A comparison of conventional and advanced 3D imaging techniques for percutaneous left atrial appendage closure.

Background: Understanding complex cardiac anatomy is essential for percutaneous left atrial appendage (LAA) closure. Conventional multi-slice computed tomography (MSCT) and transesophageal echocardiography (TEE) are now supported by advanced 3D printing and virtual reality (VR) techniques for three-dimensional visualization of volumetric data sets. This study aimed to investigate their added value for LAA closure procedures. Methods: Ten patients scheduled for interventional LAA closure were evaluated with MSCT and TEE. Patient-specific 3D printings and VR models were fabricated based on MSCT data. Ten cardiologists then comparatively assessed LAA anatomy and its procedure relevant surrounding structures with all four imaging modalities and rated their procedural utility on a 5-point Likert scale questionnaire (from 1 = strongly agree to 5 = strongly disagree). Results: Device sizing was rated highest in MSCT (MSCT: 1.9 ± 0.8; TEE: 2.6 ± 0.9; 3D printing: 2.5 ± 1.0; VR: 2.5 ± 1.1; p < 0.01); TEE, VR, and 3D printing were superior in the visualization of the Fossa ovalis compared to MSCT (MSCT: 3.3 ± 1.4; TEE: 2.2 ± 1.3; 3D printing: 2.2 ± 1.4; VR: 1.9 ± 1.3; all p < 0.01). The major strength of VR and 3D printing techniques was a superior depth perception (VR: 1.6 ± 0.5; 3D printing: 1.8 ± 0.4; TEE: 2.9 ± 0.7; MSCT: 2.6 ± 0.8; p < 0.01). The visualization of extracardiac structures was rated less accurate in TEE than MSCT (TEE: 2.6 ± 0.9; MSCT: 1.9 ± 0.8, p < 0.01). However, 3D printing and VR insufficiently visualized extracardiac structures in the present study. Conclusion: A true 3D visualization in VR or 3D printing provides an additional value in the evaluation of the LAA for the planning of percutaneous closure. In particular, the superior perception of depth was seen as a strength of a 3D visualization. This may contribute to a better overall understanding of the anatomy. Clinical studies are needed to evaluate whether a more comprehensive understanding through advanced multimodal imaging of patient-specific anatomy using VR may translate into improved procedural outcomes.

Pulmonary CT perfusion robustly measures cardiac output in the context of multilevel pulmonary occlusion: a porcine study.

BACKGROUND: To validate pulmonary computed tomography (CT) perfusion in a porcine model by invasive monitoring of cardiac output (CO) using thermodilution method. METHODS: Animals were studied at a single center, using a Swan-Ganz catheter for invasive CO monitoring as a reference. Fifteen pigs were included. Contrast-enhanced CT perfusion of the descending aorta and right and left pulmonary artery was performed. For variation purposes, a balloon catheter was inserted to block the contralateral pulmonary vascular bed; additionally, two increased CO settings were created by intravenous administration of catecholamines. Finally, stepwise capillary occlusion was performed by intrapulmonary arterial injection of 75-µm microspheres in four stages. A semiautomatic selection of AFs and a recirculation-aware tracer-kinetics model to extract the first-pass of AFs, estimating blood flow with the Stewart-Hamilton method, was implemented. Linear mixed models (LMM) were developed to calibrate blood flow calculations accounting with individual- and cohort-level effects. RESULTS: Nine of 15 pigs had complete datasets. Strong correlations were observed between calibrated pulmonary (0.73, 95% confidence interval [CI] 0.6-0.82) and aortic blood flow measurements (0.82, 95% CI, 0.73-0.88) and the reference as well as agreements (± 2.24 L/min and ± 1.86 L/min, respectively) comparable to the state of the art, on a relatively wide range of right ventricle-CO measurements. CONCLUSIONS: CT perfusion validly measures CO using LMMs at both individual and cohort levels, as demonstrated by referencing the invasive CO. RELEVANCE STATEMENT: Possible clinical applications of CT perfusion for measuring CO could be in acute pulmonary thromboembolism or to assess right ventricular function to show impairment or mismatch to the left ventricle. KEY POINTS: • CT perfusion measures flow in vessels. • CT perfusion measures cumulative cardiac output in the aorta and pulmonary vessels. • CT perfusion validly measures CO using LMMs at both individual and cohort levels, as demonstrated by using the invasive CO as a reference standard.

