The purpose of this study was to establish a specific test method for dosimetric characterization of wide-beam computed tomography (CT). For a wide beam, the dose distribution curve and the area of the curve were obtained by using pencil-like ionization chamber, a long CT dose profiler probe, a head phantom and a body phantom. The absolute dose conversion coefficient was multiplied to obtain the total integration integral of the absolute dose distribution, and then the computed tomography dose index (CTDI) value under any wide beam condition was obtained by dividing the collimation width. It was calculated that the absolute dose conversion coefficient was 1.135 under the narrow beam of 8 mm. To a 160 mm-wide beam, the value of CTDI was 7.57 mGy/100mAs after normalized in the head 80 kV CT scanning, and it was 9.80 mGy/100mAs after normalized in the body 120 kV CT scanning. The specific test method solves the problem that the previous measurement method underestimates the CTDI value.
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