Dimitrios Mitsouras

Iodinated Contrast Opacification Gradients in Normal Coronary Arteries Imaged with Prospectively ECG-Gated Single Heart Beat 320-Detector Row Computed Tomography

Background—To define and evaluate coronary contrast opacification gradients using prospectively ECG-gated single heart beat 320-detector row coronary angiography (CTA). Methods and Results—Thirty-six patients with normal coronary arteries determined by 320×0.5-mm detector row coronary CTA were retrospectively evaluated with customized image postprocessing software to measure Hounsfield Units at 1-mm intervals orthogonal to the artery center line. Linear regression determined correlation between mean Hounsfield Units and distance from the coronary ostium (regression slope defined as the distance gradient Gd), lumen cross-sectional area (Ga), and lumen short-axis diameter (Gs). For each gradient, differences between the 3 coronary arteries were analyzed with ANOVA. Linear regression determined correlations between measured gradients, heart rate, body mass index, and cardiac phase. To determine feasibility in lesions, all 3 gradients were evaluated in 22 consecutive patients with left anterior descending artery lesions ≥50% stenosis. For all 3 coronary arteries in all patients, the gradients Ga and Gs were significantly different from zero (P<0.0001), highly linear (Pearson r values, 0.77 to 0.84), and had no significant difference between the left anterior descending, left circumflex, and right coronary arteries (P>0.503). The distance gradient Gd demonstrated nonlinearities in a small number of vessels and was significantly smaller in the right coronary artery when compared with the left coronary system (P<0.001). Gradient variations between cardiac phases, heart rates, body mass index, and readers were low. Gradients in patients with lesions were significantly different (P<0.021) than in patients considered normal by CTA. Conclusions—Measurement of contrast opacification gradients from temporally uniform coronary CTA demonstrates feasibility and reproducibility in patients with normal coronary arteries. For all patients, the gradients defined with respect to the coronary lumen cross-sectional area and short-axis diameters are highly linear, not significantly influenced by the coronary artery (left anterior descending artery versus left circumflex versus right coronary artery), and have only small variation with respect to patient parameters. Preliminary evaluation of gradients across coronary artery lesions is promising but requires additional study.

Evaluation of Artery Visualizations for Heart Disease Diagnosis

Heart disease is the number one killer in the United States, and finding indicators of the disease at an early stage is critical for treatment and prevention. In this paper we evaluate visualization techniques that enable the diagnosis of coronary artery disease. A key physical quantity of medical interest is endothelial shear stress (ESS). Low ESS has been associated with sites of lesion formation and rapid progression of disease in the coronary arteries. Having effective visualizations of a patients ESS data is vital for the quick and thorough non-invasive evaluation by a cardiologist. We present a task taxonomy for hemodynamics based on a formative user study with domain experts. Based on the results of this study we developed HemoVis, an interactive visualization application for heart disease diagnosis that uses a novel 2D tree diagram representation of coronary artery trees. We present the results of a formal quantitative user study with domain experts that evaluates the effect of 2D versus 3D artery representations and of color maps on identifying regions of low ESS. We show statistically significant results demonstrating that our 2D visualizations are more accurate and efficient than 3D representations, and that a perceptually appropriate color map leads to fewer diagnostic mistakes than a rainbow color map.

Early remodeling of lower extremity vein grafts: Inflammation influences biomechanical adaptation

BACKGROUND The remodeling of vein bypass grafts after arterialization is incompletely understood. We have previously shown that significant outward lumen remodeling occurs during the first month of implantation, but the magnitude of this response is highly variable. We sought to examine the hypothesis that systemic inflammation influences this early remodeling response. METHODS A prospective observational study was done of 75 patients undergoing lower extremity bypass using autogenous vein. Graft remodeling was assessed using a combination of ultrasound imaging and two-dimensional high-resolution magnetic resonance imaging. RESULTS The vein graft lumen diameter change from 0 to 1 month (22.7% median increase) was positively correlated with initial shear stress (P = .016), but this shear-dependent response was disrupted in subjects with an elevated baseline high-sensitivity C-reactive protein (hsCRP) level of >5 mg/L. Despite similar vein diameter and shear stress at implantation, grafts in the elevated hsCRP group demonstrated less positive remodeling from 0 to 1 month (13.5% vs 40.9%, P = .0072). By regression analysis, the natural logarithm of hsCRP was inversely correlated with 0- to 1-month lumen diameter change (P = .018). Statin therapy (beta = 23.1, P = .037), hsCRP (beta = -29.7, P = .006), and initial shear stress (beta = .85, P = .003) were independently correlated with early vein graft remodeling. In contrast, wall thickness at 1 month was not different between hsCRP risk groups. Grafts in the high hsCRP group tended to be stiffer at 1 month, as reflected by a higher calculated elastic modulus (E = 50.4 vs 25.1 Mdynes/cm2, P = .07). CONCLUSIONS Early positive remodeling of vein grafts is a shear-dependent response that is modulated by systemic inflammation. These data suggest that baseline inflammation influences vein graft healing, and therefore, inflammation may be a relevant therapeutic target to improve early vein graft adaptation.

