Publications by authors named "Mark B M Hofman"

47 Publications

Altered left atrial 4D flow characteristics in patients with paroxysmal atrial fibrillation in the absence of apparent remodeling.

Sci Rep 2021 Mar 16;11(1):5965. Epub 2021 Mar 16.

Department of Cardiology, Amsterdam UMC, Amsterdam Cardiovascular Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands.

The pathophysiology behind thrombus formation in paroxysmal atrial fibrillation (AF) patients is very complex. This can be due to left atrial (LA) flow changes, remodeling, or both. We investigated differences for cardiovascular magnetic resonance (CMR)-derived LA 4D flow and remodeling characteristics between paroxysmal AF patients and patients without cardiac disease. In this proof-of-concept study, the 4D flow data were acquired in 10 patients with paroxysmal AF (age = 61 ± 8 years) and 5 age/gender matched controls (age = 56 ± 1 years) during sinus rhythm. The following LA and LA appendage flow parameters were obtained: flow velocity (mean, peak), stasis defined as the relative volume with velocities < 10 cm/s, and kinetic energy (KE). Furthermore, LA global strain values were derived from b-SSFP cine images using dedicated CMR feature-tracking software. Even in sinus rhythm, LA mean and peak flow velocities over the entire cardiac cycle were significantly lower in paroxysmal AF patients compared to controls [(13.1 ± 2.4 cm/s vs. 16.7 ± 2.1 cm/s, p = 0.01) and (19.3 ± 4.7 cm/s vs. 26.8 ± 5.5 cm/s, p = 0.02), respectively]. Moreover, paroxysmal AF patients expressed more stasis of blood than controls both in the LA (43.2 ± 10.8% vs. 27.8 ± 7.9%, p = 0.01) and in the LA appendage (73.3 ± 5.7% vs. 52.8 ± 16.2%, p = 0.04). With respect to energetics, paroxysmal AF patients demonstrated lower mean and peak KE values (indexed to maximum LA volume) than controls. No significant differences were observed for LA volume, function, and strain parameters between the groups. Global LA flow dynamics in paroxysmal AF patients appear to be impaired including mean/peak flow velocity, stasis fraction, and KE, partly independent of LA remodeling. This pathophysiological flow pattern may be of clinical value to explain the increased incidence of thromboembolic events in paroxysmal AF patients, in the absence of actual AF or LA remodeling.
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http://dx.doi.org/10.1038/s41598-021-85176-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7966746PMC
March 2021

Cochlear Implant Magnet Dislocation: Simulations and Measurements of Force and Torque at 1.5T Magnetic Resonance Imaging.

Ear Hear 2021 Mar 2. Epub 2021 Mar 2.

Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands Otolaryngology-Head and Neck Surgery, Ear and Hearing, Amsterdam Public Health Research Institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

Objectives: Dislocation of the magnet inside the implanted component of a cochlear implant (CI) can be a serious risk for patients undergoing a magnetic resonance imaging (MRI) exam. CI manufacturers aim to reduce this risk either via the design of the implant magnet or magnet housing, or by advising a compression bandage and cover over the magnet. The aim of this study is to measure forces and torque on the magnet for different CI models and assess the effectiveness of the design and preventative measures on the probability of magnet dislocation.

Design: Six CI models from four manufacturers covering all the current CI brands were included. Each model was positioned on a polystyrene head with compression bandage and magnet cover according to the recommendations of the manufacturer and tested for dislocation in a 1.5T whole-body MRI system. In addition, measurements of the displacement force in front of the MRI scanner and torque at the MRI scanner isocenter were obtained.

Results: Chance of CI magnet dislocation was observed for two CI models. The design of the magnet or magnet housing of the other models proved sufficient to prevent displacement of the magnet. The main cause for magnet dislocation was found to be the rotational force resulting from the torque experienced inside the magnet bore, which ranges from 2.4 to 16.2 N between the models, with the displacement force being lower, ranging from 1.0 to 1.8 N.

Conclusions: In vitro testing shows that two CI models are prone to the risk of magnet dislocation. In these CI models, preparation before MRI with special compression bandage and a stiff cover are of importance. But these do not eliminate the risk of pain and dislocation requiring patient consulting before an MRI exam. Newer models show a better design resulting in a significantly reduced risk of magnet dislocation.
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http://dx.doi.org/10.1097/AUD.0000000000001013DOI Listing
March 2021

Quality assurance of quantitative cardiac T1-mapping in multicenter clinical trials - A T1 phantom program from the hypertrophic cardiomyopathy registry (HCMR) study.

Int J Cardiol 2021 May 31;330:251-258. Epub 2021 Jan 31.

Oxford Centre for Clinical Magnetic Resonance Research, Oxford BRC NIHR, Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, UK.

Background: Quantitative cardiovascular magnetic resonance T1-mapping is increasingly used for myocardial tissue characterization. However, the lack of standardization limits direct comparability between centers and wider roll-out for clinical use or trials.

Purpose: To develop a quality assurance (QA) program assuring standardized T1 measurements for clinical use.

Methods: MR phantoms manufactured in 2013 were distributed, including ShMOLLI T1-mapping and reference T1 and T2 protocols. We first studied the T1 and T2 dependency on temperature and phantom aging using phantom datasets from a single site over 4 years. Based on this, we developed a multiparametric QA model, which was then applied to 78 scans from 28 other multi-national sites.

Results: T1 temperature sensitivity followed a second-order polynomial to baseline T1 values (R > 0.996). Some phantoms showed aging effects, where T1 drifted up to 49% over 40 months. The correlation model based on reference T1 and T2, developed on 1004 dedicated phantom scans, predicted ShMOLLI-T1 with high consistency (coefficient of variation 1.54%), and was robust to temperature variations and phantom aging. Using the 95% confidence interval of the correlation model residuals as the tolerance range, we analyzed 390 ShMOLLI T1-maps and confirmed accurate sequence deployment in 90%(70/78) of QA scans across 28 multiple centers, and categorized the rest with specific remedial actions.

Conclusions: The proposed phantom QA for T1-mapping can assure correct method implementation and protocol adherence, and is robust to temperature variation and phantom aging. This QA program circumvents the need of frequent phantom replacements, and can be readily deployed in multicenter trials.
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http://dx.doi.org/10.1016/j.ijcard.2021.01.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7994017PMC
May 2021

Comparison between quantitative cardiac magnetic resonance perfusion imaging and [O]HO positron emission tomography.

Eur J Nucl Med Mol Imaging 2020 07 10;47(7):1688-1697. Epub 2019 Dec 10.

Department of Cardiology, Amsterdam University Medical Centers, Vrije Universiteit, Amsterdam, the Netherlands.

Purpose: To compare cardiac magnetic resonance imaging (CMR) with [O]HO positron emission tomography (PET) for quantification of absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR) in patients with coronary artery disease (CAD).

Methods: Fifty-nine patients with stable CAD underwent CMR and [O]HO PET. The CMR imaging protocol included late gadolinium enhancement to rule out presence of scar tissue and perfusion imaging using a dual sequence, single bolus technique. Absolute MBF was determined for the three main vascular territories at rest and during vasodilator stress.

