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Abstract
Biomedical Engineering is a branch that unites engineering methods with biological and medical sciences in order to enhance the quality of our lives. It focuses on understanding intricate systems of living organisms, and on technology development, algorithms, methods, and advanced medical knowledge, while enhancing the conveyance and success of clinical medicine. With engineering principles, biomedical engineering improves the procedures and devices to overcome health care and medical problems by combining both biology and medicine with engineering principals. In the field of Biomedical Engineering, engineers usually need to have background knowledge from such different fields of engineering as electronics, mechanical, and chemical engineering. Specialties in this field like bioinstrumentation, biomechanics, biomaterials, medical imagining, clinical engineering, bioinformatics, telemedicine and rehabilitation engineering, which will be introduced in this chapter together with an overview of the field of biomedical engineering.
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The Role of 3 Tesla MRA in the Detection of Intracranial Aneurysms. Int J Vasc Med 2012; 2012:792834. [PMID: 22292121 PMCID: PMC3265088 DOI: 10.1155/2012/792834] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2011] [Accepted: 10/09/2011] [Indexed: 12/01/2022] Open
Abstract
Intracranial aneurysms constitute a common pathological entity, affecting approximately 1–8% of the general population. Their early detection is essential for their prompt treatment. Digital subtraction angiography is considered the imaging method of choice. However, other noninvasive methodologies such as CTA and MRA have been employed in the investigation of patients with suspected aneurysms. MRA is a noninvasive angiographic modality requiring no radiation exposure. However, its sensitivity and diagnostic accuracy were initially inadequate. Several MRA techniques have been developed for overcoming all these drawbacks and for improving its sensitivity. 3D TOF MRA and contrast-enhanced MRA are the most commonly employed techniques. The introduction of 3 T magnetic field further increased MRA's sensitivity, allowing detection of aneurysms smaller than 3 mm. The development of newer MRA techniques may provide valuable information regarding the flow characteristics of an aneurysm. Meticulous knowledge of MRA's limitations and pitfalls is of paramount importance for avoiding any erroneous interpretation of its findings.
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3
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Heggie JCP. Technical developments in radiology in Australasia dating from 1977. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2007; 30:160-77. [PMID: 18044300 DOI: 10.1007/bf03178423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
This article outlines the enormous technological advances that have taken place in the practice of radiology in Australasia in the 30 years since approximately 1977. These developments have led to significant improvements in image quality across all modalities, including even general radiography, which had as its genesis Roentgen's ground-breaking discovery of X-rays in 1895. However, nowhere has the development been more dramatic than in magnetic resonance imaging (MRI). This may be brought into stark reality by noting that the first MRI image of a human finger was produced in 1976 followed one year later by that of a human chest and the first MRI units were not installed in Australia and New Zealand until 1986 and 1991, respectively. The quality of these early images would be judged as laughable by today's standards where the impressive isotropic imaging that can be achieved at sub-millimetre level by both MRI and CT could not have been dreamed of 30 years ago. The review also highlights some challenges for the future of the medical physics profession.
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Affiliation(s)
- J C P Heggie
- Department Medical Engineering and Physics, St. Vincent's Hospital Melbourne, Fitzroy, VIC, Australia.
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4
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Wen H. Mapping the velocity vector onto the spin vector: two-dimensional velocity-selective spin excitation for MR flow imaging. Magn Reson Med 2001; 46:767-72. [PMID: 11590653 PMCID: PMC2885787 DOI: 10.1002/mrm.1255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This article presents a two-dimensional velocity-selective spin excitation (2D-VSP) method that enables quantitative imaging of motion in two directions in a single scan, without the need for image subtraction or combination. It is based on the idea of mapping a 2D velocity vector directly onto the transverse magnetization vector, such that the signal intensity reflects the speed of motion, while the signal phase represents the direction of motion. Experimental demonstration is presented in conjunction with an analysis of the accuracy of this method. VSP methods are often limited by inconsistent static signal suppression under variable shim and RF conditions. By using adiabatic RF pulses in a 2D-VSP composite that possesses time-reversal symmetry, consistent background suppression of 30-fold or higher was demonstrated over experimental conditions of +/-200 Hz off-resonance and 30% RF field variation.
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Affiliation(s)
- H Wen
- Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Urata J, Miyazaki M, Wada H, Nakaura T, Yamashita Y, Takahashi M. Clinical evaluation of aortic diseases using nonenhanced MRA with ECG-triggered 3D half-Fourier FSE. J Magn Reson Imaging 2001; 14:113-9. [PMID: 11477668 DOI: 10.1002/jmri.1160] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The efficacy of the nonenhanced magnetic resonance angiography (MRA) technique known as fresh-blood imaging (FBI), using electrocardiograph (ECG)-triggered 3D half-Fourier fast spin-echo (FSE), was evaluated for the detection and characterization of aortic diseases. Seventy-five consecutive patients with aortic disease underwent the FBI examination on a 1.5-T clinical imager. The results showed that the FBI technique permits clear visualization of aortic diseases, and the vessel branches and their relationship, which provides valuable information. Therefore, the nonenhanced FBI technique is appropriate to use for screening purposes.