New advances in cardiac computed tomography.

Purpose of review Applications of computed tomography (CT) for cardiac imaging have evolved rapidly with the introduction of new hardware. These advances require a technology update, particularly as the new scanners have novel, unique features. This review focuses on post-64 generation CT scanner capabilities and novel clinical research applications enabled by these technologies. Recent findings By the release date of multicenter publications to evaluate 64-detector row coronary CT, new technology advanced the state of the art in terms of key metrics such as temporal resolution and volume coverage. Moreover, cardiac CT protocols continue to evolve and spark new applications. CT is now being used for plaque detection and is being applied for stress perfusion imaging. In addition, scanners have novel strategies for single heartbeat whole coronary imaging; this has enabled evaluations of endothelial shear stress and differences in coronary contrast opacification at a single point in time. Summary Continuous improvements in technology have moved CT beyond 64-detector rows. Understanding these technical specifications will enable evaluation of current and future applications for noninvasive cardiac imaging.

Preoperative vascular mapping for facial allotransplantation: four-dimensional computed tomographic angiography versus magnetic resonance angiography.

Background: Facial allotransplantation requires a detailed arterial and venous assessment for surgical planning. Target vessels are often depleted by multiple reconstructive attempts or the severe facial injury itself. The purpose of this study was to retrospectively compare the diagnostic performance of computed tomography and magnetic resonance angiography in the preoperative assessment. Methods: Four-dimensional (three spatial planes plus time) computed tomographic and magnetic resonance images including 126 potential vessels (76 arteries and 50 veins) from five candidates were analyzed independently by two radiologists using a four-point image quality scale. Computed tomographic versus magnetic resonance image quality was compared directly, using a computed tomographic angiography consensus read as reference standard. Vessels with metal artifact on magnetic resonance imaging, computed tomography, or both underwent separate analyses to determine the impact of metal implants on image quality. Results: Considering all 126 vessels, the mean computed tomographic image quality was superior to that of magnetic resonance angiography. When considering individual vessels, all except for major neck vessels were better visualized by computed tomography. Images of 26 vessels were degraded by metal artifact; magnetic resonance image quality was inferior for those vessels. Considering images of major vessels with no metal artifact, there was no significant mean image quality difference between computed tomography and magnetic resonance imaging. Conclusions: Computed tomographic angiography should be used as the first-choice modality for preoperative imaging of facial transplant patients because, when compared with magnetic resonance imaging, the visualization of small vessels is far superior and images have fewer artifacts. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, II.

3D printed ventricular septal defect patch: a primer for the 2015 Radiological Society of North America (RSNA) hands-on course in 3D printing

Hand-held three dimensional models of the human anatomy and pathology, tailored-made protheses, and custom-designed implants can be derived from imaging modalities, most commonly Computed Tomography (CT). However, standard DICOM format images cannot be 3D printed; instead, additional image post-processing is required to transform the anatomy of interest into Standard Tessellation Language (STL) format is needed. This conversion, and the subsequent 3D printing of the STL file, requires a series of steps. Initial post-processing involves the segmentation-demarcation of the desired for 3D printing parts and creating of an initial STL file. Then, Computer Aided Design (CAD) software is used, particularly for wrapping, smoothing and trimming. Devices and implants that can also be 3D printed, can be designed using this software environment. The purpose of this article is to provide a tutorial on 3D Printing with the test case of complex congenital heart disease (CHD). While the infant was born with double outlet right ventricle (DORV), this hands-on guide to be featured at the 2015 annual meeting of the Radiological Society of North America Hands-on Course in 3D Printing focused on the additional finding of a ventricular septal defect (VSD). The process of segmenting the heart chambers and the great vessels will be followed by optimization of the model using CAD software. A virtual patch that accurately matches the patient’s VSD will be designed and both models will be prepared for 3D printing.

