Publications by authors named "Robert J Holtackers"

13 Publications

  • Page 1 of 1

A Boolean Dilemma: True or False Aneurysm?

JACC Case Rep 2021 Jan 23;3(1):112-116. Epub 2020 Dec 23.

Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands.

A feared complication of acute myocardial infarction is the formation of a cardiac pseudoaneurysm. We report a case of a gargantuan, arrhythmogenic left-ventricular pseudoaneurysm with contradictory morphological characteristics. The integrative use of high-resolution 3-dimensional magnetic resonance imaging and computed tomography proved essential for the diagnostic discrimination and successful therapeutic intervention. ().
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http://dx.doi.org/10.1016/j.jaccas.2020.09.055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8305069PMC
January 2021

Dark-blood late gadolinium enhancement cardiovascular magnetic resonance for improved detection of subendocardial scar: a review of current techniques.

J Cardiovasc Magn Reson 2021 07 22;23(1):96. Epub 2021 Jul 22.

Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, PO Box 616, Maastricht, 6200 MD, The Netherlands.

For almost 20 years, late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) has been the reference standard for the non-invasive assessment of myocardial viability. Since the blood pool often appears equally bright as the enhanced scar regions, detection of subendocardial scar patterns can be challenging. Various novel LGE methods have been proposed that null or suppress the blood signal by employing additional magnetization preparation mechanisms. This review aims to provide a comprehensive overview of these dark-blood LGE methods, discussing the magnetization preparation schemes and findings in phantom, preclinical, and clinical studies. Finally, conclusions on the current evidence and limitations are drawn and new avenues for future research are discussed. Dark-blood LGE methods are a promising new tool for non-invasive assessment of myocardial viability. For a mainstream adoption of dark-blood LGE, however, clinical availability and ease of use are crucial.
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http://dx.doi.org/10.1186/s12968-021-00777-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8296731PMC
July 2021

Impact of Field Strength in Clinical Cardiac Magnetic Resonance Imaging.

Invest Radiol 2021 Jul 13. Epub 2021 Jul 13.

From the Cardiovascular Research Institute Maastricht, Maastricht University Department of Radiology and Nuclear Medicine, Maastricht University Medical Centre, Maastricht, the Netherlands School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom Department of Medical Imaging, Peter Munk Cardiac Centre, University Health Network Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom.

Abstract: Cardiac magnetic resonance imaging (MRI) is widely applied for the noninvasive assessment of cardiac structure and function, and for tissue characterization. For more than 2 decades, 1.5 T has been considered the field strength of choice for cardiac MRI. Although the number of 3-T systems significantly increased in the past 10 years and numerous new developments were made, challenges seem to remain that hamper a widespread clinical use of 3-T MR systems for cardiac applications. As the number of clinical cardiac applications is increasing, with each having their own benefits at both field strengths, no "holy grail" field strength exists for cardiac MRI that one should ideally use. This review describes the physical differences between 1.5 and 3 T, as well as the effect of these differences on major (routine) cardiac MRI applications, including functional imaging, edema imaging, late gadolinium enhancement, first-pass stress perfusion, myocardial mapping, and phase contrast flow imaging. For each application, the advantages and limitations at both 1.5 and 3 T are discussed. Solutions and alternatives are provided to overcome potential limitations. Finally, we briefly elaborate on the potential use of alternative field strengths (ie, below 1.5 T and above 3 T) for cardiac MRI and conclude with field strength recommendations for the future of cardiac MRI.
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http://dx.doi.org/10.1097/RLI.0000000000000809DOI Listing
July 2021

Histopathological Validation of Dark-Blood Late Gadolinium Enhancement MRI Without Additional Magnetization Preparation.

J Magn Reson Imaging 2021 Jun 24. Epub 2021 Jun 24.

Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands.

Background: Conventional bright-blood late gadolinium enhancement (LGE) cardiac magnetic resonance imaging (MRI) often suffers from poor scar-to-blood contrast due to the bright blood pool adjacent to the enhanced scar tissue. Recently, a dark-blood LGE method was developed which increases scar-to-blood contrast without using additional magnetization preparation.