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Affiliation(s)
- J Urata
- Diagnostic Imaging Center, Saiseikai Kumamoto Hospital, Kumamoto, Japan
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Klarhöfer M, Csapo B, Balassy C, Szeles JC, Moser E. High-resolution blood flow velocity measurements in the human finger. Magn Reson Med 2001; 45:716-9. [PMID: 11284002 DOI: 10.1002/mrm.1096] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
MR phase contrast blood flow velocity measurements in the human index finger were performed with triggered, nontriggered, and cine acquisition schemes. A strong (G(max) = 200 mT/m), small bore (inner diameter 12 cm) gradient system inserted in a whole body 3 Tesla MR scanner allowed high-resolution imaging at short echo times, which decreases partial volume effects and flow artifacts. Arterial blood flow velocities ranging from 4.9-19 cm/sec were measured, while venous blood flow was significantly slower at 1.5-7.1 cm/sec. Taking into account the corresponding vessel diameters ranging from 800 microm to 1.8 mm, blood flow rates of 3.0-26 ml/min in arteries and 1.2-4.8 ml/min in veins are obtained. The results were compared to ultrasound measurements, resulting in comparable blood flow velocities in the same subjects. Magn Reson Med 45:716-719, 2001.
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Affiliation(s)
- M Klarhöfer
- Arbeitsgruppe NMR, Institut für Medizinische Physik, Universität Wien, Vienna, Austria
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Xu XY, Long Q, Collins MW, Bourne M, Griffith TM. Reconstruction of blood flow patterns in human arteries. Proc Inst Mech Eng H 1999; 213:411-21. [PMID: 10581968 DOI: 10.1243/0954411991535022] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Local haemodynamic factors in large arteries are associated with the pathophysiology of cardiovascular diseases such as atherosclerosis and strokes. In search of these factors and their correlation with atheroma formation, quantitative haemodynamic data in realistic arterial geometry become crucial. At present no in vivo non-invasive technique is available that can provide accurate measurement of three-dimensional blood velocities and shear stresses in curved and branching sites of vessels where atherosclerotic plaques are found frequently. This paper presents a computer modelling technique which combines state-of-the-art computational fluid dynamics (CFD) with new noninvasive magnetic resonance imaging techniques to provide the complete haemodynamic data in 'real' arterial geometries. Using magnetic resonance angiographic and velocity images acquired from the aortic bifurcation of a healthy human subject, CFD simulations have been carried out and the predicted flow patterns demonstrate the non-planar-type flow characteristics found in experimental studies.
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Affiliation(s)
- X Y Xu
- Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, London, UK
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Tamatani S, Sasaki O, Takeuchi S, Fujii Y, Koike T, Tanaka R. Detection of delayed cerebral vasospasm, after rupture of intracranial aneurysms, by magnetic resonance angiography. Neurosurgery 1997; 40:748-53; discussion 753-4. [PMID: 9092848 DOI: 10.1097/00006123-199704000-00017] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
OBJECTIVE The goal of this study was to assess the value of magnetic resonance angiography (MRA), compared with conventional angiography, in the diagnosis and follow-up monitoring of delayed cerebral vasospasm after subarachnoid hemorrhage resulting from rupture of intracranial aneurysms. METHODS For 32 patients undergoing examination by both MRA and conventional angiography during the period of risk for vasospasm, on the same day, the frequency and severity of and sequential changes in vasospasm were evaluated. The three-dimensional time-of-flight method was used. MRA was performed three times, i.e., before, during, and after the period of risk for vasospasm. Conventional angiography was performed twice, i.e., at admission and during the period of risk for vasospasm. Vasospasm was assessed at 22 regions of the cerebral arteries, including the bilateral anterior cerebral (A1, A2, and A3 segments), middle cerebral (M1, M2, and M3 segments), internal carotid (C1 and C2 segments), posterior cerebral (P1 and P2 segments), and posterior communicating arteries. RESULTS Seven patients were excluded because of poor MRA images. Twenty-two of 25 patients (125 arteries) showed vasospasm in conventional angiograms. Nineteen of the 22 patients also showed vasospasm in MRA images; however, 57 arteries (45.6%) were diagnosed as showing vasospasm by MRA, and 59 (47.2%) could not be evaluated because of artifacts. For the remaining three patients (nine arteries, 7.2%), vasospasm could not be detected by MRA. Sequential changes in vasospasm could be well evaluated by MRA. CONCLUSION MRA could be useful for management of cerebral vasospasm, although it cannot become a practical alternative to conventional angiography.
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Affiliation(s)
- S Tamatani
- Department of Neurosurgery, Niigata University, Japan
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9
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Abstract
Magnetic resonance angiography (MRA) permits the non-invasive visualization of blood flow through the effects of moving spins on the magnetic resonance signal. MRA techniques can be divided into two main classifications depending upon the primary effect responsible for contrast in the image. Angiograms can be produced using either the time-of-flight (TOF) or phase contrast (PC) methods. Each method has particular advantages and limitations as an angiographic imaging technique and these are reflected in their respective applications. This review article is intended to outline the scientific and technical development of MRA from its basis in the earliest in vitro nuclear magnetic resonance (NMR) experiments, through the implementation of in vivo angiographic techniques on whole body MRI systems, to the recent rapid expansion in MRA acquisition and processing techniques.
