Magnetic resonance imaging (MRI), formerly referred to as magnetic resonance tomography (MRT) or nuclear magnetic resonance (NMR), is a method used to visualize the inside of living organisms as well as to detect the composition of geological structures. It is primarily used to demonstrate pathological or other physiological alterations of living tissues and is a commonly used form of medical imaging. MRI has also found many novel applications outside of the medical and biological fields such as rock permeability to hydrocarbons and certain non-destructive testing methods such as produce and timber quality characterization. ^* The devices used in medicine are expensive, costing approximately $1 million USD per tesla for each unit (common field strength ranges from 0.3 to 3 teslas), with several hundred thousand dollars per year of upkeep costs.

Background

---

Nomenclature

Magnetic resonance imaging was developed from knowledge gained in the study of nuclear magnetic resonance. The original name for the medical technology is nuclear magnetic resonance imaging (NMRI), but the word nuclear is almost universally dropped. This is done to avoid the negative connotations of the word nuclear, and to prevent patients from associating the examination with radiation exposure, which is not one of the safety concerns for MRI. Scientists still use NMR when discussing non-medical devices operating on the same principles.

More on [ Magnetic resonance imaging ]

Magnetic Resonance Materials in Physics, Biology and Medicine

Eddy current effects on a clinical 7T-68 cm bore scanner
Thu, 10 Dec 2009 15:09:43 -0000
Abstract Introduction  Eddy currents induced by switching of magnetic field gradients can lead to distortions in short echo-time spectroscopy or diffusion weighted imaging. In small bore magnets, such as human head-only systems, minimization of eddy current effects is more demanding because of the proximity of the gradient coil to conducting structures. Methods  In the present study, the eddy current behavior achievable on a recently installed 7 tesla—68 cm bore head-only magnet was characterized. Results  Residual effects after compensation were shown to be on the same order of magnitude as those measured on two whole body systems (3 and 4.7 T), while using two to three fold increased gradient slewrates. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0192-0Authors Nils Kickler, Ecole Polytechnique Fédérale de Lausanne Laboratory for Functional and Metabolic Imaging Lausanne SwitzerlandWietske van der Zwaag, Ecole Polytechnique Fédérale de Lausanne Laboratory for Functional and Metabolic Imaging Lausanne SwitzerlandRalf Mekle, Ecole Polytechnique Fédérale de Lausanne Laboratory for Functional and Metabolic Imaging Lausanne SwitzerlandTobias Kober, Ecole Polytechnique Fédérale de Lausanne Laboratory for Functional and Metabolic Imaging Lausanne SwitzerlandJose P. Marques, Ecole Polytechnique Fédérale de Lausanne Laboratory for Functional and Metabolic Imaging Lausanne SwitzerlandGunnar Krueger, Advanced Clinical Imaging Technology, Siemens Medical Solutions-CIBM Lausanne SwitzerlandRolf Gruetter, Ecole Polytechnique Fédérale de Lausanne Laboratory for Functional and Metabolic Imaging Lausanne Switzerland Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243
Absolute quantification of perfusion using dynamic susceptibility contrast MRI: pitfalls and possibilities
Thu, 03 Dec 2009 18:21:52 -0000
Abstract  Absolute quantification of cerebral blood flow, cerebral blood volume and mean transit time is desirable in the determination of tissue viability thresholds and tissue at risk in acute ischaemic stroke, as well as in cases where a global reduction in cerebral blood flow is expected, for example, in patients with dementia or depressive disorders. Absolute values are also useful when comparing sequential examinations of tissue perfusion parameters, for example, in the monitoring and follow-up of various kinds of therapy. Regardless of the method employed, a number of assumptions and approximations must be made to obtain absolute measures of perfusion. Furthermore, the different stages of data acquisition and processing are associated with various degrees of uncertainty. In this review, the problems