Reade Andrew De Leacy MBBS, Abstract Co-Author: Nothing to Disclose

Idoia Corcuera Solano MD, Presenter: Nothing to Disclose

Lawrence N. Tanenbaum MD, Abstract Co-Author: Speaker, General Electric Compnny Speaker, Bracco Group Speaker, Bayer AG Speaker, Siemens AG

Lower kVp settings for brain CTA offer improved contrast resolution and signal to noise at lower radiation dose. We evaluated the efficacy of 70 kVp and 80 kVp time resolved/4D whole brain CTA extracted from perfusion studies obtained in patients with suspected acute stroke.   

The institutional review board approved this retrospective study. 37 patients who underwent CTP/ TR CTA of the brain for the investigation of stroke between 12/2012 and 11/2013 were enrolled in this study. 17 patients were imaged using an 80kVp protocol and 20 patients using a 70kVp protocol. Independent subjective assessment of image quality against expected standards of quality for CTA was performed in a blinded fashion by a consensus read of two Neuroradiologists in 16 out of 37 cases (8 from each of the 70kVp and 80kVp groups) using a 5-point scale. The remaining 21 cases could not be qualitatively assessed, as the isotropic data were not preserved in archive. CTDI values for all 37 studies were recorded and the 70 and 80 kVp studies compared. Signal to noise ratios were calculated from the peak arterial phase of the dynamic datasets. Quantitative variables were assessed using Mann-Whitney U test analysis. Qualitative variables were compared using the Student t test for unpaired samples with Welch’s correction.     

Both 70 and 80 kVp CTA groups provided image quality that matched or exceeded expectations. The 70kVp CTA provided statistically significant higher SNR with greater contrast enhancement at 45% lower CTDIvol compared to 80kVp.  

Time resolved CTA studies at both 70 kVp and 80kVp provide acceptable image quality in the assessment of acute stroke. The 70 kVp studies provided greater enhancement and higher SNR and were lower in dose than those at 80 kVp.

Time resolved CTA can be extracted from whole brain perfusion studies avoiding the radiation and iodine dose of a dedicated exam and providing critical dynamic information unobtainable with a static study. This evaluation proves these studies are acceptable in quality and could replace dedicated CTA studies in this setting. Comparison of the efficacy of the 70 kVp studies to those obtained at 80 kVp reveals greater contrast enhancement efficacy and lower dose. This validation study may encourage the widespread adoption of 70kVp CTP/Dynamic 4D CTA techniques in patients with suspected stroke.

De Leacy, R, Corcuera Solano, I, Tanenbaum, L, Time Resolved CT Angiography of the Brain: 70kVp Outperforms 80kVp.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14011560.html