Results: CMR measurements of regional stress MBF and MFR showed only moderate correlation to those obtained using PET (r = 0.39; P < 0.001 for stress MBF and r = 0.36; P < 0.001 for MFR). Bland-Altman analysis revealed a significant bias of 0.2 ± 1.0 mL/min/g for stress MBF and - 0.5 ± 1.2 for MFR. CMR-derived stress MBF and MFR demonstrated area under the curves of respectively 0.72 (95% CI: 0.65 to 0.79) and 0.76 (95% CI: 0.69 to 0.83) and had optimal cutoff values of 2.35 mL/min/g and 2.25 for detecting abnormal myocardial perfusion, defined as [O]HO PET-derived stress MBF ≤ 2.3 mL/min/g and MFR ≤ 2.5. Using these cutoff values, CMR and PET were concordant in 137 (77%) vascular territories for stress MBF and 135 (80%) vascular territories for MFR.

Conclusion: CMR measurements of stress MBF and MFR showed modest agreement to those obtained with [O]HO PET. Nevertheless, stress MBF and MFR were concordant between CMR and [O]HO PET in 77% and 80% of vascular territories, respectively.
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http://dx.doi.org/10.1007/s00259-019-04641-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7248026PMC
July 2020

Cardiac Magnetic Resonance for Evaluating Nonculprit Lesions After Myocardial Infarction: Comparison With Fractional Flow Reserve.

JACC Cardiovasc Imaging 2020 03 18;13(3):715-728. Epub 2019 Sep 18.

Department of Cardiology, Amsterdam University Medical Centers, location VUmc, Amsterdam, the Netherlands; Department of Cardiology, Radboud University Medical Centers, Nijmegen, the Netherlands. Electronic address:

Objectives: This study sought to determine the agreement between cardiac magnetic resonance (CMR) imaging and invasive measurements of fractional flow reserve (FFR) in the evaluation of nonculprit lesions after ST-segment elevation myocardial infarction (STEMI). In addition, we investigated whether fully quantitative analysis of myocardial perfusion is superior to semiquantitative and visual analysis.

Background: The agreement between CMR and FFR in the evaluation of nonculprit lesions in patients with STEMI with multivessel disease is unknown.

Methods: Seventy-seven patients with STEMI with at least 1 intermediate (diameter stenosis 50% to 90%) nonculprit lesion underwent CMR and invasive coronary angiography in conjunction with FFR measurements at 1 month after primary intervention. The imaging protocol included stress and rest perfusion, cine imaging, and late gadolinium enhancement. Fully quantitative, semiquantitative, and visual analysis of myocardial perfusion were compared against a reference of FFR. Hemodynamically obstructive was defined as FFR ≤0.80.

Results: Hemodynamically obstructive nonculprit lesions were present in 31 (40%) patients. Visual analysis displayed an area under the curve (AUC) of 0.74 (95% confidence interval [CI]: 0.62 to 0.83), with a sensitivity of 73% and a specificity of 70%. For semiquantitative analysis, the relative upslope of the stress signal intensity time curve and the relative upslope derived myocardial flow reserve had respective AUCs of 0.66 (95% CI: 0.54 to 0.77) and 0.71 (95% CI: 0.59 to 0.81). Fully quantitative analysis did not augment diagnostic performance (all p > 0.05). Stress myocardial blood flow displayed an AUC of 0.76 (95% CI: 0.64 to 0.85), with a sensitivity of 69% and a specificity of 77%. Similarly, MFR displayed an AUC of 0.82 (95% CI: 0.71 to 0.90), with a sensitivity of 82% and a specificity of 71%.

Conclusions: CMR and FFR have moderate-good agreement in the evaluation of nonculprit lesions in patients with STEMI with multivessel disease. Fully quantitative, semiquantitative, and visual analysis yield similar diagnostic performance.
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http://dx.doi.org/10.1016/j.jcmg.2019.07.019DOI Listing
March 2020

Quantification of cutaneous allergic reactions using 3D optical imaging: A feasibility study.

Skin Res Technol 2020 Jan 18;26(1):67-75. Epub 2019 Aug 18.

Department of Dermatology, Academic Tattoo Clinic Amsterdam, Amsterdam UMC, Amsterdam, The Netherlands.

Background: User-independent quantitative measures of cutaneous allergic reactions can help the physicians manage and evaluate the treatment of cutaneous allergic reactions. In this paper, we present and validate a method to quantify the elevation, volume and area of cutaneous allergic reactions to red tattoos.

Methods: The skin surface of allergic tattoo reactions was imaged using an optical 3D scanner. The in-house developed analysis tool measured the elevation, volume and area of the lesions, compared to a reference surface. This reference surface was created by 3D interpolation of the skin after manual removal of the lesions. The error of the interpolation tool was validated using a digital arm model. The error of our optical scanner was determined using a 3D printed lesion phantom. The clinical feasibility of the method was tested in 83 lesions in 17 patients.

Results: The method showed clear potential to assess skin elevation, volume change and area of an allergic reaction. The validation measurements revealed that the error due to interpolation increases for larger interpolation areas and largely determined the error in the clinical measurements. Lesions with a width ≥4 mm and an elevation ≥0.4 mm could be measured with an error below 26%. Patient measurements showed that lesions up to 600 mm could be measured accurately, and elevation and volume changes could be assessed at follow-up.

Conclusion: Quantification of cutaneous allergic reactions to red tattoos using 3D optical scanning is feasible and may objectify skin elevation and improve management of the allergic reaction.
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http://dx.doi.org/10.1111/srt.12765DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7003777PMC
January 2020

In-vivo validation of interpolation-based phase offset correction in cardiovascular magnetic resonance flow quantification: a multi-vendor, multi-center study.

J Cardiovasc Magn Reson 2019 05 20;21(1):30. Epub 2019 May 20.

Cardiovascular Magnetic Resonance Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.

Background: A velocity offset error in phase contrast cardiovascular magnetic resonance (CMR) imaging is a known problem in clinical assessment of flow volumes in vessels around the heart. Earlier studies have shown that this offset error is clinically relevant over different systems, and cannot be removed by protocol optimization. Correction methods using phantom measurements are time consuming, and assume reproducibility of the offsets which is not the case for all systems. An alternative previously published solution is to correct the in-vivo data in post-processing, interpolating the velocity offset from stationary tissue within the field-of-view. This study aims to validate this interpolation-based offset correction in-vivo in a multi-vendor, multi-center setup.

Methods: Data from six 1.5 T CMR systems were evaluated, with two systems from each of the three main vendors. At each system aortic and main pulmonary artery 2D flow studies were acquired during routine clinical or research examinations, with an additional phantom measurement using identical acquisition parameters. To verify the phantom acquisition, a region-of-interest (ROI) at stationary tissue in the thorax wall was placed and compared between in-vivo and phantom measurements. Interpolation-based offset correction was performed on the in-vivo data, after manually excluding regions of spatial wraparound. Correction performance of different spatial orders of interpolation planes was evaluated.

Results: A total of 126 flow measurements in 82 subjects were included. At the thorax wall the agreement between in-vivo and phantom was - 0.2 ± 0.6 cm/s. Twenty-eight studies were excluded because of a difference at the thorax wall exceeding 0.6 cm/s from the phantom scan, leaving 98. Before correction, the offset at the vessel as assessed in the phantom was - 0.4 ± 1.5 cm/s, which resulted in a - 5 ± 16% error in cardiac output. The optimal order of the interpolation correction plane was 1st order, except for one system at which a 2nd order plane was required. Application of the interpolation-based correction revealed a remaining offset velocity of 0.1 ± 0.5 cm/s and 0 ± 5% error in cardiac output.

Conclusions: This study shows that interpolation-based offset correction reduces the offset with comparable efficacy as phantom measurement phase offset correction, without the time penalty imposed by phantom scans.

Trial Registration: The study was registered in The Netherlands National Trial Register (NTR) under TC 4865 . Registered 19 September 2014. Retrospectively registered.
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http://dx.doi.org/10.1186/s12968-019-0538-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6526620PMC
May 2019

Summarizing the 4D image stack of ultrafast dynamic contrast enhancement MRI of breast cancer in 3D using color intensity projections.

