Pooyan Sahbaee, Presenter: Nothing to Disclose

William Paul Segars PhD, Abstract Co-Author: Nothing to Disclose

Ehsan Samei PhD, Abstract Co-Author: Research Grant, Siemens AG Research Grant, General Electric Company Research Grant, Carestream Health, Inc

To quantify the radiation dose variation as a function of time due to the contrast medium (CM) administration in multiphase liver CT scan across a library of 5D XCAT models. 

The dose estimation was performed on a library of 58 adult extended cardiac-torso (XCAT) models. To generate the 5D XCAT patient models, a unique method was developed to incorporate the dynamics of CM propagation into our 4D XCAT (as demonstrated in our prior work, the fourth dimension reflects the heart and respiratory motions) anthropomorphic models. The models were created based on patient-specific iodine concentration-time results from our computational CM propagation computer model for different injection protocols, such that each organ in a patient model subjected to a specific injection protocol was assigned to its own unique CM time-concentration curve. The radiation dose to individual organs in the models was estimated from a four-phase (pre-contrast, arterial, portal venous, and delayed phases) liver CT examination modeled via a validated Monte Carlo simulation software package (PENELOPE). For each scan time point after the injection, 80 million photons were initiated and tracked through the phantoms. Finally, the dose to the liver was tallied from the deposited energy.

The liver CT scan simulation results from 5D XCAT models subjected to a commonly used injection protocol (120 mL of 350 mgI/mL CM at 4 mL/s) indicated up to 10%, 32%, and 24% increases in radiation dose delivered to the liver for arterial phase (to 9.45mGy), portal venous phase (to 11.29 mGy), and delayed phase (to 10.65 mGy), respectively.  

Administration of contrast medium in enhanced CT scan not only remarkably affects the CT image quality (thus the reason for its use), but also notably increases the radiation dose. Particularly, multiple acquisitions in several enhanced CT protocols accentuate the radiation dose as a critical objective in optimization of the protocols.

The study aimed to provide a methodology to incorporate the contrast medium propagation in XCAT models, thus building toward an opportunity to optimize radiation dose and injection protocol in concert.

Sahbaee, P, Segars, W, Samei, E, Multi-phase CT: Impact of Contrast Medium Propagation on Radiation Dose across a Population of Patient Models.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005695.html