Technological Advancements in Echocardiographic Assessment of Thoracic Aortic Dilatation: Head to Head Comparison Among Multidetector Computed Tomography, 2-Dimensional, and 3-Dimensional Echocardiography Measurements.

PURPOSE: The aim of this study was to evaluate the feasibility and accuracy of 2-dimensional (2D) and 3-dimensional (3D) transthoracic echocardiography (2DTTE, 3DTTE) versus multidetector computed tomography (MDCT) in patients with ascending aortic (AA) dilation. MATERIALS AND METHODS: Fifty consecutive patients with AA dilation were evaluated by 2DTTE, X-plane (XP) 3DTTE, and MDCT. Aorta diameters were measured at aortic annulus, aortic root (SIN), sinotubular junction, AA, aortic arch before the prebrachiocephalic artery (PRE), and before left subclavian artery (INTRA). Leading edge-to-leading edge (L-L) and inner-to-inner (I-I) measurements were compared with MDCT data. RESULTS: Feasibility, quality of imaging, and accuracy was high with all echocardiographic methods. Specifically for MDCT maximum SIN diameter, the best correlation and agreement was obtained using XP maximum diameter at 3DTTE (MDCT: 44.8±7.4 mm vs. XP: 44.4±7.4 mm; r=0.975; bias=-0.4 mm). The same was true for AA maximum diameter at MDCT (MDCT: 46.6±8.1 mm vs. XP: 47.5±8.1 mm; r=0.991; bias=0.1 mm). For aortic arch the best correlation and agreement with MDCT were as follows: 2DTTE L-L diameter for arch PRE (MDCT: 37.9±5.3 mm vs. TTE: 36.6±4.5 mm; r=0.927; bias=-0.9 mm) and MDCT minimum diameter with XP minimum diameter for arch INTRA (MDCT: 28.2±5.0 mm vs. TTE 28.8±4.7 mm; r=0.939; bias=-0.3 mm). CONCLUSION: In patients with aortic dilatation or aneurysm, new techniques (mainly 2D-3D probes allowing XP views) facilitate accuracy of aortic measurements at different sites of the vessel and allow standardization of analysis to better compare with MDCT.

Application of a Simple Quantitative Assessment of Atherosclerotic Lesions in Freshly Isolated Aortas from Rabbits.

Rabbits are widely used for the study of atherosclerosis; however, the lack of a unified and quantitative analysis of atheroma limits data interpretation and comparisons between laboratories. In this study, we applied a simple quantitative method, referred to as the oil red O (ORO) dye-eluting method, for analysis of atherosclerotic plaques in freshly isolated aortas. It employs ORO staining of the plaques followed by elution of the dye that is subjected to quantitative measurement. Atherosclerosis was induced in rabbits by feeding a 1% (w/w) high cholesterol diet for 4 or 12 weeks. Thoracic aortas were isolated and sufficiently stained by ORO. These dyes were easily and completely extracted by 100% ethanol and quantified by spectrophotometric measurement at 510 nm. A series of cross-sectional slices at 100-µm intervals were counterstained by elastic van Gieson. It was found that there was a highly positive correlation between the dye concentration and the amount of plaque tissue, determined as volume of plaques (regression coefficient r2: 0.8792, p < 0.001). The color equivalence of the dye content was expressed as µg/mm2 of intimal aorta area to allow direct comparisons among aortas. The color equivalences of ORO content in rabbits fed 12 weeks were almost 5.0 times higher than those fed 4 weeks. Thus, this ORO dye-eluting method is useful for quantification of atherosclerotic plaques in aortas in rabbits, as well as other animal models.

Multiple Hidden Markov Model for Pathological Vessel Segmentation.

One of the obstacles that prevent the accurate delineation of vessel boundaries is the presence of pathologies, which results in obscure boundaries and vessel-like structures. Targeting this limitation, we present a novel segmentation method based on multiple Hidden Markov Models. This method works with a vessel axis + cross-section model, which constrains the classifier around the vessel. The vessel axis constraint gives our method the potential to be both physiologically accurate and computationally effective. Focusing on pathological vessels, we reap the benefits of the redundant information embedded in multiple vessel-specific features and the good statistical properties coming with Hidden Markov Model, to cover the widest possible spectrum of complex situations. The performance of our method is evaluated on synthetic complex-structured datasets, where we achieve a 91% high overlap ratio. We also validate the proposed method on a real challenging case, segmentation of pathological abdominal arteries. The performance of our method is promising, since our method yields better results than two state-of-the-art methods on both synthetic datasets and real clinical datasets.