J Magn Reson Imaging 2019 05 14;49(5):1391-1399. Epub 2018 Oct 14.

Department of Physics and Medical, Technology, Amsterdam University Medical Center, Amsterdam, Netherlands.

Background: Each ultrafast dynamic contrast-enhanced (DCE) MRI sequence for breast cancer generates thousands of images in a 4D stack that need to be reviewed by a radiologist.

Purpose: To assess whether color intensity projections (CIP) effectively summarizes-using only the time of arrival (ToA) and amount of signal enhancement (AoE) of the contrast agent-the thousands of ultrafast images.

Study Type: Retrospective cohort clinical trial.

Subjects: The study included 89 patients who had been scanned with an MRI beast protocol, of which 26 had breast cancer and 63 did not.

Field Strength/sequence: The 115-second ultrafast DCE sequence at 3T acquired 19 consecutive frames every 4.26 seconds with 152 slices per frame, yielding a 4D stack with 2888 2D images for each of water and fat.

Assessment: For each slice of the water 4D stack a single CIP image was generated that encoded the ToA in the hue (red, orange, yellow, green, cyan, blue) and AoE in the brightness. Each of three experienced radiologists assigned a Breast Imaging and Reporting Data System (BI-RADS) score for each patient, first using only the CIP images, and subsequently using both CIP and the full 4D stack.

Statistical Tests: The one-sided Fisher's exact test was used to determine statistical significance of both the sensitivity and specificity between the CIP alone and the CIP plus 4D stack.

Results: All malignancies were detected using only CIP by at least one of the radiologists. The CIP and CIP+4D sensitivities for reader 1 were 96% and 96% (P = 0.57), specificities were 59% and 65% (P = 0.29). For reader 2, the values were 96% and 100% (P = 0.51) with 62% and 71% (P = 0.17). For reader 3 the values were 92% and 96% (P = 0.50) with 51% and 62% (P = 0.07).

Data Conclusion: With a 95% sensitivity, CIP provides an effective summary of ultrafast DCE images of breast cancer.

Level Of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1391-1399.
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http://dx.doi.org/10.1002/jmri.26521DOI Listing
May 2019

Evaluation of the Novel PET Tracer [C]HACH242 for Imaging the GluN2B NMDA Receptor in Non-Human Primates.

Mol Imaging Biol 2019 08;21(4):676-685

Department of Radiology & Nuclear Medicine, Amsterdam UMC, VU University Medical Center, Amsterdam, The Netherlands.

Purpose: There are currently no positron emission tomography (PET) radiotracers for the GluN2B (NR2B) binding sites of brain N-methyl-D-aspartate (NMDA) receptors. In rats, the GluN2B antagonist Ro25-6981 reduced the binding of N-((5-(4-fluoro-2-[C]methoxyphenyl)pyridin-3-yl)methyl)cyclopentanamin ([C]HACH242). This paper reports the evaluation of [C]HACH242 PET in non-human primates at baseline and following administration of the GluN2B negative allosteric modulator radiprodil.

Procedures: Eight 90-min dynamic [C]HACH242 PET scans were acquired in three male anaesthetised rhesus monkeys, including a retest session of subject 1, at baseline and 10 min after intravenous 10 mg/kg radiprodil. Standardised uptake values (SUV) were calculated for 9 brain regions. Arterial blood samples were taken at six timepoints to characterise pharmacokinetics in blood and plasma. Reliable input functions for kinetic modelling could not be generated due to variability in the whole-blood radioactivity measurements.

Results: [C]HACH242 entered the brain and displayed fairly uniform uptake. The mean (± standard deviation, SD) T was 17 ± 7 min in baseline scans and 24 ± 15 min in radiprodil scans. The rate of radioligand metabolism in plasma (primarily to polar metabolites) was high, with mean parent fractions of 26 ± 10 % at 20 min and 8 ± 5 % at 85 min. Radiprodil increased [C]HACH242 whole-brain SUV in the last PET frame by 25 %, 1 %, 3 and 17 % for subjects 1, 2, 3 and retest of subject 1, respectively. The mean brain to plasma ratio was 5.4 ± 2.6, and increased by 39 to 110 % in the radiprodil condition, partly due to lower parent plasma radioactivity of -11 to -56 %.

Conclusions: The present results show that [C]HACH242 has a suitable kinetic profile in the brain and low accumulation of lipophilic radiometabolites. Radiprodil did not consistently change [C]HACH242 brain uptake. These findings may be explained by variations in cerebral blood flow, a low fraction of specifically bound tracer, or interactions with endogenous NMDA receptor ligands at the binding site. Further experiments of ligand interactions are necessary to facilitate the development of radiotracers for in vivo imaging of the ionotropic NMDA receptor.
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http://dx.doi.org/10.1007/s11307-018-1284-xDOI Listing
August 2019

MRI and Additive Manufacturing of Nasal Alar Constructs for Patient-specific Reconstruction.

Sci Rep 2017 08 30;7(1):10021. Epub 2017 Aug 30.

Department of Plastic, Reconstructive and Hand Surgery, VU University Medical Centre, Amsterdam, 1081HV, the Netherlands, Amsterdam Movement Sciences, Amsterdam, The Netherlands.

Surgical reconstruction of cartilaginous defects remains a major challenge. In the current study, we aimed to identify an imaging strategy for the development of patient-specific constructs that aid in the reconstruction of nasal deformities. Magnetic Resonance Imaging (MRI) was performed on a human cadaver head to find the optimal MRI sequence for nasal cartilage. This sequence was subsequently used on a volunteer. Images of both were assessed by three independent researchers to determine measurement error and total segmentation time. Three dimensionally (3D) reconstructed alar cartilage was then additively manufactured. Validity was assessed by comparing manually segmented MR images to the gold standard (micro-CT). Manual segmentation allowed delineation of the nasal cartilages. Inter- and intra-observer agreement was acceptable in the cadaver (coefficient of variation 4.6-12.5%), but less in the volunteer (coefficient of variation 0.6-21.9%). Segmentation times did not differ between observers (cadaver P = 0.36; volunteer P = 0.6). The lateral crus of the alar cartilage was consistently identified by all observers, whereas part of the medial crus was consistently missed. This study suggests that MRI is a feasible imaging modality for the development of 3D alar constructs for patient-specific reconstruction.
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http://dx.doi.org/10.1038/s41598-017-10602-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577227PMC
August 2017

The influence of microvascular injury on native T1 and T2* relaxation values after acute myocardial infarction: implications for non-contrast-enhanced infarct assessment.

Eur Radiol 2018 Feb 18;28(2):824-832. Epub 2017 Aug 18.

Department of Cardiology, VU University Medical Centre, ZH 5F012, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands.

Objectives: Native T1 mapping and late gadolinium enhancement (LGE) imaging offer detailed characterisation of the myocardium after acute myocardial infarction (AMI). We evaluated the effects of microvascular injury (MVI) and intramyocardial haemorrhage on local T1 and T2* values in patients with a reperfused AMI.

Methods: Forty-three patients after reperfused AMI underwent cardiovascular magnetic resonance imaging (CMR) at 4 [3-5] days, including native MOLLI T1 and T2* mapping, STIR, cine imaging and LGE. T1 and T2* values were determined in LGE-defined regions of interest: the MI core incorporating MVI when present, the core-adjacent MI border zone (without any areas of MVI), and remote myocardium.

