With the enhancement of national income level, the number of computed tomography (CT) exams to diagnose
diseases is increasing more and more. To utilize the data for the safety control of X-ray, the image quality of the
environmental radiation at the boundaries in the radiation zone of the exam rooms by type of CT using highenergy
electromagnetic wave. The locations of the environmental radiation measurement were shielding wall of
the door for patients, door for patients, door to CT control room, shielding wall of the door for CT control
room, and window to see the patients, and the glass dosimeters were installed 150 to 170 cm above the floor
considering the location of the device to be measured for 3 months and analyzed. The environmental radiations
in the MDCT room were measured with 3.09 ± 2.31 mSv, 0.51 ± 0.12 mSv, 0.99 ± 0.43 mSv, 0.27 ± 0.03 mSv, and
0.18 ± 0.03 mSv at the door to the control room, the wall of the control room, door for patients, door wall, and
window to see the patients, respectively. In the mobile CT room, the radiation was detected only at the door of
the control room with 1.65 ± 0.15 mSv, and no radiation was detected at the other boundaries. In the PET-CT
room, the radiations were detected with 0.18 ± 0.03 mSv and 0.27 ± 0.03 mSv at the door and door wall, respectively,
without detection at the other boundaries. Upon the results of image quality by CT devices, very satisfactory
outcomes were found in terms of contrast, clarity of the boundaries, and detection rate of lesions in all the
acquired images, and also very satisfactory in the functional evaluations of the organs in PET-CT only. These
results are anticipated to be used as the reference data to establish the systemic and efficient systems and policies
in the safety control of X-ray in the future.