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Wiström E, Hyacinthe JN, Lê TP, Gruetter R, Capozzi A. 129Xe Dynamic Nuclear Polarization Demystified: The Influence of the Glassing Matrix on the Radical Properties. J Phys Chem Lett 2024; 15:2957-2965. [PMID: 38453156 PMCID: PMC10961830 DOI: 10.1021/acs.jpclett.4c00177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 02/14/2024] [Accepted: 02/21/2024] [Indexed: 03/09/2024]
Abstract
129Xe dissolution dynamic nuclear polarization (DNP) is a controversial topic. The gold standard technique for hyperpolarized xenon magnetic resonance imaging (MRI) is spin exchange optical pumping, which received FDA approval in 2022. Nevertheless, the versatility of DNP for enhancing the signal of any NMR active nucleus might provide new perspectives for hyperpolarized 129Xe NMR/MRI. Initial publications about 129Xe DNP underlined the increased complexity in the sample preparation and lower polarization levels when compared to more conventional 13C-labeled molecules, at same experimental conditions, despite very close gyromagnetic ratios. Herein, we introduce, using a Custom Fluid Path system, a user-friendly and very robust sample preparation method. Moreover, investigating the radical properties at real DNP conditions by means of LOngitudinal Detected Electron Spin Resonance, we discovered a dramatic shortening of the electron spin longitudinal relaxation time (T1e) of nitroxyl radicals in xenon DNP samples' matrices, with respect to more commonly used water:glycerol ones. Mitigating those challenges through microwave frequency modulation, we achieved over 20% 129Xe polarization without employing any deuterated solvent.
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Affiliation(s)
- Emma Wiström
- LIFMET,
Institute of Physics, École Polytechnique
Fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland
| | - Jean-Noël Hyacinthe
- LIFMET,
Institute of Physics, École Polytechnique
Fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland
| | - Thanh Phong Lê
- LIFMET,
Institute of Physics, École Polytechnique
Fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland
| | - Rolf Gruetter
- LIFMET,
Institute of Physics, École Polytechnique
Fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland
| | - Andrea Capozzi
- LIFMET,
Institute of Physics, École Polytechnique
Fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland
- HYPERMAG,
Department of Health Technology, Technical
University of Denmark, Building 349, 2800 Kgs Lyngby, Denmark
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Lê TP, Hyacinthe JN, Capozzi A. Multi-sample/multi-nucleus parallel polarization and monitoring enabled by a fluid path technology compatible cryogenic probe for dissolution dynamic nuclear polarization. Sci Rep 2023; 13:7962. [PMID: 37198242 DOI: 10.1038/s41598-023-34958-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 05/10/2023] [Indexed: 05/19/2023] Open
Abstract
Low throughput is one of dissolution Dynamic Nuclear Polarization (dDNP) main shortcomings. Especially for clinical and preclinical applications, where direct 13C nuclei polarization is usually pursued, it takes hours to generate one single hyperpolarized (HP) sample. Being able to hyperpolarize more samples at once represents a clear advantage and can expand the range and complexity of the applications. In this work, we present the design and performance of a highly versatile and customizable dDNP cryogenic probe, herein adapted to a 5 T "wet" preclinical polarizer, that can accommodate up to three samples at once and, most importantly, it is capable of monitoring the solid-state spin dynamics of each sample separately, regardless of the kind of radical used and the nuclear species of interest. Within 30 min, the system was able to dispense three HP solutions with high repeatability across the channels (30.0 ± 1.2% carbon polarization for [1-13C]pyruvic acid doped with trityl radical). Moreover, we tested multi-nucleus NMR capability by polarizing and monitoring simultaneously 13C, 1H and 129Xe. Finally, we implemented [1-13C]lactate/[1-13C]pyruvate polarization and back-to-back dissolution and injection in a healthy mouse model to perform multiple-substrate HP Magnetic Resonance Spectroscopy (MRS) at 14.1 T.