Multimodality Assessment of Ascending Aortic Diameters: Comparison of Different Measurement Methods.

BACKGROUND: Transthoracic echocardiography (TTE), multidetector computed tomography (MDCT), and magnetic resonance imaging (MRI) have been widely used to monitor aortic diameters, with no consensus as to the best measurement approach. Thus, the aim of this study was to establish the best measurement methods by two-dimensional (2D) TTE, MDCT, and MRI to achieve comparable aortic diameters. METHODS: One hundred forty patients with severe aortic valvular disease or aortic dilatation were prospectively evaluated using 2D TTE and MDCT (n = 70) or MRI (n = 70). The aorta was measured at three different levels: sinuses of Valsalva, sinotubular junction, and ascending aorta. Three different measurements were made by 2D TTE-inner edge to inner edge, leading edge to leading edge (L-L), and outer edge to outer edge-and then compared with the inner edge-to-inner edge and outer edge-to-outer edge measurements of cusp-to-cusp and cusp-to-commissure diameters by MDCT or MRI. Inter- and intraobserver variability was analyzed. RESULTS: Aortic diameters by 2D TTE, MDCT, and MRI showed excellent inter- and intraobserver variability using all conventions. Significant underestimation was observed of all aortic diameters assessed by 2D TTE using the inner edge-to-inner edge convention compared with those obtained by MDCT or MRI (P < .0001). However, excellent accuracy was observed by 2D TTE when the L-L convention was used and compared with the internal diameter by MDCT and MRI (mean differences, 0.6 ± 2.6 mm [P = .158] for MDCT and 0.4 ± 3.5 mm [P = .852] for MRI). Cusp-to-cusp diameters were slightly larger than cusp-to-commissure diameters. The diameter by 2D TTE using the L-L convention correlated best with the noncoronary cusp-to-right coronary cusp diameter determined by both MDCT and MRI. CONCLUSIONS: Aortic root and ascending aortic diameters measured by 2D TTE using the L-L convention showed accurate and reproducible values compared with internal diameters assessed by MDCT or MRI. This approach permits a multimodality follow-up of patients with aortic diseases and avoids disparities in measurements obtained by different conventions.

A Glyoxalase-1 Knockdown Does Not Have Major Short Term Effects on Energy Expenditure and Atherosclerosis in Mice.

Objective. Glyoxalase-1 is an enzyme detoxifying methylglyoxal (MG). MG is a potent precursor of advanced glycation endproducts which are regarded to be a key player in micro- and macrovascular damage. Yet, the role of Glo1 in atherosclerosis remains unclear. In this study, the effect of Glo1 on mouse metabolism and atherosclerosis is evaluated. Methods. Glo1 knockdown mice were fed a high fat or a standard diet for 10 weeks. Body weight and composition were investigated by Echo MRI. The PhenoMaster system was used to measure the energy expenditure. To evaluate the impact of Glo1 on atherosclerosis, Glo1(KD) mice were crossed with ApoE-knockout mice and fed a high fat diet for 14 weeks. Results. Glo1 activity was significantly reduced in heart, liver, and kidney lysates derived from Glo1(KD) mice. Yet, there was no increase in methylglyoxal-derived AGEs in all organs analyzed. The Glo1 knockdown did not affect body weight or body composition. Metabolic studies via indirect calorimetry did not show significant effects on energy expenditure. Glo1(KD) mice crossed to ApoE(-/-) mice did not show enhanced formation of atherosclerosis. Conclusion. A Glo1 knockdown does not have major short term effects on the energy expenditure or the formation of atherosclerotic plaques.

Assessment of altered three-dimensional blood characteristics in aortic disease by velocity distribution analysis.