Results: Average T1 in the MI core was higher than in the MI border zone and remote myocardium. However, in the 20 (47%) patients with MVI, MI core T1 was lower than in patients without MVI (MVI 1048±78ms, no MVI 1111±89ms, p=0.02). MI core T2* was significantly lower in patients with MVI than in those without (MVI 20 [18-23]ms, no MVI 31 [26-39]ms, p<0.001).

Conclusion: The presence of MVI profoundly affects MOLLI-measured native T1 values. T2* mapping suggested that this may be the result of intramyocardial haemorrhage. These findings have important implications for the interpretation of native T1 values shortly after AMI.

Key Points: • Microvascular injury after acute myocardial infarction affects local T1 and T2* values. • Infarct zone T1 values are lower if microvascular injury is present. • T2* mapping suggests that low infarct T1 values are likely haemorrhage. • T1 and T2* values are complimentary for correctly assessing post-infarct myocardium.
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http://dx.doi.org/10.1007/s00330-017-5010-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5740192PMC
February 2018

Changes in remote myocardial tissue after acute myocardial infarction and its relation to cardiac remodeling: A CMR T1 mapping study.

PLoS One 2017 23;12(6):e0180115. Epub 2017 Jun 23.

Departments of Cardiology, VU University Medical Center, Amsterdam, the Netherlands.

Objectives: To characterize the temporal alterations in native T1 and extracellular volume (ECV) of remote myocardium after acute myocardial infarction (AMI), and to explore their relation to left ventricular (LV) remodeling.

Methods: Forty-two patients with AMI successfully treated with primary PCI underwent cardiovascular magnetic resonance after 4-6 days and 3 months. Cine imaging, late gadolinium enhancement, and T1-mapping (MOLLI) was performed at 1.5T. T1 values were measured in the myocardial tissue opposite of the infarct area. Myocardial ECV was calculated from native- and post-contrast T1 values in 35 patients, using a correction for synthetic hematocrit.

Results: Native T1 of remote myocardium significantly decreased between baseline and follow-up (1002 ± 39 to 985 ± 30ms, p<0.01). High remote native T1 at baseline was independently associated with a high C-reactive protein level (standardized Beta 0.32, p = 0.04) and the presence of microvascular injury (standardized Beta 0.34, p = 0.03). ECV of remote myocardium significantly decreased over time in patients with no LV dilatation (29 ± 3.8 to 27 ± 2.3%, p<0.01). In patients with LV dilatation, remote ECV remained similar over time, and was significantly higher at follow-up compared to patients without LV dilatation (30 ± 2.0 versus 27 ± 2.3%, p = 0.03).

Conclusions: In reperfused first-time AMI patients, native T1 of remote myocardium decreased from baseline to follow-up. ECV of remote myocardium decreased over time in patients with no LV dilatation, but remained elevated at follow-up in those who developed LV dilatation. Findings from this study may add to an increased understanding of the pathophysiological mechanisms of cardiac remodeling after AMI.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180115PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482488PMC
September 2017

Insights into cardiac involvement in ankylosing spondylitis from cardiovascular magnetic resonance.

Heart 2017 05 16;103(10):745-752. Epub 2016 Nov 16.

Departments of Cardiology, VU University Medical Center, Amsterdam, The Netherlands.

Objective: To evaluate cardiac involvement in patients with ankylosing spondylitis using cardiac magnetic resonance (CMR).

Methods: Patients with ankylosing spondylitis without cardiovascular symptoms or known cardiovascular disease were screened by transthoracic echocardiography (TTE) for participation in this exploratory CMR study. We prospectively enrolled 15 ankylosing spondylitis patients with an abnormal TTE for further tissue characterisation using late gadolinium enhancement (LGE) and T1 mapping. T1 mapping was used to calculate myocardial extracellular volume (ECV). Disease activity was assessed by C reactive protein (CRP) and erythrocyte sedimentation rate (ESR) measurements.

Results: In the total of 15 included patients, 14 had a complete CMR exam (mean age 62 years, 93% male and mean disease duration 21 years). Left ventricular (LV) diastolic dysfunction was the most common finding on TTE (79%), followed by aortic root dilatation (14%), right ventricular (RV) dilatation (7%) and RV dysfunction (7%). CMR revealed focal hyperenhancement in three patients (21%), all with a particular pattern of enhancement. LV dysfunction, as defined by a LV ejection fraction below 55%, was observed in five patients (36%). Myocardial ECV was correlated with the CRP concentration (R=0.78, p<0.01) and ESR level (R=0.73, p<0.01).

Conclusions: In patients with ankylosing spondylitis, CMR with cine imaging and LGE identified global LV dysfunction and focal areas of hyperenhancement. Myocardial ECV, quantified by CMR T1 mapping, was associated with the degree of disease activity. These results may suggest the presence of cardiac involvement in ankylosing spondylitis and may show the potential of ECV as a marker for disease monitoring.
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http://dx.doi.org/10.1136/heartjnl-2016-310667DOI Listing
May 2017

Increased native T1-values at the interventricular insertion regions in precapillary pulmonary hypertension.

Int J Cardiovasc Imaging 2016 Mar 16;32(3):451-9. Epub 2015 Oct 16.

Department of Physics and Medical Technology, ICaR-VU, VU University Medical Center, de Boelelaan 1117, PK-1Y138, 1081HV, Amsterdam, The Netherlands.

Cardiac magnetic resonance imaging of the pressure overloaded right ventricle (RV) of precapillary pulmonary hypertension (PH) patients, exhibits late gadolinium enhancement at the interventricular insertion regions, a phenomenon which has been linked to focal fibrosis. Native T1-mapping is an alternative technique to characterize myocardium and has the advantage of not requiring the use of contrast agents. The aim of this study was to characterize the myocardium of idiopathic pulmonary arterial hypertension (IPAH), systemic scleroderma related PH (PAH-Ssc) and chronic thromboembolic PH (CTEPH) patients using native T1-mapping and to see whether native T1-values were related to disease severity. Furthermore, we compared native T1-values between the different precapillary PH categories. Native T1-mapping was performed in 46 IPAH, 14 PAH-SSc and 10 CTEPH patients and 10 control subjects. Native T1-values were assessed using regions of interest at the RV and LV free wall, interventricular septum and interventricular insertion regions. In PH patients, native T1-values of the interventricular insertion regions were significantly higher than the native T1-values of the RV free wall, LV free wall and interventricular septum. Native T1-values at the insertion regions were significantly related to disease severity. Native T1-values were not different between IPAH, PAH-Ssc and CTEPH patients. Native T1-values of the interventricular insertion regions are significantly increased in precapillary PH and are related to disease severity. Native T1-mapping can be developed as an alternative technique for the characterization of the interventricular insertion regions and has the advantage of not requiring the use of contrast agents.
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http://dx.doi.org/10.1007/s10554-015-0787-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4751160PMC
March 2016

In-vivo T1 cardiovascular magnetic resonance study of diffuse myocardial fibrosis in hypertrophic cardiomyopathy.

J Cardiovasc Magn Reson 2014 Apr 25;16:28. Epub 2014 Apr 25.

Department of Cardiology, ICaR-VU, VU University Medical Center, De Boelelaan 1117, Amsterdam 1081 HV, the Netherlands.

Background: In hypertrophic cardiomyopathy (HCM), autopsy studies revealed both increased focal and diffuse deposition of collagen fibers. Late gadolinium enhancement imaging (LGE) detects focal fibrosis, but is unable to depict interstitial fibrosis. We hypothesized that with T1 mapping, which is employed to determine the myocardial extracellular volume fraction (ECV), can detect diffuse interstitial fibrosis in HCM patients.

