MRI-based determination of reference values of thoracic aortic wall thickness in a general population

Aorta Wall Stress during Exercise in Patients with an Ascending Thoracic Aortic Aneurysm: Insights from a Case Series

Individuals with ascending thoracic aortic aneurysm (ATAA) are recommended to avoid intense exercise for fear of marked increases in aortic wall stress (AWS). However, no study has measured AWS during exercise. The aim of this case series was to examine AWS during "light-to-moderate" aerobic exercise in individuals with ATAA and healthy control (CON) participants.Three clinically stable patients with ATAA (2 male, mean age: 74 ± 1 years) and 3 CON (2 male, mean age: 69 ± 7 years) were studied on 2 separate days. Day 1: a maximal cardiopulmonary exercise test was performed to measure peak aerobic power (VO2peak), maximal heart rate, and blood pressure (BP). Day 2: cardiac and aortic magnetic resonance imaging were performed at rest and during submaximal (3-5 metabolic equivalents) "stepper" exercise during which cardiac output (Qc), aorta diameters, wall thickness, and BP were measured. Circumferential ascending and descending AWS were calculated in accord with LaPlace Law, whereas aorta mechanical efficiency was derived as the AWS/Qc slope.Patients with ATAA demonstrated lower median VO2peak (18.2 vs. 24.1 mL/kg/min). During exercise, the absolute ascending (ATAA: 257 vs. CON: 269 kPa) and descending AWS increased (ATAA: 224 vs. CON: 207 kPa), and ∆AWS during exercise was similar between ATAA and CON (Ascending, ATAA: 79 vs. CON: 62 kPa; Descending, ATAA: 64 vs. CON: 55 kPa). During exercise, ascending and descending AWS were 76 to 83% below ATAA rupture thresholds (i.e., 800-1,200 kPa) in all patients. Finally, exercise Qc was 17% lower and the ascending AWS/Qc slope was 30% higher in ATAA (16 kPa/L/min) versus CON (12 kPa/L/min).Our findings demonstrate "light-to-moderate" aerobic exercise produces similar AWS responses between ATAA and CON and is well below aneurysmal rupture thresholds. The higher AWS/Qc slope in ATAA suggests decreased aortic mechanical efficiency and may be a useful measure for exercise prescription for these patients.

Effect of a reduced arterial axial pre-stretch ratio during aging on the cardiac output and cerebral blood flow in the healthy elders

BACKGROUND AND OBJECTIVE

It is an indisputable physiological phenomenon that the arterial axial pre-stretch ratio (AAPSR) decreases with age, but little attention has been paid to the effect of this reduction on chronic diseases during aging.

METHODS

Here we reported an experimental method to simulate arteries aging, developed a fluid-structure interaction model with the effect of AAPSR changes, and compared it with the anatomy data and structural parameters of the human thoracic aorta.

RESULTS

We showed that with the process of aging, the decrease of AAPSR leads to a decline of arterial elasticity, a decrease of arterial elastic strain energy, which weakens the ability to promote blood circulation, the corresponding decrease in cardiac output (CO) and cerebral blood flow (CBF) causes distal organ and body tissue ischemia, which is one of the main causes of increased blood pressure and decreased cerebral perfusion in the elderly.

CONCLUSIONS

Thus, reduced AAPSR is the one of main manifestation of arteries aging and has an important impact on hypertension and hypoperfusion of the brain in the process of human aging. The research contributes to a better understanding of the physiological and pathological mechanisms of aging-related diseases.

Validation evidence with experimental and clinical data to establish credibility of TAVI patient-specific simulations

PURPOSE

The objective of this study is to validate a novel workflow for implementing patient-specific finite element (FE) simulations to virtually replicate the Transcatheter Aortic Valve Implantation (TAVI) procedure.

METHODS

Seven patients undergoing TAVI were enrolled. Patient-specific anatomical models were reconstructed from pre-operative computed tomography (CT) scans and subsequentially discretized, considering the native aortic leaflets and calcifications. Moreover, high-fidelity models of CoreValve Evolut R and Acurate Neo2 valves were built. To determine the most suitable material properties for the two stents, an accurate calibration process was undertaken. This involved conducting crimping simulations and fine-tuning Nitinol parameters to fit experimental force-diameter curves. Subsequently, FE simulations of TAVI procedures were conducted. To validate the reliability of the implemented implantation simulations, qualitative and quantitative comparisons with post-operative clinical data, such as angiographies and CT scans, were performed.

RESULTS

For both devices, the simulation curves closely matched the experimental data, indicating successful validation of the valves mechanical behaviour. An accurate qualitative superimposition with both angiographies and CTs was evident, proving the reliability of the simulated implantation. Furthermore, a mean percentage difference of 1,79 ± 0,93 % and 3,67 ± 2,73 % between the simulated and segmented final configurations of the stents was calculated in terms of orifice area and eccentricity, respectively.

CONCLUSION

This study shows the successful validation of TAVI simulations in patient-specific anatomies, offering a valuable tool to optimize patients care through personalized pre-operative planning. A systematic approach for the validation is presented, laying the groundwork for enhanced predictive modeling in clinical practice.

Quantitative analysis of systemic perfusion and cerebral blood flow in the modeling of aging and orthostatic hypotension

Introduction: Orthostatic hypotension (OH) is common among the older population. The mechanism hypothesized by OH as a risk factor for cognitive decline and dementia is repeated transient cerebral blood flow deficiency. However, to our knowledge, quantitative evaluation of cardiac output and cerebral blood flow due to acute blood pressure changes resulting from postural changes is rare. Methods: We report a new fluid-structure interaction model to analyze the quantitative relationship of cerebral blood flow during OH episodes. A device was designed to simulate the aging of blood vessels. Results and Discussion: The results showed that OH was associated with decreased transient cerebral blood flow. With the arterial aging, lesions, the reduction in cerebral blood flow is accelerated. These findings suggest that systolic blood pressure regulation is more strongly associated with cerebral blood flow than diastolic blood pressure, and that more severe OH carries a greater risk of dementia. The model containing multiple risk factors could apply to analyze and predict for individual patients. This study could explain the hypothesis that transient cerebral blood flow deficiency in recurrent OH is associated with cognitive decline and dementia.