Direct contribution of the sensory cortex to the judgment of stimulus duration.

Decision making frequently depends on monitoring the duration of sensory events. To determine whether, and how, the perception of elapsed time derives from the neuronal representation of the stimulus itself, we recorded and optogenetically modulated vibrissal somatosensory cortical activity as male rats judged vibration duration. Perceived duration was dilated by optogenetic excitation. A second set of rats judged vibration intensity; here, optogenetic excitation amplified the intensity percept, demonstrating sensory cortex to be the common gateway both to time and to stimulus feature processing. A model beginning with the membrane currents evoked by vibrissal and optogenetic drive and culminating in the representation of perceived time successfully replicated rats' choices. Time perception is thus as deeply intermeshed within the sensory processing pathway as is the sense of touch itself, suggesting that the experience of time may be further investigated with the toolbox of sensory coding.

Left atrial appendage sizing for percutaneous closure in virtual reality-a feasibility study.

Background and aims: The complex and highly variable three-dimensional anatomy of the left atrial appendage (LAA) makes planning and device sizing for interventional occlusion procedures (LAAC) challenging. Several imaging modalities [e.g. echocardiography, multi-slice computed tomography (MSCT)] are used for this purpose. Virtual reality (VR) is an emerging imaging technique to immerse into a three-dimensional left atrium and appendage, offering unprecedented options of visualization and measurement. This study aimed to investigate the feasibility, accuracy and reproducibility of visualizing the LAA in VR for preprocedural planning of LAAC. Methods and results: Twenty-one patients (79 ± 7 years, 62% male) who underwent LAAC at University Hospital Düsseldorf were included in our study. A dedicated software generated three-dimensional VR models from preprocedural MSCT imaging data. Conventional measurements of LAA dimensions (ostium, landing zone and depth) using a commercially available software were compared to measurements in VR: MSCT and VR ostium min. (r = 0.93), max. (r = 0.80) and mean (r = 0.88, all p < 0.001) diameters as well as landing zone (LZ) min. (r = 0.84), max. (r = 0.86) and mean diameters (r = 0.90, all p < 0.001) showed strong correlations. Three-dimensional orientation was judged superior by physicians in VR compared to MSCT (p < 0.05). Conclusion: Virtual reality visualization of the left atrium and appendage based on MSCT data is feasible and allows precise and reproducible measurements in planning of LAA occlusion procedures with enhanced 3D orientation. Further studies need to explore additional benefits of three-dimensional visualization for operators in preprocedural planning.

LYN kinase programs stromal fibroblasts to facilitate leukemic survival via regulation of c-JUN and THBS1.

Microenvironmental bystander cells are essential for the progression of chronic lymphocytic leukemia (CLL). We have discovered previously that LYN kinase promotes the formation of a microenvironmental niche for CLL. Here we provide mechanistic evidence that LYN regulates the polarization of stromal fibroblasts to support leukemic progression. LYN is overexpressed in fibroblasts of lymph nodes of CLL patients. LYN-deficient stromal cells reduce CLL growth in vivo. LYN-deficient fibroblasts show markedly reduced leukemia feeding capacity in vitro. Multi-omics profiling reveals that LYN regulates the polarization of fibroblasts towards an inflammatory cancer-associated phenotype through modulation of cytokine secretion and extracellular matrix composition. Mechanistically, LYN deletion reduces inflammatory signaling including reduction of c-JUN expression, which in turn augments the expression of Thrombospondin-1, which binds to CD47 thereby impairing CLL viability. Together, our findings suggest that LYN is essential for rewiring fibroblasts towards a leukemia-supportive phenotype.

Soluble amyloid-ß precursor peptide does not regulate GABAB receptor activity.

