Population dose from medical exposure in Taiwan for 2008

The largest contribution to the population dose from man-made ionizing radiation sources is the medical exposure. Exposure to patients from medical examinations is of interest because it is a global indicator for the quality of radiology practice. Due to the different healthcare systems and the considerable variations in the equipment and manpower in radiology, the population dose from medical exposure varies by a large extent in different countries. This dose from different diagnostic procedures provides information that can be used to establish national reference levels. It is also useful to determine the priority in terms of dose reduction so as to optimize the protection of patients in a cost-effective manner. In the present work, the collective effective doses due to different medical modalities were estimated for the Taiwan population in 2008.

The collective effective dose from medical exposure was calculated using information on the number of procedures and the average effective dose per procedure. The frequency of procedures was extracted from the National Health Insurance (NHI) research database. The enrollment of Taiwan population in the NHI program was 99.48% in 2008. The average effective dose per procedure was derived from hospital surveys, measured data, and published results.

Estimates of the collective effective dose were made for different medical modalities, i.e., the conventional radiography and fluoroscopy, computed tomography, interventional fluoroscopy, nuclear medicine, and dental radiography. Each modality was further divided into relevant classes by the body part or organ system. Among 23 037 031 Taiwan population in 2008, the annual examination frequencies per 1000 population were 550, 55.1, 15.6, 13.6, and 112 for the conventional radiography and fluoroscopy, computed tomography, interventional fluoroscopy, nuclear medicine, and dental radiography, respectively. The corresponding collective effective doses were 3277, 8608, 2743, 2303, and 28 man-Sv, respectively. Thus, the average effective dose per caput was 0.74 mSv, which was in the range of 0.3-1.5 mSv for the 12 European countries estimated for 2008.

In the period from 1997 to 2008, the procedure frequency per 1000 population increased by a factor of 2.3 for computed tomography, 2.2 for interventional fluoroscopy, 1.8 for conventional radiography and fluoroscopy, and 1.5 for nuclear medicine. It demonstrated that the medical utilization of imaging facilities raised rapidly.