On the necessity to include arterial pre-stress in patient-specific simulations of minimally invasive procedures

Transcatheter aortic valve implantation (TAVI) and thoracic endovascular aortic repair (TEVAR) are minimally invasive procedures for treating aortic valves and diseases. Finite element simulations have proven to be valuable tools in predicting device-related complications. In the literature, the inclusion of aortic pre-stress has not been widely investigated. It plays a crucial role in determining the biomechanical response of the vessel and the device-tissue interaction. This study aims at demonstrating how and when to include the aortic pre-stress in patient-specific TAVI and TEVAR simulations. A percutaneous aortic valve and a stent-graft were implanted in aortic models reconstructed from patient-specific CT scans. Two scenarios for each patient were compared, i.e., including and neglecting the wall pre-stress. The neglection of pre-stress underestimates the contact pressure of 48% and 55%, the aorta stresses of 162% and 157%, the aorta strains of 77% and 21% for TAVI and TEVAR models, respectively. The stent stresses are higher than 48% with the pre-stressed aorta in TAVI simulations; while, similar results are obtained in TEVAR cases. The distance between the device and the aorta is similar with and without pre-stress. The inclusion of the aortic wall pre-stress has the capability to give a better representation of the biomechanical behavior of the arterial tissues and the implanted device. It is suggested to include this effect in patient-specific simulations replicating the procedures.

Uncertainty quantification of the wall thickness and stiffness in an idealized dissected aorta

Personalized treatment informed by computational models has the potential to markedly improve the outcome for patients with a type B aortic dissection. However, existing computational models of dissected walls significantly simplify the characteristic false lumen, tears and/or material behavior. Moreover, the patient-specific wall thickness and stiffness cannot be accurately captured non-invasively in clinical practice, which inevitably leads to assumptions in these wall models. It is important to evaluate the impact of the corresponding uncertainty on the predicted wall deformations and stress, which are both key outcome indicators for treatment optimization. Therefore, a physiology-inspired finite element framework was proposed to model the wall deformation and stress of a type B aortic dissection at diastolic and systolic pressure. Based on this framework, 300 finite element analyses, sampled with a Latin hypercube, were performed to assess the global uncertainty, introduced by 4 uncertain wall thickness and stiffness input parameters, on 4 displacement and stress output parameters. The specific impact of each input parameter was estimated using Gaussian process regression, as surrogate model of the finite element framework, and a δ moment-independent analysis. The global uncertainty analysis indicated minor differences between the uncertainty at diastolic and systolic pressure. For all output parameters, the 4th quartile contained the major fraction of the uncertainty. The parameter-specific uncertainty analysis elucidated that the material stiffness and relative thickness of the dissected membrane were the respective main determinants of the wall deformation and stress. The uncertainty analysis provides insight into the effect of uncertain wall thickness and stiffness parameters on the predicted deformation and stress. Moreover, it emphasizes the need for probabilistic rather than deterministic predictions for clinical decision making in aortic dissections.

Towards biomechanics-based pre-procedural planning for thoracic endovascular aortic repair of aortic dissection

BACKGROUND AND OBJECTIVE

Although thoracic aortic endovascular repair (TEVAR) has shown promising outcomes in the treatment of patients with complicated type B aortic dissection, complications still occur after TEVAR that can lead to catastrophic events. Biomechanical interactions between the stent-graft (SG) and the local aortic tissue play a critical role in determining the outcome of TEVAR. Different SG design may cause different biomechanical responses in the treated aorta, but such information is not known at the time of pre-procedural planning. By developing patient-specific virtual stent-graft deployment tools, it is possible to analyse and compare the biomechanical impact of different SGs on the local aorta for individual patients.

METHODS

A finite element based virtual SG deployment model was employed in this study. Computational simulations were performed on a patient-specific model of type B aortic dissection, accounting for details of the SG design and the hyperelastic behaviour of the aortic wall. Based on the geometry reconstructed from the pre-TEVAR CTA scan, the patient-specific aortic dissection model was created and pre-stressed. Parametric models of three different SG products (SG1, SG2 and SG3) were built with two different lengths for each design. The SG models incorporated different stent and graft materials, stent strut patterns, and assembly approaches. Using our validated SG deployment simulation framework, virtual trials were performed on the patient-specific aortic dissection model using different SG products and varying SG lengths.

CONCLUSION

Simulation results for different SG products suggest that SG3 with a longer length (SG3-long) would be the most appropriate device for the individual patient. Compared to SG1-short (the SG deployed in the patient), SG3-long followed the true lumen tortuosity closely, resulted in a more uniform true lumen expansion and a significant reduction in peak stress in the distal landing zone. These simulation results are promising and demonstrate the feasibility of using the virtual SG deployment model to assist clinicians in pre-procedural planning.

Position-based dynamics simulator of vessel deformations for path planning in robotic endovascular catheterization

A major challenge during autonomous navigation in endovascular interventions is the complexity of operating in a deformable but constrained workspace with an instrument. Simulation of deformations for it can provide a cost-effective training platform for path planning. Aim of this study is to develop a realistic, auto-adaptive, and visually plausible simulator to predict vessels' global deformation induced by the robotic catheter's contact and cyclic heartbeat motion. Based on a Position-based Dynamics (PBD) approach for vessel modeling, Particle Swarm Optimization (PSO) algorithm is employed for an auto-adaptive calibration of PBD deformation parameters and of the vessels movement due to a heartbeat. In-vitro experiments were conducted and compared with in-silico results. The end-user evaluation results were reported through quantitative performance metrics and a 5-Point Likert Scale questionnaire. Compared with literature, this simulator has an error of 0.23±0.13% for deformation and 0.30±0.85mm for the aortic root displacement. In-vitro experiments show an error of 1.35±1.38mm for deformation prediction. The end-user evaluation results show that novices are more accustomed to using joystick controllers, and cardiologists are more satisfied with the visual authenticity. The real-time and accurate performance of the simulator make this framework suitable for creating a dynamic environment for autonomous navigation of robotic catheters.