Amyloid-ß precursor protein (APP) regulates neuronal activity through the release of secreted APP (sAPP) acting at cell surface receptors. APP and sAPP were reported to bind to the extracellular sushi domain 1 (SD1) of GABAB receptors (GBRs). A 17 amino acid peptide (APP17) derived from APP was sufficient for SD1 binding and shown to mimic the inhibitory effect of sAPP on neurotransmitter release and neuronal activity. The functional effects of APP17 and sAPP were similar to those of the GBR agonist baclofen and blocked by a GBR antagonist. These experiments led to the proposal that sAPP activates GBRs to exert its neuronal effects. However, whether APP17 and sAPP influence classical GBR signaling pathways in heterologous cells was not analyzed. Here, we confirm that APP17 binds to GBRs with nanomolar affinity. However, biochemical and electrophysiological experiments indicate that APP17 does not influence GBR activity in heterologous cells. Moreover, APP17 did not regulate synaptic GBR localization, GBR-activated K+ currents, neurotransmitter release, or neuronal activity in vitro or in vivo. Our results show that APP17 is not a functional GBR ligand and indicate that sAPP exerts its neuronal effects through receptors other than GBRs.

[Ischemic heart disease : More than just chronic CAD]. / Ischämische Herzkrankheit : Mehr als nur chronische KHK.

CLINICAL/METHODOLOGICAL ISSUE: Myocardial ischemia as a reduction in perfusion with therefore oxygen deficiency of vital cardiomyocytes. Thus primary and secondary prophylaxis of myocardial infarction and it's complications. STANDARD RADIOLOGICAL METHODS: Adenosine-regadenoson stress magnetic resonance imaging (AR-stress MRI), computed tomography coronary angiography (CTCA). METHODOLOGICAL INNOVATIONS: Non-invasive stress testing using AR-stress MRI to exclude relevant obstructive coronary artery disease (CAD). PERFORMANCE: Meta-analysis: The diagnosis of obstructive CAD at the coronary artery level has a pooled sensitivity of 87.7% and a specificity of 88.6%. Diagnostic accuracy is better than single photon emission computed tomography (SPECT; AUC 0.89 vs. 0.74). ACHIEVEMENTS: AR-stress MRI can be used to assess myocardial ischemia in the setting of obstructive CAD. Current clinical guidelines for myocardial revascularization have strengthened the use of stress MRI in patients with intermediate risk of CAD and stable symptoms. Cardiac MR imaging using late gadolinium enhancement (LGE) is considered gold standard for myocardial viability assessment in vivo. Both viability and ischemia are considered prognostic factors for major adverse cardiac events. PRACTICAL RECOMMENDATIONS: AR-stress MRI is used to diagnose myocardial ischemia in combination with viability imaging (LGE). Dobutamine-atropine (DoA) stress MRI is an alternative in the setting of contraindications for AR or specific clinical questions.

The scaffold protein NEDD9 is necessary for leukemia-cell migration and disease progression in a mouse model of chronic lymphocytic leukemia.

The scaffold protein NEDD9 is frequently upregulated and hyperphosphorylated in cancers, and is associated with poor clinical outcome. NEDD9 promotes B-cell adhesion, migration and chemotaxis, pivotal processes for malignant development. We show that global or B-cell-specific deletion of Nedd9 in chronic lymphocytic leukemia (CLL) mouse models delayed CLL development, markedly reduced disease burden and resulted in significant survival benefit. NEDD9 was required for efficient CLL cell homing, chemotaxis, migration and adhesion. In CLL patients, peripheral NEDD9 expression was associated with adhesion and migration signatures as well as leukocyte count. Additionally, CLL lymph nodes frequently expressed high NEDD9 levels, with a subset of patients showing NEDD9 expression enriched in the CLL proliferation centers. Blocking activity of prominent NEDD9 effectors, including AURKA and HDAC6, effectively reduced CLL cell migration and chemotaxis. Collectively, our study provides evidence for a functional role of NEDD9 in CLL pathogenesis that involves intrinsic defects in adhesion, migration and homing.