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Affiliation(s)
- M J Graves
- Department of Radiology, St George's Hospital, London, UK
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10
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Dousset V, Degrèze P, Mièze S, Sesay M, Basse-Cathalinat B, Caillé JM. Magnetization transfer on in vitro circulating blood: implications for time-of-flight MR angiography. J Magn Reson Imaging 1995; 5:786-8. [PMID: 8748505 DOI: 10.1002/jmri.1880050630] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Effects of magnetization transfer were evaluated in vitro on circulating blood. Various velocities were tested from 0 to 72 cm/second. Decrease signal intensity caused by magnetization transfer effects was inversely proportional to inflow velocity. It reached 10% at very low velocities and disappeared at velocities higher than 30 cm/second.
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Affiliation(s)
- V Dousset
- Department of Neuroradiology, Hospital Pellegrin, Bordeaux, France
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Kashitani N, Kimoto S, Tsunoda M, Ito T, Tsuji T, Ono A, Hiraki Y. Portal blood flow in the presence or absence of diffuse liver disease: measurement by phase contrast MR imaging. ABDOMINAL IMAGING 1995; 20:197-200. [PMID: 7620403 DOI: 10.1007/bf00200392] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND In patients with diffuse liver disease, the portal flow dynamics change markedly in accordance with disease progression and would provide a useful index of progression of stage. METHODS Portal blood flow (PBF) was measured by phase contrast magnetic resonance imaging (MRI) in 21 patients with diffuse liver disease and 20 healthy volunteers. The MRI method was validated by a flow phantom study. The mean PBF could be measured in 6.8 min without breath-holding. RESULTS Doppler ultrasound measurements of PBF volume were obtained reproducibly in all the healthy volunteers and were shown to correlate with the MRI values (Doppler: 12.5 +/- 3.2 cm3/s, MRI: 12.0 +/- 3.3 cm3/s; mean +/- SD). The PBF volume of patients with chronic hepatitis showed no significant difference from that of the healthy volunteers. In patients with liver cirrhosis, the PBF volume ranged from 5.01 to 32.3 cm3/s. A significant increase in PBF volume was caused in one patient by massive intrahepatic shunting and a significant decrease was caused in two patients by massive extrahepatic shunting. CONCLUSIONS The measurement of PBF by phase contrast MRI is clinically useful in predicting intrahepatic or extrahepatic shunting in patients with liver cirrhosis, and may be of value in detecting the progression of stage in diffuse liver diseases.
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Affiliation(s)
- N Kashitani
- Department of Radiology, Okayama University, Medical School, Japan
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13
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Ikawa F, Sumida M, Uozumi T, Kuwabara S, Kiya K, Kurisu K, Arita K, Satoh H. Comparison of three-dimensional phase-contrast magnetic resonance angiography with three-dimensional time-of-flight magnetic resonance angiography in cerebral aneurysms. SURGICAL NEUROLOGY 1994; 42:287-92. [PMID: 7974121 DOI: 10.1016/0090-3019(94)90394-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Magnetic resonance angiography (MRA) can be divided into two types: namely, the phase-contrast (PC) method and the time-of-flight (TOF) method. The purpose of this study is to determine which method is better suited to demonstrate cerebral aneurysms. In a total of 27 cerebral aneurysms confirmed by cerebral angiography, both three-dimensional (3-D) PC and 3-D TOF methods were performed, and the corresponding findings were compared with conventional cerebral angiographic findings. Aneurysm visualization was grouped into three categories: "good" when clearly distinguishable, "fair" if distinguishable when reconstructed, and "poor" if completely undistinguishable. All MRAs were independently interpreted by two neurosurgeons in our institute. Sensitivity was 92.6% when MRA was performed with the TOF method, whereas it was 70.4% when performed with the PC method. In conclusion, the TOF method was more useful for demonstrating the aneurysms than the PC method due to its higher spatial resolution and shorter imaging time.
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Affiliation(s)
- F Ikawa
- Department of Neurosurgery, Hiroshima University School of Medicine, Japan
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15
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Abstract
With the increasing use of three-dimensional MRI techniques it is becoming necessary to explore automated techniques for locating pathology in the volume images. The suitability of a specific technique to locate and identify healthy tissues of the brain was examined as a first step toward eventually identifying pathology in images. This technique, called multispectral image segmentation, is based on the classification of tissue types in an image according to their characteristics in various spectral regions. The spectral regions chosen for this study were the hydrogen spin-lattice relaxation time T1, spin-spin relaxation time T2, and spin density, rho. Single-echo, spin-echo magnetic resonance images of axial slices through the brain at the level of the lateral ventricles were recorded on a 1.5 Tesla imager from 20 volunteers ranging in age from 17 to 72 years. These images were used to calculate the T1, T2, and rho images used for the classification. Tissue classification was performed by locating clusters of pixels in a three-dimensional T1(-1)-T2(-1)-rho histogram. Gray matter, white matter, cerebrospinal fluid, meninges, muscle, and adipose tissues were readily classified in magnetic resonance images of the volunteers with a single set of T1, T2, and rho values. Cluster characteristics, such as size, shape, and location, provided information on the imaging procedure and tissue characteristics.