A fluid-structure interaction model accounting arterial vessels as a key part of the blood-flow engine for the analysis of cardiovascular diseases

According to the classical Windkessel model, the heart is the only power source for blood flow, while the arterial system is assumed to be an elastic chamber that acts as a channel and buffer for blood circulation. In this paper we show that in addition to the power provided by the heart for blood circulation, strain energy stored in deformed arterial vessels in vivo can be transformed into mechanical work to propel blood flow. A quantitative relationship between the strain energy increment and functional (systolic, diastolic, mean and pulse blood pressure) and structural (stiffness, diameter and wall thickness) parameters of the aorta is described. In addition, details of blood flow across the aorta remain unclear due to changes in functional and other physiological parameters. Based on the arterial strain energy and fluid-structure interaction theory, the relationship between physiological parameters and blood supply to organs was studied, and a corresponding mathematical model was developed. The findings provided a new understanding about blood-flow circulation, that is, cardiac output allows blood to enter the aorta at an initial rate, and then strain energy stored in the elastic arteries pushes blood toward distal organs and tissues. Organ blood supply is a key factor in cardio-cerebrovascular diseases (CCVD), which are caused by changes in blood supply in combination with multiple physiological parameters. Also, some physiological parameters are affected by changes in blood supply, and vice versa. The model can explain the pathophysiological mechanisms of chronic diseases such as CCVD and hypertension among others, and the results are in good agreement with epidemiological studies of CCVD.

A comprehensive analysis of the intramural segment in interarterial anomalous coronary arteries using computed tomography angiography

Aims

An anomalous coronary artery originating from the opposite sinus of Valsalva (ACAOS) with an interarterial course can be assessed using computed tomography angiography (CTA) for the presence of high-risk characteristics associated with sudden cardiac death. These features include a slit-like ostium, acute angle take-off, proximal luminal narrowing, and an intramural segment. To date, no robust CTA criteria exist to determine the presence of an intramural segment. We aimed to deduct new CTA parameters to distinguish an intramural course of interarterial ACAOS.

Methods and results

Twenty-five patients with an interarterial ACAOS (64% female, mean age 46 years, 88% right ACAOS) from two academic hospitals were evaluated. Inclusion criteria were the availability of a preoperative CTA scan (0.51 mm slice thickness) and peroperative confirmation of the intramural segment. Using multiplanar reconstruction of the CTA, the distance between the lumen of the aorta and the lumen of the ACAOS [defined as ‘interluminal space’ (ILS)] was assessed at 2 mm intervals along the intramural segment. Analysis showed a mean ILS of 0.69 ± 0.15 mm at 2 mm from the ostium. At the end of the intramural segment where the ACAOS becomes non-intramural, the mean ILS was significantly larger (1.27 ± 0.29 mm, P < 0.001). Interobserver agreement evaluation showed good reproducibility (intraclass correlation coefficient 0.77, P < 0.001). Receiver operator characteristic analysis demonstrated that at a cut-off ILS of <0.95 mm, an intramural segment can be diagnosed with 100% sensitivity and 84% specificity.

Conclusion

The ILS is introduced as a novel and robust CTA parameter to identify an intramural course of interarterial ACAOS. An ILS of <0.95 mm is indicative of an intramural segment.

A mathematical model for biomechanical behavior of the aortic arch

The aortic arch plays a significant role in homeostatic mechanisms to retain blood pressure at stable balance in the cardiovascular system. Therefore, the objective is to estimate and identify cardiovascular illness imposed by the abnormal blood hemodynamic domain. In this regard, hemodynamic forces are monitored by the baroreflex of the artery wall. Therefore, these receptors quickly detect the abnormal stress magnitudes in the aortic arterial wall. The present study presents a 3D aortic arch model extracted by a Computerized tomography scan. Also, the numerical solution was carried out by ANSYS 2020 R1 in view of Fluid-Structure Interaction After that, we found wall shear stress (WSS), pressure, and velocity in the fluid domain. Also, the normal stress was analyzed to determine the aortic arch baroreflex location in the solid range. In this regard, higher WSS values are measured at the supra-aortic branches going out the aortic arch that reached 42.5 Pa. Also, higher normal stress happened at the aortic root and the supra-aortic branches and reached approximately 200 kPa at peak systole.

SHIP-MR and Radiology: 12 Years of Whole-Body Magnetic Resonance Imaging in a Single Center

The Study of Health in Pomerania (SHIP), a population-based study from a rural state in northeastern Germany with a relatively poor life expectancy, supplemented its comprehensive examination program in 2008 with whole-body MR imaging at 1.5 T (SHIP-MR). We reviewed more than 100 publications that used the SHIP-MR data and analyzed which sequences already produced fruitful scientific outputs and which manuscripts have been referenced frequently. Upon reviewing the publications about imaging sequences, those that used T1-weighted structured imaging of the brain and a gradient-echo sequence for R2* mapping obtained the highest scientific output; regarding specific body parts examined, most scientific publications focused on MR sequences involving the brain and the (upper) abdomen. We conclude that population-based MR imaging in cohort studies should define more precise goals when allocating imaging time. In addition, quality control measures might include recording the number and impact of published work, preferably on a bi-annual basis and starting 2 years after initiation of the study. Structured teaching courses may enhance the desired output in areas that appear underrepresented.

In Vitro Validation of Regional Circumferential Strain Assessment in a Phantom Aortic Model Using Cine Displacement Encoding With Stimulated Echoes MRI

BACKGROUND

A novel application of cine Displacement ENcoding with Stimulated Echoes Magnetic Resonance Imaging (DENSE MRI) has recently been described to assess regional heterogeneities in circumferential strain around the aortic wall in vivo; however, validation is first required for successful clinical translation.

PURPOSE

To validate the quantification of regional circumferential strain around the wall of an aortic phantom using DENSE MRI.

STUDY TYPE

In vitro phantom study.

POPULATION

Three polyvinyl alcohol aortic phantoms with eight axially oriented nitinol wires embedded evenly around the walls.

FIELD STRENGTH/SEQUENCE

3 T; gradient-echo aortic DENSE MRI with spiral cine readout, gradient-echo phase-contrast MRI (PCMR) with Cartesian cine readout.

ASSESSMENT

Phantoms were connected to a pulsatile flow loop and peak DENSE-derived regional circumferential Green strains at 16 equally spaced sectors around the wall were assessed according to previously published algorithms. "True" regional circumferential strains were calculated by manually tracking displacements of the nitinol wires by two independent observers. Normalized circumferential strains (NCS) were calculated by dividing regional strains by the mean strain. Finally, DENSE-derived regional strain was corrected by multiplying regional DENSE NCS by the mean strain calculated from the diameter change on the PCMR.

STATISTICAL TESTS

One-sample t-test, Paired-sample t-test, and analysis of variance with Bonferroni correction, coefficient of variation (CoV), Bland-Altman analysis; P < 0.05 was considered statistically significant.

