7 research outputs found
Small calcified coronary atherosclerotic plaque simulation model: minimal size and attenuation detectable by 64-MDCT and MicroCT
Efficiency of Iterative Metal Artifact Reduction Algorithm (iMAR) Applied to Brain Volume Perfusion CT in the Follow-up of Patients after Coiling or Clipping of Ruptured Brain Aneurysms
Quantitative Comparison of Commercial and Non-Commercial Metal Artifact Reduction Techniques in Computed Tomography
3D cone-beam CT guidance, a novel technique in renal biopsyāresults in 41 patients with suspected renal masses
Small calcified coronary atherosclerotic plaque simulation model:minimal size and attenuation detectable by 64-MDCT and MicroCT
Zero calcium score may not reflect the absence of calcifications as small calcifications could be missed. This study aimed to evaluate minimal size and minimal attenuation of coronary calcifications detectable by computed tomography (CT) and to determine the minimal spatial resolution required for detecting calcification onset. Using open source CT simulation software, CTSim(Ā©), several 50%-stenotic coronary artery phantoms were designed with 5Ā Ī¼m resolution, realistic morphology and tissue-specific Hounsfield Unit (HU) values. The plaque had an attenuation resembling fibrous plaque and contained a single calcification. X-ray projections were simulated with settings resembling non-contrast-enhanced 64 multi detector-row CT (64-MDCT). Scanning and reconstruction were simulated with spatial resolution of a 64-MDCT (0.4mm) and of a MicroCT (48Ā Ī¼m). Starting from a single calcium granule, the calcification was simulated to grow in size and attenuation until it could be detected using clinically accepted calcium determination scheme on MicroCT and 64-MDCT images. The smallest coronary calcifications detectable at MicroCT and 64-MDCT, which had a realistic attenuation (ā1,024 to 3,072Ā HU), were of 25Ā Ī¼m and 215Ā Ī¼m diameter, respectively. The area was overestimated 7.7 and 8.8 times, respectively. Calcifications with smaller size need to have an unrealistically high attenuation to be detectable by 64-MDCT. In conclusion, 64-MDCT is only able to detect coronary calcifications with minimal diameter of 215Ā Ī¼m. Consequently, early onset of calcification in coronary plaque will remain invisible when using CT and a zero calcium score can not exclude the presence of coronary calcification
Non-calcified coronary atherosclerotic plaque visualization on CT:effects of contrast-enhancement and lipid-content fractions
<p>Computed tomography (CT) may characterize lipid-rich and presumably rupture-prone non-calcified coronary atherosclerotic plaque based on its Hounsfield-Unit (HU), but still inconclusively. This study aimed to evaluate factors influencing the HU-value of non-calcified plaque using software simulation. Several realistic virtual plaqueburdened coronary phantoms were constructed at 5 mu m resolution. CT scanning was simulated with settings resembling a 64-row multi-detector CT (64-MDCT) and reconstructed at 64-MDCT (0.4 mm) and MicroCT (48 mu m) resolutions. Influences of lumen contrast-enhancement, stenosis-grades, and plaque compositions on plaque visualization were analyzed. Lumen contrast-enhancement and mean plaque HU-value were positively correlated (R-2 > 0.92), with approximately the same slopes for all plaque compositions. Percentage lipid-content and mean plaque HU-value were negatively correlated (R-2 > 0.98). Stenosis-grade and noise had minimal influence on the correlations. Influence of lumen contrast-enhancement on plaque HU-value was following a specific exponentially declining pattern (y = Ae(-I >> x) + c) from the lumen border until 2-pixel radius. Outside 2-pixel radius, plaque HU-values deviated maximally 5 HU from non-contrast-enhanced reference. Thus, to avoid lumen contrast-enhancement influence, plaques should be measured outside 2-pixel radius from the lumen border. Based on the patterns found, a lumen influence correction algorithm may be developed. HU-based plaque percentage lipid-content determination might serve as an alternative plaque characterization method. However, its applicability is still hindered by many inherent limitations.</p>