46y old male, suspected of pulmonary embolism. Positive D-dimer. Stabbing pain left thoracic.

Diagnosis

No pulmonal embolism. Lymphadenopathies paratracheal and hilair. Suspicious for lung nodule.

Protocol

Comments

Nice visualization of the left superior intercostal vein (LSIV). Dual Energy CTA will help you in making the diagnosis. It will show perfusion defects when a clot is occluding the thoracic vessel(s).
Use 80 kV on tube B when patient is below 80kg, to optimize dose.

[caseItem]

[/caseItem]

Materials and Methods

Seventy-six consecutive patients underwent computed tomographic pulmonary angiography (CTPA) in dual-source high-pitch mode (pitch 3.0, 100 kV, 180 mAs, 50mL contrast material) without breathing commands. PA enhancement, image noise, signal to noise ratio, overall image quality, incidence of total or partial interruption of the contrast column in the PAs, and heart motion-related and breathing-related artifacts of the diaphragm and pulmonary structures were recorded.

Results
Mean central and peripheral PA attenuation was 404±104 and 453±119HU; mean image noise was 11±2 HU; mean examination time was 0.67±0.09 s; and mean dose-length product was 142±31mGycm. There were no motion artifacts of the diaphragm or pulmonary vessels related to breathing or heart motion. There was no case of partial or total interruption of the contrast column in the PA tree. No examination was rated nondiagnostic.

Conclusion
High-pitch dual-source CTPA in freely breathing patients effectively produces images that are free of artifacts related to breathing and cardiac motion. Hence, Valsalva-related artifacts can be eliminated using this technique.

Full text: J Thorac Imaging. 2012 Apr 5. [Epub ahead of print]
Authors: Bauer RW, Schell B, Beeres M, Wichmann JL, Bodelle B, Vogl TJ, Kerl JM.

Diagnosis
Interrupted aortic arch type b, with a patent ductus arteriosus supplying the descending aorta. The left subclavian artery arises from the proximal descending aorta. The patient additionally had a large ventricular septal defect (VSD).

Protocol

Comments
The patient was free breathing during scan acquisition.

[caseItem]

[/caseItem]

Co Author: Dr. John Lesser

This case has been submitted to the Siemens Image Quality Contest 2011.

Materials and Methods
In all, 40 patients (mean age 71±11.8 years, body mass index (BMI) 25.7±3.8 kg/m², range 18.8-33.8 kg/m²) underwent 64-slice thoracoabdominal CTA (contrast material: 80 mL, 5 mL/s) using an automated tube potential selection algorithm (CAREkV), which optimizes tube-potential (70-140 kV) and tube-current (138.8±18.6 effective mAs, range 106-177 mAs) based on the attenuation profile of the topogram and on the diagnostic task. Image quality was semiquantitatively assessed by 2 blinded and independent readers (scores 1: excellent to 5: nondiagnostic). Attenuation and noise were measured by another 2 blinded and independent readers. Contrast-to-noise ratio was calculated. The CT dose index (CTDIvol) was recorded and compared with the estimated CTDIvol of a standard 120 kV protocol without using the algorithm in each patient. Selected tube potentials were correlated with BMI and attenuation of the topogram.

Results
Diagnostic image quality was obtained in all patients (excellent: 14; good: 21; moderate: 5; interreader agreement: κ=0.78). Mean attenuation, noise, and contrast-to-noise ratio were 260.8±63.5 Hounsfield units, 15.5±3.3 Hounsfield units, and 14±4.2, respectively, with good to excellent agreement between readers (r=0.50-0.99, P<0.01 each). Automated attenuation-based tube potential selection resulted in a kV-reduction from 120 to 100 kV in 23 patients and to 80 kV in 1 patient, whereas tube potential increased to 140 kV in 1 patient. Automatically selected tube potential showed a significant correlation with both BMI (r=0.427, P<0.05) and attenuation of the topogram (r=0.831, P<0.001). CTDIvol (7.95±2.6 mGy) was significantly lower when using the algorithm compared with the standard 120 kV protocol (10.59±1.8 mGy, P<0.001), corresponding to an overall dose reduction of 25.1%.

Conclusion
Automated attenuation-based tube potential selection based on the attenuation profile of the topogram is feasible, provides a diagnostic image quality of body CTA, and reduces overall radiation dose by 25% as compared with a standard protocol with 120 kV.