Methods: T1 mapping with a modified Look-Locker Inversion Recovery (MOLLI) pulse sequence was used to calculate ECV in manifest HCM (n = 16) patients and in healthy controls (n = 14). ECV was determined in areas where focal fibrosis was excluded with LGE.

Results: The total group of HCM patients showed no significant changes in mean ECV values with respect to controls (0.26 ± 0.03 vs 0.26 ± 0.02, p = 0.83). Besides, ECV in LGE positive HCM patients was comparable with LGE negative HCM patients (0.27 ± 0.03 vs 0.25 ± 0.03, p = 0.12).

Conclusions: This study showed that HCM patients have a similar ECV (e.g. interstitial fibrosis) in myocardium without LGE as healthy controls. Therefore, the additional clinical value of T1 mapping in HCM seems limited, but future larger studies are needed to establish the clinical and prognostic potential of this new technique within HCM.
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http://dx.doi.org/10.1186/1532-429X-16-28DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4026831PMC
April 2014

Cell therapy in reperfused acute myocardial infarction does not improve the recovery of perfusion in the infarcted myocardium: a cardiac MR imaging study.

Radiology 2014 Jul 8;272(1):113-22. Epub 2014 Mar 8.

From the Department of Cardiology, VU University Medical Center, Amsterdam, De Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands (L.F.H.J.R., R.N., A.M.B., M.B.M.H., A.C.v.R.); ICIN-Netherlands Heart Institute (ICIN-NHI), Utrecht, the Netherlands (L.F.H.J.R., R.N., A.H., A.M.v.d.L., R.D., P.A.v.d.V.); Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands (A.H., A.M.v.d.L., R.D., J.G.P.T., J.J.P.); Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands (P.A.v.d.V., R.A.T.); and Department of Cardiology, Erasmus University Medical Center, Rotterdam, the Netherlands (F.Z.).

Purpose: To investigate the effects of cell therapy on myocardial perfusion recovery after treatment of acute myocardial infarction (MI) with primary percutaneous coronary intervention (PCI).

Materials And Methods: In this HEBE trial substudy, which was approved by the institutional review board (trial registry number ISRCTN95796863), the authors assessed the effects of intracoronary infusion with bone marrow-derived mononuclear cells (BMMCs) or peripheral blood-derived mononuclear cells (PBMCs) on myocardial perfusion recovery by using cardiac magnetic resonance (MR) imaging after revascularization. In 152 patients with acute MI treated with PCI, cardiac MR imaging was performed after obtaining informed consent-before randomization to BMMC, PBMC, or standard therapy (control group)-and repeated at 4-month follow-up. Cardiac MR imaging consisted of cine, rest first-pass perfusion, and late gadolinium enhancement imaging. Perfusion was evaluated semiquantitatively with signal intensity-time curves by calculating the relative upslope (percentage signal intensity change). The relative upslope was calculated for the MI core, adjacent border zone, and remote myocardium. Perfusion differences among treatment groups or between baseline and follow-up were assessed with the Wilcoxon signed rank or Mann-Whitney U test.

Results: At baseline, myocardial perfusion differed between the MI core (median, 6.0%; interquartile range [IQR], 4.1%-8.0%), border zone (median, 8.4%; IQR, 6.4%-10.2%), and remote myocardium (median, 12.2%; IQR, 10.5%-15.9%) (P < .001 for all), with equal distribution among treatment groups. These interregional differences persisted at follow-up (P < .001 for all). No difference in perfusion recovery was found between the three treatment groups for any region.

Conclusion: After revascularization of ST-elevation MI, cell therapy does not augment the recovery of resting perfusion in either the MI core or border zone.
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http://dx.doi.org/10.1148/radiol.14131121DOI Listing
July 2014

Combined non-invasive functional and anatomical diagnostic work-up in clinical practice: the magnetic resonance and computed tomography in suspected coronary artery disease (MARCC) study.

Eur Heart J 2013 Jul 7;34(26):1990-8. Epub 2013 Mar 7.

Interuniversity Cardiology Institute of the Netherlands, Utrecht, The Netherlands.

Aims: The combined use of cardiac computed tomography (CT) coronary angiography (CTCA) and myocardial perfusion imaging allows the non-invasive evaluation of coronary morphology and function. Cardiovascular magnetic resonance (CMR) imaging has several advantages: it can simultaneously assess myocardial perfusion, ventricular and valvular function, cardiomyopathy, and aortic disease and does not involve any additional ionizing radiation. We investigated the combined use of cardiac CT and CMR for the diagnostic evaluation of patients with suspected coronary artery disease (CAD) in clinical practice.

Methods And Results: A total of 192 patients with low or intermediate pre-test probability of CAD underwent CTCA and CMR. All patients with obstructive CAD on CTCA and/or myocardial ischaemia on CMR were referred for invasive coronary angiography (ICA). Fractional flow reserve was measured in case of intermediate lesions (30-70% diameter stenosis) on ICA. Additional cardiac and extra-cardiac findings by CTCA and CMR were registered. The combination of CTCA and CMR significantly improved specificity and overall accuracy (94 and 91%) for the detection of significant CAD compared with their use as a single technique (CTCA 39 and 57%, P < 0.0001; CMR 82 and 83%, P = 0.016). No events were recorded during follow-up (18 ± 6 months) in 104 patients who did not undergo ICA. Furthermore, the combined strategy provided an alternative diagnosis in 19 patients.

Conclusion: The combined use of CTCA and CMR significantly improved specificity and overall diagnostic accuracy for the detection of significant CAD and allowed the detection of alternative (extra-)cardiac disease in patients without significant CAD.
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http://dx.doi.org/10.1093/eurheartj/eht077DOI Listing
July 2013

Normal variation of magnetic resonance T1 relaxation times in the human population at 1.5 T using ShMOLLI.

J Cardiovasc Magn Reson 2013 Jan 20;15:13. Epub 2013 Jan 20.

Department of Cardiovascular Medicine, Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, UK.

Background: Quantitative T1-mapping is rapidly becoming a clinical tool in cardiovascular magnetic resonance (CMR) to objectively distinguish normal from diseased myocardium. The usefulness of any quantitative technique to identify disease lies in its ability to detect significant differences from an established range of normal values. We aimed to assess the variability of myocardial T1 relaxation times in the normal human population estimated with recently proposed Shortened Modified Look-Locker Inversion recovery (ShMOLLI) T1 mapping technique.

Methods: A large cohort of healthy volunteers (n = 342, 50% females, age 11-69 years) from 3 clinical centres across two countries underwent CMR at 1.5T. Each examination provided a single average myocardial ShMOLLI T1 estimate using manually drawn myocardial contours on typically 3 short axis slices (average 3.4 ± 1.4), taking care not to include any blood pool in the myocardial contours. We established the normal reference range of myocardial and blood T1 values, and assessed the effect of potential confounding factors, including artefacts, partial volume, repeated measurements, age, gender, body size, hematocrit and heart rate.

Results: Native myocardial ShMOLLI T1 was 962 ± 25 ms. We identify the partial volume as primary source of potential error in the analysis of respective T1 maps and use 1 pixel erosion to represent "midwall myocardial" T1, resulting in a 0.9% decrease to 953 ± 23 ms. Midwall myocardial ShMOLLI T1 was reproducible with an intra-individual, intra- and inter-scanner variability of ≤2%. The principle biological parameter influencing myocardial ShMOLLI T1 was the female gender, with female T1 longer by 24 ms up to the age of 45 years, after which there was no significant difference from males. After correction for age and gender dependencies, heart rate was the only other physiologic factor with a small effect on myocardial ShMOLLI T1 (6ms/10bpm). Left and right ventricular blood ShMOLLI T1 correlated strongly with each other and also with myocardial T1 with the slope of 0.1 that is justifiable by the resting partition of blood volume in myocardial tissue. Overall, the effect of all variables on myocardial ShMOLLI T1 was within 2% of relative changes from the average.