Purpose: We aim to histopathologically validate this dark-blood LGE method in a porcine animal model with induced myocardial infarction (MI).

Study Type: Prospective.

Animal Model: Thirteen female Yorkshire pigs.

Field Strength/sequence: 1.5 T, two-dimensional phase-sensitive inversion-recovery radiofrequency-spoiled turbo field-echo.

Assessment: MI was experimentally induced by transient coronary artery occlusion. At 1-week and 7-week post-infarction, in-vivo cardiac MRI was performed including conventional bright-blood and novel dark-blood LGE. Following the second MRI examination, the animals were sacrificed, and histopathology was obtained. Matching LGE slices and histopathology samples were selected based on anatomical landmarks. Independent observers, while blinded to other data, manually delineated the endocardial, epicardial, and infarct borders on either LGE images or histopathology samples. The percentage of infarcted left-ventricular myocardium was calculated for both LGE methods on a per-slice basis, and compared with histopathology as reference standard. Contrast-to-noise ratios were calculated for both LGE methods at 1-week and 7-week post-infarction.

Statistical Tests: Pearson's correlation coefficient and paired-sample t-tests were used. Significance was set at P < 0.05.

Results: A combined total of 24 matched LGE and histopathology slices were available for histopathological validation. Dark-blood LGE demonstrated a high level of agreement compared to histopathology with no significant bias (-0.03%, P = 0.75). In contrast, bright-blood LGE showed a significant bias of -1.57% (P = 0.03) with larger 95% limits of agreement than dark-blood LGE. Image analysis demonstrated significantly higher scar-to-blood contrast for dark-blood LGE compared to bright-blood LGE, at both 1-week and 7-weeks post-infarction.

Data Conclusion: Dark-blood LGE without additional magnetization preparation provides superior visualization and quantification of ischemic scar compared to the current in vivo reference standard.

Level Of Evidence: 1 TECHNICAL EFFICACY STAGE: 2.
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http://dx.doi.org/10.1002/jmri.27805DOI Listing
June 2021

Transforming a pre-existing MRI environment into an interventional cardiac MRI suite.

J Cardiovasc Electrophysiol 2021 Aug 4;32(8):2090-2096. Epub 2021 Jul 4.

Department of Cardiology, Maastricht University Medical Center, Maastricht, The Netherlands.

Aims: To illustrate the practical and technical challenges along with the safety aspects when performing MRI-guided electrophysiological procedures in a pre-existing diagnostic magnetic resonance imaging (MRI) environment.

Methods And Results: A dedicated, well-trained multidisciplinary interventional cardiac MRI team (iCMR team), consisting of electrophysiologists, imaging cardiologists, radiologists, anaesthesiologists, MRI physicists, electrophysiological (EP) and MRI technicians, biomedical engineers, and medical instrumentation technologists is a prerequisite for a safe and feasible implementation of CMR-guided electrophysiological procedures (iCMR) in a pre-existing MRI environment. A formal dry run "mock-up" to address the entire spectrum of technical, logistic, and safety issues was performed before obtaining final approval of the Board of Directors. With this process we showed feasibility of our workflow, safety protocol, and bailout procedures during iCMR outside the conventional EP lab. The practical aspects of performing iCMR procedures in a pre-existing MRI environment were addressed and solidified. Finally, the influence on neighbouring MRI scanners was evaluated, showing no interference.

Conclusion: Transforming a pre-existing diagnostic MRI environment into an iCMR suite is feasible and safe. However, performing iCMR procedures outside the conventional fluoroscopic lab, poses challenges with technical, practical, and safety aspects that need to be addressed by a dedicated multi-disciplinary iCMR team.
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http://dx.doi.org/10.1111/jce.15128DOI Listing
August 2021

Topical Application of Glycerol Increases Penetration Depth of Optical Coherence Tomography in Diagnosis of Basal Cell Carcinoma.

Acta Derm Venereol 2021 Jun 22;101(6):adv00474. Epub 2021 Jun 22.