RESULTS

Aortic DENSE MRI significantly overestimated circumferential strain compared to the wire-tracking method (mean difference and SD 0.030 ± 0.014, CoV 0.31). However, NCS demonstrated good agreement between DENSE and wire-tracking data (mean difference 0.000 ± 0.172, CoV 0.15). After correcting the DENSE-derived regional strain, the mean difference in regional circumferential strain between DENSE and wire-tracking was significantly reduced to 0.006 ± 0.008, and the CoV was reduced to 0.18.

DATA CONCLUSION

For aortic phantoms with mild spatial heterogeneity in circumferential strain, the previously published aortic DENSE MRI technique successfully assessed the regional NCS distribution but overestimated the mean strain. This overestimation is correctable by computing a more accurate mean circumferential strain using a separate cine scan.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Aortic Calcification in Takayasu Arteritis: Risk Factors and Relationship With Activity and Vascular Lesion. It Is Not Only an Aging Question

INTRODUCTION

Aortic calcification is a frequent finding in Takayasu arteritis (TA). The aim of this study was to evaluate the risk factors for aortic calcification in TA and its relationship with disease activity and the presence and type of vascular lesion.

METHODS

Nineteen patients with TA underwent nonenhanced computed tomography to measure the calcium score of the aorta and its main branches, which were divided into 13 segments. In each segment, the type of vascular lesion was evaluated by noninvasive angiography. Clinical risk factors and disease activity scores were recorded.

RESULTS

Eighteen of 19 patients (95%) were women, with a median age of 25 years. Median of calcium score was 69 AU (0-12,465 AU). Eleven of 19 patients (57.9%) had calcium score greater than 0. Age, evolution time, and dyslipidemia were higher in patients with calcium, whereas the National Institutes Health and Dabague disease activity scores were lower. There was no association between the presence of calcium and vascular lesion: 60 of 160 segments (37.5%) without calcium had some lesion, compared with 24 of 68 (35.3%) with calcium score greater than 0, p = 0.75. However, occlusion was more frequent in patients with calcium, whereas wall thickening was in those without calcium.

CONCLUSIONS

Aortic calcification in TA is related to age, evolution time, and abnormalities in lipid profile and occlusion and, inversely with some activity scores. Identification of calcification could be useful in identifying patients that even without significant lesions might have accelerated atherosclerosis, and who might be benefited with specific treatment.

Patient-Specific Virtual Stent-Graft Deployment for Type B Aortic Dissection: A Pilot Study of the Impact of Stent-Graft Length

Thoracic endovascular aortic repair (TEVAR) has been accepted as a standard treatment option for complicated type B aortic dissection. Distal stent-graft-induced new entry (SINE) is recognised as one of the main post-TEVAR complications, which can lead to fatal prognosis. Previous retrospective cohort studies suggested that short stent-graft (SG) length (<165 mm) might correlate with increased risk of distal SINE. However, the influence of SG length on changes in local biomechanical conditions before and after TEVAR is unknown. In this paper, we aim to address this issue using a virtual SG deployment simulation model developed for application in type B aortic dissection. Our model incorporates detailed SG design and hyperelastic behaviour of the aortic wall. By making use of patient-specific geometry reconstructed from pre-TEVAR computed tomography angiography (CTA) scan, our model can predict post-TEVAR SG configuration and wall stress. Virtual SG deployment simulations were performed on a patient who underwent TEVAR with a short SG (158 mm in length), mimicking the actual clinical procedure. Further simulations were carried out on the same patient geometry but with different SG lengths (183 mm and 208 mm) in order to evaluate the effect of SG length on changes in local stress in the treated aorta. Comparisons of simulation results for different SG lengths showed the location of maximum stress varied with the SG length. With the short SG (deployed in the patient), the maximum von Mises stress of 238.9 kPa was found on the intimal flap at the distal landing zone where SINE was identified at 3-month follow-up. Increasing the SG length caused the maximum von Mises stress to move away from the distal landing zone where stress values were reduced by approximately 17% with the medium-length SG and by 60% with the long SG. This pilot study demonstrates the potential of using the virtual SG deployment model as a pre-surgical planning tool to help select the most appropriate SG length for individual patients.

Aortic Delamination-A Possible Precursor of Impending Catastrophe

Aortic diameter is a powerful predictor of adverse aortic events, such as aortic rupture or dissection, forming the basis of prophylactic surgical repair criteria. Limited evidence is available regarding the association of aortic wall thickness (AWT) with these adverse aortic events. We present the case and surgical video of a 73-year-old man with chest pain and an increased AWT, who underwent ascending aortic repair and deep hemiarch placement under deep hypothermic circulatory arrest. Surgical pathology demonstrated evidence of aortic delamination and medial separation, indicative of an impending dissection. The patient recovered uneventfully, and his chest pain ultimately resolved after open repair. In this patient, increased AWT was felt to be the precursor to a potential aortic catastrophe.

Aortic Thickness: A Forgotten Paradigm in Risk Stratification of Aortic Disease

BACKGROUND

 This study aimed at risk-stratifying aortic dilatation using aortic wall thickness (AWT) and comparing methods of AWT assessment.

METHODS

 Demographic, epidemiological, and perioperative data on 72 consecutive aortic surgeries (age = 62 years[standard deviation (SD) = 12] years) performed by a single surgeon were collected from hospital database. Aortic thickness was measured on computed tomography scans, as well as intraoperatively in four quadrants, at the level of aortic sinuses, as well as midascending aorta, using calipers. Aortic wall stress was calculated using standard mathematical formulae.

RESULTS

 The ascending aorta was 48.2 (SD = 8) mm and the mean thickness at ascending aorta level was 1.9 (SD = 0.3) mm. There was congruence between imaging and intraoperative measurements of thickness, as well as between the radiologist and surgeon. Preoperatively, 16 patients had multiple imaging studies showing an average rate of growth of 1.2 mm per year without significant difference in thickness. The wider the aorta, the thinner was the lateral or convex wall. Aortic stenosis (p = 0.01), lateral to medial wall thickness ratio (p = 0.04), and history of hypertension (p = 0.00), all had protective effect on aortic root stress. The ascending aortic stress was directly affected by age (p = 0.03) and inversely related to lateral to medial wall thickness ratio (p = 0.03).

CONCLUSION

 Aortic thickness can be measured preoperatively and easily confirmed intraoperatively. Risk stratification based on both aortic thickness and diameter (stress calculations) would better predict acute aortic events in dilated aortas and define aortic resection criteria more objectively.

