Materials and methods
Thirty-three patients underwent carotid CT angiography on a second generation dual source CT system. Simultaneous acquisitions of 100 and 140kV data sets in arterial phase were performed. Two examiners evaluated overall bone suppression with a 3-point scale (1=poor; 3=excellent) and image quality regarding integrity of the vessel lumen of different vessel segments (n=26) with a 5-point scale (1=poor; 5=excellent), CTA source data served as the reference.

Results
Excellent bone suppression could be achieved in the head and neck. Only minor bone remnants occurred, mean score for bone removal was 2.9. Mean score for vessel integrity was 4.3. Eight hundred fifty-seven vessel segments could be evaluated. Six hundred thirty-five segments (74%) showed no lumen alteration, 65 segments (7.6%) lumen alterations <10%, 27 segments (3.1%) lumen alterations >10% resulting in a total luminal reduction <50%, 17 segments (2%) lumen alterations of more than 10% resulting in a total luminal reduction >50%, and 113 segments (13.2%) showed a gap in the vessel course (100% total lumen reduction). Artificial gaps of the vessel lumen occurred in 28 vessel segments due to artifacts caused by dental hardware and in all but one (65) ophthalmic arteries.

Conclusions
Excellent bone suppression could be achieved, DE imaging with 100 and 140kV lead to improved image quality and vessel integrity in the shoulder region than previously reported. The ophthalmic artery still cannot be adequately visualized.

Authors: Lell MM, Hinkmann F, Nkenke E, Schmidt B, Seidensticker P, Kalender WA, Uder M, Achenbach S.
Full text: Eur J Radiol. 2010 Nov;76(2):e6-12. Epub 2009 Oct 9.

Results
All scans were considered of diagnostic quality for their indication. At high-speed CTA, mean kV and mAs were 118±7 and 197±78, respectively, compared to 120±1 and 259±78 for conventional CTA (p<0.05). Mean volume CT dose index (CTDIvol), Dose Length Product (DLP), and effective dose (ED) were 8.28±2.37mGy, 575±176mGy*cm, and 8.0±2.5mSv at high-speed CTA versus 18.22±7.59mGy, 1151±472mGy*cm, and 16.1±6.6mSv at conventional CTA (p<0.001). Mean vessel attenuation at high-speed CTA was not different from conventional CTA (346±91 vs 336±67 HU for AscA, 344±100 vs 331±63 HU for DescA, 348±90 vs 327±63 HU for AbdA and 347±102 vs 326±68 HU for IlA, p=ns), while significantly less iodine contrast medium was injected for high-speed CTA (102±18mL vs 110±17mL, p<0.05). In 19 patients who had undergone both high-speed and conventional CTA, radiation dose was reduced by 45% (p<0.001), while differences in contrast medium volume and enhancement were non-significant.

Conclusion
High-speed CTA of the aorta results in up to 50% reduction of radiation dose, with maintained image quality and vessel attenuation.

Clinical relevance/application
High-speed CTA is a promising technique for significantly reducing CTA-related radiation dose in non-obese patients.

Submission Type: Scientific Presentations RSNA 2011

Authors: R Vliegenthart, MD,PHD, Groningen, Groningen NETHERLANDS; G W Rowe, BS; P Apfaltrer, MD; R Brothers, RT; M Oudkerk, MD, PhD; U Schoepf, MD

Patients and methods
A total of 176 consecutive patients referred for dual-source CTA were randomized to three protocols: group 1 using prospective ECG-triggering (100 kV, 330 mAs), group 2 a retrospectively gated “MinDose” sequence (100 kV, 330 mAs) and group 3 a standard spiral sequence (120 kV, 400 mAs). If image quality in low-dose groups 1 or 2 was non-diagnostic, an additional standard CT examination (as in group 3) was performed.

Results
Non-diagnostic image quality was found in 11/56, 4/55, and 2/65 patients (46/896, 4/880 and 3/1,040 coronary segments) in groups 1, 2 and 3, respectively. Median (interquartile ranges) volumes of contrast material, CTDI(vol), DLP and effective dose for low-dose groups 1 and 2 and for standard group 3 were 92.5 (11.3), 75.0 (2.5) and 75.0 (9.0) ml; 8.0 (1.4), 16.8 (4.8) and 48.1 (14.2) mGy; 108.0 (27.3), 246.0 (93.0) and 701.0 (207.8) mGy cm; and 1.5 (0.4), 3.4 (1.3) and 9.8 (2.9) mSv, respectively.

Conclusion
A staged coronary CTA protocol with an initial low-dose approach and addition of a standard sequence–should image quality be too low–can lead to a substantial reduction in radiation exposure.

Authors: Pflederer T, Jakstat J, Marwan M, Schepis T, Bachmann S, Kuettner A, Anders K, Lell M, Muschiol G, Ropers D, Daniel WG, Achenbach S.

Full text: Eur Radiol. 2010 May;20(5):1197-206. Epub 2009 Nov 5.

