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AJNR - American Journal of Neuroradiology

Published ahead of print on April 10, 2008
doi: 10.3174/ajnr.A1073

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Multiphase CT Angiography versus Single-Phase CT Angiography: Comparison of Image Quality and Radiation Dose

C.-Y. Yang^a, Y.-F. Chen^a, C.-W. Lee^a, A. Huang^a, Y. Shen^b, C. Wei^b and H.-M. Liu^a

^a Department of Medical Imaging, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
^b General Electrics Yokogawa Medical System, Tokyo, Japan

View larger version (118K): [in this window] [in a new window]   Fig 1. Sequential images of MP-CTA are displayed to show the flow dynamics of a patient with suggested stroke. The right MCA is not initially enhanced in the early arterial phase, and opacification of the distal branches of the right MCA via the collaterals can be appreciated later. The temporal sequence of enhancement also helps differentiate arteries and veins (window/level = 1000/100).

View larger version (99K): [in this window] [in a new window]   Fig 2. Sequential images of MP-CTA are displayed to show flow dynamics of a case of DAVF. Increased early draining veins around the left Sylvian fissure, as well as the mildly engorged deep venous drainage, could be observed on the left side (window/level = 1000/100).

View larger version (9K): [in this window] [in a new window]   Fig 3. Graph shows CT number as a function of iodine concentration. A, The linear relationships for 2 tube-voltage settings are as follows: at 80 kVp/180 mAs, y = 43.25x + 48.05 (r = 0.997); and at 120 kVp/350 mAs, y = 27.55x + 24.00 (r = 0.996). B, The relationship between iodine concentration and SNR is as follows: for SP-CTA, SNR = 8.577 x iodine concentration +12.864 (r = 0.985); for MP-CTA, SNR = 9.704 x iodine concentration + 13.573 (r = 0.973).

View larger version (8K): [in this window] [in a new window]   Fig 4. Boxplot of arterial attenuation in 50 patients scanned with both SP-CTA and MP-CTA protocols. Error bars indicate the range of values of arterial attenuation. Boxes contain all values within the 25th–75th percentiles (interquartile range), and thick black lines represent the median. The arterial enhancement peak phase of the MP-CTA is shown for comparison. A, Boxplot of attenuation of the exact same region of the largest artery in the scanning range, representing enhancement in the large vessel. The 3 circles are outliers measured in 1 patient. B, Boxplot of attenuation of the exact same region of the M2 segment in the scanning range, representing enhancement in the small vessel.

View larger version (107K): [in this window] [in a new window]   Fig 5. Comparison of image quality between MP-CTA and SP-CTA. A single section of MP-CTA (A), SP-CTA (B), and MIP reconstruction of MP-CTA (C) and SP-CTA (D) is demonstrated. The MP-CTA images were acquired 10–15 minutes after the SP-CTA; therefore, we could find images at almost the same level for comparison. The phase of maximal arterial enhancement of MP-CTA was selected. Higher attenuation of the vascular opacification is easily appreciated in the MP-CTA. Note that venous contamination in the SP-CTA is greater than that in the MP-CTA, which is more obvious in MIP images; and it may interfere with the differentiation of the arteries and veins. The occlusion of right MCA can be detected in both methods. The MP-CTA is noisier, and the contour of the vessels appears coarser than that in SP-CTA. All images were presented with the same window setting (window/level = 1000/100).