PURPOSE: To test the feasibility of velocity distribution analysis for identifying altered three-dimensional (3D) flow characteristics in patients with aortic disease based on 4D flow MRI volumetric analysis. METHODS: Forty patients with aortic (Ao) dilation (mid ascending aortic diameter MAA = 40 ± 7 mm, age = 56 ± 17 years, 11 females) underwent cardiovascular MRI. Four groups were retrospectively defined: mild Ao dilation (n = 10; MAA < 35 mm); moderate Ao dilation (n = 10; 35 < MAA < 45 mm); severe Ao dilation (n = 10; MAA > 45 mm); Ao dilation+aortic stenosis AS (n = 10; MAA > 35 mm and peak velocity > 2.5 m/s). The 3D PC-MR angiograms were computed and used to obtain a 3D segmentation of the aorta which was divided into four segments: root, ascending aorta, arch, descending aorta. Radial chart displays were used to visualize multiple parameters representing segmental changes in the 3D velocity distribution associated with aortic disease. RESULTS: Changes in the velocity field and geometry between cohorts resulted in distinct hemodynamic patterns for each aortic segment. Disease progression from mild to Ao dilation + AS resulted in significant differences (P < 0.05) in flow parameters across cohorts and increased radial chart size for root and ascending aorta segments by 146% and 99%, respectively. CONCLUSION: Volumetric 4D velocity distribution analysis has the potential to identify characteristic changes in regional blood flow patterns in patients with aortic disease.

[Biochemical and morphological assessment of the functional state of the endothelium in reconstructive operations on the abdominal aorta in animal experiments].

The article deals with the analysis of biochemical and morphological alterations in the functional state of the endothelium of laboratory animals after a reconstructive surgical intervention on the abdominal aorta. These alterations were assessed at various terms following operative treatment in the comparison group and intact control group. The authors carried out of computer-assisted morphometry of the reconstruction zone on histological preparations for correct interpretation of the biochemical alterations and assessment of the correlation between the studied biochemical indices in blood and the arterial wall.

Computational assessment of bicuspid aortic valve wall-shear stress: implications for calcific aortic valve disease.

The bicuspid aortic valve (BAV) is associated with a high prevalence of calcific aortic valve disease (CAVD). Although abnormal hemodynamics has been proposed as a potential pathogenic contributor, the native BAV hemodynamic stresses remain largely unknown. Fluid-structure interaction models were designed to quantify the regional BAV leaflet wall-shear stress over the course of CAVD. Systolic flow and leaflet dynamics were computed in two-dimensional tricuspid aortic valve (TAV) and type-1 BAV geometries with different degree of asymmetry (10 and 16% eccentricity) using an arbitrary Lagrangian­Eulerian approach. Valvular performance and regional leaflet wallshear stress were quantified in terms of valve effective orifice area (EOA), oscillatory shear index (OSI) and temporal shear magnitude (TSM). The dependence of those characteristics on the degree of leaflet calcification was also investigated. The models predicted an average reduction of 49% in BAV peak-systolic EOA relative to the TAV. Regardless of the anatomy, the leaflet wall-shear stress was side-specific and characterized by high magnitude and pulsatility on the ventricularis and low magnitude and oscillations on the fibrosa. While the TAV and non-coronary BAV leaflets shared similar shear stress characteristics, the base of the fused BAV leaflet fibrosa exhibited strong abnormalities, which were modulated by the degree of calcification (6-fold, 10-fold and 16-fold TSM increase in the normal, mildly and severely calcified BAV, respectively, relative to the normal TAV). This study reveals the existence of major differences in wall-shear stress pulsatility and magnitude on TAV and BAV leaflets. Given the ability of abnormal fluid shear stress to trigger valvular inflammation, the results support the existence of a mechano-etiology of CAVD in the BAV.

Coronary artery calcification and coronary atherosclerotic disease.

The presence of coronary artery calcium is closely associated with the presence of atherosclerotic lesions in the coronary vasculature. Detection of coronary calcium by imaging techniques has evolved over the last few decades and has become especially more sophisticated with advanced imaging technology. Whereas the status of coronary artery calcium as a marker of increased cardiovascular risk is well established, the indication for testing continues to be a topic of debate.

Assessment of the relationship between aortic pulse wave velocity and aortic arch calcification.