Accuracy of arterial [18F]-Fluorodeoxyglucose uptake quantification: A kinetic modeling study

2-deoxy-2- [18F] fluoro-D-glucose (FDG) PET is commonly used for the assessment of vessel wall inflammation. Guidelines for analysis of arterial wall FDG signal recommend the use of the average of maximal standardized uptake value (mean SUVmax) and target-to-blood (mean TBRmax) ratio. However, these methods have not been validated against a gold standard such as tissue activity ex vivo or net uptake rate of FDG (Ki) obtained using kinetic modeling. We sought to evaluate the accuracy of mean SUVmax and mean TBRmax for aortic wall FDG signal quantification in comparison with the net uptake rate of FDG.

METHODS

Dynamic PET data from 13 subjects without prior history of cardiovascular disease who enrolled in a study of vascular inflammation were used for this analysis. Ex vivo measurement of plasma activity was used as the input function and voxel-by-voxel Patlak analysis was performed with t* = 20 minute to obtain the Ki image. The FDG signal in the ascending aortic wall was quantified on PET images following recent guidelines for vascular imaging to determine mean SUVmax and mean TBRmax.

RESULTS

The Ki in the ascending aortic wall did not correlate with mean SUVmax (r = 0.10, P = NS), but correlated with mean TBRmax (r = 0.82, P < 0.001) (Figure 1B). Ki and Ki_max strongly correlated (R = 0.96, P < 0.0001) and similar to Ki, Ki_max did not correlate with mean SUVmax (r = 0.17, P = NS), but correlated with mean TBRmax (r = 0.83, P < 0.001).

CONCLUSIONS

Kinetic modeling supports the use of mean TBRmax as a surrogate for the net uptake rate of FDG in the arterial wall. These results are relevant to any PET imaging agent, regardless of the biological significance of the tracer uptake in the vessel wall.

One-Stop MR Neurovascular Vessel Wall Imaging With a 48-Channel Coil System at 3 T

OBJECTIVE

The purpose of this article was to build a radio frequency (RF) coil system to achieve high vessel wall image quality with coverage extending from the aortic arch to the intracranial vessels.

METHODS

A 48-channel coil system was built and characterized at a 3 tesla (T) Magnetic Resonance Imaging (MRI) scanner (uMR 790, Shanghai United Imaging Healthcare, Shanghai, China). The coil's performance was compared with a commercially available 36-channel coil system. By human studies, signal-to-noise ratio (SNR) units were evaluated and g-factors were calculated in the transverse planes of the brain and neck regions.

RESULTS

The SNR was increased by at least 28% in the brain region and up to fourfold in the neck region. The average g-factor with the acceleration factor, R = 3, was lowered by 21% in the transverse plane of the neck region. Intracranial and carotid arterial wall images with an isotropic spatial resolution of 0.63 mm were acquired within 7.7 minutes and thoracic aorta wall images with an isotropic spatial resolution of 1.1 mm were acquired within 2.7 minutes with the 48-channel coil system. The vessel wall can be more clearly visualized with the 48-channel coil system compared with the 36-channel coil system.

CONCLUSION

A 48-channel coil system was developed and demonstrated superior performance for vessel wall imaging at the intracranial and cervical carotid arteries compared with a commercial 36-channel coil.

SIGNIFICANCE

The 48-channel coil system is potentially useful for clinical diagnostics, especially when attempting to diagnose ischemic stroke.

Normal Diameter and Growth Rate of Infrarenal Aorta and Common Iliac Artery in Chinese Population Measured by Contrast-Enhanced Computed Tomography

BACKGROUND

In previous studies, the growth rate and diameter of infrarenal aorta was paucity of Chinese data. This study aim to evaluate the normal inside diameter and growth rate of the infrarenal aorta and common iliac artery in Chinese adult population and to explore the relationship between related factors and the arterial diameter.

METHODS

A retrospective study was performed among 1,340 hospitalized adult patients undergoing contrast-enhanced abdominopelvic computed tomography from April 2017 to March 2018 in our hospital. The inside diameter of infrarenal aorta and common iliac artery was measured. Linear regression was used to analyze the relationship between various factors and arterial diameter. Kruskal-Wallis H test was used to analyze the relationship between the arterial diameter and age. Mann-Whitney U test was used to analyze the relationship between arterial diameter and sex.

RESULTS

The inside diameter of the infrarenal aorta was 16.49 ± 2.12 mm in male patients and 14.50 ± 1.73 mm in female patients. In male patients, the right common iliac artery was 9.77 ± 1.75 mm, and the left was 9.65 ± 1.76 mm. In female patients, the right common iliac artery was 8.59 ± 1.31 mm and the left was 8.45 ± 1.28 mm. Comparing the oldest group with the youngest, the infrarenal aortic diameter increased 27.32% in male patients and 30.11% in female patients. Right common iliac artery increased 25.13% in male patients and 30.30% in female patients. Left common iliac artery increased 25.19% in male patients and 34.26% in female patients. The growth rate increased at the beginning, reached its peak at the age of 50-60 years, and then decreased. Multiple linear regression analysis results showed that sex, age, body surface area (BSA), hypertension, and cancer were significantly correlated with the diameter of infrarenal aorta. Sex, age, BSA, and hypertension were correlated with the diameter of right common iliac artery. Sex, age, BSA, and cancer were correlated with the diameter of left common iliac artery.

CONCLUSIONS

The diameter of the infrarenal abdominal aorta and common iliac artery of Chinese people is smaller than that of other countries. The abdominal aortic aneurysm (AAA) guideline might be developed based on the basic diameter to suit patients with AAA and a different basic abdominal aortic diameter. Artery diameter was increased by the age, and female patients have smaller diameter and larger arterial growth rate than male patients. Female and young patients with AAA may choose more oversize grafts for endovascular AAA repair.