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Affiliation(s)
- Thanh Phong Lê
- LIFMET, Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), Station 6, 1015, Lausanne, Switzerland
| | - Jean-Noël Hyacinthe
- LIFMET, Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), Station 6, 1015, Lausanne, Switzerland
- Image Guided Intervention Laboratory, Department of Radiology and Medical Informatics, University of Geneva, 4 Rue Gabrielle - Perret - Gentil, 1211, Geneva, Switzerland
- Geneva School of Health Sciences, HES-SO University of Applied Sciences and Arts Western Switzerland, 47 Avenue de Champel, 1206, Geneva, Switzerland
| | - Andrea Capozzi
- LIFMET, Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), Station 6, 1015, Lausanne, Switzerland.
- HYPERMAG, Department of Health Technology, Technical University of Denmark, Building 349, 2800, Kgs Lyngby, Denmark.
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Lê TP, Gruetter R, Jorge J, Ipek Ö. Segmenting electroencephalography wires reduces radiofrequency shielding artifacts in simultaneous electroencephalography and functional magnetic resonance imaging at 7 T. Magn Reson Med 2022; 88:1450-1464. [PMID: 35575944 PMCID: PMC9323442 DOI: 10.1002/mrm.29298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 04/16/2022] [Accepted: 04/18/2022] [Indexed: 12/05/2022]
Abstract
Purpose Simultaneous scalp electroencephalography and functional magnetic resonance imaging (EEG‐fMRI) enable noninvasive assessment of brain function with high spatial and temporal resolution. However, at ultra‐high field, the data quality of both modalities is degraded by mutual interactions. Here, we thoroughly investigated the radiofrequency (RF) shielding artifact of a state‐of‐the‐art EEG‐fMRI setup, at 7 T, and design a practical solution to limit this issue. Methods Electromagnetic field simulations and MR measurements assessed the shielding effect of the EEG setup, more specifically the EEG wiring. The effectiveness of segmenting the wiring with resistors to reduce the transmit field disruption was evaluated on a wire‐only EEG model and a simulation model of the EEG cap. Results The EEG wiring was found to exert a dominant effect on the disruption of the transmit field, whose intensity varied periodically as a function of the wire length. Breaking the electrical continuity of the EEG wires into segments shorter than one quarter RF wavelength in air (25 cm at 7 T) reduced significantly the RF shielding artifacts. Simulations of the EEG cap with segmented wires indicated similar improvements for a moderate increase of the power deposition. Conclusion We demonstrated that segmenting the EEG wiring into shorter lengths using commercially available nonmagnetic resistors is effective at reducing RF shielding artifacts in simultaneous EEG‐fMRI. This prevents the formation of RF‐induced standing waves, without substantial specific absorption rate (SAR) penalties, and thereby enables benefiting from the functional sensitivity boosts achievable at ultra‐high field.
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Affiliation(s)
- Thanh Phong Lê
- Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Geneva School of Health Sciences, HES-SO University of Applied Sciences and Arts Western Switzerland, Geneva, Switzerland
| | - Rolf Gruetter
- Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - João Jorge
- Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.,CSEM - Swiss Center for Electronics and Microtechnology, Neuchâtel, Switzerland
| | - Özlem Ipek
- CIBM Center for Biomedical Imaging - Animal Imaging and Technology, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.,School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
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Lê TP, Hyacinthe JN, Capozzi A. How to improve the efficiency of a traditional dissolution dynamic nuclear polarization (dDNP) apparatus: Design and performance of a fluid path compatible dDNP/LOD-ESR probe. J Magn Reson 2022; 338:107197. [PMID: 35344922 DOI: 10.1016/j.jmr.2022.107197] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 03/12/2022] [Accepted: 03/14/2022] [Indexed: 06/14/2023]
Abstract
Dissolution Dynamic Nuclear Polarization (dDNP) was invented almost twenty years ago. Ever since, hardware advancement has observed 2 trends: the quest for DNP at higher field and, more recently, the development of cryogen free polarizers. Despite the DNP community is slowly migrating towards "dry" systems, many "wet" polarizers are still in use. Traditional DNP polarizers can use up to 100 L of liquid helium per week, but are less sensitive to air contamination and have higher cooling power. These two characteristics make them very versatile when it comes to new methods development. In this study we retrofitted a 5 T/1.15 K "wet" DNP polarizer with the aim of improving cryogenic and DNP performance. We designed, built, and tested a new DNP insert that is compatible with the fluid path (FP) technology and a LOgitudinal Detected Electron Spin Resonance (LOD-ESR) probe to investigate radical properties at real DNP conditions. The new hardware increased the maximum achievable polarization and the polarization rate constant of a [1-13C]pyruvic acid-trityl sample by a factor 1.5. Moreover, the increased liquid He holding time together with the possibility to constantly keep the sample space at low pressure upon sample loading and dissolution allowed us to save about 20 L of liquid He per week.