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Affiliation(s)
- L M Fletcher
- Center for Imaging Science, Rochester Institute of Technology, NY 14623
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Guilfoyle D, Mansfield P, Packer K. Fluid flow measurement in porous media by echo-planar imaging. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0022-2364(92)90319-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Crawley AP, Cohen MS, Yucel EK, Poncelet B, Brady TJ. Single-shot magnetic resonance imaging: applications to angiography. Cardiovasc Intervent Radiol 1992; 15:32-42. [PMID: 1537063 DOI: 10.1007/bf02733897] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recently developed technologies that allow the collection of magnetic resonance imaging (MRI) in as little as 26 msec have been explored in their application to angiography. Advantages are demonstrated in scan time reduction, insensitivity to patient motion (especially in abdominal applications), flow quantification, and temporal resolution. We demonstrate that because such single-shot techniques are inherently resistant to flow dephasing during acquisition that allow for sustained high signal intensities to be achieved when images must be combined through the cardiac cycle. Such high temporal resolution scans may be utilized for the collection of time-resolved angiograms. With these techniques we demonstrate the collection of complete MR angiograms in the course of reasonable 10-25 sec breath holds. The relative simplicity of the technique, coupled with its overall short acquisition time, allows us to incorporate angiography into other imaging protocols without adding significant time burdens. Results to date are promising for further improvements in spatial resolution, without extension of scan time.
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Affiliation(s)
- A P Crawley
- Massachusetts General Hospital NMR Center, Charlestown 02129
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18
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Abstract
Magnetic resonance angiography (MRA) places high demands on instrumentation capabilities. Magnetic gradient strength capabilities, main magnetic field strength and homogeneity, and eddy current compensation all play a role in determining the quality of the flow studies. In addition, radiofrequency coil design and use is governed by the specific vascular territories of interest. Once the instrumentational and pulse sequence considerations have been optimized, the postprocessing and display of the acquired three-dimensional data sets is of key importance. Great strides have been made in addressing instrumentation needs for MRA, but further improvements are anticipated.
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Affiliation(s)
- D Saloner
- Radiology Service, VA Medical Center, San Francisco, CA 94121
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Dumoulin CL, Souza SP, Hardy CJ, Ash SA. Quantitative measurement of blood flow using cylindrically localized Fourier velocity encoding. Magn Reson Med 1991; 21:242-50. [PMID: 1745123 DOI: 10.1002/mrm.1910210209] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A procedure for the quantitative measurement of blood velocity was developed and evaluated in the portal vein, aorta, and vena cava of healthy volunteers. This procedure utilizes Fourier velocity encoding and can be performed with or without cardiac gating. The accuracy of velocity measurements is determined by the accuracy of the gradient subsystem. Flow measurements derived from the velocity measurement are further limited in their accuracy by the luminal cross-section measurement. Spatial localization is accomplished with an excitation pulse having a cylindrical rather than slab geometry. Data are acquired in the presence of a readout gradient to provide resolution along the cylindrical axis.
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Affiliation(s)
- C L Dumoulin
- General Electric Research and Development Center, Schenectady, New York 12301
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Krug B, Kugel H, Friedmann G, Bunke J, van Dijk P, Schmidt R, Hirche HJ. MR imaging of poststenotic flow phenomena: experimental studies. J Magn Reson Imaging 1991; 1:585-91. [PMID: 1790384 DOI: 10.1002/jmri.1880010512] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Poststenotic flow patterns were analyzed in a flow phantom with a 1.5-T magnetic resonance (MR) imager, with use of different MR imaging and MR angiographic pulse sequences. Spin-echo, fast field-echo, two-dimensional inflow (multiple single-section technique), and flow-adjusted-gradient sequences were applied. For the spin-echo sequences, modulus and phase images were reconstructed from each data set. The length of the region of poststenotic changes in signal amplitude and phase measured at a constant flow rate increased with stenosis grade. Likewise, the length of the region of poststenotic changes measured at a constant stenosis grade increased with flow rate. Moreover, the results depended on the alignment of the flow direction with the readout gradient. Comparison of modulus and phase images allowed discrimination of turbulent and nonturbulent flow, which yields additional information on stenosis grade in clinical MR angiography.
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Affiliation(s)
- B Krug
- Department of Radiology, University of Cologne, Germany
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21
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Cho ZH, Mun CW, Friedenberg RM. NMR angiography of coronary vessels with 2-D planar image scanning. Magn Reson Med 1991; 20:134-43. [PMID: 1943654 DOI: 10.1002/mrm.1910200114] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
On the basis of the principles of the time-of-flight method and the 3-D angiogram obtained by the 2-D planar image scanning technique using 90 degrees RF pulses with short repetition time, we have obtained a coronary angiogram around the heart including the coronary arteries and veins. The cine NMR imaging technique is also incorporated in synchronizing ECG R waves to reduce the motion artifact and at the same time to induce the saturation effect on the static samples. Images of the large bulk blood flow corresponding to the heart chamber and descending aorta are further removed by postprocessing. The final 3-D angiogram is then formed by stacking the 2-D images and contrast is further enhanced by the maximum ray tracing algorithm.