Conclusion
In non-obese patients with a low and stable heart rate, prospectively ECG-triggered high-pitch spiral coronary CTA provides excellent image quality at a consistent dose below 1.0 mSv.

Authors: Achenbach S, Marwan M, Ropers D, Schepis T, Pflederer T, Anders K, Kuettner A, Daniel WG, Uder M, Lell MM.
Full text: Eur Heart J. 2010 Feb;31(3):340-6. Epub 2009 Nov 5.

Materials and methods
Vessel phantoms (diameter 2-4 mm) were attached to a robotic device to simulate cardiac motion and scanned with a DSCT system. The phantoms had either inserts leading to 50% stenosis or carried stents. Images were evaluated for motion artifacts and measurements of the normal, stenotic, and in-stent lumen at different heart rates (50-120 bpm) were performed. Quantile regression analysis was performed to investigate heart rate dependence of the measurement errors.

Results
Visualization of the stenoses and stents was possible without motion artifacts at heart rates of up to 120 bpm. Image quality was similar for the static (0 bpm) and the dynamic (50-120 bpm) scans. Errors for diameter measurements of the vessel lumen and the stenotic lumen were low (3-mm vessel: 1-2%), but considerable for in-stent diameter measurements (3-mm stent: 27-32%). A window/level setting of 1500/300 Hounsfield units was more favorable for stent evaluation. No heart rate dependence was found.

Conclusions
Depiction of coronary stents with DSCT is possible across a large range of simulated heart rates without motion artifacts and with image quality superior to that of previous generations of CT scanners.

Authors: Lell MM, Panknin C, Saleh R, Sayre JW, Schmidt B, Dinh H, Ruehm SG.
Full text: Invest Radiol. 2007 Jul;42(7):536-41.

Methods
Thirty-six patients were examined with various CT protocols and modes (helical scan, n = 27; sequential scan, n = 9) either using a 64-slice dual-source or a 128-slice CT system. Blood samples were obtained before and 30 min after CT. Lymphocytes were isolated, stained against the phosphorylated histone variant γ-H2AX, and DSBs were visualised by using fluorescence microscopy.

Results
DSB yields 30 min after CTA ranged from 0.04 to 0.71 per cell and showed a significant correlation to DLP (ρ = 0.81, p < 0.00001). Median DSB yield and median DLP were significantly lower after sequential compared to helical CT examinations (0.11 vs. 0.37 DSBs/cell and 249 vs. 958 mGy cm, p < 0.00001). Additional calcium scoring led to an increase in DLP (p = 0.15) and DSB levels (p = 0.04). DSB levels normalised to the DLP showed a significant correlation to the attenuation of the blood (ρ = 0.53, p = 0.01) and a negative correlation to the body mass index of the patients (ρ = -0.37, p = 0.06).

Conclusion
γ-H2AX immunofluorescence microscopy allows one to determine dose-related effects on x-ray-induced DSB levels and to consider individual factors which cannot be monitored by physical dose measurements.

Authors: Kuefner MA, Grudzenski S, Hamann J, Achenbach S, Lell M, Anders K, Schwab SA, Häberle L, Löbrich M, Uder M.
Full text: Eur Radiol. 2010 Dec;20(12):2917-24. Epub 2010 Jul 13.

Purpose
To evaluate the feasibility and performance of dual energy CT (DECT) during arterial phase in coronary CT angiography for the detection of chronic infarction compared with late enhancement MRI (LE-MRI) and histopathology in a porcine model of reperfused myocardial infarction.

Material and Methods
Myocardial infarctions were induced by 30 min occlusion of the proximal left anterior descending coronary artery in eight minipigs. DECT, post-contrast LE-MRI and histopathology were performed 60 days after infarct induction. The CT scan was performed in dual energy mode using a dedicated protocol. Myocardial iodine distribution was superimposed as color maps on grey scale multiplanar reformats of the heart. Two radiologists in consensus interpreted all imaging studies for presence of gadolinium uptake at LE-MRI reduced iodine content at DECT and hypoenhanced areas in the initial 100 kV coronary CT angiography images that were acquired during the DECT-acquisition. Results were compared with histopathology.

Results
Based on evaluable segments, DECT showed a sensitivity and specificity of 0.72 and 0.88; LE-MRI showed a sensitivity and specificity of 0.78 and 0.92; and the 100 kV data-set of the DECT scan showed a sensitivity and specificity of 0.60 and 0.93, respectively, for the detection of histological proved ischemia.

Conclusion
DECT during arterial phase coronary CT angiography, which is ordinarily used for coronary artery evaluation, is feasible for the detection of a chronic reperfused myocardial infarction.

Authors: Kerl JM, Deseive S, Tandi C, Kaiser C, Kettner M, Korkusuz H, Lehmann R, Herzog C, Schoepf UJ, Vogl TJ, Bauer RW.
Full text: Acta Radiol. 2011 Aug 26. [Epub ahead of print]