Pediatric heterozygous familial hypercholesterolemia patients have locally increased aortic pulse wave velocity and wall thickness at the aortic root

Familial hypercholesterolemia (FH) is an autosomal dominant disorder that affects 1 in 250 people. Aortic stiffness, measured by pulse wave velocity (PWV), is an independent predictor for cardiovascular events. Young FH patients are a unique group with early vessel wall disease that may serve to elucidate the determinants of aortic stiffness. We hypothesized that young FH patients would have early changes in aortic stiffness compared to healthy, age- and sex-matched reference values. Thirty-three FH patients ( ≥ 7 years age; mean age 14.6 ± 3.3 years; 26/33 on statin therapy) underwent cardiac MRI. PWV was determined using propagation of flow waveform from aortic arch phase contrast images. Distensibility and aortic wall thickness (AWT) were measured at the ascending, proximal descending, and diaphragmatic aorta. Ventricular volumes and left ventricular (LV) myocardial mass were measured from 2D cine images. These parameters were compared to age- and sex-matched reference values. FH patients had significantly higher PWV (4.5 ± 0.8 vs. 3.5 ± 0.3 m/s; p < 0.001), aortic distensibility, and ascending aortic wall thickness (1.37 ± 0.18 vs. 1.30 ± 0.02 mm; p < 0.05) compared to reference. There was no difference in aortic area or descending aortic wall thickness between groups. Young FH patients had aortic changes with increased aortic pulse wave velocity in the setting of increased aortic distensibility, accompanied by increased thickness of the ascending aortic wall. Presence of these early findings in young patients despite the majority being on statin therapy support enhanced screening and aggressive treatment of familial hypercholesterolemia to prevent potential future cardiovascular events.

Patient-specific simulation of transcatheter aortic valve replacement: impact of deployment options on paravalvular leakage

Transcatheter aortic valve replacement (TAVR) has emerged as an effective alternative to conventional surgical valve replacement in high-risk patients afflicted by severe aortic stenosis. Despite newer-generation devices enhancements, post-procedural complications such as paravalvular leakage (PVL) and related thromboembolic events have been hindering TAVR expansion into lower-risk patients. Computational methods can be used to build and simulate patient-specific deployment of transcatheter aortic valves (TAVs) and help predict the occurrence and degree of PVL. In this study finite element analysis and computational fluid dynamics were used to investigate the influence of procedural parameters on post-deployment hemodynamics on three retrospective clinical cases affected by PVL. Specifically, TAV implantation depth and balloon inflation volume effects on stent anchorage, degree of paravalvular regurgitation and thrombogenic potential were analyzed for cases in which Edwards SAPIEN and Medtronic CoreValve were employed. CFD results were in good agreement with corresponding echocardiography data measured in patients in terms of the PVL jets locations and overall PVL degree. Furthermore, parametric analyses demonstrated that positioning and balloon over-expansion may have a direct impact on the post-deployment TAVR performance, achieving as high as 47% in PVL volume reduction. While the model predicted very well clinical data, further validation on a larger cohort of patients is needed to verify the level of the model's predictions in various patient-specific conditions. This study demonstrated that rigorous and realistic patient-specific numerical models could potentially serve as a valuable tool to assist physicians in pre-operative TAVR planning and TAV selection to ultimately reduce the risk of clinical complications.

Assessing regional left ventricular thickening dysfunction and dyssynchrony via personalized modeling and 3D wall thickness measurements for acute myocardial infarction

BACKGROUND

Existing clinical diagnostic and assessment methods could be improved to facilitate early detection and treatment of cardiac dysfunction associated with acute myocardial infarction (AMI) to reduce morbidity and mortality.

PURPOSE

To develop 3D personalized left ventricular (LV) models and thickening assessment framework for assessing regional wall thickening dysfunction and dyssynchrony in AMI patients.

STUDY TYPE

Retrospective study, diagnostic accuracy.

SUBJECTS

Forty-four subjects consisting of 15 healthy subjects and 29 AMI patients.

FIELD STRENGTH/SEQUENCE

1.5T/steady-state free precession cine MRI scans; LGE MRI scans.

ASSESSMENT

Quantitative thickening measurements across all cardiac phases were correlated and validated against clinical evaluation of infarct transmurality by an experienced cardiac radiologist based on the American Heart Association (AHA) 17-segment model.

STATISTICAL TEST

Nonparametric 2-k related sample-based Kruskal-Wallis test; Mann-Whitney U-test; Pearson's correlation coefficient.

RESULTS

Healthy LV wall segments undergo significant wall thickening (P < 0.05) during ejection and have on average a thicker wall (8.73 ± 1.01 mm) compared with infarcted wall segments (2.86 ± 1.11 mm). Myocardium with thick infarct (ie, >50% transmurality) underwent remarkable wall thinning during contraction (thickening index [TI] = 1.46 ± 0.26 mm) as opposed to healthy myocardium (TI = 4.01 ± 1.04 mm). For AMI patients, LV that showed signs of thinning were found to be associated with a significantly higher percentage of dyssynchrony as compared with healthy subjects (dyssynchrony index [DI] = 15.0 ± 5.0% vs. 7.5 ± 2.0%, P < 0.01). Also, a strong correlation was found between our TI and left ventricular ejection fraction (LVEF) (r = 0.892, P < 0.01), and moderate correlation between DI and LVEF (r = 0.494, P < 0.01).

DATA CONCLUSION

The extracted regional wall thickening and DIs are shown to be strongly correlated with infarct severity, therefore suggestive of possible practical clinical utility.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1006-1019.

MRI-derived aortic characteristics after pregnancy: The AMBITYON study

OBJECTIVES

Pregnancy and pregnancy complications have been associated with increased arterial stiffness even at young age. In this study we assessed the impact of parity on CMR-derived aortic characteristics as early markers of atherosclerosis and arterial stiffness in healthy women between 25 and 35 years.

STUDY DESIGN

We studied 68 women who participated in the AMBITYON study, a prospective population-based cohort study for assessment of atherosclerotic burden by MRI and traditional CVD risk factors in healthy, young adults. Of these women, 40 (58.8%) were nulliparous, 13 (19.1%) were primiparous and 15 (22.1%) were multiparous.

MAIN OUTCOME MEASURES

Descending thoracic aortic wall thickness (AWT) and pulse wave velocity (PWV) were measured using 3.0T CMR.

RESULTS

AWT measurements were similar between nulliparous women and primi- or multiparous women (1.6 mm ± 0.2 mm vs. 1.6 mm ± 0.2 mm; p = 0.79). Correction for age and systolic blood pressure did not change these results. Applying percentile based cut-off values showed a non-significant increase in AWT in parous women. PWV measurements did not differ between nulliparous women and parous women (4.5 m/s ± 0.7 m/s vs. 4.5 m/s ± 0.8 m/s; p = 0.78). Correction for age and systolic blood pressure did not influence these results. Using percentile based cut-off values, showed an increasing likelihood of higher PWV-values in parous women, although not statistically significant.