CoRad-19 - Modular Digital Teaching during the SARS-CoV-2 Pandemic. / CoRad-19 ­ Modulare Digitale Lehre während der SARS-CoV-2-Pandemie.

PURPOSE: During the SARS-CoV-2 pandemic, higher education worldwide had to switch to digital formats. The purpose of this study was to evaluate CoRad-19, a digital teaching tool created by the German Radiological Society for medical students during the COVID-19 pandemic. MATERIALS AND METHODS: A total of 13 German-speaking universities implemented CoRad-19 in their curriculum and partially or completely replaced their classes with the online courses. Previous experience and contact with radiology and the participants' opinions regarding the medium of e-learning were surveyed using a custom questionnaire. The subjective level of knowledge regarding the individual modules was also surveyed before and after participation to measure learning effects. The data of 994 medical students from the participating sites were analyzed and compared intraindividually using the Friedman test. RESULTS: From 4/1/2020-10/1/2020, 451 complete data sets from a total of 994 surveys were included. E-learning was rated "very useful" both before and after course participation (4 [IQR 3-4], p = 0.527, r = 0.16). E-learning as a method was also rated as a "very good" medium both before and after participation (4 [IQR 3-4], p = 0.414, r = 0.17). After participation, participants rated radiology as particularly suitable for digital teaching (before: 3 [IQR 3-4] vs. after 4 [IQR 3-4], p = 0.005, r = 0.6). Significant learning gains were measurable in all course modules (p ≤ 0.009). Post-hoc analysis showed interest in radiology to increase significantly after course participation (p = 0.02). CONCLUSION: In the representative survey, significant learning effects were observed in all course modules. In addition, it should be particularly emphasized that the students' interest in radiology was increased by course participation. Thus, the German Radiological Society provided significant support to German-speaking medical faculties with respect to maintaining excellent education using CoRad-19. KEY POINT: · Co-Rad-19 course participation results in measurable subjective learning effects and increases student interest in radiology.. CITATION FORMAT: · Brendlin AS, Molwitz I, Oechtering TH et al. CoRad-19 - Modular Digital Teaching during the SARS-CoV-2 Pandemic. Fortschr Röntgenstr 2022; 194: 644 - 651.

Frequency-selective signal enhancement by a passive dual coil resonator for magnetic particle imaging.

Objective.Magnetic particle imaging (MPI) visualizes the spatial distribution of magnetic nanoparticles. MPI already provides excellent temporal and good spatial resolution, however, to achieve translation into clinics, further advances in the fields of sensitivity, image reconstruction and tracer performance are needed. In this work, we propose a novel concept to enhance the MPI signal and image resolution by a purely passive receive coil insert for a preclinical MPI system.Approach.The passive dual coil resonator (pDCR) provides frequency-selective signal enhancement. This is enabled by the adaptable resonance frequency of the pDCR network, which is galvanically isolated from the MPI system and composed of two coaxial solenoids connected via a capacitor. The pDCR aims to enhance frequency components related to high mixing orders, which are crucial to achieve high spatial resolution.Main Results.In this study, system matrix measurements and image acquisitions of a resolution phantom are carried out to evaluate the performance of the pDCR compared to the integrated receive unit of the preclinical MPI and a dedicated rat-sized receive coil. Frequency-selective signal increase and spatial resolution enhancement are demonstrated.Significance.Common dedicated receive coils come along with noise-matched receive networks, which makes them costly and difficult to reproduce. The presented pDCR is a purely passive coil insert that gets along without any additional receive electronics. Therefore, it is cost-efficient, easy-to-handle and adaptable to other MPI scanners and potentially other applications providing the basis for a new breed of passive MPI receiver systems.

Influence of rivaroxaban compared to vitamin K antagonist treatment upon development of cardiovascular calcification in patients with atrial fibrillation and/or pulmonary embolism.