Department of Dermatology, Maastricht University Medical Centre+, 6229HX Maastricht, The Netherlands. E-mail:

Optical coherence tomography is a non-invasive imaging technique that enables high-resolution in vivo imaging of skin. Although optical coherence tomography is promising for diagnosing basal cell carcinoma, its limited penetration depth may impede basal cell carcinoma subtyping. This study evaluated whether topical application of glycerol can increase penetration depth and improve the image quality and visibility of characteristic features of basal cell carcinoma. A total of 61 patients with a total of 72 basal cell carcinomas were included. Optical coherence tomography scans were obtained before and after application of an 85% glyce-rol solution. The mean penetration depth of each optical coherence tomography scan was acquired by automatically tracing both skin surface and the point of signal loss using a custom-made MATLAB program. Mean ± standard deviation penetration depth increased from 883 ± 108 to 904 ± 88 µm before and after glycerol application, respectively (p = 0.005). Topical application of glycerol leads to a significant 2.4% increase in penetration depth. However, no significant differences in image quality and visibility of basal cell carcinoma features were found.
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http://dx.doi.org/10.2340/00015555-3811DOI Listing
June 2021

Steadily Increasing Inversion Time Improves Blood Suppression for Free-Breathing 3D Late Gadolinium Enhancement MRI With Optimized Dark-Blood Contrast.

Invest Radiol 2021 May;56(5):335-340

Philips Healthcare, Guildford, United Kingdom.

Materials And Methods: Fifty consecutive patients with previous cardiac arrhythmias, scheduled for high-resolution 3D LGE MRI, were prospectively enrolled between October 2017 and February 2020. Free-breathing 3D dark-blood LGE MRI with high isotropic resolution (1.6 × 1.6 × 1.6 mm) was performed using a conventional fixed TI (n = 25) or a dynamic TI (n = 25). The average increase in blood nulling TI per minute was obtained from Look-Locker scans before and after the 3D acquisition in the first fixed TI group. This average increment in TI was used as input to calculate the dynamic increment of the initial blood nulling TI value as set in the second dynamic TI group. Regions of interest were drawn in the left ventricular blood pool to assess mean signal intensity as a measure for blood pool suppression. Overall image quality, observer confidence, and scar demarcation were scored on a 3-point scale.

Results: Three-dimensional dark-blood LGE data sets were successfully acquired in 46/50 patients (92%). The calculated average TI increase of 2.3 ± 0.5 ms/min obtained in the first fixed TI group was incorporated in the second dynamic TI group and led to a significant decrease of 72% in the mean blood pool signal intensity compared with the fixed TI group (P < 0.001). Overall image quality (P = 0.02), observer confidence (P = 0.02), and scar demarcation (P = 0.01) significantly improved using a dynamic TI.

Conclusions: A steadily increasing dynamic TI improves blood pool suppression for optimized dark-blood contrast and increases observer confidence in free-breathing 3D dark-blood LGE MRI with high isotropic resolution.
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http://dx.doi.org/10.1097/RLI.0000000000000747DOI Listing
May 2021

Complementing sparse vascular imaging data by physiological adaptation rules.

J Appl Physiol (1985) 2021 03 29;130(3):571-588. Epub 2020 Oct 29.

Department of Biomedical Engineering, Maastricht University, Maastricht, The Netherlands.

Mathematical modeling of pressure and flow waveforms in blood vessels using pulse wave propagation (PWP) models has tremendous potential to support clinical decision making. For a personalized model outcome, measurements of all modeled vessel radii and wall thicknesses are required. In clinical practice, however, data sets are often incomplete. To overcome this problem, we hypothesized that the adaptive capacity of vessels in response to mechanical load could be utilized to fill in the gaps of incomplete patient-specific data sets. We implemented homeostatic feedback loops in a validated PWP model to allow adaptation of vessel geometry to maintain physiological values of wall stress and wall shear stress. To evaluate our approach, we gathered vascular MRI and ultrasound data sets of wall thicknesses and radii of central and arm arterial segments of 10 healthy subjects. Reference models (i.e., termed RefModel, = 10) were simulated using complete data, whereas adapted models (AdaptModel, = 10) used data of one carotid artery segment only, and the remaining geometries in this model were estimated using adaptation. We evaluated agreement between RefModel and AdaptModel geometries, as well as that between pressure and flow waveforms of both models. Limits of agreement (bias ± 2 SD of difference) between AdaptModel and RefModel radii and wall thicknesses were 0.2 ± 2.6 mm and -140 ± 557 µm, respectively. Pressure and flow waveform characteristics of the AdaptModel better resembled those of the RefModels as compared with the model in which the vessels were not adapted. Our adaptation-based PWP model enables personalization of vascular geometries even when not all required data are available. To benefit personalized pulse wave propagation (PWP) modeling, we propose a novel method that, instead of relying on extensive data sets on vascular geometries, incorporates physiological adaptation rules. The developed vascular adaptation model adequately predicted arterial radius and wall thickness compared with ultrasound and MRI estimates, obtained in humans. Our approach could be used as a tool to facilitate personalized modeling, notably in case of missing data, as routinely found in clinical settings.
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http://dx.doi.org/10.1152/japplphysiol.00250.2019DOI Listing
March 2021

