Room: AAPM ePoster Library
Due to tube power limitations, low kVp scanning is typically limited to pediatric and low BMI patients. This study investigates the potential of a high power tube to reduce the kVp and dose for different patient sizes.
A water-equivalent phantom with contrast inserts, adaptive to three patient sizes (small (20x20cm), medium (35x25 cm), large (38x30 cm)) is scanned on a 256slice CT (Revolution CT, GE Healthcare) with a high-power tube. CT data was acquired using a reference clinical abdominal protocol (120 kVp and noise index 18) and with manual settings across an anergy range of 70-140 kVp and a tube current range of 30-1300 mA, and reconstructed with ASIRV50. Mean CT values and standard deviations were measured in the contrast inserts to derive the contrast-to-noise ratio (CNR) for all image data sets. Radiation doses and CNR values were compared to those of the clinical reference to find dose optimized kVp settings.
For the clinical abdominal scan, the reference contrast was 130 HU with a CNR of 6.7. For the high-power tube, the dose optimized kVp’s to preserve this CNR were 70, 80, and 100 kVp for the small, medium and large phantom, respectively, resulting in CTDI dose reductions of 92%, 50% and 7% compared to a 120 kVp scan. The corresponding mA values level with and exceed the max mA values of the standard clinical tube for the medium and large phantom, respectively.
Compared to standard CT tubes, high power tubes with low-kVp high-mA combinations allow to shift the acquisition kVp further towards lower kVp levels for medium to large sized patients, with important radiation dose reduction.