AbstractID: 7474 Title: Influence of Phantom Diameter, kVp and Scan Mode upon CT Radiation Doses
According to the AAPM protocol, CT radiation doses are measured with a 16 cm
acrylic phantom to represent an adult head and a 32 cm acrylic phantom to
represent an adult body. Recently the CT radiation doses to pediatric patients has
received considerable attention. Hence it is important to understand the
dependence of the CT radiation dose upon the size of the phantom, the kVp selected
and the scan mode employed.
This presentation will examine the relationship between the CT radiation dose and
the phantom size for a variety of different CT scanners. Data will be presented for
phantom sizes ranging from 6 cm to 32 cm. X-ray tube potential from 80 - 140 kVp
were utilized for the measurements. The scan modes utilized for the measurements
included: consecutive axial scans, single-slice helical scans with variable pitch and
multi-slice helical scans with variable pitch.
The results are consolidated into simplified equations which related the phantom
diameter and kVp to the measured radiation doses. Some generalizations are made
about the relationship between the scan modes of the various CT types to the
measured radiation doses. Finally, this information is used to estimate pediatric
CT radiation doses for modern units.