CONCLUSIONS

Direct measurement of aortic AWT and PWV by CMR showed no difference between nulliparous and parous women, probably indicating limited effect of pregnancy on arterial stiffness and early markers of atherosclerosis.

TRIAL REGISTRATION

Netherlands Trial Register (NTR) number: 4742.

Ex vivo vessel wall thickness measurements of the human circle of Willis using 7T MRI

BACKGROUND AND AIMS

MRI can detect intracranial vessel wall thickening before any luminal stenosis is present. Apart from representing a vessel wall lesion, wall thickening could also reflect normal (age-related) variations in vessel wall thickness present throughout the intracranial arterial vasculature. The aim of this study was to perform vessel wall thickness measurements of the major intracranial arteries in ex vivo circle of Willis (CoW) specimens using 7T MRI, to obtain more detailed information about wall thickness variations of the intracranial arteries.

METHODS

Fifteen human CoW specimens were scanned at 7T MRI with an ultrahigh-resolution T₁-weighted sequence. Five specimens were used for validation of MRI measurements with histology and evaluation of inter-rater reliability and agreement. The other 10 specimens from patients with (n = 5) and without (n = 5) cerebrovascular disease were used for vessel wall thickness measurements over the entire length of the major arterial segments of the CoW using MRI only.

RESULTS

MRI measurements showed excellent agreement with histology. Mean wall thickness varied from 0.45 to 0.66 mm, minimum wall thickness from 0.31 to 0.42 mm, maximum wall thickness from 0.52 to 0.86 mm, and normalized wall index from 0.64 to 0.75. On average, vessel walls were thicker for symptomatic patients compared to asymptomatic patients.

CONCLUSIONS

High-resolution MRI enables accurate measurement of vessel wall thickness in ex vivo CoW specimens. Vessel wall thickness measurements over the entire length of segments showed considerable variation both within and between arterial segments of patients.

Effect of Balloon-Expandable Transcatheter Aortic Valve Replacement Positioning: A Patient-Specific Numerical Model

Transcatheter aortic valve replacement (TAVR) has emerged as a life-saving and effective alternative to surgical valve replacement in high-risk, elderly patients with severe calcific aortic stenosis. Despite its early promise, certain limitations and adverse events, such as suboptimal placement and valve migration, have been reported. In the present study, it was aimed to evaluate the effect of various TAVR deployment locations on the procedural outcome by assessing the risk for valve migration. The deployment of a balloon-expandable Edwards SAPIEN valve was simulated via finite element analysis in a patient-specific calcified aortic root, which was reconstructed from CT scans of a retrospective case of valve migration. The deployment location was parametrized in three configurations and the anchorage was quantitatively assessed based on the contact between the stent and the native valve during the deployment and recoil phases. The proximal deployment led to lower contact area between the native leaflets and the stent which poses higher risk for valve migration. The distal and midway positions resulted in comparable outcomes, with the former providing a slightly better anchorage. The approach presented might be used as a predictive tool for procedural planning in order to prevent prosthesis migration and achieve better clinical outcomes.

Reference Values for Cardiac and Aortic Magnetic Resonance Imaging in Healthy, Young Caucasian Adults

Background

Reference values for morphological and functional parameters of the cardiovascular system in early life are relevant since they may help to identify young adults who fall outside the physiological range of arterial and cardiac ageing. This study provides age and sex specific reference values for aortic wall characteristics, cardiac function parameters and aortic pulse wave velocity (PWV) in a population-based sample of healthy, young adults using magnetic resonance (MR) imaging.

Materials and Methods

In 131 randomly selected healthy, young adults aged between 25 and 35 years (mean age 31.8 years, 63 men) of the general-population based Atherosclerosis-Monitoring-and-Biomarker-measurements-In-The-YOuNg (AMBITYON) study, descending thoracic aortic dimensions and wall thickness, thoracic aortic PWV and cardiac function parameters were measured using a 3.0T MR-system. Age and sex specific reference values were generated using dedicated software. Differences in reference values between two age groups (25–30 and 30–35 years) and both sexes were tested.

Results

Aortic diameters and areas were higher in the older age group (all p<0.007). Moreover, aortic dimensions, left ventricular mass, left and right ventricular volumes and cardiac output were lower in women than in men (all p<0.001). For mean and maximum aortic wall thickness, left and right ejection fraction and aortic PWV we did not observe a significant age or sex effect.

Conclusion

This study provides age and sex specific reference values for cardiovascular MR parameters in healthy, young Caucasian adults. These may aid in MR guided pre-clinical identification of young adults who fall outside the physiological range of arterial and cardiac ageing.

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.

Intima-media thickness of the descending aorta in patients with bicuspid aortic valve

Objective

A bicuspid aortic valve (BAV) is associated with accelerated aortic valve disease (AVD) and abnormalities in aortic elasticity. We investigated the intima-media thickness of the descending aorta (AoIMT) in patients with AVD with or without an ascending aortic aneurysm (AscAA), in relation to BAV versus tricuspid aortic valve (TAV) phenotype, type of valve disease, cardiovascular risk factors, and single-nucleotide polymorphisms (SNPs) with a known association with carotid IMT.

Methods and results

368 patients (210 with BAV, 158 with TAV,); mean age 64 ± 13 years) were examined using transesophageal echocardiography (TEE) before valvular and/or aortic surgery. No patient had a coronary disease (CAD). The AoIMT was measured on short-axis TEE images of the descending aorta using a semi-automated edge-detection technique. AoIMT was univariately (P < 0.05) related to age, blood pressure, smoking, creatinine, highly sensitive C-reactive protein, HDL, valve hemodynamics and BAV. In the TAV subgroup it was also associated with the rs200991 SNP. Using multivariate regression analysis, age was the main determinant for AoIMT (P < 0.001), followed by male gender (P = 0.02), BAV was no longer a significant predictor of AoIMT. AoIMT was still related to the rs200991 SNP in TAV (P = 0.034), and to creatinine in BAV (P = 0.019), when other variables were accounted for.

Conclusions

Intima-media thickness of the descending aorta is not affected by aortic valve morphology (BAV/TAV); age is the main determinant of AoIMT. Genetic markers (SNPs) known to influence IMT in the carotid artery seem to correlate to IMT in the descending aorta only in patients with TAV.

