William Phelps Shuman MD, Presenter: Research Grant, General Electric Company

Janet M. Busey MS, Abstract Co-Author: Nothing to Disclose

Lee M. Mitsumori MD, MS, Abstract Co-Author: Nothing to Disclose

Eunice Choi BS, Abstract Co-Author: Nothing to Disclose

Kent M. Koprowicz, Abstract Co-Author: Nothing to Disclose

To evaluate dual energy CT (DECT) abdominal aortography performed with 50% iodine dose reduction and reconstructed at four spectral energy levels.

We prospectively performed DECT abdominal aortography in 8 patients utilizing a 50% reduced iodine dose compared to single energy CT aortography performed at a prior date with a routine dose of iodine. Axial and coronal 2.5 mm images were reconstructed at 40, 50, 70, and 77 keV. For each keV image set, HU density was measured at 7 intravascular levels and in muscle. Image noise was measured in subcutaneous fat. Two blinded reviewers working separately looked at the 32 randomized image sets and subjectively scored both aortic vascular enhancement and image noise.

Dual energy reduced iodine dose CT aortograms utilized an average of 22.8 grams of iodine, compared to 45.1 grams for single energy routine iodine dose CT. Average measured aortic density was highest at 40 keV (882 HU) with 50 keV next highest (579 HU) followed by 70 keV (284 HU) and 77 keV (233 HU)(p <0.001). Of the 224 vascular density measurements, 0% were below a threshold of 250 HU at 40 keV, 7% at 50 keV, 14% at 70 keV, and 61% at 77 keV. Contrast to noise ration was highest (22.1) at 50 keV. Subjective vascular enhancement was excellent or good at 40, 50 and 70 keV. Subjective image noise scores were significantly better for images reconstructed at 77, 70, and 50 keV compared to 40 keV (p < 0.001). Interobserver variability for subjective scores was good. Mean BMI was 24 ± 2.5 kg/m2. Mean effective radiation dose was 8.7 ± 2.9 mSv.

DECT aortography performed with 50% iodine dose reduction resulted in dense enhancement of the abdominal aorta. The contrast to noise ratio in the aorta was greatest at 50 keV.

DECT performed with 50% reduced iodine dose may result in acceptable abdominal aortography and thus  might be useful in patients with compromised renal function.

Shuman, W, Busey, J, Mitsumori, L, Choi, E, Koprowicz, K, Dual Energy Spectral CT Abdominal Aortography with 50% Iodine Dose Reduction:  Vascular Contrast HU Density, Noise, and Subjective Image Quality.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12028816.html