OBJECTIVES: We aimed to assess arterial stiffness parameters and to investigate the relationship between these parameters and aortic calcification in patients with aortic arch calcification and without symptomatic atherosclerotic disease. STUDY DESIGN: The population of this study consisted of 41 patients with aortic arch calcification verified by chest X-ray (group I, 17 males, mean age 70±5 years) and individuals without aortic arch calcification (group II, 17 males, mean age 68±6 years). Subjects with symptomatic or known vascular disease were excluded from the study. The arterial stiffness parameters of all subjects were measured non-invasively with a SphygmoCor device. Aortic pulse wave velocity (PWV), augmentation pressure (AP), augmentation index (AIx) and heart rate normalized augmentation index (AIx@75) were used as parameters of arterial stiffness. RESULTS: The two groups were compared according to demographic characteristics, medications currently being taken, and levels of serum lipids. There was no significant difference between the groups. AP in group I was significantly higher than that of group II (p=0.002). AIx and AIx@75 were similar in both groups. Aortic PWV of group I was significantly higher than that of group II (p<0.0001). CONCLUSION: According to the results of this study, the presence of aortic calcification, verified by chest radiography, was associated with increased aortic PWV.

Assessment of atherosclerotic plaques in a rabbit model by delayed-phase contrast-enhanced CT angiography: comparison with histopathology.

The aim of this study was to compare delayed-phase computed tomography angiography (CTA) attenuation values with histopathology, in ability to differentiate between fibrous and lipid-rich plaques in an experimental rabbit model. Twelve atherosclerotic rabbits underwent CTA of the abdominal aorta. The scan protocol included early-phase scans (EP), delayed scans at 90 s after contrast injection (DP(90s)), delayed scans at 10 min after contrast injection (DP(10min)), and delayed scan with saline infusion (DP(Saline)). Plaque composition was analyzed by histopathology (% of lipid-rich, fibrous and macrophage areas) and CT attenuation values in Hounsfield units. Using histopathology as the reference standard (n = 119), the overall sensitivity, specificity and accuracy of 64-slice CTA for the detection of plaques was 59, 100 and 79% for the EP scans; 88, 100 and 94% for the DP(90s) scans; 81, 100 and 90% for the DP(10min) scans; and 53, 100 and 76% for the DP(Saline) scans. CT density measurements showed a substantial overlap between fibrous and lipid-rich plaques, and poor correlations with the percentage of macrophage areas in both fibrous and lipid-rich plaques (r = 0.408, and r = 0.333). In delayed-phase 64-slice CTA, DP(90s) images have the best diagnostic performance for the detection of aortic plaques.

[Study of the efficacy and safety of losartan versus atenolol for aortic dilation in patients with Marfan syndrome]. / Valoración de la eficacia y la seguridad del losartán frente al atenolol en la prevención de la dilatación de la aorta en el síndrome de Marfan.

INTRODUCTION AND OBJECTIVES: Marfan syndrome is an inherited disease of the connective tissue. Recent trials have indicated the use of losartan (a transforming growth factor beta inhibitor) in these patients prevents aortic root enlargement. The aim of our clinical trial is to assess the efficacy and safety of losartan versus atenolol in the prevention of progressive dilation of the aorta in patients with Marfan syndrome. METHODS: This is a phase III clinical trial conducted in two institutions. A total of 150 subjects diagnosed with Marfan syndrome, aged between 5 and 60 years, of both sexes, and who meet the Ghent diagnostic criteria will be included in the study, with 75 patients per treatment group. It will be a randomized, double blind trial with parallel assignment to atenolol versus losartan (50 mg per day in patients below 50 kg and 100 mg per day in patients over 50 kg). Both growth and distensibility of the aorta will be assessed with echocardiography and magnetic resonance. Follow-up will be 3 years. CONCLUSIONS: Efficacy of losartan versus atenolol in the prevention of progressive dilation of the aorta, improved aortic distensibility, and prevention of adverse events (aortic dissection or rupture, cardiovascular surgery, or death) will be assessed in this study. It will also show the possible treatment benefits at different age ranges and with relation to the initial level of aortic root dilation.

Risk factors for late mortality after endovascular repair of the thoracic aorta.