High levels of thyroid-stimulating hormone are associated with aortic wall thickness in the general population

OBJECTIVES

Our aim was to investigate the association of thyroid function defined by serum concentrations of thyroid-stimulating hormone (TSH) with thoracic aortic wall thickness (AWT) as a marker of atherosclerotic processes.

METHODS

We pooled data of 2,679 individuals from two independent population-based surveys of the Study of Health in Pomerania. Aortic diameter and AWT measurements were performed on a 1.5-T MRI scanner at the concentration of the right pulmonary artery displaying the ascending and the descending aorta.

RESULTS

TSH, treated as continuous variable, was significantly associated with descending AWT (β = 0.11; 95 % confidence interval (CI) 0.02-0.21), while the association with ascending AWT was not statistically significant (β = 0.20; 95 % CI -0.01-0.21). High TSH (>3.29 mIU/L) was significantly associated with ascending (β = 0.12; 95 % CI 0.02-0.23) but not with descending AWT (β = 0.06; 95 % CI -0.04-0.16). There was no consistent association between TSH and aortic diameters.

CONCLUSIONS

Our study demonstrated that AWT values increase with increasing serum TSH concentrations. Thus, a hypothyroid state may be indicative for aortic atherosclerosis. These results fit very well to the findings of previous studies pointing towards increased atherosclerotic risk in the hypothyroid state.

KEY POINTS

• Serum TSH concentrations are positively associated with aortic wall thickness. • Serum TSH concentrations are not associated with the aortic diameters. • Serum 3,5-diiodothyronine concentrations may be positively associated with aortic wall thickness.

Initial stress symmetry and its applications in elasticity

An initial stress within a solid can arise to support external loads or from processes such as thermal expansion in inert matter or growth and remodelling in living materials. For this reason, it is useful to develop a mechanical framework of initially stressed solids irrespective of how this stress formed. An ideal way to do this is to write the free energy density Ψ in terms of initial stress τ and the elastic deformation gradient F , so we write Ψ = Ψ ( F , τ ). In this paper, we present a new constitutive condition for initially stressed materials, which we call the initial stress symmetry (ISS). We focus on two consequences of this condition. First, we examine how ISS restricts the possible choices of free energy densities Ψ = Ψ ( F , τ ) and present two examples of Ψ that satisfy the ISS. Second, we show that the initial stress can be derived from the Cauchy stress and the elastic deformation gradient. To illustrate, we take an example from biomechanics and calculate the optimal Cauchy stress within an artery subjected to internal pressure. We then use ISS to derive the optimal target residual stress for the material to achieve after remodelling, which links nicely with the notion of homeostasis.

Assessment of atherosclerosis in large vessel walls: A comprehensive review of FDG-PET/CT image acquisition protocols and methods for uptake quantification

There is growing evidence showing the importance of fluorodeoxyglucose positron emission tomography (FDG-PET) in the evaluation of vessel wall inflammation and atherosclerosis. Although this imaging modality has been increasingly used, there are various methods for image acquisition and evaluating FDG uptake activity in the vessel walls and atherosclerotic lesions, including qualitative visual scaling, semi-quantitative, and quantitative evaluations. Using each of these image acquisition protocols and measurement methods may result in different findings. In this review, we are going to describe the various image acquisition methods and common measurement strategies reflected in the literature and discuss their advantages and flaws.

Quantifying [¹⁸F]fluorodeoxyglucose uptake in the arterial wall: the effects of dual time-point imaging and partial volume effect correction

PURPOSE

The human arterial wall is smaller than the spatial resolution of current positron emission tomographs. Therefore, partial volume effects should be considered when quantifying arterial wall (18)F-FDG uptake. We evaluated the impact of a novel method for partial volume effect (PVE) correction with contrast-enhanced CT (CECT) assistance on quantification of arterial wall (18)F-FDG uptake at different imaging time-points.

METHODS

Ten subjects were assessed by CECT imaging and dual time-point PET/CT imaging at approximately 60 and 180 min after (18)F-FDG administration. For both time-points, uptake of (18)F-FDG was determined in the aortic wall by calculating the blood pool-corrected maximum standardized uptake value (cSUVMAX) and cSUVMEAN. The PVE-corrected SUVMEAN (pvcSUVMEAN) was also calculated using (18)F-FDG PET/CT and CECT images. Finally, corresponding target-to-background ratios (TBR) were calculated.

RESULTS

At 60 min, pvcSUVMEAN was on average 3.1 times greater than cSUVMAX (P < .0001) and 8.5 times greater than cSUVMEAN (P < .0001). At 180 min, pvcSUVMEAN was on average 2.6 times greater than cSUVMAX (P < .0001) and 6.6 times greater than cSUVMEAN (P < .0001).

CONCLUSION

This study demonstrated that CECT-assisted PVE correction significantly influences quantification of arterial wall (18)F-FDG uptake. Therefore, partial volume effects should be considered when quantifying arterial wall (18)F-FDG uptake with PET.

Cardiovascular risk factors and thoracic aortic wall thickness in a general population

PURPOSE

To evaluate the association of cardiovascular risk factors with wall thickness of the ascending and descending thoracic aorta in the general population.

MATERIALS AND METHODS

The study included 1,176 individuals (523 women) 21-83 years old from the Study of Health in Pomerania without history of stroke or myocardial infarction. Aortic wall thickness (AWT) was determined by cine magnetic resonance imaging. The associations of AWT with the cardiovascular risk factors male sex, age, smoking, body mass index (BMI), systolic and diastolic blood pressure, hemoglobin A1c, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides were assessed by multivariable linear regression models, and interaction effects were tested.

RESULTS

Male sex (β = .086, P < .001), age (β = .006, P < .001), and BMI (β = .013, P < .001) were positively associated with the AWT of the ascending aorta. Male sex (β = .105, P < .001), age (β = .006, P < .001), current smoker (β = .044, P = .010), BMI (β = .013, P < .001), and HDL-C (β = .057, P = .008) revealed a positive association with AWT of the descending aorta. LDL-C (β = -.024, P = .009; β = -.018, P = .010) was inversely associated with the AWT of the ascending and descending aorta, respectively. Triglyceride levels (β = .024, P = .027; β = .018, P = .024) showed a positive association with the AWT of the ascending and descending aorta, respectively, in men, but not in women.

CONCLUSIONS

Established cardiovascular risk factors, including male sex, older age, smoking, high BMI, and high triglyceride levels, were associated with increasing thoracic AWT of the ascending and descending aorta. High HDL-C and low LDL-C levels were correlated with AWT.