Huong Tran MS, Abstract Co-Author: Nothing to Disclose

Choonsik Lee PhD, Abstract Co-Author: Nothing to Disclose

Vana M. Derderian BS, Presenter: Nothing to Disclose

Les Roger Folio DO, MPH, Abstract Co-Author: Nothing to Disclose

Elizabeth C. Jones MD, Abstract Co-Author: Nothing to Disclose

To develop and apply a CT radiation dose estimation method accounting for IV iodinated contrast in computational phantom-based Monte Carlo simulations for more accurate scan and organ-specific radiation dose. We assessed the impact of time-dependent contrast phase and tube voltage (kVp) on organ radiation dose in multiphase body CT.

An adult male computational phantom and CT scanner modeling within Monte Carlo n-particle extended (MCNPX2.6) code simulated x-ray photon interactions for a standard clinical Contrast-Enhanced body CT (CECT). Elemental composition of chest, abdominal and pelvic organs was adjusted to reflect the addition of iodinated contrast media (Isovue-300™) using predicted pharmacokinetic data of body contrast distribution. We modeled contrast phases (non-contrast, arterial, venous) at 120, 100 and 80 kVp; organ dose estimates were obtained with 2.6 million simulations on a supercomputer cluster.

Estimated organ dose showed greatest increase at the 120 kVp venous phase (absolute change: 1.9-10.3 mGy) in kidneys (361%), adrenals (379%), spleen (266%) and colon (228%) compared to non-contrast. Overall dose reduction was shown at lower kVp (100kVp: 37%, 80kVp: 73%) in all phases with largest magnitude of dose reduction in the same abdominal organs. Average dose increase was 15% from non-contrast to arterial and 84% continuing to venous. Lowering kVp reduced doses to near (100kVp) or below (80kVp) the non-contrast dose. Pelvic and thoracic organs received predicted radiation scatter.

Iodinated contrast increases organ radiation dose proportional to iodine accumulation and elapsed time, with the highest doses received by kidneys, adrenals, spleen and colon in the venous phase. Reducing organ doses by lowering kVp is effective in the presence of iodinated contrast media in all phases. Inclusion of iodinated contrast in radiation dose assessment is warranted.

Though clinical significance is currently unknown, increased x-ray absorption and energy deposition linked to tissue concentrations of iodinated contrast media increases non-uniform radiation dose distribution to organs during CT scanning. This can be accounted for by computational phantoms, allowing scan and patient-specific modeling which more closely approximates routine clinical CT scanning.

Tran, H, Lee, C, Derderian, V, Folio, L, Jones, E, Estimating the Role of Iodinated IV Contrast Media in Organ Radiation Dose: Effects of Vascular Phase and Tube Voltage in Multiphase Body CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014735.html