Conclusion: Native T1-mapping using ShMOLLI generates reproducible and consistent results in normal individuals within 2% of relative changes from the average, well below the effects of most acute forms of myocardial disease. The main potential confounder is the partial volume effect arising from over-inclusion of neighbouring tissue at the manual stages of image analysis. In the study of cardiac conditions such as diffuse fibrosis or small focal changes, the use of "myocardial midwall" T1, age and gender matching, and compensation for heart rate differences may all help to improve the method sensitivity in detecting subtle changes. As the accuracy of current T1 measurement methods remains to be established, this study does not claim to report an accurate measure of T1, but that ShMOLLI is a stable and reproducible method for T1-mapping.
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http://dx.doi.org/10.1186/1532-429X-15-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3610210PMC
January 2013

Technical note: building a combined cyclotron and MRI facility: implications for interference.

Med Phys 2013 Jan;40(1):012303

Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands.

Purpose: With the introduction of hybrid PET∕MRI systems, it has become more likely that the cyclotron and MRI systems will be located close to each other. This study considered the interference between a cyclotron and a superconducting MRI system.

Methods: Interactions between cyclotrons and MRIs are theoretically considered. The main interference is expected to be the perturbation of the magnetic field in the MRI due to switching on or off the magnetic field of the cyclotron. MR imaging is distorted by a dynamic spatial gradient of an external inplane magnetic field larger than 0.5-0.04 μT∕m, depending on the specific MR application. From the design of a cyclotron, it is expected that the magnetic fringe field at large distances behaves as a magnetic dipolar field. This allows estimation of the full dipolar field and its spatial gradients from a single measurement. Around an 18 MeV cyclotron (Cyclone, IBA), magnetic field measurements were performed on 5 locations and compared with calculations based upon a dipolar field model.

Results: At the measurement locations the estimated and measured values of the magnetic field component and its spatial gradients of the inplane component were compared, and found to agree within a factor 1.1 for the magnetic field and within a factor of 1.5 for the spatial gradients of the field. In the specific case of the 18 MeV cyclotron with a vertical magnetic field and a 3T superconducting whole body MR system, a minimum distance of 20 m has to be considered to prevent interference.

Conclusions: This study showed that a dipole model is sufficiently accurate to predict the interference of a cyclotron on a MRI scanner, for site planning purposes. The cyclotron and a whole body MRI system considered in this study need to be placed more than 20 m apart, or magnetic shielding should be utilized.
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http://dx.doi.org/10.1118/1.4772188DOI Listing
January 2013

A multi-center inter-manufacturer study of the temporal stability of phase-contrast velocity mapping background offset errors.

J Cardiovasc Magn Reson 2012 Oct 20;14:72. Epub 2012 Oct 20.

Royal Brompton Hospital, London, UK.

Background: Phase-contrast velocity images often contain a background or baseline offset error, which adds an unknown offset to the measured velocities. For accurate flow measurements, this offset must be shown negligible or corrected. Some correction techniques depend on replicating the clinical flow acquisition using a uniform stationary phantom, in order to measure the baseline offset at the region of interest and subtract it from the clinical study. Such techniques assume that the background offset is stable over the time of a patient scan, or even longer if the phantom scans are acquired later, or derived from pre-stored background correction images. There is no published evidence regarding temporal stability of the background offset.

Methods: This study assessed the temporal stability of the background offset on 3 different manufacturers' scanners over 8 weeks, using a retrospectively-gated phase-contrast cine acquisition with fixed parameters and at a fixed location, repeated 5 times in rapid succession each week. A significant offset was defined as 0.6 cm/s within 50 mm of isocenter, based upon an accuracy of 10% in a typical cardiac shunt measurement.

Results: Over the 5 repeated cine acquisitions, temporal drift in the baseline offset was insignificant on two machines (0.3 cm/s, 0.2 cm/s), and marginally insignificant on the third machine (0.5 cm/s) due to an apparent heating effect. Over a longer timescale of 8 weeks, insignificant drift (0.4 cm/s) occurred on one, with larger drifts (0.9 cm/s, 0.6 cm/s) on the other machines.

Conclusions: During a typical patient study, background drift was insignificant. Extended high gradient power scanning with work requires care to avoid drift on some machines. Over the longer term of 8 weeks, significant drift is likely, preventing accurate correction by delayed phantom corrections or derivation from pre-stored background offset data.
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http://dx.doi.org/10.1186/1532-429X-14-72DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3514147PMC
October 2012

T1 mapping shows increased extracellular matrix size in the myocardium due to amyloid depositions.

Circ Cardiovasc Imaging 2012 May;5(3):423-6

Cardiovascular MRI, VU Medical Center, ZH 4 D 36, PO Box 7057, 1007 MB Amsterdam, The Netherlands.

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http://dx.doi.org/10.1161/CIRCIMAGING.112.973438DOI Listing
May 2012

Accurate perioperative flow measurement of the portal vein and hepatic and renal artery: a role for preoperative MRI?

Eur J Radiol 2012 Sep 2;81(9):2042-8. Epub 2011 Jul 2.

Department of Surgery, VU University Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.

Background: Quantification of abdominal blood flow is essential for a variety of gastrointestinal and hepatic topics such as liver transplantation or metabolic flux measurement, but those need to be performed during surgery. It is not clear whether Duplex Doppler Ultrasound during surgery or MRI before surgery is the tool to choose.

Objective: To examine whether preoperative evaluation of abdominal blood flow using MRI could prove to be a useful and reliable alternative for the perioperative sonographic approach.

Methods: In this study portal and renal venous flow and hepatic arterial flow were sequentially quantified by preoperative MRI, preoperative and perioperative Duplex Doppler Ultrasound (DDUS). 55 Patients scheduled for major abdominal surgery were studied and methods and settings were compared. Additionally, average patient population values were compared.

Results: Mean (±SD) plasmaflow measured by perioperative DDUS, preoperative DDUS and MRI, respectively was 433±200/423±162/507±96 ml/min (portal vein); 96±70/74±41/108±91 ml/min (hepatic artery); 248±139/201±118/219±69 ml/min (renal vein). No differences between the different settings of DDUS measurement were detected. Equality of mean was observed for all measurements. Bland Altman Plots showed widespread margins. Hepatic arterial flow measurements correlated with each other, but portal and renal venous flow correlations were absent.

Conclusions: Surgery and method (DDUS vs. MRI) do not affect mean flow values. Individual comparison is restricted due to wide range in measurements. Since MRI proves to be more reliable with respect to inter-observer variability, we recommend using mean MRI results in experimental setups.
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http://dx.doi.org/10.1016/j.ejrad.2011.06.023DOI Listing
September 2012

Sequence optimization to reduce velocity offsets in cardiovascular magnetic resonance volume flow quantification--a multi-vendor study.

J Cardiovasc Magn Reson 2011 Mar 9;13:18. Epub 2011 Mar 9.

Department of Physics and Medical Technology, ICaR-VU, VU University Medical Center, Amsterdam, the Netherlands.

Purpose: Eddy current induced velocity offsets are of concern for accuracy in cardiovascular magnetic resonance (CMR) volume flow quantification. However, currently known theoretical aspects of eddy current behavior have not led to effective guidelines for the optimization of flow quantification sequences. This study is aimed at identifying correlations between protocol parameters and the resulting velocity error in clinical CMR flow measurements in a multi-vendor study.

