Introduction Traditionally angiographic Computed Tomography (CTA) is performed with varying contrast concentrations which can have limiting effects for simultaneous visualization of vasculature, implanted devices, and surrounding tissue. It is often challenging to window CTA images to visualize low attenuating brain parenchyma and high attenuating flow diverters or Onyx. Diluting the contrast would reduce the gray scale value on the vasculature and therefore allow visibility of tissue and vasculature simultaneously. However there are no guidelines on contrast dilution. Addressed here is a technique to reduce contrast and improve image quality in the presence of embolic agents and flow diverters.
Methods In this study, cone beam CT based computed angiographic imaging (20 s DR, syngo DynaCT, Siemens Healthineers, Forchheim, Germany) was performed on a Vascular Simulations Replicator (Stony Brook, NY) with 3D printed head that is composed of material that mimics a human head (phantom). Cone beam CT images of the phantom were acquired with contrast percentage varied between 0, 3, 5, 10, 15, 20, 25% with a constant flow rate of 3 ml/sec and 66 cc of contrast for both Pipeline (Stryker, USA) and Onyx embolic agent (Medtronic, USA). Average gray scale values were measured for all pertinent structures (parent artery, Pipeline or Onyx, Bone, Background) using region of interest (ROI) circles placed in relevant structures and contrast to noise ratio (CNR) was measured.
Analysis The attenuation in parent artery increases with higher contrast concentration for both pipelines and partially embolized AVM’s with Onyx. For visualization, the CNR scale values of the parent artery which match that of bone are ideal. Up to 15% dilution is adequate for visualizing Pipeline and its relationship to the parent and higher concentration of contrast (20%) is required to differentiate the residual AVM from the Onyx (figure 1).
Conclusion Contrast concentration affects the attenuation of various structures and needs to be varied depending on the goals of cone beam CT imaging to facilitate visualization of relevant structures simultaneously.
Disclosures J. DiNitto: 5; C; Siemens Medical Solutions. E. Duckworth: None. A. Cheema: None. T. Abuelem: None. A. Arthur: 2; C; Siemens. P. Kan: None. G. Chintalapani: 5; C; Siemens Medical Solutions.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.