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Affiliation(s)
- Thanh Phong Lê
- Geneva School of Health Sciences, HES-SO University of Applied Sciences and Arts Western Switzerland, Avenue de Champel 47, 1206 Geneva, Switzerland; LIFMET, Institute of Physics, École polytechnique fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland
| | - Jean-Noël Hyacinthe
- Geneva School of Health Sciences, HES-SO University of Applied Sciences and Arts Western Switzerland, Avenue de Champel 47, 1206 Geneva, Switzerland; Image Guided Interventions Laboratory, Department of Radiology and Medical Informatics, University of Geneva, Rue Gabrielle-Perret-Gentil 4, 1211 Geneva, Switzerland
| | - Andrea Capozzi
- LIFMET, Institute of Physics, École polytechnique fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland; HYPERMAG, Department of Health Technology, Technical University of Denmark, Building 349, 2800 Kgs Lyngby, Denmark.
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Hyacinthe JN, Buscemi L, Lê TP, Lepore M, Hirt L, Mishkovsky M. Evaluating the potential of hyperpolarised [1- 13C] L-lactate as a neuroprotectant metabolic biosensor for stroke. Sci Rep 2020; 10:5507. [PMID: 32218474 PMCID: PMC7099080 DOI: 10.1038/s41598-020-62319-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Accepted: 03/05/2020] [Indexed: 01/06/2023] Open
Abstract
Cerebral metabolism, which can be monitored by magnetic resonance spectroscopy (MRS), changes rapidly after brain ischaemic injury. Hyperpolarisation techniques boost 13C MRS sensitivity by several orders of magnitude, thereby enabling in vivo monitoring of biochemical transformations of hyperpolarised (HP) 13C-labelled precursors with a time resolution of seconds. The exogenous administration of the metabolite L-lactate was shown to decrease lesion size and ameliorate neurological outcome in preclinical studies in rodent stroke models, as well as influencing brain metabolism in clinical pilot studies of acute brain injury patients. The aim of this study was to demonstrate the feasibility of measuring HP [1-13C] L-lactate metabolism in real-time in the mouse brain after ischaemic stroke when administered after reperfusion at a therapeutic dose. We showed a rapid, time-after-reperfusion-dependent conversion of [1-13C] L-lactate to [1-13C] pyruvate and [13C] bicarbonate that brings new insights into the neuroprotection mechanism of L-lactate. Moreover, this study paves the way for the use of HP [1-13C] L-lactate as a sensitive molecular-imaging biosensor in ischaemic stroke patients after endovascular clot removal.
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Affiliation(s)
- Jean-Noël Hyacinthe
- Geneva School of Health Sciences, HES-SO University of Applied Sciences and Arts Western Switzerland, Geneva, Switzerland.,Image Guided Intervention Laboratory, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Lara Buscemi
- Department of Clinical Neurosciences, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Thanh Phong Lê
- Geneva School of Health Sciences, HES-SO University of Applied Sciences and Arts Western Switzerland, Geneva, Switzerland.,Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Mario Lepore
- Centre d'Imagerie Biomédicale (CIBM), École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Lorenz Hirt
- Department of Clinical Neurosciences, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Mor Mishkovsky
- Laboratory of Functional and Metabolic Imaging, École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.
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Ludwig PE, Vaucher AC, Lê TP, Suter Y. Two Bronze Medals for Switzerland at the 46th International Chemistry Olympiad in Hanoi, Vietnam. Chimia (Aarau) 2015; 69:71-72. [DOI: 10.2533/chimia.2015.71] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Abstract
Muscular and perimembranous ventricular septal defects can be closed with nitinol plugs or spiral coils. Displacement and embolization of the device are well known complications that usually occur during or early after the procedure. We present the case of a 12-year-old boy with asymptomatic coil displacement detected at a routine examination 5 months after closure of a perimembranous ventricular septal defect.