Methods: Nine 1.5T scanners of three different types/vendors were studied. Measurements were performed on a large stationary phantom. Starting from a clinical breath-hold flow protocol, several protocol parameters were varied. Acquisitions were made in three clinically relevant orientations. Additionally, a time delay between the bipolar gradient and read-out, asymmetric versus symmetric velocity encoding, and gradient amplitude and slew rate were studied in adapted sequences as exploratory measurements beyond the protocol. Image analysis determined the worst-case offset for a typical great-vessel flow measurement.

Results: The results showed a great variation in offset behavior among scanners (standard deviation among samples of 0.3, 0.4, and 0.9 cm/s for the three different scanner types), even for small changes in the protocol. Considering the absolute values, none of the tested protocol settings consistently reduced the velocity offsets below the critical level of 0.6 cm/s neither for all three orientations nor for all three scanner types. Using multilevel linear model analysis, oblique aortic and pulmonary slices showed systematic higher offsets than the transverse aortic slices (oblique aortic 0.6 cm/s, and pulmonary 1.8 cm/s higher than transverse aortic). The exploratory measurements beyond the protocol yielded some new leads for further sequence development towards reduction of velocity offsets; however those protocols were not always compatible with the time-constraints of breath-hold imaging and flow-related artefacts.

Conclusions: This study showed that with current systems there was no generic protocol which resulted into acceptable flow offset values. Protocol optimization would have to be performed on a per scanner and per protocol basis. Proper optimization might make accurate (transverse) aortic flow quantification possible for most scanners. Pulmonary flow quantification would still need further (offline) correction.
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http://dx.doi.org/10.1186/1532-429X-13-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3065419PMC
March 2011

Evaluation of model-independent deconvolution techniques to estimate blood perfusion.

Annu Int Conf IEEE Eng Med Biol Soc 2010 ;2010:2602-7

Department of Pulmonology of VU University Medical Center, 1007 MB, Amsterdam, The Netherlands.

This report evaluates several methods to estimate blood perfusion and residue functions in dynamic contrast enhanced (DCE) MRI. Among these are model-dependent and model-independent techniques. All methods were applied to series of Monte Carlo simulations to evaluate the accuracy in order to reproduce different underlying vascular residue functions and blood perfusions. Of the model-independent approaches the use of B-splines with Tikhonov regularization was shown to have a reasonable accuracy in blood perfusion estimations and was less biased than all model-dependent approaches. This technique seems most promising for application to experimental data.
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http://dx.doi.org/10.1109/IEMBS.2010.5626615DOI Listing
March 2011

Comparison of dual to single contrast bolus magnetic resonance myocardial perfusion imaging for detection of significant coronary artery disease.

J Magn Reson Imaging 2010 Jul;32(1):88-93

Department of Cardiology, VU University Medical Center, Amsterdam, the Netherlands.

Purpose: To investigate the incremental diagnostic value of dual-bolus over single-contrast-bolus first pass magnetic resonance myocardial perfusion imaging (MR-MPI) for detection of significant coronary artery disease (CAD).

Materials And Methods: Patients (n = 49) with suspected CAD underwent first pass adenosine stress and rest MR-MPI and invasive coronary angiography (CA). Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) was injected with a prebolus (1 mL) and a large bolus (0.1 mmol/kg). For the single-bolus technique, the arterial input function (AIF) was obtained from the large-contrast bolus. For the dual-bolus technique, the AIF was reconstructed from the prebolus. Absolute myocardial perfusion was calculated by Fermi-model constrained deconvolution. Receiver operating characteristic (ROC) analysis was used to investigate diagnostic accuracy of MR myocardial perfusion imaging for detection of significant CAD on CA at vessel-based analysis.

Results: The area under the curve (AUC) of the minimal stress perfusion value for the detection of significant CAD using the single-bolus and dual-bolus technique was 0.85 +/- 0.04 (95% confidence interval [CI], 0.77-0.93) and 0.77 +/- 0.05 (95% CI, 0.67-0.86), respectively.

Conclusion: In this study the dual-bolus technique had no incremental diagnostic value over single-bolus technique for detection of significant CAD with the used contrast concentrations.
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http://dx.doi.org/10.1002/jmri.22231DOI Listing
July 2010

Low to intermediate probability of coronary artery disease: comparison of coronary CT angiography with first-pass MR myocardial perfusion imaging.

Radiology 2010 Feb 20;254(2):384-92. Epub 2010 Jan 20.

Department of Cardiology, VU University Medical Center, De Boelelaan 1117, Room 5F003, 1081 HV Amsterdam, the Netherlands.

Purpose: To compare coronary computed tomographic (CT) angiography with first-pass magnetic resonance (MR) myocardial perfusion imaging in patients with chest pain and low to intermediate probability of coronary artery disease (CAD).

Materials And Methods: Local ethics committee approval and patient written informed consent were obtained. Patients with chest pain and low to intermediate pretest probability of CAD underwent both coronary CT angiography and MR myocardial perfusion imaging. Coronary CT angiographic and MR myocardial perfusion images were analyzed qualitatively by blinded observers. Obstructive CAD was defined as more than 50% diameter stenosis at coronary CT angiography. Data were expressed with 95% confidence intervals (CIs) calculated from binomial expression.

Results: In 145 (94.2%) of 154 eligible patients, both coronary CT angiography and MR myocardial perfusion imaging were performed successfully. Mean age was 57 years +/- 10 (standard deviation), and 45.5% of patients were male. Mean interval between coronary CT angiography and MR myocardial perfusion imaging was 4.6 days +/- 3.0; median was 5.0 days. CT coronary angiography revealed obstructive CAD in 52 (35.9%) patients and 78 (17.9%) coronary arteries. At MR myocardial perfusion imaging, myocardial ischemia was demonstrated in 33 (22.8%) patients and 59 (13.6%) vessel territories. Of patients without CAD at coronary CT angiography, 90.5% (57 of 63; 95% CI: 82.6%, 95.0%) had normal myocardial perfusion at MR myocardial perfusion imaging. Of patients with nonobstructive CAD, 83.3% (25 of 30; 95% CI: 69.5%, 91.6%) had normal myocardial perfusion at MR myocardial perfusion imaging. Myocardial ischemia was detected at MR myocardial perfusion imaging in 42.3% (22 of 52; 95% CI: 29.5%, 56%) of patients with obstructive CAD at coronary CT angiography.

Conclusion: MR myocardial perfusion imaging and coronary CT angiography have complementary roles in evaluation of patients who are suspected of having CAD. Coronary CT angiography can be used to reliably rule out CAD, but its capability to demonstrate hemodynamically significant CAD is limited. The combination of both techniques enables the clinician to evaluate morphology and functional relevance of CAD comprehensively and noninvasively.
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http://dx.doi.org/10.1148/radiol.09090802DOI Listing
February 2010

Improved correction of spatial inhomogeneities of surface coils in quantitative analysis of first-pass myocardial perfusion imaging.

J Magn Reson Imaging 2010 Jan;31(1):227-33

Department of Physics, ICaR-VU, VU University Medical Center, Amsterdam, the Netherlands.

Purpose: To test whether image normalization using either a separate 3D proton-density (PD)-weighted prescan, or 2D PD-weighted images prior to the perfusion series, improves correction of differences in spatial sensitivity induced by radiofrequency (RF) surface receiver coils. Originally, this correction was applied using the baseline signal in the myocardium before arrival of the contrast agent. This is of importance, as quantitative analysis of magnetic resonance (MR) myocardial perfusion using deconvolution with the arterial input assumes equal signal sensitivity over the heart.