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Affiliation(s)
- Z H Cho
- Department of Electrical Sciences, Korea Advanced Institute of Science, Cheongyangni, Seoul
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22
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Dumoulin CL, Souza SP, Darrow RD, Pelc NJ, Adams WJ, Ash SA. Simultaneous acquisition of phase-contrast angiograms and stationary-tissue images with Hadamard encoding of flow-induced phase shifts. J Magn Reson Imaging 1991; 1:399-404. [PMID: 1790361 DOI: 10.1002/jmri.1880010403] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
A technique for the simultaneous acquisition of three-dimensional phase-contrast angiograms and stationary-tissue images is described. Hadamard multiplexed encoding of flow information permits image acquisition times that are a third shorter than those of previous phase-contrast methods. The encoding scheme described also enables differentiation of flow-induced phase shifts from phase shifts due to resonance offset conditions such as field inhomogeneities and chemical shift. Display strategies that combine this phase information with the flow image are described.
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Affiliation(s)
- C L Dumoulin
- General Electric Research and Development Center, Schenectady, NY 12308
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23
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Hou P, Parker DL, Blatter DD, Robison RO. Hybrid MR angiography and Fourier velocity imaging using two echo 3D acquisition. Magn Reson Med 1991; 19:203-8. [PMID: 2046536 DOI: 10.1002/mrm.1910190121] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Fourier velocity imaging can be accomplished without cardiac gating from the second echo of a standard 3D MR angiography sequence. The stepped bipolar velocity encoding gradient is obtained by adding a gradient pulse opposite in area to the spatial phase encoding gradient. In this technique, Fourier images of three spatial coordinates are obtained from the first echo and images of two spatial coordinates and one velocity component are obtained from the second echo.
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Affiliation(s)
- P Hou
- Department of Physics, LDS Hospital/University of Utah, Salt Lake City 84143
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24
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Abstract
Multiple overlapping thin 3D slab acquisition is presented as a magnitude contrast (time of flight) technique which combines advantages from multiple thin slice 2D and direct 3D volume acquisitions to obtain high-resolution cross-sectional images of vessel detail. Details of implementation and example images are presented.
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Affiliation(s)
- D L Parker
- Department of Medical Informatics, LDS Hospital/University of Utah, Salt Lake City 84143
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25
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Bini W, Prawitz R, Rodríguez Díaz J, Samii M. Experiencia inicial con la MRi-angio en el estudio de lesiones de la base de cráneo. Neurocirugia (Astur) 1991. [DOI: 10.1016/s1130-1473(91)70921-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Kido DK, Barsotti JB, Rice LZ, Rothenberg BM, Panzer RJ, Souza SP, Dumoulin CL. Evaluation of the carotid artery bifurcation: comparison of magnetic resonance angiography and digital subtraction arch aortography. Neuroradiology 1991; 33:48-51. [PMID: 2027445 DOI: 10.1007/bf00593333] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Thirty-four carotid artery bifurcations were examined using both magnetic resonance angiography (MRA) and digital subtraction arch aortography to determine their accuracy when compared to selective carotid angiography. The sensitivity of MRA was 73% and its specificity was 91% when compared with selective carotid angiography. The sensitivity of arch aortography was 27% and its specificity was 100%.
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Affiliation(s)
- D K Kido
- Department of Diagnostic Radiology, University of Rochester Medical Center, New York
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28
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Maki JH, MacFall JR, Johnson GA. The use of gradient flow compensation to separate diffusion and microcirculatory flow in MRI. Magn Reson Med 1991; 17:95-107. [PMID: 1712421 DOI: 10.1002/mrm.1910170114] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This paper describes a new MR imaging technique termed Modified Stejskal Tanner versus Flow Compensation (MST/FC) for the separation of diffusion and microcirculatory flow. The theory behind the sequence is explained, along with a five-component model of microcirculation applicable to any "perfusion" imaging technique. Phantom data is presented showing that (1) diffusion effects can be matched between MST and FC (suggesting the possibility of flow-compensated diffusion imaging), and (2) the technique is a quantitative method of separating diffusion and slow (less than 0.25 mm/s) tortuous flow through a Sephadex column. Furthermore, animal images show the technique to be feasible and quantitative in measuring rat brain microcirculation under normal, vasodilated (hypercarbia), and no-flow (post mortem) conditions.
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Affiliation(s)
- J H Maki
- Duke University Medical Center, Durham, North Carolina 27710
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29
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Lanzer P, Gross G, Nanda N, Pohost G. Timing of data acquisition determines image quality in femoropopliteal phase-sensitive MR angiography. Angiology 1990; 41:817-24. [PMID: 2221460 DOI: 10.1177/000331979004101002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
To study the effects of timing of data acquisition on quality of femoropopliteal magnetic resonance (MR) angiograms, the authors studied 16 healthy men, mean age 34.3 +/- 6 years, by color Doppler imaging and by phase-sensitive (PS) MR angiography. PS MR imaging was performed at 1.5T using a flow adjustable gradient (FLAG) pulse sequence. The images were graded in a blinded fashion by two independent observers. Of 16 MR angiograms consisting of 141 angiographic images (AI), 45 (31.9%) were diagnostic. At least 1 diagnostic AI was obtained in each subject, and 38 (84.4%) of the diagnostic images were acquired within the first 120 milli-seconds (ms) of the systolic flow pulse. The highest yield of diagnostic images (90.9%) was obtained in the interval of thirty to sixty ms before the peak flow velocity. In healthy man diagnostic PS MR angiography requires triggering to the femoropopliteal systolic flow pulse. The highest yield of diagnostic images is acquired during the flow pulse acceleration.