OBJECTIVE: This study was conducted to identify risk factors for late mortality after thoracic endovascular aortic repair (TEVAR). METHODS: A retrospective analysis of consecutive TEVAR was conducted. Medical record review, telephone contact, or query of the Social Security Death Index was used to determine 30-day and late survival. Late mortality was assessed with respect to patient characteristics at the time of the initial treatment, preoperative laboratory values, pathology, clinical presentation, and treatment adjuncts. Significant univariate predictors of death were entered into a multivariate Cox proportional hazards model. RESULTS: From 1998 to 2009, 252 patients (149 men; mean age, 68 years) underwent TEVAR for degenerative thoracic aortic aneurysm (TAA, n = 143), type B dissection (n = 62), mycotic aneurysm (n = 13), traumatic disruption (n = 12), penetrating ulcer or intramural hematoma (n = 10), anastomotic pseudoaneurysm (n = 4), or other pathology (n = 8). The 30-day mortality was 9.5%, with stroke or spinal cord injury in 5.6%. Mean follow-up was 22 +/- 22 months. Kaplan-Meier mean survival was 53 months. Predictors of late mortality by univariate analysis included age (P < .01), cardiac arrhythmia (P = .03), chronic obstructive pulmonary disease (P = .05), aneurysm diameter (P < .01), rupture (P < .01), debranching (P = .02), leukocytosis (white blood cell count > 10.0 x 10(3)/microL; P < .01), albumin, (P < .01), and creatinine > 1.7 mg/dL (P = .01). Multivariate predictors of mortality included rupture (hazard ratio [HR], 3.10; 95% confidence interval [CI], 1.02-9.44; P = .03), debranching (HR, 2.20; 95% CI, 1.09-4.24; P = .03), preoperative leukocytosis (HR, 1.23; 95% CI, 1.09-1.39; P = .001), and aneurysm diameter (HR, 1.02; 95% CI, 1.01-1.03; P = .04). Subgroup analysis of patients undergoing TEVAR for asymptomatic, nonruptured TAA demonstrated that debranching (HR, 2.47; 95% CI, 1.13-5.39; P = .02), White blood cell count (HR, 1.19; 95% CI, 1.01-1.40; P < .04), and aneurysm diameter (HR, 1.03; 95% CI, 1.01-1.05, P < .01) remain independently predictive of late mortality. CONCLUSIONS: Preoperative leukocytosis, aneurysm diameter, and concurrent debranching independently predict late mortality irrespective of clinical presentation and may assist in risk stratification.

Pharmacological inhibition of C-C chemokine receptor 2 decreases macrophage infiltration in the aortic root of the human C-C chemokine receptor 2/apolipoprotein E-/- mouse: magnetic resonance imaging assessment.

UNLABELLED: Purpose- This study assessed the pharmacological effect of a novel selective C-C chemokine receptor (CCR) 2 antagonist (GSK1344386B) on monocyte/macrophage infiltration into atherosclerotic plaque using magnetic resonance imaging (MRI) in an atherosclerotic mouse model. METHODS AND RESULTS: Apolipoprotein E(-/-) mice expressing human CCR2 were fed a Western diet (vehicle group) or a Western diet plus10 mg/kg per day of GSK1344386B (GSK1344386B group). After the baseline MRI, mice were implanted with osmotic pumps containing angiotensin II, 1000 ng/kg per minute, to accelerate lesion formation. After five weeks of angiotensin II administration, mice received ultrasmall superparamagnetic iron oxide, an MRI contrast agent for the assessment of monocyte/macrophage infiltration to the plaque, and underwent imaging. After imaging, mice were euthanized, and the heart and aorta were harvested for ex vivo MRI and histopathological examination. After 5 weeks of dietary dosing, there were no significant differences between groups in body or liver weight or plasma cholesterol concentrations. An in vivo MRI reflected a decrease in ultrasmall superparamagnetic iron oxide contrast agent uptake in the aortic arch of the GSK1344386B group (P<0.05). An ex vivo MRI of the aortic root also reflected decreased ultrasmall superparamagnetic iron oxide uptake in the GSK1344386B group and was verified by absolute iron analysis (P<0.05). Although there was no difference in aortic root lesion area between groups, there was a 30% reduction in macrophage area observed in the GSK1344386B group (P<0.05). CONCLUSIONS: An MRI was used to noninvasively assess the decreased macrophage content in the atherosclerotic plaque after selective CCR2 inhibition.