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Affiliation(s)
- Stefan Kotthoff
- Department of Pediatric Cardiology, University Children's Hospital Muenster, Muenster, Germany.
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Ewert P, Kretschmar O, Peters B, Abdul Khaliq H, Nagdyman N, Schulze-Neick I, Bass J, Lê TP, Lange PE. Interventioneller Verschluss angeborener Ventrikelseptumdefekte. ACTA ACUST UNITED AC 2004; 93:147-55. [PMID: 14963681 DOI: 10.1007/s00392-004-1040-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2003] [Accepted: 10/21/2003] [Indexed: 10/26/2022]
Abstract
We report on the transcatheter closure of ventricular septal defects (VSD) in 26 patients with Amplatzer Occluders and Nit- Occlud Coil Systems. Twenty-one patients had a perimembranous and 5 patients a muscular VSD. Patients' age range was 5 months to 59 years (median 8 years) and their body weight 4.5 kg to 167 kg (median 28 kg). Defect diameters were 3-11 mm (median 5 mm). Sixteen patients had left ventricular volume overload and 7 patients pulmonary hypertension (median 50% of systemic pressure). Seven patients suffered from trivial or mild aortic regurgitation. Twenty-eight devices (4-12 mm; median 8 mm) were implanted (16 Amplatzer, 12 Nit-Occlud) through sheaths of 4F to 9F (median 7F). Fluoroscopy times were 8.3- 56.5 min (median 26.2 min). One coil was surgically explanted directly after intervention. One patient needed pulmonary banding due to additional VSDs. After a follow-up of 7 months (1-12 months), 2 patients had a small and 9 a minimal residual shunt. Thirteen defects were completely closed. Transcatheter closure of VSDs with new devices seems to be a promising therapy for suitable defects in different hemodynamic conditions in patients of every age.
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Affiliation(s)
- P Ewert
- Abteilung für Angeborene Herzfehler, Deutsches Herzzentrum Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
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Weil J, Razek V, Lê TP. Echocardiography before, during, and after interventions. J Interv Cardiol 2001; 14:339-43. [PMID: 12053394 DOI: 10.1111/j.1540-8183.2001.tb00342.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Before intervention, a detailed echocardiographic examination is mandatory for the decision whether this procedure will be necessary, possible, and safe. During intervention, transesophageal echocardiography (TEE) is needed for the continuous monitoring of the procedure, immediate assessment of results, and complications. TEE results in a significant reduction of fluoroscopy time. After intervention, echocardiography provides information on long-term results and newly developed complications.
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Affiliation(s)
- J Weil
- University Hospital Hamburg-Eppendorf, Department Pediatric Cardiology, Martinistrasse 52, D-20246 Hamburg, Germany.
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Pfeiffer D, Omran H, Otto J, Lê TP, Neugebauer A, Lüderitz B. Transvasal closure of interatrial defects using the Babic double-umbrella occluder system. Thorac Cardiovasc Surg 1998; 46:134-40. [PMID: 9714488 DOI: 10.1055/s-2007-1010210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The purpose of the study was to assess the feasibility and safety of closure of atrial septal defects and patent foramen ovale by means of a new interventional technique. Transvasal closure of ostium secundum atrial septal defect and patent foramen ovale was performed in 18 patients using an occluder system for atrial septal defects. Two patients had undergone unsuccessful direct surgical closure years before. Implantation and follow-up were controlled using radiographic views both with and without contrast injection, transthoracic and multiplane transesophageal echocardiographic imaging, color Doppler sonography, and computed tomography. The defect was closed in 16 patients using 19 procedures. Removal of the devices through the sheath was indicated in 4 patients because of placement failure. Intraprocedural complications were ventricular fibrillation in one patient and fixation of the device in Chiari's network in an additional one. During 7-26 months follow-up occluder damage was seen in two patients and perforation of the left atrium in one patient. Thickening on the occluder surface was observed in two patients. There was no death. The system for closure of atrial septal defect is feasible and safe in patients with defects < or = 27 mm in diameter. Long-term observation of outcome is limited yet.