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Affiliation(s)
- P Lanzer
- Department of Medicine, University of Alabama, Birmingham
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30
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Lanzer P, Bohning D, Groen J, Gross G, Nanda N, Pohost G. Aortoiliac and femoropopliteal phase-based NMR angiography: a comparison between FLAG and RSE. Magn Reson Med 1990; 15:372-85. [PMID: 2233217 DOI: 10.1002/mrm.1910150304] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
To assess the performance of FLAG and RSE NMR angiography 22 aortoiliac (AI) and 22 femoropopliteal (FP) angiograms in 11 healthy males, mean age 38 +/- 7.6 years, were acquired. The image quality was graded in a blinded fashion by two independent readers. The readers grades were not statistically different (kappa = 0.5696). The representation of diagnostic images was 6/11 FLAG and 8/11 RSE AI as well as 8/11 FLAG and 8/11 RSE FP. On back-to-back comparison six RSE AI and seven RSE FP were graded better than their FLAG counterparts. Although these differences did not achieve a statistical significance RSE NMR angiography provided consistently better images and appears preferable for imaging of the peripheral vascular system in normal subjects.
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Affiliation(s)
- P Lanzer
- University of Alabama, Department of Medicine, Birmingham 35294
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31
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Sardashti M, Schwartzberg DG, Stomp GP, Dixon WT. Spin-labeling angiography of the carotids by presaturation and simplified adiabatic inversion. Magn Reson Med 1990; 15:192-200. [PMID: 2392046 DOI: 10.1002/mrm.1910150203] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A new adiabatic inversion pulse is tested for a spin-labeling subtraction angiography method. Adiabatic nature of the pulse is achieved by ramping the gradient during the RF pulse. In addition, with cardiac triggering, any irregularity of the heartbeat would decrease cancellation of the static tissue after subtraction. A 90 degree presaturation pulse applied to prevent this suppresses the background intensity from the static tissue by a factor greater than 2. Slice angiograms of carotid arteries are presented.
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Affiliation(s)
- M Sardashti
- Frederik Philips Research Center, Department of Radiology, Best, The Netherlands
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32
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Kim JH, Cho ZH. 3-D MR angiography with scanning 2-D images--simultaneous data acquisition of arteries and veins (SAAV). Magn Reson Med 1990; 14:554-61. [PMID: 2355837 DOI: 10.1002/mrm.1910140313] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A 3-D MR angiography using a scanning 2-D planar imaging technique with the 90 degrees flip angle steady-state free precession sequence is presented. This method, in essence, is the rapid scanning of 2-D images to form a 3-D volume image. The method is then extended to the simultaneous acquisition of the separated images of the arteries and veins. Using the proposed method a set of separate angiograms of 3-D artery and vein of a volunteer's head of imaging volume of 220 X 220 X 120 mm was obtained with total imaging time of 16.5 min.
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Affiliation(s)
- J H Kim
- Department of Electrical Science, Korea Advanced Institute of Science, Cheongyangni, Seoul
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33
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Smith MA. The measurement and visualisation of vessel blood flow by magnetic resonance imaging. CLINICAL PHYSICS AND PHYSIOLOGICAL MEASUREMENT : AN OFFICIAL JOURNAL OF THE HOSPITAL PHYSICISTS' ASSOCIATION, DEUTSCHE GESELLSCHAFT FUR MEDIZINISCHE PHYSIK AND THE EUROPEAN FEDERATION OF ORGANISATIONS FOR MEDICAL PHYSICS 1990; 11:101-23. [PMID: 2194733 DOI: 10.1088/0143-0815/11/2/001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- M A Smith
- Department of Medical Physics, University of Leeds, Leeds General Infirmary, UK
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34
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Ogawa S, Lee TM, Nayak AS, Glynn P. Oxygenation-sensitive contrast in magnetic resonance image of rodent brain at high magnetic fields. Magn Reson Med 1990; 14:68-78. [PMID: 2161986 DOI: 10.1002/mrm.1910140108] [Citation(s) in RCA: 1272] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
At high magnetic fields (7 and 8.4 T), water proton magnetic resonance images of brains of live mice and rats under pentobarbital anesthetization have been measured by a gradient echo pulse sequence with a spatial resolution of 65 x 65-microns pixel size and 700-microns slice thickness. The contrast in these images depicts anatomical details of the brain by numerous dark lines of various sizes. These lines are absent in the image taken by the usual spin echo sequence. They represent the blood vessels in the image slice and appear when the deoxyhemoglobin content in the red cells increases. This contrast is most pronounced in an anoxy brain but not present in a brain with diamagnetic oxy or carbon monoxide hemoglobin. The local field induced by the magnetic susceptibility change in the blood due to the paramagnetic deoxyhemoglobin causes the intra voxel dephasing of the water signals of the blood and the surrounding tissue. This oxygenation-dependent contrast is appreciable in high field images with high spatial resolution.