BACKGROUND: Vitamin K antagonists (VKA) such as warfarin or phenprocoumon have been the mainstay of therapy for long-term oral anticoagulant therapy (OAT) in patients with atrial fibrillation or with pulmonary embolism. Due to interferences with matrix Gla-protein, an important vitamin K-dependent local calcification inhibitor in cardiovascular structures, VKA antagonists stimulate cardiovascular calcification (CVC). In contrast, rivaroxaban, a nonvitamin K-dependent oral anticoagulant (NOAC), should be neutral in terms of CVC. We seek to investigate these potential differences in CVC development between VKA versus NOACs in a randomized controlled trial (RCT). METHODS: The influence of rivaroxaban compared to vitamin K antagonist treatment upon development of cardiovascular calcification in patients with atrial fibrillation and/or pulmonary embolism trial (NCT02066662) is a multicenter, prospective RCT with a two-arm, open-label study design. The primary endpoint is the progression of coronary and aortic valve calcification (quantified as calcification volume score) as assessed by cardiac computed tomography (CT) at 24 months in patients either treated by rivaroxaban or VKA. A total of 192 patients were randomized in a 1:1 fashion. The main inclusion criteria were the presence of atrial fibrillation and/or pulmonary embolism with the indication for OAT and pre-existent coronary calcification. The development of CVC will be assessed by follow-up CT at 12 and 24 months. RESULTS: In total 192 patients (median age 70, 72% male) were enrolled over a period of 5 years and followed up for 2 years.

Current Status of Cardiovascular Imaging in Germany: Structured Data from the National Certification Program, ESCR Registry, and Survey among Radiologists.

PURPOSE: In the light of the increasing importance of cardiovascular cross-sectional imaging in current guidelines, the goal of this study is to provide a comprehensive overview of cardiovascular imaging (CVI) offered by radiological institutions across Germany. MATERIALS AND METHODS: Data were extracted from the national certification program database of the German Roentgen Society (DRG) from 2015-2021. A nationwide online survey among radiology institutes (university hospitals, non-university hospitals, and private practices) was conducted for 2019, and data was extracted from the European Society of Cardiovascular Radiology (ESCR) registry. The data collection's key points included the number of centers and individuals certified for CVI, the number of cardiac CT and MRI examinations performed, the reporting habits, and the participation in the ESCR registry. RESULTS: 71 centers and 1278 persons, both with a substantial increase since 2015, were registered and certified by the DRG to perform CVI. According to the survey, a total of 69,286 CT and 64,281 MRI examinations were performed annually. Data from the survey and the ESCR registry indicated that reporting was mostly done solely by radiologists or, to a lesser degree, in joint consensus meetings with non-radiologists. The overall participation rate in the ESCR registry was 48 % among the survey's participants. CONCLUSION: This comprehensive analysis demonstrates that high-quality CVI by radiologists is available nationwide. The current challenges are to provide the best medical and technical quality of CVI by radiology for patient care and to ensure economic sustainability in the German health care system to accommodate the predicted substantial need for CVI in the future. KEY POINTS: · High-quality advanced CVI service by radiologists is available nationwide.. · Highly qualified specialist knowledge is widely represented from university to private practices.. · Certification programs successfully contribute to the dissemination & deepening of CVI expertise.. · The ESCR registry is an established international tool for the documentation of CVI.. CITATION FORMAT: · Sieren M, Maintz D, Gutberlet M et al. Current Status of Cardiovascular Imaging in Germany: Structured Data from the National Certification Program, ESCR Registry, and Survey among Radiologists. Fortschr Röntgenstr 2022; 194: 181 - 191.

Vitamin K1 and progression of cardiovascular calcifications in hemodialysis patients: the VitaVasK randomized controlled trial.

