An evaluation of computed tomography dose index measurements using a pencil ionisation chamber and small detectors

The aim of this study was to compare the values of the computed tomography dose index 100 (CTDI 100
) obtained using two small detectors (i.e. a small ionisation chamber and a small solid state
detector) with those obtained from a 100 mm pencil ionisation chamber for various input CT
parameters: beam width, kVp, mAs, pitch, and head-body phantom variation. The measurement of CTDI
100 using the 100 mm pencil chamber was carried out in a single rotation of axial mode, while the
measurement using small detectors was carried out in helical mode. The differences of CTDI 100
values obtained with two small detectors were about 7% for all variations. The differences of CTDI
100 values obtained with small detectors and a 100 mm pencil ionisation chamber for beam widths of
more than 4 mm were within 40%. However, for the narrowest beam widths (4 mm), the difference
between them was very large (about 150%).

Source: Journal of Radiological Protection - January 4, 2019 Category: Physics Authors: Choirul Anam, Toshioh Fujibuchi, Freddy Haryanto, Rena Widita, Idam Arif and Geoff Dougherty Source Type: research