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Affiliation(s)
- S Ogawa
- AT&T Bell Laboratories, Murray Hill, New Jersey 07974
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35
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Lanzer P, McKibbin W, Bohning D, Pohost G. Quantitation of abdominal aortic wall dynamics in man by gradient echo NMR imaging. Magn Reson Med 1990; 13:407-15. [PMID: 2325541 DOI: 10.1002/mrm.1910130308] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
To determine the magnitude of the pulsatile (P), translational (T), and composite (C) aortic wall motion and to predict its effect on endothelial edge definition in vascular NMR imaging, 10 healthy volunteers, mean age 42.5 +/- 13 years, were studied. In each subject a series of transverse high-resolution (0.6 X 0.6 mm; TR = 40 ms) gradient echo images spanning the cardiac cycle were generated and the aortic wall motion dynamics were analyzed. The group data expressed as a mean +/- SD in millimeters, P = 0.87 +/- 0.34 (mm), T = 2.71 +/- 1.07, and C = 3.39 +/- 1.081, indicate that a significant displacement of the endothelial aortic edge (up to 5.6 pixels in high-resolution imaging) occurs during the cardiac cycle in normotensive healthy volunteers. The displacement of this magnitude suggests that cardiac cycle synchronized aortic NMR imaging should be used to improve endothelial edge definition.
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Affiliation(s)
- P Lanzer
- University of Alabama, Department of Medicine, Birmingham 35294
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36
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Tarnawski M, Padayachee S, West DJ, Graves MJ, Ayton VT, Taylor MG, Smith MA. The measurement of time-averaged flow by magnetic resonance imaging using continuous acquisition in the carotid arteries and its comparison with Doppler ultrasound. CLINICAL PHYSICS AND PHYSIOLOGICAL MEASUREMENT : AN OFFICIAL JOURNAL OF THE HOSPITAL PHYSICISTS' ASSOCIATION, DEUTSCHE GESELLSCHAFT FUR MEDIZINISCHE PHYSIK AND THE EUROPEAN FEDERATION OF ORGANISATIONS FOR MEDICAL PHYSICS 1990; 11:27-36. [PMID: 2182272 DOI: 10.1088/0143-0815/11/1/002] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A continuous acquisition method was used to measure the time-averaged flow in the carotid arteries of 10 normal volunteers, using an interleaved flow-sensitive and flow-compensated field echo sequence on a 1.5 T magnetic resonance (MR) system. Validation of the sequence and technique was performed using a pulsatile rotating phantom. The measured flow rates for the common carotid arteries were compared with Doppler ultrasound values obtained immediately after the MR measurement using a Duplex scanner. The correlation (r = 0.52, P less than 0.01) was significant with data spread accounted for by the inherent errors of both techniques. The difference between time-averaged flow measured by MR and Doppler ultrasound was 1.9%. Short-term reproducibility of each technique was assessed by consecutive measurements with values of 6.8% and 6.6% respectively for MR and Doppler; measurements after a 2 - 4 week interval gave a long-term reproducibility of 11.8% and 9.8% respectively. The advantages of continuous acquisition make the method suitable for non-invasive flow measurements, particularly for vessels that are not accessible to ultrasound.
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Affiliation(s)
- M Tarnawski
- Division of Radiological Sciences, UMDS, Guy's Hospital, London, UK
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37
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Lanzer P, McKibbin W, Bohning D, Thorn B, Gross G, Cranney G, Nanda N, Pohost G. Aortoiliac imaging by projective phase sensitive MR angiography: effects of triggering and timing of data acquisition on image quality. Magn Reson Imaging 1990; 8:107-16. [PMID: 2338891 DOI: 10.1016/0730-725x(90)90243-u] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
To assess the ability of projective phase sensitive magnetic resonance (MR) angiography to visualize the aortoiliac vascular segment, and to determine the effects of triggering and timing of data acquisition om image quality, we studied 18 healthy volunteers, mean age 33.3 +/- 11 years, by color Doppler imaging and by MR angiography. MR angiography was performed at 1.5 T using a flow-adjustable gradient-echo (FLAG) sequence operated in both ECG-triggered and non-triggered acquisition modes. The images were graded in a blinded fashion by two independent observers. The data were analyzed using Pearson's chi-square analysis. Eighteen triggered time-resolved and 17 non-triggered, time-averaged MR angiograms consisting of 252 and 17 angiographic images, (AI) respectively, were analyzed. In the triggered mode 69 (27.4%) AI and in the non-triggered mode 2 (11.8%) AI were diagnostic. At least one triggered diagnostic AI was obtained in each subject. The image grades were not statistically different between observers (kappa = 0.6686). In the triggered mode diagnostic images were acquired within +/- 90 msec of the peak systolic flow velocity determined by Doppler. The proportion of diagnostic images in the triggered mode was highest (73.3%) within a 30-msec interval before the peak flow. In healthy subjects the aortoiliac segment is reliably visualized by FLAG MR angiography. The optimum results are achieved using the triggered acquisition mode and timing acquisition to the initial 180 msec of the abdominal aortic systolic flow pulse.