Authors: Winklehner A, Goetti R, Baumueller S, Karlo C, Schmidt B, Raupach R, Flohr T, Frauenfelder T, Alkadhi H.
Full text: Invest Radiol. 2011 Dec;46(12):767-73

Background
Initial studies indicate a prognostic value of the technique; however, the level of evidence as well as exact independent risk estimates remain unclear.

Methods
We searched PubMed, EMBASE, and the Cochrane Library through January 2010 for studies that followed up ≥ 100 subjects for ≥ 1 year and reported at ≥ 1 hazard ratio (HR) of interest. Risk estimates for the presence of significant coronary stenosis (primary endpoint; ≥ 50% diameter stenosis), left main coronary artery stenosis, each coronary stenosis, 3-vessel disease, any plaque, per coronary segment containing plaque, and noncalcified plaque were derived in random effect regression analysis, and causes of heterogeneity were determined in meta-regression analysis.

Results
We identified 11 eligible articles including 7,335 participants (age 59.1 ± 2.6 years, 62.8% male) with suspected coronary artery disease. The presence of ≥ 1 significant coronary stenosis (9 studies, 3,670 participants, and 252 outcome events [6.8%] with 62% revascularizations) was associated with an annualized event rate of 11.9% (6.4% in studies excluding revascularization). The corresponding HR was 10.74 (98% confidence interval [CI]: 6.37 to 18.11) and 6.15 (95% CI: 3.22 to 11.74) in studies excluding revascularization. Adjustment for coronary calcification did not attenuate the prognostic significance (p = 0.79). The estimated HRs for left main stenosis, presence of plaque, and each coronary segment containing plaque were 6.64 (95% CI: 2.6 to 17.3), 4.51 (95% CI: 2.2 to 9.3), and 1.23 (95% CI: 1.17 to 1.29), respectively.

Conclusions
Presence and extent of coronary artery disease on coronary computed tomography angiography are strong, independent predictors of cardiovascular events despite heterogeneity in endpoints, categorization of computed tomography findings, and study population.

Authors: Bamberg F, Sommer WH, Hoffmann V, Achenbach S, Nikolaou K, Conen D, Reiser MF, Hoffmann U, Becker CR.
Full text: J Am Coll Cardiol. 2011 Jun 14;57(24):2426-36.

He is an expert in cardiovascular imaging, Dual Energy CT, and dose reduction.

Read more about Dr. Gregor Pache or ask him questions about DSCT.

Methods
Twenty-five patients underwent thoraco-abdominal CTA with 128-slice dual-source CT, operating both tubes at 120 kV. Full-dose (FD) images were reconstructed with FBP and were compared to half-dose (HD) images with FBP and HD-images with sinogram-affirmed iterative reconstruction (SAFIRE), both reconstructed using data from only one tube-detector-system. Image quality and sharpness of the aortic contour were assessed. Vessel attenuation and noise were measured, contrast-to-noise-ratio was calculated.

Results
Noise as image quality deteriorating artefact occurred in 24/25 (96%) HD-FBP but not in FD-FBP and HD-raw data-based iterative reconstruction datasets (p < 0.001). Other artefacts occurred with similar prevalence among the datasets. Sharpness of the aortic contour was higher for FD-FBP and HD-raw data-based iterative reconstruction as compared to HD-FBP (p < 0.001). Aortoiliac attenuation was similar among all datasets (p > 0.05). Lowest noise was found for HD-raw data-based iterative reconstruction (7.23HU), being 9.4% lower than that in FD-FBP (7.98HU, p < 0.05) and 30.8% lower than in HD-FBP images (10.44HU, p < 0.001). Contrast-to-noise-ratio was lower in HD-FBP (p < 0.001) and higher in HD-raw data-based iterative reconstruction (p < 0.001) as compared to FD-FBP.

Conclusion
Intra-individual comparisons of image quality of body CTA suggest that raw data-based iterative reconstruction allows for dose reduction >50% while maintaining image quality.

Key Points:

• Raw data-based iterative reconstruction reduces image noise and improves image quality as compared to filtered back projection
• At a similar radiation dose, raw data-based iterative reconstruction improves the sharpness of vessel contours
• In body CTA a dose reduction of >50% might be possible when using raw data-based iterative reconstructions, while image quality can be maintained.

Authors: Winklehner A, Karlo C, Puippe G, Schmidt B, Flohr T, Goetti R, Pfammatter T, Frauenfelder T, Alkadhi H.
Full text: Eur Radiol. 2011 Dec;21(12):2521-6.