Endovascular repair of the thoracic aorta: predictors of 30-day mortality in patients on the New Zealand Thoracic Aortic Stent Database (NZ TAS).

OBJECTIVES: To evaluate data in the New Zealand Thoracic Aortic Stent database to try and identify a scoring system that could predict 30-day mortality in patients undergoing stenting of the descending thoracic aorta (TEVAR). DESIGN: Retrospective analysis of the New Zealand thoracic aortic stent database between December 2001 and August 2007. MATERIALS AND METHODS: The 30-day mortality of the 122 patients is 7.38% (n=9). Risk factors were recorded based on the Society of Thoracic Surgeons (STS) risk score. Glasgow aneurysm score was calculated and the pathology being treated analysed. Univariate analysis was carried out. RESULTS: The mortality of three pathology groups was compared. 30-day mortality was 2.04% (n=1) in the elective aneurysm group, 17.95% (n=7) in the complicated Stanford type B dissection group, and 0% (n=0) in the trauma group. Thirty-day mortality is significantly higher in the dissection group compared with the elective aneurysm (p=0.02) and trauma (p=0.03) groups. The most frequent risk factors in the dissection group of patients were peripheral vascular disease, smoking and hypertension. Although percentage mortality is higher with increasing GAS, the results are not statistically significant (p=0.34). No independent risk factors were identified from the STS risk score data. CONCLUSION: No specific risk score system seems to be able to predict mortality in TEVAR patients.

Detection of aortic calcification during vertebral fracture assessment (VFA) compared to digital radiography.

BACKGROUND: Cardiovascular disease is the most common cause of mortality among post-menopausal women. Our objective was to determine whether or not lateral spine images obtained on a bone densitometer to detect prevalent vertebral fracture can also accurately detect radiographic abdominal aortic calcification (AAC), an important risk factor for cardiovascular disease independent of clinical risk factors. METHODOLOGY/PRINCIPAL FINDINGS: One hundred seventy four postmenopausal women had bone densitometry, lateral spine densitometry imaging (called vertebral fracture assessment, or VFA), and lateral spine digital radiographs. Radiographs and VFA images were scored for AAC using a previously validated 24 point scale and a simplified, new 8 point scale (AAC-8). One hundred fifty six (90%) of the VFA images were evaluable for AAC. The non-parametric intraclass correlation coefficient between VFA and radiographic 24 point and AAC-8 readings, respectively, were 0.80 (95% C.I. 0.68-0.87) and 0.76 (95% C.I. 0.65-0.84). Areas under receiver operating characteristics (ROC) curves for VFA to detect those with a radiographic 24-point AAC score >or=5 were 0.86 (95% C.I. 0.77-0.94) using the 24 point scale and 0.84 (95% C.I. 0.76-0.92) using the AAC-8 scale. CONCLUSION/SIGNIFICANCE: VFA imaging intended to detect prevalent vertebral fracture can also detect radiographic AAC, an important cardiovascular disease risk factor. Since bone densitometry is recommended for all women age 65 and older, VFA imaging at the time of bone densitometry offers an opportunity to assess this risk factor in the post-menopausal female population at very little incremental time and expense.

Time-resolved 3D MR velocity mapping at 3T: improved navigator-gated assessment of vascular anatomy and blood flow.

PURPOSE: To evaluate an improved image acquisition and data-processing strategy for assessing aortic vascular geometry and 3D blood flow at 3T. MATERIALS AND METHODS: In a study with five normal volunteers and seven patients with known aortic pathology, prospectively ECG-gated cine three-dimensional (3D) MR velocity mapping with improved navigator gating, real-time adaptive k-space ordering and dynamic adjustment of the navigator acceptance criteria was performed. In addition to morphological information and three-directional blood flow velocities, phase-contrast (PC)-MRA images were derived from the same data set, which permitted 3D isosurface rendering of vascular boundaries in combination with visualization of blood-flow patterns. RESULTS: Analysis of navigator performance and image quality revealed improved scan efficiencies of 63.6%+/-10.5% and temporal resolution (<50 msec) compared to previous implementations. Semiquantitative evaluation of image quality by three independent observers demonstrated excellent general image appearance with moderate blurring and minor ghosting artifacts. Results from volunteer and patient examinations illustrate the potential of the improved image acquisition and data-processing strategy for identifying normal and pathological blood-flow characteristics. CONCLUSION: Navigator-gated time-resolved 3D MR velocity mapping at 3T in combination with advanced data processing is a powerful tool for performing detailed assessments of global and local blood-flow characteristics in the aorta to describe or exclude vascular alterations.