Clinical value of dark-blood late gadolinium enhancement cardiovascular magnetic resonance without additional magnetization preparation.

J Cardiovasc Magn Reson 2019 07 29;21(1):44. Epub 2019 Jul 29.

Department of Cardiovascular Imaging, School of Biomedical Engineering and Imaging Sciences, King's College London, 4th Floor, Lambeth Wing, St Thomas' Hospital, London, SE1 7EH, UK.

Background: For two decades, bright-blood late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) has been considered the reference standard for the non-invasive assessment of myocardial viability. While bright-blood LGE can clearly distinguish areas of myocardial infarction from viable myocardium, it often suffers from poor scar-to-blood contrast, making subendocardial scar difficult to detect. Recently, we proposed a novel dark-blood LGE approach that increases scar-to-blood contrast and thereby improves subendocardial scar conspicuity. In the present study we sought to assess the clinical value of this novel approach in a large patient cohort with various non-congenital ischemic and non-ischemic cardiomyopathies on both 1.5 T and 3 T CMR scanners of different vendors.

Methods: Three hundred consecutive patients referred for clinical CMR were randomly assigned to a 1.5 T or 3 T scanner. An entire short-axis stack and multiple long-axis views were acquired using conventional phase sensitive inversion recovery (PSIR) LGE with TI set to null myocardium (bright-blood) and proposed PSIR LGE with TI set to null blood (dark-blood), in a randomized order. The bright-blood LGE and dark-blood LGE images were separated, anonymized, and interpreted in a random order at different time points by one of five independent observers. Each case was analyzed for the type of scar, per-segment transmurality, papillary muscle enhancement, overall image quality, observer confidence, and presence of right ventricular scar and intraventricular thrombus.

Results: Dark-blood LGE detected significantly more cases with ischemic scar compared to conventional bright-blood LGE (97 vs 89, p = 0.008), on both 1.5 T and 3 T, and led to a significantly increased total scar burden (3.3 ± 2.4 vs 3.0 ± 2.3 standard AHA segments, p = 0.015). Overall image quality significantly improved using dark-blood LGE compared to bright-blood LGE (81.3% vs 74.0% of all segments were of highest diagnostic quality, p = 0.006). Furthermore, dark-blood LGE led to significantly higher observer confidence (confident in 84.2% vs 78.4%, p = 0.033).

Conclusions: The improved detection of ischemic scar makes the proposed dark-blood LGE method a valuable diagnostic tool in the non-invasive assessment of myocardial scar. The applicability in routine clinical practice is further strengthened, as the present approach, in contrast to other recently proposed dark- and black-blood LGE techniques, is readily available without the need for scanner adjustments, extensive optimizations, or additional training.
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http://dx.doi.org/10.1186/s12968-019-0556-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6661833PMC
July 2019

Symptomatic Carotid Plaques Demonstrate Less Leaky Plaque Microvasculature Compared With the Contralateral Side: A Dynamic Contrast-Enhanced Magnetic Resonance Imaging Study.