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Affiliation(s)
- D Pfeiffer
- Department of Cardiology, University of Leipzig, Germany
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Schmitz AJ, Weinzheimer HR, Fahnenstich H, Lê TP, Redel DA, Kowalewski S. Color Doppler echocardiographic evaluation of tricuspid regurgitation and systolic pulmonary artery pressure in the full-term and preterm newborn. Angiology 1997; 48:725-34. [PMID: 9269143 DOI: 10.1177/000331979704800809] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Color Doppler echocardiography of tricuspid valve regurgitation (TR) is a valid, noninvasive method of determining systolic pulmonary artery pressure (SPAP). In a prospective study the authors examined 56 healthy full-term newborns (group I), 36 healthy preterm newborns (group II), and 10 preterm newborns with severe respiratory distress syndrome requiring surfactant replacement therapy (group III). Doppler studies were repeated until the transtricuspid gradient was < 20 mm Hg. In 83.3% of children a reproducible spectral curve was recorded at least once. The authors estimated the transtricuspid gradient delta p (RV-RA) by using the modified Bernoulli equation. Within the first twenty-four hours delta p (RV-RA) was < 20 mm Hg in 72.7%, 50%, and 25% of children with measurable TR in groups I, II, and III, respectively, increasing to 91.1%, 78.6%, and 55.6% within forty-eight hours. There was no significant correlation between SPAP and gestational age, birth weight, mode of delivery, and ductal closing time. Continuous holosystolic envelope tracing of TR was recorded in 16.6%. In these patients delta p (RV-RA) was measured markedly higher (mean of 30.1 mm Hg) than in the others (mean 17.3 mm Hg). The authors conclude that there is a high prevalence of TR in neonates, which allows estimation of SPAP in > 80% of newborns without considerable impairment. Normalization of SPAP takes place within four days in most patients, but there is a delay in preterm infants with severe respiratory distress syndrome.
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Affiliation(s)
- A J Schmitz
- Department of Cardiology and Neonatology, Children's Hospital, University of Bonn, Germany
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Lu JH, Mielke R, Lê TP, Emons D, Kowalewski S. [Schizencephaly]. Klin Padiatr 1990; 202:106-8. [PMID: 2325349 DOI: 10.1055/s-2007-1025498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Schizencephaly is a developmental disorder of the human brain caused by a defect of neuronal migration. We observed a 7 month old african boy suffering from nystagmus and hemiparesis. The neuroimaging reveals a large cleft in cortical and subcortical structures and typical changes of polymicrogyria. In the differential-diagnosis encephaloclastic porencephaly should be considered.
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Affiliation(s)
- J H Lu
- Universitäts-Kinderklinik Bonn
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Redel DA, Lê TP. [Diagnosis of congenital heart defects using color-coded Doppler echocardiography]. Herz 1986; 11:296-302. [PMID: 3781465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Color Doppler echocardiography (CDE) enables visualization of blood flow and of cardiac morphology within color coded two-dimensional images. The diagnostic usefulness of this method in pediatric cardiology has been analyzed based on studies performed in 2414 children. Normal cardiac findings were seen in 769 patients according to the clinical and echocardiographic examinations. Normal diastolic inflow into the ventricles in the apical four-chamber-view is characterized by a similar distribution of the color spectrum across the inflow tracts, blood flowing on the two sides of the heart is completely separated from each other. Normal systolic outflow imaged from parasternal position shows an increase in velocity in the outflow tract passing through the semilunar valves without any change in flow patterns. Heart disease was present in 1645 patients, simple cardiac defects were found in 1473 cases and complex heart disease in 172 cases. Shunt lesions are detectable by the demonstration of blood flow in regions where normally no flow is detectable, flow velocities being pathologically increased in many cases. Diagnostic sensitivity and specificity of CDE as compared to invasive procedures is between 96 and 98%. In left-to-right shunting the shunt flow can be followed into the right-sided cardiovascular regions where its extent is a measure for the size of the shunt as indicated by initial results. In ventricular septal defects, bidirectional shunting is indicative of a rise in pressure in the right ventricle and can be reliably detected with the use of CDE. In valvular stenoses high flow velocities are found in the appropriate time which are associated with turbulence and poststenotic eddies.(ABSTRACT TRUNCATED AT 250 WORDS)
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