceeds the specified threshold dose. Therefore safety standard guidelines that contain basic requirements for quality control (Quality Control -QC) must be obeyed. One of the test activities included in the QC program is the linearity test of X-ray radiation output.

The image quality factor is not merely a matter of whether the image is repeated or not, but also has a wide range of information and also has to maintain the protection method for the patient is the reception of the dose due to radiographic action. So it is necessary to monitor the patient's dose using the EI value. The factors that determine the EI value are the exposure factor and the thickness of the object or BMI (Body Mass Index). Exposure factors (kV and mAs) are factors that have been commonly used as patient dose monitoring, where the tube voltage is a component that changes more often with a relatively constant tube current. The study used data on patients with Thoracic examination at the age of 20-65 years which were then categorized into BMI. The analysis was carried out on the EI value contained in the radiographic image. The results showed that BMI in the normal, Light Grade Fat (LGF), Heavy Grade Fat (HGF) categories, respectively, the EI values were 1562, 1679, and 1955 for the female sex, and 1266, 1600, and 1821 for the male gender.  Significantly (P?0.05) the EI value showed difference between female and male sexes.