The MDCT parameters affecting radiation dose include tube voltage, tube current, change of beam collimation, and size
of the human body. The purpose of this study was to measure and evaluate radiation dose for MDCT parameters. A
comparative analysis of the radiation dose according to before and after the calibration of the ionization chamber was
performed. The ionization chamber was used for measuring radiation dose in the MDCT, as well as of CTDI<sub>W</sub> according
to temperature and pressure correction factors in the CT room. As a result, the patient dose of CTDI<sub>W</sub> values linearly
increased as tube voltage and current were increased, and nonlinearly decreased as beam collimation was increased. And
the CTDI<sub>W</sub> value which was reflected calibration factors, as well as correction factors of temperature and pressure, was
found to be greater by the range of 0.479 ~ 3.162 mGy in effective radiation dose than the uncorrected value. Also,
Under the abdomen routine CT conditions used in hospitals, patient exposure dose showed a difference of a maximum of
0.7 mSv between before and after the application of such factors. These results imply that the calibration of the ion
chamber, and the application of temperature and pressure of the CT room are crucial in measuring and calculating
patient exposure dose.
Number of radiologic exams using digital imaging systems has rapidly increased with advanced imaging technologies.
However, it has not been paid attention to the radiation dose in clinical situations. It was the motivation to study
radiation dosimetry in the DR system. The objective of this study was to measure beam quality and patient's dose using
DR system and to compare them to both IEC standard and IAEA guidelines. The measured average dose for chest and
abdomen was 1.376 mGy and 9.501 mGy, respectively, compared to 0.4 mGy and 10.0 mGy in IAEA guidelines. The
results also indicated that the DR system has a lower radiation beam quality than that of the IEC standard. The results
showed that the patients may be exposed higher radiation for chest exams and lower radiation for abdomen exams using
DR system. IAEA Guidelines were prepared based on western people which may be different weight and height for
patients compared them to Korean. In conclusion, a new guideline for acceptable DR dosimetry for Korean patients may
need to be developed with further studies for large populations. We believe that this research greatly help to introduce
the importance of the dosimetry in diagnostic radiology in Korea. And, a development of database for dosimetry in
diagnostic radiology will become an opportunity of making aware of radiation safety of medical examination to patient.