[Report on the 89th Scientific Assembly and Annual Meeting of the Radiological Society of North America--analysis of radiation dose by a change of a scan parameter of multi-slice computed tomography by a film method].
OBJECTIVE
It is for a purpose of this study to measure radiation dose by analyzing a dose profile of multi-slice computed tomography varying with helical pitch and a row slice thickness difference complicatedly.


METHODS
We used multi-slice computed tomography, and helical pitch and row slice thickness change and scanned the helical scan. I used CTDI phantom of a diameter of 25 cm and I inserted roentgen diagnosis use film UR-2(new) which I put between my own phantom in center and 1 cm away from the outer surface and scanned it. And the provided level profile was converted into a dose profile with the dose-density curve which I made beforehand. I analyzed radiation dose than the dose profile.


RESULTS
In multi-slice computed tomography, radiation dose varied with assembly of row slice thickness and helical pitch. The change of a dose profile changed in a phantom surface part complicatedly. The maximum dose by the measurement of this time was 29 mGy in row slice thickness 0.5 mm, assembly of helical pitch 2.5. In addition, the minimum dose was 6.8 mGy in row slice thickness 3.0 mm, assembly of helical pitch 5.5. And, as for the difference of maximum dose in the same dose profile and the smallest dose, there were about 20 % in row slice thickness 1.0 mm, assembly of helical pitch 5.5.


CONCLUSIONS
The dosimetry of multi-slice computed tomography by a film method enabled it to measure a change of a dose profile by a difference of a scan parameter by high interest solution ability. In addition, it is a method more superior in dosimetry of multi-slice computed tomography spreading through a Z-axis direction broadly than determination by computed tomography use ionization chamber dosimeter. Because radiation dose increases by a scan in thin row slice thickness and small helical pitch, care is necessary.
Akagi
Noriaki
N
Central Division of Radiology, Okayama University Hospital.
Ohkawa
Y
Y
Kadohisa
S
S
Nakagiri
Y
Y
Hiraki
Y
Y
D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*