CT Angiography for Surgical Planning in Face Transplantation Candidates

SUMMARY: Facial allotransplantation replaces missing facial structures with anatomically identical tissues, providing desired functional, esthetic, and psychosocial benefits far superior to those of conventional methods. On the basis of very encouraging initial results, it is likely that more procedures will be performed in the near future. Typical candidates have extremely complex vascular anatomy due to severe injury and/or multiple prior reconstructive attempts; thus, each procedure is uniquely determined by the defects and vascular anatomy of the candidate. We detail CT angiography vascular mapping, noting the clinical relevance of the imaging, the angiosome concept and noninvasive delineation of the key vessels, and current controversies related to the vascular anastomoses.

Coronary pressure-derived fractional flow reserve in the assessment of coronary artery stenoses

ObjectivesCatheter-based angiography is the reference-standard to establish coronary anatomy. While routinely employed clinically, lumen assessment correlates poorly with physiological measures of ischaemia. Moreover, functional studies to identify and localise ischaemia before elective angiography are often not available. This article reviews fractional flow reserve (FFR) and its role in guiding patient management for patients with a potentially haemodynamic significant coronary lesion.MethodsThis review discusses the theory, evidence, indications, and limitations of FFR. Also included are emerging non-invasive imaging FFR surrogates currently under evaluation for accuracy with respect to standard FFR.ResultsCoronary pressure-derived fractional flow reserve (FFR) rapidly assesses the haemodynamic significance of individual coronary artery lesions and can readily be performed in the catheterisation laboratory. The use of FFR has been shown to effectively guide coronary revascularization procedures leading to improved patient outcomes.ConclusionsFFR is an invaluable modality in guiding coronary disease treatment decisions. It is safe, cost-effective and leads to improved patient outcomes. Non-invasive imaging modalities to assess the physiologic significance of CAD are currently being  developed and evaluated.Key points• Coronary pressure-derived fractional flow reserve (FFR) is an important adjunct to angiography.• FFR is an invaluable technique in guiding coronary disease treatment decisions.• FFR is safe, cost-effective and leads to improved patient outcomes.• New directions include CT-based non-invasive conventional FFR surrogates for functional lesion significance.

Surgical planning for composite tissue allotransplantation of the face using 320-detector row computed tomography.

We report initial surgical planning computed tomographic protocols for composite tissue allotransplantation of the face. This complex procedure replaces missing facial structures with anatomically identical tissues, restoring form and function. Achieved results are superior to those accomplished with conventional techniques. As a growing number of patients/recipients have undergone multiple reconstructions, vascular imaging plays an increasingly critical role in surgical planning and successful execution of the operation.

Association of global and local low endothelial shear stress with high-risk plaque using intracoronary 3D optical coherence tomography: Introduction of ‘shear stress score’

Aims The association of low endothelial shear stress (ESS) with high-risk plaque (HRP) has not been thoroughly investigated in humans. We investigated the local ESS and lumen remodelling patterns in HRPs using optical coherence tomography (OCT), developed the shear stress score, and explored its association with the prevalence of HRPs and clinical outcomes. Methods and results A total of 35 coronary arteries from 30 patients with stable angina or acute coronary syndrome (ACS) were reconstructed with three dimensional (3D) OCT. ESS was calculated using computational fluid dynamics and classified into low, moderate, and high in 3-mm-long subsegments. In each subsegment, (i) fibroatheromas (FAs) were classified into HRPs and non-HRPs based on fibrous cap (FC) thickness and lipid pool size, and (ii) lumen remodelling was classified into constrictive, compensatory, and expansive. In each artery the shear stress score was calculated as metric of the extent and severity of low ESS. FAs in low ESS subsegments had thinner FC compared with high ESS (89 ± 84 vs.138 ± 83 µm, P < 0.05). Low ESS subsegments predominantly co-localized with HRPs vs. non-HRPs (29 vs. 9%, P < 0.05) and high ESS subsegments predominantly with non-HRPs (9 vs. 24%, P < 0.05). Compensatory and expansive lumen remodelling were the predominant responses within subsegments with low ESS and HRPs. In non-stenotic FAs, low ESS was associated with HRPs vs. non-HRPs (29 vs. 3%, P < 0.05). Arteries with increased shear stress score had increased frequency of HRPs and were associated with ACS vs. stable angina. Conclusion Local low ESS and expansive lumen remodelling are associated with HRP. Arteries with increased shear stress score have increased frequency of HRPs and propensity to present with ACS.