The contrast of iodine to soft tissue (water) decreases with higher tube voltage in reconstructed 3D X-ray images.
Improved acquisition protocols with a tube voltage of about 80 kV for imaging iodine have been proposed earlier for
diagnostic CT imaging. We investigate the contrast-to-noise ratio (CNR) and the CNR-to-dose ratio (CDR) for different
concentrations of iodinated contrast agent inserts in water background. The tube voltage of the protocol is lowered from
123 kV to 83 kV in 10 kV steps. Measurements with 16 different settings of tube voltage, current and Copper (Cu) filter
settings are investigated. The weighted computed tomography dose index (CTDIW) for the new protocol settings is
Four protocols with tube voltages between 83 kV and 103 kV and similar X-ray dose are compared to the original
protocol. An iodine-water contrast phantom, containing a water filled cylinder with 5 tubes of different mixtures of
iodine contrast agent inside a 32 cm PMMA ring, is imaged with each protocol. Increased contrast of the iodine filled
tubes to the water background is clearly visible in the reconstructed volumes for lower tube voltage and less copper
filtering. The CNR increased by about 100% for the 83 kV protocols compared to 123 kV and the dose utility in terms of
the CDR even by 350%. The best results are obtained with the (83 kV, 561 mA, 0.4 mm Cu) - protocol. This protocol
may improve iodine contrast agent visibility in various 3D imaging applications. For large patients a higher tube voltage,
e.g. the (103 kV, 325 mA, 0.4 mm Cu) - protocol, may be used to avoid tube power limitations at 83 kV. This protocol
still has improved iodine contrast compared to the 123 kV protocol and a larger tube power reserve.