Objective
We evaluated the accuracy for detection of myocardial blood volume deficits in DECT and SCT compared with 99m-Tc-Sestamibi-SPECT (single-photon emission CT) during rest and stress.

Methods
47 patients underwent rest/stress SPECT myocardial perfusion imaging and cardiac DECT on a dual-source CT scanner. The A- and B-tubes were operated with 140 kV and 80 kV/100 kV, respectively. DECT raw data were reconstructed by (1) only using high-energy (140 kV) CT spectra, (2) only using low-energy (80 kV/100 kV) CT spectra, (3) merging data (30% low- and 70% high-energy CT spectra), and (4) DECT-based iodine maps. Two independent, blinded observers analyzed all CT data according to each of the 4 reconstruction strategies for myocardial blood volume deficits.

Results
Specificity and positive predictive values were relatively similar between the 4 reconstruction strategies, with highest specificity (98%) of SCT datasets based on 140 kV for mixed perfusion deficits seen on SPECT. DECT iodine maps showed highest sensitivity, negative predictive value, and accuracy of 91%, 97%, and 93%, respectively, for mixed perfusion deficits. Analysis with receiver operating characteristics showed highest area under the curve values (0.84-0.93) with the use of DECT iodine maps in the detection of purely fixed and mixed perfusion deficits.

Conclusion
DECT iodine maps show superior performance for the detection of fixed and mixed perfusion deficits compared with SCT spectra.

Authors: Arnoldi E, Lee YS, Ruzsics B, Weininger M, Spears JR, Rowley CP, Chiaramida SA, Costello P, Reiser MF, Schoepf UJ.
Full text: J Cardiovasc Comput Tomogr. 2011 Nov;5(6):421-9. Epub 2011 Oct 25.

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.

Diagnosis
Coronary arteries have been constructed and clearly visible, like the VSD. Even with a very high heart rate of 153, the coronary arteries are well depicted. The scan was performed with the prospective sequential technique without the use of padding, because you are only interested in the visualization of the coronaries and the heart anatomy. There is no need for coronary analysis. Scan Trigger was placed at the T-wave to catch the least movement of the heart.
Altogether, this will give you a dose optimized scan protocol with the least possible movement at a temporal resolution of 75ms.

Protocol

Comments
The scan was performed with bolustracking technique. The reason was that the i.v. cannula was placed on the forehead, allowing the use of a manual delay is not recommended. No coarctatio aortae was shown. CT is a quick and reliable technique in visualization of the coronaries or heart anatomy. In combination with Flash technique there is no need of sedation.

[caseItem]

[/caseItem]

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

Diagnosis
Urate crystal deposits > 2 mm correlated to 100 % with pain at the exact given location. All patients with urate crystal deposits > 2 mm had increased uric acid blood levels, either actually or reported. These patients were then finally diagnosed with gout, taking all performed examinations into consideration. Urate crystal deposits ≤ 2 mm did not correlate in any instance with pain exactly at the deposit site. The uric acid blood levels in these patients at the time of the examination were partly elevated (43 %) partly normal (57 %). In patients with no detectable urate crystal deposits, the uric acid blood levels were normal. The existing symptoms were explained through differential diagnosis (some of which were found during the Dual Energy CT examination).

Protocol

Comments
Dual Energy CT allows the quantitative imaging of urate crystal deposits. A minimum size of the urate crystal deposits > 2 mm seems to be the pre-requisite for inducing clinical symptoms. Taking into consideration the size of the urate crystal deposits, the diagnosis of clinically manifested gout can be reliably made. Patients, of course, prefer the non-invasive acquisition protocol in comparison to invasive punctures.

[caseItem]

[/caseItem]

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.

Diagnosis
CT examination in aorta totalis protocol. Normal thoracic aortic calibre.
Ascending aorta has a diameter of 34mm, 22mm aortic arch to the aortic
descending 16mm. Brachiocephalic barrels showed patency, some calcifications
in the LAD. Normal calibre abdominal aorta, infrarenal diameter 17mm.
Iliac vessels to the extent showed patency. Visceral vessels showed
patency. No evidence of aneurysm.

Protocol

Comments
In this case, screening for familial aneurysm, low dose is even more important. Dose was around 1.1mSv and also because of the high pitch mode, contrast media material was saved (only 50ml iodine with saline push).

[caseItem]

[/caseItem]