Dawn Renae Engelkemier MD, Presenter: Nothing to Disclose

Afshin Karimi MD, Abstract Co-Author: Instructor, Heart Imaging Technologies, LLC Research agreement, General Electric Company

To demonstrate the adequacy of low volume contrast enhanced CT for thoracic imaging. Utilizing a total volume of 15 mL of contrast in an average size patient, reasonable quality diagnostic images can be obtained.

Selected patients who were referred for routine clinical imaging with intravenous contrast were protocoled to receive low volume contrast CT if there was a relative contraindication to iodinated contrast. Relative contraindications included renal insufficiency (GFR of 30-59, CR 1.2-1.7) and history of non-life threatening reaction to compounds other than iodinated contrast. Using 100 Kv technique and smart prep (GE Wisconsin, USA) with minimum delays, a contrast enhanced chest CT was performed with a 50/50 dilution of Optiray 350 given at 3 mL/sec in a volume of 30 mL. The pulmonary artery was used as bolus trigger with threshold Hounsfield of units of 100 HU. A 30 mL saline chaser was used in the second part of the injection. Smart MA technique was utilized.

Adequate opacification of the aorta and pulmonary artery was obtained with the injection protocol described.  No adverse reactions were reported. All studies were diagnostic for thoracic imaging analysis. In cases where a large mass was involved, a lesser degree of mass/parenchyma enhancement was achieved. There was relatively decreased enhancement of the upper abdomen, particularly liver, which was not the primary focus of the exam. Due to the dynamic nature of the contrast bolus, a few cases of mixing artifacts presenting as venous filling defects were identified. The use of 100 kV technique produced greater enhancement of vascular structures at a lower overall radiation dose to the patient.

Use of low volume contrast reagent provides adequate soft tissue enhancement for lymph node/vascular delineation within the mediastinum and can yield diagnostic contrast enhanced thoracic CT for most routine clinical applications. Although no allergic contrast reactions occured in the selected cases, allergic contrast reactions are idiosyncratic and unpredictable.  Lower volume contrast dose can be helpful in thoracic imaging of patients who may be at risk for iodinated contrast induced renal insufficiency.

Lower contrast volume may be a potentially safer imaging strategy for patients with relative contraindications to iodinated contrast, but who would benefit from contrast enhanced thoracic CT imaging.

Engelkemier, D, Karimi, A, Low Volume Contrast-enhanced Thoracic CT as an Alternative Imaging Strategy.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9009379.html