The development of multi-detector computed tomography (MDCT) scanners has contributed to the swift acquisition of highly detailed three-dimensional images that were formerly unobtainable from the single-detector CT (SDCT) devices. Obtaining more detailed image data inevitably causes an increase of X-ray dose, and that varies with, the scanning procedures and type of devices. We measured the X-ray doses from currently used CT devices (60 devices in 50 facilities) for scans of the head and abdomen. X-ray dose evaluation was performed by using the CTDIvol indicated in the IEC standards. An ionization-chamber CT dosimeter corrected to the national standard was used to the dosimetry of X-ray, and acrylic cylinders of diameter 16 cm for head scanning and 32 cm for abdominal scanning used as the phantoms. The results showed that the CTDIvol obtained by using air kerma in PMMA was an average of 62.48 mGy for head scans and 16.76 mGy for abdominal scanning. The difference of the CTDIvol between facilities was around to three standard deviation for both head and abdominal scanning. The X-ray dose was greatest for eight-row devices, and did not increase substantially even for 16-row and 64-row multi-detector devices. On the contrary, it showed a tendency to decrease.