J Am Heart Assoc 2019 04;8(8):e011832

1 Department of Radiology and Nuclear Medicine Maastricht University Medical Centre Maastricht The Netherlands.

Background Rupture of a vulnerable carotid atherosclerotic plaque is an important underlying cause of ischemic stroke. Increased leaky plaque microvasculature may contribute to plaque vulnerability. These immature microvessels may facilitate entrance of inflammatory cells into the plaque. The objective of the present study is to investigate whether there is a difference in plaque microvasculature (the volume transfer coefficient K) between the ipsilateral symptomatic and contralateral asymptomatic carotid plaque using noninvasive dynamic contrast-enhanced magnetic resonance imaging. Methods and Results Eighty-eight patients with recent transient ischemic attack or ischemic stroke and ipsilateral >2 mm carotid plaque underwent 3 T magnetic resonance imaging to identify plaque components and to determine characteristics of plaque microvasculature. The volume transfer coefficient K, indicative for microvascular density, flow, and permeability, was calculated for the ipsilateral and asymptomatic plaque, using a pharmacokinetic model (Patlak). Presence of a lipid-rich necrotic core, intraplaque hemorrhage, and a thin and/or ruptured fibrous cap was assessed on multisequence magnetic resonance imaging . We found significantly lower K in the symptomatic carotid plaque compared with the asymptomatic side (0.057±0.002 min versus 0.062±0.002 min; P=0.033). There was an increased number of slices with intraplaque hemorrhage (0.9±1.6 versus 0.3±0.8, P=0.002) and lipid-rich necrotic core (1.4±1.9 versus 0.8±1.4, P=0.016) and a higher prevalence of plaques with a thin and/or ruptured fibrous cap (32% versus 17%, P=0.023) at the symptomatic side. Conclusions K was significantly lower in symptomatic carotid plaques, indicative for a decrease of plaque microvasculature in symptomatic plaques. This could be related to a larger amount of necrotic tissue in symptomatic plaques. Clinical Trial Registration URL : http://www.clinicaltrials.gov.uk . Unique identifier: NCT 01208025.
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http://dx.doi.org/10.1161/JAHA.118.011832DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6507193PMC
April 2019

Dark-blood late gadolinium enhancement without additional magnetization preparation.

J Cardiovasc Magn Reson 2017 Aug 23;19(1):64. Epub 2017 Aug 23.

Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom.

Background: This study evaluates a novel dark-blood late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (CMR) method, without using additional magnetization preparation, and compares it to conventional bright-blood LGE, for the detection of ischaemic myocardial scar. LGE is able to clearly depict myocardial infarction and macroscopic scarring from viable myocardium. However, due to the bright signal of adjacent left ventricular blood, the apparent volume of scar tissue can be significantly reduced, or even completely obscured. In addition, blood pool signal can mimic scar tissue and lead to false positive observations. Simply nulling the blood magnetization by choosing shorter inversion times, leads to a negative viable myocardium signal that appears equally as bright as scar due to the magnitude image reconstruction. However, by combining blood magnetization nulling with the extended grayscale range of phase-sensitive inversion-recovery (PSIR), a darker blood signal can be achieved whilst a dark myocardium and bright scar signal is preserved.

Methods: LGE was performed in nine male patients (63 ± 11y) using a PSIR pulse sequence, with both conventional viable myocardium nulling and left ventricular blood nulling, in a randomized order. Regions of interest were drawn in the left ventricular blood, viable myocardium, and scar tissue, to assess contrast-to-noise ratios. Maximum scar transmurality, scar size, circumferential scar angle, and a confidence score for scar detection and maximum transmurality were also assessed. Bloch simulations were performed to simulate the magnetization levels of the left ventricular blood, viable myocardium, and scar tissue.

Results: Average scar-to-blood contrast was significantly (p < 0.001) increased by 99% when nulling left ventricular blood instead of viable myocardium, while scar-to-myocardium contrast was maintained. Nulling left ventricular blood also led to significantly (p = 0.038) higher expert confidence in scar detection and maximum transmurality. No significant changes were found in scar transmurality (p = 0.317), normalized scar size (p = 0.054), and circumferential scar angle (p = 0.117).

