Calcified Vascular Plaque Specimens: Assessment with Cardiac Dual-Energy Multidetector CT in Anthropomorphically Moving Heart Phantom

Boll, Daniel T.; Merkle, Elmar M.; Paulson, Erik K.; Mirza, Rizvan; Fleiter, Thorsten

doi:10.1148/radiol.2483071576

Cited by 87 publications

(44 citation statements)

References 24 publications

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“…Optimized monoenergetic images have a significantly higher SNR than 120-kVp composite images, and they might contribute to more accurate evaluation, particularly when contrast enhancement is poor. Monoenergetic imaging also reportedly has the advantage of reducing beam-hardening artifacts that are caused by the wide beam-energy of X-rays [7]. However, we could not validate this feature in the present study because of difficulties in quantifying such artifacts.…”

Section: Discussionmentioning

confidence: 60%

“…Secondly, the iodine component can be directly extracted and the bone component can be removed using the material decomposition theory [2], a technique that has been recently applied to abdominal virtual noncontrast imaging [3,4], lung perfusion [5] and bone removal angiography [6]. Thirdly, monoenergetic images can be produced at any effective energy level by calculating two polyenergetic images at high-and low-tube energy, and thus optimal contrast-enhanced images can be generated with less beam hardening artifacts [7].…”

Section: Introductionmentioning

confidence: 99%

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Optimization of energy level for coronary angiography with dual-energy and dual-source computed tomography

Okayama

Seno

Soeda

et al. 2011

Int J Cardiovasc Imaging

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Dual-energy computed tomography (DE-CT) uses polyenergetic X-rays at 100- and 140-kVp tube energy, and generates 120-kVp composite images that are referred to as polyenergetic images (PEIs). Moreover, DE-CT can produce monoenergetic images (MEIs) at any effective energy level. We evaluated whether the image quality of coronary angiography is improved by optimizing the energy levels of DE-CT. We retrospectively evaluated data sets obtained from 24 consecutive patients using cardiac DE-CT at 100- and 140-kVp tube energy with a dual-source scanner. Signal-to-noise ratios (SNRs) were evaluated in the left ascending coronary artery in PEIs, and in MEIs reconstructed at 40, 50, 60, 70, 80, 90, 100, 130, 160 and 190 keV. Energy levels of 100, 120 and 140 kVp generated the highest SNRs in PEIs from 10, 12 and 2 patients, respectively, at 60, 70 and 80 keV in MEIs from 2, 10 and 10 patients, respectively, and at 90 and 100 keV in those from one patient each. Optimization of the energy level for each patient increased the SNR by 16.6% in PEIs (P < 0.0001) and by 18.2% in MEIs (P < 0.05), compared with 120-kVp composite images. The image quality of coronary angiography using DE-CT can be improved by optimizing the energy level for individual patients.

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Section: Discussionmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Optimization of energy level for coronary angiography with dual-energy and dual-source computed tomography

Okayama

Seno

Soeda

et al. 2011

Int J Cardiovasc Imaging

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“…[4][5][6][7][8][9][10][11][12][13] Different approaches for DECT imaging include dual-source CT, 5 rapid kV switching, 2,14 and dual-layer ͑sandwich͒ detectors. 4,15 The dual-source CT approach became commercially available in 2006. 5,6 The dual-source CT ͑DSCT͒ scanner ͑SOMATOM Definition, Siemens Healthcare, Forchheim, Germany͒ has two x-ray tubes and two corresponding arrays of detectors.…”

Section: Introductionmentioning

confidence: 99%

Improved dual‐energy material discrimination for dual‐source CT by means of additional spectral filtration

