Yunjing Xue MD, Presenter: Nothing to Disclose

Qing Duan MD, Abstract Co-Author: Nothing to Disclose

Jin Wei, Abstract Co-Author: Nothing to Disclose

Lin LIN, Abstract Co-Author: Nothing to Disclose

To compare the image quality, radiation dose and contrast medium (CM) dose of Gemstone spectral imaging (GSI) protocol with 3ml/s injection rate, a 100-kVp protocol with 4ml/s rate and a conventional 120-kVp protocol with 5ml/s rate in carotid CTA.

With local ethical committee approval, 63 patients were prospectively enrolled in the study, CM (320 mg I/mL) were used: 21 were scanned with parameters of 120 kVp, 240 mAs,using CM of 320 mgI/mL with 5ml/s injection rate, another 22 were scanned with 100 kVp, 288 mAs, 50% ASiR, using the same CM with 4ml/s injection rate, and the other 20 were scanned with GSI mode, 315 mAs, 50% ASiR with 3 ml/s injection rate. Monochromatic images of 60keV were evaluated in GSI group. Image quality (IQ) of the three groups was compared in terms of arterial enhancement, noise, signal-noise-ratio (SNR) and contrast-to-noise ratio (CNR). The effective dose (ED) of radiation and contrast dose were calculated and compared. Data were analyzed by using One-way ANOVA test.

The 100-kVp group (443.28±72.58 HU) showed significantly higher enhancement in carotid artery compared to 120-kVp (376.60±62.42 HU) and GSI (365.69±69.43HU) groups (p<0.05, respectively). Both 100-kVp and GSI groups showed significantly lower noise in carotid (11.31±2.20HU, 9.78±2.88HU) and three main branches of thoracic aorta arteries (19.21±3.61HU, 19.05±6.40HU) than 120-kVp group (26.69±4.68HU) (p<0.05, respectively) whereas there was no significant difference in CNR and SNR among three groups (all of them P>0.05). Compared with 120-kVp group (3.21±0.30mSv, 67.5±13.72ml), the ED and CM dose reduced 10.9 % and 26.79 % in GSI group (2.86±0.07mSv, 49.42±8.91ml), and 25.86% and 12.89 % in 100-kVp group (2.38±0.002mSv, 58.80±9.81ml), respectively. There was significant difference in comparison between any two groups both in ED and CM dose (all of them P<0.05).

Among these three protocols, the GSI (50%ASiR, 3ml/s) used the lowest CM dose while the 100-kVp (50%ASiR, 4ml/s) protocol had the lowest radiation dose. Both GSI and 100-kVp could reduce noise of carotid and three main branches of thoracic aorta and therefore improve IQ.

Compared with the 100-kVp protocol, GSI protocol can provide more information. We can balance the image quality, useful information, radiation dose and CM dose of 100-kVp or spectral scanning and choose the optimized CTA protocol to achieve the best clinical effect.

Xue, Y, Duan, Q, Wei, J, LIN, L, Carotid CT Angiography: Comparison among Low-tube-Voltage Imaging, Monochromatic Imaging and Conventional Imaging with Different Contrast Injection Rate.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14008463.html