Conclusions: Nulling left ventricular blood magnetization for PSIR LGE leads to improved scar-to-blood contrast and increased expert confidence in scar detection and scar transmurality. As no additional magnetization preparation is used, clinical application on current MR systems is readily available without the need for extensive optimizations, software modifications, and/or additional training.
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http://dx.doi.org/10.1186/s12968-017-0372-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568308PMC
August 2017

Uncertainty quantification and sensitivity analysis of an arterial wall mechanics model for evaluation of vascular drug therapies.

Biomech Model Mechanobiol 2018 02 28;17(1):55-69. Epub 2017 Jul 28.

Department of Biomedical Engineering, CARIM School for Cardiovascular Diseases, Maastricht University, Universiteitssingel 50, Room 3.358, 6229 ER, Maastricht, The Netherlands.

Quantification of the uncertainty in constitutive model predictions describing arterial wall mechanics is vital towards non-invasive assessment of vascular drug therapies. Therefore, we perform uncertainty quantification to determine uncertainty in mechanical characteristics describing the vessel wall response upon loading. Furthermore, a global variance-based sensitivity analysis is performed to pinpoint measurements that are most rewarding to be measured more precisely. We used previously published carotid diameter-pressure and intima-media thickness (IMT) data (measured in triplicate), and Holzapfel-Gasser-Ogden models. A virtual data set containing 5000 diastolic and systolic diameter-pressure points, and IMT values was generated by adding measurement error to the average of the measured data. The model was fitted to single-exponential curves calculated from the data, obtaining distributions of constitutive parameters and constituent load bearing parameters. Additionally, we (1) simulated vascular drug treatment to assess the relevance of model uncertainty and (2) evaluated how increasing the number of measurement repetitions influences model uncertainty. We found substantial uncertainty in constitutive parameters. Simulating vascular drug treatment predicted a 6% point reduction in collagen load bearing ([Formula: see text]), approximately 50% of its uncertainty. Sensitivity analysis indicated that the uncertainty in [Formula: see text] was primarily caused by noise in distension and IMT measurements. Spread in [Formula: see text] could be decreased by 50% when increasing the number of measurement repetitions from 3 to 10. Model uncertainty, notably that in [Formula: see text], could conceal effects of vascular drug therapy. However, this uncertainty could be reduced by increasing the number of measurement repetitions of distension and wall thickness measurements used for model parameterisation.
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http://dx.doi.org/10.1007/s10237-017-0944-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5807551PMC
February 2018

Head orientation should be considered in ultrasound studies on carotid artery distensibility.

J Hypertens 2016 08;34(8):1551-5

aDepartment of Radiology bDepartment of Biomedical Engineering cCARIM School for Cardiovascular Diseases dDepartment of Internal Medicine, Maastricht University Medical Centre, Maastricht, The Netherlands.

Introduction: During ultrasound distensibility assessment of the carotid artery, the patient's head is usually rotated sideward and slightly upward to optimize visibility of the carotid segment. Head rotation may affect vessel length and thus the longitudinal strain of the arterial segment. Because the longitudinal and circumferential mechanical behaviour of an artery are intrinsically related, head rotation may influence circumferential mechanics and thereby measured distensibility.

Methods: In 12 apparently healthy volunteers (age 22 ± 3 years, mean ± SD, 6 men/6 women), we investigated whether head rotation led to a change in absolute and relative distension of the common carotid artery (CCA) by performing ultrasound examinations with the head in two orientations. Additionally, CCA length was measured in both orientations with MRI to assess whether indeed a change in length occurred because of head rotation. Rotation-induced longitudinal strain was calculated from these lengths.

Results: We found a significant decrease of 0.054 mm (6.8%, P = 0.001) and 0.007 (5.6%, P = 0.019) in absolute and relative distension with head rotation, respectively. MRI measurements showed a significant rotation-induced longitudinal strain of 1.7 ± 2.3% (P = 0.032).

Conclusion: We conclude that consistent head rotation during a CCA ultrasound assessment causes a significant and clinically relevant bias in carotid artery distension measurements. The impact of unstandardized use of head rotation in studies with carotid distensibility as an outcome measure can therefore not be neglected; thus, standardization is highly recommendable.
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http://dx.doi.org/10.1097/HJH.0000000000000985DOI Listing
August 2016
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