Background: Cardiovascular calcifications are prevented by matrix Gla protein (MGP), a vitamin K-dependent protein. Haemodialysis patients exhibit marked vitamin K deficiency. The randomized, prospective, open-label, multicentre VitaVasK trial analysed whether vitamin K1 supplementation reduces progression of coronary artery calcifications (CACs) and thoracic aortic calcifications (TACs). Methods: Patients with pre-existing CACs were randomized to continue on standard care or to additionally receive 5 mg of vitamin K1 orally thrice weekly. Hierarchically ordered primary endpoints were progression of TAC and CAC in computed tomography scans at 18 months. Linear mixed effects models with repeated measures at baseline and 12 and 18 months assessed treatment effects after adjusting for study site. Results: Of 60 randomized patients, 20 dropped out for reasons unrelated to vitamin K1, resulting in 23 control and 17 vitamin K1 patients. The trial was stopped early due to slow recruitment. At 18 months, the average TAC progression was 56% lower in the vitamin K1 compared with the control group (p = .039). CAC significantly progressed within the control group, but not within the vitamin K1 group. Average progression at 18 months was 68% lower in the vitamin K1 compared to the control group (P = .072). Vitamin K1 reduced plasma levels of pro-calcific uncarboxylated MGP by 69% at 18 months. No treatment-related adverse events were noted. Conclusion: Vitamin K1 intervention is a potent, safe and cost-effective approach to correct vitamin K deficiency and to potentially reduce cardiovascular calcification in this high-risk population.

Cardiovascular Evaluation of Liver Transplant Patients by Using Coronary Calcium Scoring in ECG-Synchronized Computed Tomographic Scans.

BACKGROUND: The goal of cardiac evaluation of patients awaiting orthotopic liver transplantation (OLT) is to identify the patients at risk for cardiovascular events (CVEs) in the peri- and postoperative periods by opportunistic evaluation of coronary artery calcium (CAC) in non-gated abdominal computed tomographs (CT). METHODS: We hypothesized that in patients with OLT, a combination of Lee's revised cardiac index (RCRI) and CAC scoring would improve diagnostic accuracy and prognostic impact compared to non-invasive cardiac testing. Therefore, we retrospectively evaluated 169 patients and compared prediction of CVEs by both methods. RESULTS: Standard workup identified 22 patients with a high risk for CVEs during the transplant period, leading to coronary interventions. Eighteen patients had a CVE after transplant and a CAC score > 0. The combination of CAC and RCRI ≥ 2 had better negative (NPV) and positive predictive values (PPV) for CVEs (NPV 95.7%, PPV 81.6%) than standard non-invasive stress tests (NPV 92.0%, PPV 54.5%). CONCLUSION: The cutoff value of CAC > 0 by non-gated CTs combined with RCRI ≥ 2 is highly sensitive for identifying patients at risk for CVEs in the OLT population.

White Paper: Radiology Curriculum for Undergraduate Medical Education in Germany and Integration into the NKLM 2.0. / White Paper: Curriculum Radiologie für das Studium der Humanmedizin und Implementierung in den NKLM 2.0.

OBJECTIVE: The aim was to develop a new curriculum for radiology in medical studies, to reach a national consensus and to integrate it into the new national competence-based learning objectives catalog (NKLM 2.0). In this statement of the German Radiological Society (DRG), the process of curriculum development is described and the new curriculum is presented together with suggestions for practical implementation. MATERIALS AND METHODS: The DRG has developed a new curriculum for radiology. This was coordinated nationally among faculty via an online survey and the result was incorporated into the NKLM 2.0. Furthermore, possibilities for the practical implementation of the competency-based content are shown and different teaching concepts are presented. RESULTS: The developed curriculum is competency-based and aims to provide students with important skills and abilities for their future medical practice. The general part of the curriculum is divided into the topics "Radiation Protection", "Radiological Methods" and radiologically-relevant "Digital Skills". Furthermore, there is a special part on the individual organ systems and the specific diseases. In order to implement this in a resource-saving way, new innovative teaching concepts are needed that combine the advantages of face-to-face teaching in small groups for practical and case-based learning with digital teaching offers for resource-saving teaching of theoretical content. CONCLUSION: We have created a uniform radiology curriculum for medical studies in Germany, coordinated it nationally and integrated it into the NKLM 2.0. The curriculum forms the basis of a uniform mandatory radiology teaching and should be the basis for the individual curriculum development of each faculty and strengthen the position of radiology in the interdisciplinary context. KEY POINTS: · A radiology curriculum for undergraduate medical education was developed.. · The curriculum was brought into agreement among the faculties in Germany and integrated into the NKLM 2.0.. · This curriculum is intended to be the basis for curriculum development and to strengthen the position of radiology.. · In order to implement the competence-based teaching, new innovative teaching concepts are necessary.. CITATION FORMAT: · Dettmer S, Barkhausen J, Volmer E et al. White Paper: Radiology Curriculum for Undergraduate Medical Education in Germany and Integration into the NKLM 2.0. Fortschr Röntgenstr 2021; 193: 1294 - 1303.