et al. 2009

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The use of additional spectral filtration for dual-energy ͑DE͒ imaging using a dual-source CT ͑DSCT͒ system was investigated and its effect on the material-specific DE ratio was evaluated for several clinically relevant materials. The x-ray spectra, data acquisition, and reconstruction processes for a DSCT system ͑Siemens Definition͒ were simulated using information provided by the system manufacturer, resulting in virtual DE images. The factory-installed filtration for the 80 kV spectrum was left unchanged to avoid any further reductions in tube output, and only the filtration for the high-energy spectrum was modified. Only practical single-element filter materials within the atomic number range of 40Յ Z Յ 83 were evaluated, with the aim of maximizing the separation between the two spectra, while maintaining similar noise levels for high-and low-energy images acquired at the same tube current. The differences between mean energies and the ratio of the 140 and 80 kV detector signals, each integrated below 80 keV, were evaluated. The simulations were performed for three attenuation scenarios: Head, body, and large body. The large body scenario was evaluated for the DE acquisition mode using the 100 and 140 kV spectra. The DE ratio for calcium hydroxyapatite ͑simulating bone or calcifications͒, iodine, and iron were determined for CT images simulated using the modified and factory-installed filtration. Several filter materials were found to perform well at proper thicknesses, with tin being a good practical choice. When image noise was matched between the low-and high-energy images, the spectral difference in mean absorbed energy using tin was increased from 25.7 to 42.7 keV ͑head͒, from 28.6 to 44.1 keV ͑body͒, and from 20.2 to 30.2 keV ͑large body͒. The overlap of the signal spectra for energies below 80 keV was reduced from 78% to 31% ͑head͒, from 93% to 27% ͑body͒, and from 106% to 79% ͑large body͒. The DE ratio for the body attenuation scenario increased from 1.45 to 1.91 ͑calcium͒, from 1.84 to 3.39 ͑iodine͒, and from 1.73 to 2.93 ͑iron͒ with the additional tin filtration compared to the factory filtration. This use of additional filtration for one of the x-ray tubes used in dual-source DECT dramatically increased the difference between material-specific DE ratios, e.g., from 0.39 to 1.48 for calcium and iodine or from 0.28 to 1.02 for calcium and iron. Because the ability to discriminate between different materials in DE imaging depends primarily on the differences in DE ratios, this increase is expected to improve the performance of any material-specific DECT imaging task. Furthermore, for the large patient size and in conjunction with a 100/140 kV acquisition, the use of additional filtration decreased noise in the low-energy images and increased contrast in the DE image relative to that obtained with 80/140 kV and no additional filtration.

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“…Of note, this dynamic cardiac phantom has been used previously for evaluating temporal and spatial resolution, as well as assessing coronary calcium score accuracy. 22,39,40 However, the use of a physical phantom does introduce inherent limitations to the applicability of this study. The images of the cardiac phantom do not represent the true anatomy of the beating heart in human subjects.…”

Section: Discussionmentioning

confidence: 99%

Computerized method for evaluating diagnostic image quality of calcified plaque images in cardiac CT: Validation on a physical dynamic cardiac phantom

et al. 2010

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Purpose:In cardiac computed tomography ͑CT͒, important clinical indices, such as the coronary calcium score and the percentage of coronary artery stenosis, are often adversely affected by motion artifacts. As a result, the expert observer must decide whether or not to use these indices during image interpretation. Computerized methods potentially can be used to assist in these decisions. In a previous study, an artificial neural network ͑ANN͒ regression model provided assessability ͑image quality͒ indices of calcified plaque images from the software NCAT phantom that were highly agreeable with those provided by expert observers. The method predicted assessability indices based on computer-extracted features of the plaque. In the current study, the ANN-predicted assessability indices were used to identify calcified plaque images with diagnostic calcium scores ͑based on mass͒ from a physical dynamic cardiac phantom. The basic assumption was that better quality images were associated with more accurate calcium scores. Methods: A 64-channel CT scanner was used to obtain 500 calcified plaque images from a physical dynamic cardiac phantom at different heart rates, cardiac phases, and plaque locations. Two expert observers independently provided separate sets of assessability indices for each of these images. Separate sets of ANN-predicted assessability indices tailored to each observer were then generated within the framework of a bootstrap resampling scheme. For each resampling iteration, the absolute calcium score error between the calcium scores of the motion-contaminated plaque image and its corresponding stationary image served as the ground truth in terms of indicating images with diagnostic calcium scores. The performances of the ANN-predicted and observer-assigned indices in identifying images with diagnostic calcium scores were then evaluated using ROC analysis. Results: Assessability indices provided by the first observer and the corresponding ANN performed similarly ͑AUC OBS1 = 0.80 ͓0.73, 0.86͔ vs AUC ANN1 = 0.88 ͓0.82, 0.92͔͒ as that of the second observer and the corresponding ANN ͑AUC OBS2 = 0.87 ͓0.83, 0.91͔ vs AUC ANN2 = 0.90 ͓0.85, 0.94͔͒. Moreover, the ANN-predicted indices were generated in a fraction of the time required to obtain the observer-assigned indices. Conclusions: ANN-predicted assessability indices performed similar to observer-assigned assessability indices in identifying images with diagnostic calcium scores from the physical dynamic cardiac phantom. The results of this study demonstrate the potential of using computerized methods for identifying images with diagnostic clinical indices in cardiac CT images.

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Calcified Vascular Plaque Specimens: Assessment with Cardiac Dual-Energy Multidetector CT in Anthropomorphically Moving Heart Phantom

Abstract: Dual-energy multidetector CT with novel postprocessing techniques enhanced accuracy of calcified plaque quantification by reducing effects of tissue blooming and beam hardening beyond single-energy multidetector CT.

Cited by 87 publications

References 24 publications

Optimization of energy level for coronary angiography with dual-energy and dual-source computed tomography

Optimization of energy level for coronary angiography with dual-energy and dual-source computed tomography

Improved dual‐energy material discrimination for dual‐source CT by means of additional spectral filtration

Computerized method for evaluating diagnostic image quality of calcified plaque images in cardiac CT: Validation on a physical dynamic cardiac phantom

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