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Affiliation(s)
- P Lanzer
- Department of Medicine, University of Alabama at Birmingham 35294
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38
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Mitchell DG, Carabasi A. Vascular applications of magnetic resonance imaging. Ann Vasc Surg 1989; 3:400-19. [PMID: 2688735 DOI: 10.1016/s0890-5096(06)60169-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- D G Mitchell
- Thomas Jefferson University Hospital, Department of Radiology, Philadelphia, Pennsylvania
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39
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Abstract
A method of subtraction angiography that has an acquisition time of 8 s per slice is described. Flow-compensated and uncompensated measurements are acquired in an interleaved fashion using limited flip angles and gradient refocusing. Magnitude images are reconstructed and subtracted to generate the angiogram. Results were generated in vivo in the imaging of the carotid bifurcation of several human volunteers. Susceptibility and inhomogeneity induced artifacts are prominent in thick slices, but can be greatly reduced by imaging several thin slices and adding them together. Thin slices do not require dephasing gradients to reduce the dynamic range, and there is no signal cancellation in overlapping vessels. The method is ideal for acquiring scout angiograms, and with averaging may produce images of diagnostic quality.
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Affiliation(s)
- J N Lee
- Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710
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40
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Dumoulin CL, Cline HE, Souza SP, Wagle WA, Walker MF. Three-dimensional time-of-flight magnetic resonance angiography using spin saturation. Magn Reson Med 1989; 11:35-46. [PMID: 2747515 DOI: 10.1002/mrm.1910110104] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A three-dimensional Fourier transform magnetic resonance imaging technique is presented. This procedure can be used to selectively detect flowing material such as blood in arteries and veins. Since flow is detected in a manner in which velocity-induced phase shifts are compensated, signal loss arising from complex flow and turbulence is minimized. The flow image is sensitive to all velocity components of flow. Applications of this technique are limited, however, to relatively straight vessels having appreciable flow. Examples of application of this technique to healthy and diseased carotid arteries are shown.
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Affiliation(s)
- C L Dumoulin
- General Electric Research and Development Center, Schenectady, New York 12301
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41
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Villringer A, Seiderer M, Bauer WM, Laub G, Haberl RL, Einhäupl KM. Diagnosis of superior sagittal sinus thrombosis by three-dimensional magnetic resonance flow imaging. Lancet 1989; 1:1086-7. [PMID: 2566040 DOI: 10.1016/s0140-6736(89)92490-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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42
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Marshall EA, Listinsky JJ, Ceckler TL, Szumowski J, Bryant RG, Hornak JP. Magnetic resonance imaging using a ribbonator: hand and wrist. Magn Reson Med 1989; 9:369-78. [PMID: 2710001 DOI: 10.1002/mrm.1910090308] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A modified version of a single-turn solenoid with rectangular symmetry, which we call a ribbonator, provides excellent magnetic resonance images of the hand and wrist when used as both the transmitter and the receiver in a 1.5-T clinical imaging system. The very high RF efficiency provides excellent signal-to-noise and anatomical resolution. Design equations and RF properties of the resonator are discussed.
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Affiliation(s)
- E A Marshall
- Department of Biophysics, University of Rochester, New York 14642
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43
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Abstract
Bipolar flow-encoding gradients can be used in a three-dimensional magnetic resonance imaging procedure to provide a noninvasive measure of in vivo blood flow. The resulting volume angiogram is a three-dimensional data matrix which can be retrospectively analyzed and displayed in a variety of ways. This angiographic technique provides good suppression of signals arising from stationary tissue, thereby permitting the visualization of small vessels having relatively slow flow. This suppression is obtained by modulating the amplitude of the flow-encoding gradient pulse to either cancel the stationary tissue signal or displace it relative to the flow signal in the volume image.
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Affiliation(s)
- C L Dumoulin
- GE Research and Development Center, Schenectady, New York 12301
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44
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Tasciyan TA, Lee JN, Riederer SJ, DeCastro JB, Hedlund LW, Herfkens RJ, Spritzer CE. Fast limited flip angle MR subtraction angiography. Magn Reson Med 1988; 8:261-74. [PMID: 3060701 DOI: 10.1002/mrm.1910080304] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A fast MR angiography method is introduced that is capable of generating difference images of blood vessels in scan times of 10-20 s. This is an order of magnitude faster than many previous methods. The fundamental concept of this approach is to use cardiac gating and acquire several phase encodings at least twice during each cardiac cycle using limited flip angles (LFAs) and repetition times in the 20 to 50 ms range. The encodings acquired during diastole are subtracted from those acquired during systole to generate the difference image. The contrast in the difference image is due both to the influx of unsaturated spins and to the loss of phase coherence of systolic blood moving at high velocity along a magnetic gradient. The systolic peak of the cardiac cycle is determined during reconstruction by shifting the systolic and diastolic "windows" until the difference signal is maximized. Ghost artifacts due to pulsatile flow are eliminated by a phase reordering technique similar in concept to those developed for suppression of breathing artifacts. Arteries in thick slices are successfully imaged and initial in vivo results are presented.
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Affiliation(s)
- T A Tasciyan
- Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710
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45
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Abstract
A time-resolved phase contrast magnetic resonance angiography technique is described. This technique provides a series of angiograms obtained at different phases of the cardiac cycle. Such a series of angiograms can be used to evaluate blood flow dynamics. For example, turbulent flow in the regions of vessel bifurcations is easily demonstrated and followed during systole and diastole. Retrograde flow can also be observed. Dynamic angiography can be particularly useful in distinguishing transient image features, such as signal voids due to turbulent flow, from static features arising from vessel morphology.
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Affiliation(s)
- C L Dumoulin
- General Electric Corporate Research and Development Center, Schenectady, New York 12301
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