Time coding in rat dorsolateral striatum.

To assess the role of dorsolateral striatum (DLS) in time coding, we recorded neuronal activity in rats tasked with comparing the durations of two sequential vibrations. Bayesian decoding of population activity revealed a representation of the unfolding of the trial across time. However, further analyses demonstrated a distinction between the encoding of trial time and perceived time. First, DLS did not show a privileged representation of the stimulus durations compared with other time spans. Second, higher intensity vibrations were perceived as longer; however, time decoded from DLS was unaffected by vibration intensity. Third, DLS did not encode stimulus duration differently on correct versus incorrect trials. Finally, in rats trained to compare the intensities of two sequential vibrations, stimulus duration was encoded even though it was a perceptually irrelevant feature. These findings lead us to posit that temporal information is inherent to DLS activity irrespective of the rat's ongoing percept.

Image-derived mean velocity measurement for prediction of coronary flow reserve in a canonical stenosis phantom using magnetic particle imaging.

INTRODUCTION: Aim of this study is to evaluate whether magnetic particle imaging (MPI) is capable of measuring velocities occurring in the coronary arteries and to compute coronary flow reserve (CFR) in a canonical phantom as a preliminary study. METHODS: For basic velocity measurements, a circulation phantom was designed containing replaceable glass tubes with three varying inner diameters, matching coronary-vessel diameters. Standardised boluses of superparamagnetic-iron-oxide-nanoparticles were injected and visualised by MPI. Two image-based techniques were competitively applied to calibrate the respective glass tube and to compute the mean velocity: full-duration-at-half-maximum (FDHM) and tracer dilution (TD) method. For CFR-calculation, four necessary settings of the circulation model of a virtual vessel with an inner diameter of 4 mm were generated using differently sized glass tubes and a stenosis model. The respective velocities in stenotic glass tubes were computed without recalibration. RESULTS: On velocity level, comparison showed a good agreement (rFDHM = 0.869, rTD = 0.796) between techniques, preferably better for 4 mm and 6 mm inner diameter glass tubes. On CFR level MPI-derived CFR-prediction performed considerably inferior with a relative error of 20-44%. CONCLUSIONS: MPI has the ability to reliably measure coronary blood velocities at rest as well as under hyperaemia and therefore may be suitable for CFR calculation. Calibration-associated accuracy of CFR-measurements has to be improved substantially in further studies.

Flow velocity quantification by exploiting the principles of the Doppler effect and magnetic particle imaging.

Changes in blood flow velocity play a crucial role during pathogenesis and progression of cardiovascular diseases. Imaging techniques capable of assessing flow velocities are clinically applied but are often not accurate, quantitative, and reliable enough to assess fine changes indicating the early onset of diseases and their conversion into a symptomatic stage. Magnetic particle imaging (MPI) promises to overcome these limitations. Existing MPI-based techniques perform velocity estimation on the reconstructed images, which restricts the measurable velocity range. Therefore, we developed a novel velocity quantification method by adapting the Doppler principle to MPI. Our method exploits the velocity-dependent frequency shift caused by a tracer motion-induced modulation of the emitted signal. The fundamental theory of our method is deduced and validated by simulations and measurements of moving phantoms. Overall, our method enables robust velocity quantification within milliseconds, with high accuracy, no radiation risk, no depth-dependency, and extended range compared to existing MPI-based velocity quantification techniques, highlighting the potential of our method as future medical application.