Comparison of different MRI techniques for the assessment of thoracic aortic pathology: 3D contrast enhanced MR angiography, turbo spin echo and balanced steady state free precession.

PURPOSE: The purpose of this study was to compare two non-contrast 2D techniques with the current contrast-enhanced MRI standard 3D technique for the routine assessment of thoracic aortic pathologies. METHODS: One hundred patients with suspected or known thoracic aortic diseases were examined with a 1.5 T scanner using 2D turbo spin echo (TSE), 2D balanced steady state free precession (balanced SSFP) and 3D contrast-enhanced MR angiography (CE-MRA). The diameters of the aorta at predefined levels were measured. The feasibility to visualize the aortic root and supra-aortic branches was tested. All morphologic abnormalities of the aorta, the aortic wall and the aortic valve, as well as image quality of TSE and balanced SSFP influencing the diagnosis were analysed. RESULTS: Compared to CE-MRA, balanced SSFP and TSE allowed for the detection of a significantly higher number of relevant pathologies (thickened aortic wall and signs of emergency) in less time. No significant differences were found among the sequences for the identification of aneurysms, dissection membranes and thrombi. No single technique was able to address all clinically relevant issues. TSE was associated with a better image quality compared to balanced SSFP, which however did not translate into a significantly improved diagnostic accuracy. CONCLUSION: The total number of pathologic findings was higher using 2D TSE and balanced SSFP when compared to 3D CE-MRA. None of the techniques applied could address all clinically relevant issues. The major drawback of TSE is its relatively long scanning time while balanced SSFP is associated with more artifacts.

In vivo 16-slice, multidetector-row computed tomography for the assessment of experimental atherosclerosis: comparison with magnetic resonance imaging and histopathology.

BACKGROUND: Noninvasive imaging can detect early atherosclerotic disease. Magnetic resonance imaging (MRI), because of its excellent spatial resolution, is already established as a tool for plaque characterization. Sixteen-slice, multidetector-row computed tomography (MDCT) was recently introduced into the field of cardiac imaging, with promising results for noninvasive angiography. We compared the capabilities of MDCT and MRI for the assessment of noncalcified, atherosclerotic plaques. METHODS AND RESULTS: Six atherosclerotic rabbits underwent in vivo imaging by MDCT and 1.5-T MRI. MDCT parameters were 120 kV, 120 mA/s, collimation 12x0.75, and spatial resolution 0.6x0.6 mm. MRI parameters were as follows: for proton density, repetition time/echo time (TR/TE) 2300/5.6; for T2, TR/TE 2300/62; and for T1, TR/TE 800/5.6; slice thickness was 3 mm and spatial resolution, 0.3x0.3 mm. Blinded analysis of 3-mm axial reconstructions from MDCT and the carefully matched MRI images (182 sections) showed excellent agreement between both modalities. MDCT yielded a slightly larger lumen area, anteroposterior diameters, and lateral diameters, with no significant differences in total vessel area. The sensitivity and specificity, respectively, to detect noncalcified, atherosclerotic plaques were 89% and 77% for MDCT and 97% and 94% for MRI. Fibrous-rich and lipid-rich plaque could not be differentiated visually, although they showed different attenuation properties (116+/-27 vs 51+/-25 Hounsfield units, P<0.01). CONCLUSIONS: Both techniques allow reliable detection of noncalcified, atherosclerotic plaques and accurate assessment of vessel areas and diameters. MDCT offers the additive value of a very short image acquisition time when compared with MRI. The subtle measurement differences found between modalities may be due to the better spatial resolution of MRI, which probably explains its superiority for tissue characterization.