Materials And Methods: First-pass myocardial perfusion measurements were obtained in 13 patients without known coronary artery disease. Absolute perfusion values were assessed for 18 myocardial segments without any normalization and using the three different normalization methods.

Results: Using 2D or 3D PD-weighted normalization, similar mean perfusion values were found, but with reduced spatial variance over the 18 segments. The relative dispersion of perfusion at rest was 23% and 35% for the 3D prescan normalization and the baseline normalization, respectively. With 2D and 3D PD-weighted prescan normalization the relative dispersion was closer to the expected physiological heterogeneity.

Conclusion: PD-weighted prescan normalization proved to be a valuable addition to quantitative analysis of myocardial perfusion, and better than baseline-based normalization.
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http://dx.doi.org/10.1002/jmri.21998DOI Listing
January 2010

3D velocity quantification in the heart: improvements by 3D PC-SSFP.

J Magn Reson Imaging 2009 Nov;30(5):947-55

Department of Physics and Medical Technology, ICaR-VU, VU University Medical Center, Amsterdam, the Netherlands.

Purpose: To test whether a 3D imaging sequence with phase contrast (PC) velocity encoding based on steady-state free precession (SSFP) improves 3D velocity quantification in the heart compared to the currently available gradient echo (GE) approach.

Materials And Methods: The 3D PC-SSFP sequence with 1D velocity encoding was compared at the mitral valve in 12 healthy subjects with 3D PC-GE at 1.5T. Velocity measurements, velocity-to-noise-ratio efficiency (VNR(eff)), intra- and interobserver variability of area and velocity measurements, contrast-to-noise-ratio (CNR), and artifact sensitivity were evaluated in both long- and short-axis orientation.

Results: Descending aorta mean and peak velocities correlated well (r(2) = 0.79 and 0.93) between 3D PC-SSFP and 3D PC-GE. At the mitral valve, mean velocity correlation was moderate (r(2) = 0.70 short axis, 0.56 long axis) and peak velocity showed good correlation (r(2) = 0.94 short axis, 0.81 long axis). In some cases VNR(eff) was higher, in others lesser, depending on slab orientation and cardiac phase. Intra- and interobserver variability was generally better for 3D PC-SSFP. CNR improved significantly, especially at end systole. Artifact levels did not increase.

Conclusion: 3D SSFP velocity quantification was successfully tested in the heart. Blood-myocardium contrast improved significantly, resulting in more reproducible velocity measurements for 3D PC-SSFP at 1.5T.
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http://dx.doi.org/10.1002/jmri.21933DOI Listing
November 2009

Impact of alcohol septal ablation on left anterior descending coronary artery blood flow in hypertrophic obstructive cardiomyopathy.

Int J Cardiovasc Imaging 2009 Jun 22;25(5):511-8. Epub 2009 Feb 22.

Department of Cardiology, ICaR-VU, VU University Medical Center, De Boelelaan 1117, Amsterdam, The Netherlands.

Objectives: The aim of this study was to evaluate the effects of alcohol septal ablation (ASA) on coronary blood flow in symptomatic hypertrophic obstructive cardiomyopathy (HOCM) using cardiac MR (CMR) coronary flow measurements. Background CMR flow mapping enables quantification of coronary blood flow in a noninvasive way. Both left ventricular outflow tract (LVOT) gradient reduction and myocardial scarring after ASA are expected to influence left anterior descending (LAD) coronary blood flow.

Methods: Cine, contrast-enhanced (CE) imaging and breath-hold CMR phase contrast velocity mapping were performed at baseline and 1 and 6 months after ASA in seven patients. Changes of coronary blood flow were related to left ventricular (LV) mass reduction, enzyme release, volume of ethanol administered, LVOT gradient reduction, and LV rate pressure product (LVRPP).

Results: A significant mass reduction was observed both in the target septal myocardium and in the total myocardium (both P < 0.01). Mean myocardial infarct size was 23 +/- 12 g (range 7.3-41.6 g). LVRPP decreased from 13,268 +/- 2,212 to 10,685 +/- 3,918 at 1 month (P = 0.05) and 9,483 +/- 2,496 mmHg beats/min at 6 months' follow-up (P < 0.01). LAD coronary blood flow decreased from 100 +/- 37 ml/min at baseline to 84 +/- 54 ml/min (P = 0.09) at 1 month and 67 +/- 33 ml/min at 6 months follow-up (P < 0.01). A significant correlation was found between the change in LVRPP and LAD coronary flow at 1 month follow-up (r = 0.83, P = 0.02). CE-infarct size tended to modulate the blood flow changes over time (P = 0.12); no correlation was observed between enzyme release, volume of ethanol or both septal and total mass reduction and coronary blood flow.

Conclusion: The reduction in coronary blood flow is primarily associated with diminished LV loading conditions, whereas the induction of metabolically inactive myocardial scar tissue by ASA did not significantly influence the changes in coronary blood flow.
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http://dx.doi.org/10.1007/s10554-009-9437-2DOI Listing
June 2009

Assessment of microvascular obstruction and prediction of short-term remodeling after acute myocardial infarction: cardiac MR imaging study.

Radiology 2009 Feb 22;250(2):363-70. Epub 2009 Jan 22.

Departments of Cardiology and Physics and Medical Technology, VU University Medical Center, Amsterdam, the Netherlands.

Purpose: To evaluate which cardiac magnetic resonance (MR) imaging technique for detection of microvascular obstruction (MVO) best predicts left ventricular (LV) remodeling after acute myocardial infarction (MI).

Materials And Methods: This study had local ethics committee approval; all patients gave written informed consent. Sixty-three patients with first acute MI, treated with primary stent placement and optimal medical therapy, underwent cine MR imaging at 4-7 days and at 4 months after MI. Presence of MVO was qualitatively evaluated at baseline by using three techniques: (a) a single-shot saturation-recovery gradient-echo first-pass perfusion sequence (early hypoenhancement), mean time, 1.09 minutes +/- 0.07 (standard deviation) after contrast material administration; (b) a three-dimensional segmented saturation-recovery gradient-echo sequence (intermediate hypoenhancement), mean time, 2.17 minutes +/- 0.26; and (c) a two-dimensional segmented inversion-recovery gradient-echo late gadolinium enhancement sequence (late hypoenhancement), mean time, 13.32 minutes +/- 1.26. Contrast-to-noise ratios (CNRs) were calculated from the signal-to-noise ratios of the infarcted myocardium and MVO areas. Univariable linear regression analysis was used to identify the predictive value of each MR imaging technique.

Results: Early hypoenhancement was detected in 44 (70%) of 63 patients; intermediate hypoenhancement, in 39 (62%); and late hypoenhancement, in 37 (59%). Late hypoenhancement was the strongest predictor of change in LV end-diastolic and end-systolic volumes over time (beta = 14.3, r = 0.40, P = .001 and beta = 11.3, r = 0.44, P < .001, respectively), whereas intermediate and late hypoenhancement had comparable predictive values of change in LV ejection fraction (beta = -3.1, r = -0.29, P = .02 and beta = -2.8, r = -0.27, P = .04, respectively). CNR corrected for spatial resolution was significantly superior for late enhancement compared with the other sequences (P < .001).

Conclusion: By using cardiac MR imaging, late hypoenhancement is the best prognostic marker of LV remodeling, with highest CNR between the infarcted myocardium and MVO regions.
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http://dx.doi.org/10.1148/radiol.2502080739DOI Listing
February 2009