of particular relevance to absolute quantification of cerebral perfusion parameters using dynamic susceptibility contrast magnetic resonance imaging are discussed, and possible solutions are outlined. Content Type Journal ArticleCategory Review ArticleDOI 10.1007/s10334-009-0190-2Authors Linda Knutsson, Lund University, Lund University Hospital Department of Medical Radiation Physics 221 85 Lund SwedenFreddy Ståhlberg, Lund University, Lund University Hospital Department of Medical Radiation Physics 221 85 Lund SwedenRonnie Wirestam, Lund University, Lund University Hospital Department of Medical Radiation Physics 221 85 Lund Sweden Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243
3D T1-mapping for the characterization of deep vein thrombosis
Sat, 28 Nov 2009 07:04:38 -0000
Abstract Purpose  The aim of this work was to investigate fast T 1-mapping for the characterization of deep vein thrombosis (DVT). Methods  The accuracy and reproducibility of the T 1-mapping sequence was tested in phantoms and in 8 healthy volunteers on a 1.5 T clinical scanner using a 32-channel array coil. Furthermore, the feasibility of the technique was tested in 5 patients diagnosed with DVT by measuring the volume and T 1 values of the thrombus at 5 time points over a period of 6 months. Results  The results of the phantom and volunteer study showed a high accuracy and reproducibility for the quantification of T 1. The resolution of the T 1-maps was high enough to identify small anatomical structures. T 1 values derived for normal blood and various other tissues were comparable to those reported in the literature. In all patients, the T 1 times of thrombi showed decreased values (T 1 = 843 ± 91 ms) in the acute phase and recovered back to normal values of blood (T 1 = 1,317 ± 36 ms) after 6 months. Conclusions  Measurement of all relevant T 1 values of acute thrombi and normal blood achieved accurate and reproducible results in vivo. Fast T 1 quantification of the thrombus can provide information about tissue characteristics such as thrombus resolution. Such a quantitative MRI technique may be valuable in studying the factors that influence natural resolution and in evaluating treatment effects that enhance this process. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0189-8Authors Ulrike Blume, King’s College London, St Thomas Hospital Division of Imaging Sciences, The Rayne Institute 4th Floor Lambeth Wing London SE1 7EH UKJames Orbell, St Thomas Hospital Academic Department of Surgery, Cardiovascular Division London UKMatthew Waltham, St Thomas Hospital Academic Department of Surgery, Cardiovascular Division London UKAlberto Smith, St Thomas Hospital Academic Department of Surgery, Cardiovascular Division London UKReza Razavi, King’s College London, St Thomas Hospital Division of Imaging Sciences, The Rayne Institute 4th Floor Lambeth Wing London SE1 7EH UKTobias Schaeffter, King’s College London, St Thomas Hospital Division of Imaging Sciences, The Rayne Institute 4th Floor Lambeth Wing London SE1 7EH UK Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Number 6 / December, 2009
High-resolution 3D magnetic resonance imaging and quantification of carious lesions and dental pulp in vivo
Thu, 19 Nov 2009 07:40:54 -0000
Abstract Objective  The purpose of the study was to assess the feasibility of MRI of three-dimensional visualization and quantification of carious lesions, as well as measurement of the distance between the lesion and dental pulp in vivo. Materials and methods  High-resolution 3D MRI was performed to measure seven carious lesions in vivo using gelatinous gadolinium-based oral contrast medium in combination with an intraoral radio frequency receiver coil on a clinical 1.5 T MRI scanner. Extension of the carious lesion in three spatial dimensions and the minimum distance between the lesion and dental pulp were quantified. When possible, the result was compared to an X-ray projection and an impression of the lesion taken using a plastic impression material before and after dental treatment. Results  Carious lesions, including pit and fissure, approximal lesions, and occult dentin caries, could be visualized due to the MRI signal rise in the porous affected dentin. The minimum distance between the carious lesion and dental pulp could be determined in all cases. Conclusion  The results presented demonstrate the feasibility of high-resolution dental MRI to three-dimensionally visualize and quantify carious lesions, including approximal and occult caries lesions, and measure the minimum distance to the dental pulp. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0188-9Authors Olga Tymofiyeva, University of Wuerzburg Department of Experimental Physics 5 Am Hubland 97074 Wuerzburg GermanyJulian Boldt, University of Wuerzburg Department of Prosthodontics, Dental School Pleicherwall 2 97070 Wuerzburg GermanyKurt Rottner, University of Wuerzburg Department of Prosthodontics, Dental School Pleicherwall 2 97070 Wuerzburg GermanyFlorian Schmid, University of Wuerzburg Department of Experimental Physics 5 Am Hubland 97074 Wuerzburg GermanyErnst-Juergen Richter, University of Wuerzburg Department of Prosthodontics, Dental School Pleicherwall 2 97070 Wuerzburg GermanyPeter M. Jakob, University of Wuerzburg Department of Experimental Physics 5 Am Hubland 97074 Wuerzburg Germany Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Number 6 / December, 2009
Detection of polyunsaturated omega-6 fatty acid in human malignant prostate tissue by 1D and 2D high-resolution magic angle spinning NMR spectroscopy
Tue, 17 Nov 2009 23:49:29 -0000
Abstract Object  Polyunsaturated omega-6 fatty acids (PUFAs) have been shown to promote prostate cancer. Here, we describe the use of HRMAS NMR spectroscopy to detect omega-6 PUFA species in prostate tissues. Materials and methods  Samples originating from non-malignant (n = 54) and malignant (n = 27) prostate tissues (from 27 prostatectomized men) were studied by 1D 1H, 2D 1H–1H and 1H–13C HRMAS NMR spectroscopy followed by histopathological characterization. Results  HRMAS NMR proved to be a powerful, non-destructive method to identify and characterize PUFAs. The omega-6 PUFA was found in 15% of examined human prostate tumors. Conclusion  It is possible to detect PUFAs in prostate tissues using our NMR-based spectroscopic approach. Content Type Journal ArticleCategory Short CommunicationDOI 10.1007/s10334-009-0187-xAuthors Katarina Stenman, Umeå University and University Hospital of Northern Sweden Department of Radiation Sciences, Diagnostic Radiology Umeå 901 87 SwedenJón B. Hauksson, Umeå University and University Hospital of Northern Sweden Radiation Physics Umeå SwedenGerhard Gröbner, Umeå University Department of Chemistry Umeå SwedenPär Stattin, Umeå University and University Hospital of Northern Sweden Department of Surgery and Perioperative Sciences, Urology and Andrology Umeå SwedenAnders Bergh, Umeå University and University Hospital of Northern Sweden Department of Medical Biosciences Pathology Umeå SwedenKatrine Riklund, Umeå University and University Hospital of Northern Sweden Department of Radiation Sciences, Diagnostic Radiology Umeå 901 87 Sweden Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Number 6 / December, 2009
Structural–acoustic modal analysis of cylindrical shells: application to MRI scanner systems
Mon, 26 Oct 2009 18:00:23 -0000
Abstract Object  The acoustic noise in a magnetic resonance imaging (MRI) scanner bore is mainly introduced by the vibration of gradient coils. The interaction between acoustic modes in the scanner bore and structure modes in the coil structure leads to structural–acoustic coupling. In order to implement quiet MRI design, the structural–acoustic coupling mechanism in MRI machines needs to be fully investigated. Materials and method  Structural analysis was first implemented using Love’s classical shell theory. The concept of a “virtually closed cavity” was used in the acoustic modal analysis of the gradient coil duct. The dispersion curves and the number of modes per frequency band were used to reveal modal distribution properties for both structural modes and acoustic modes. Structural–acoustic coupling modes were identified by superposition of the dispersion diagrams of the structural waves and acoustic waves. Experimental validation was implemented separately for the structural analysis and acoustic analysis. Results  Independent structural modes and acoustic modes and their distribution patterns were calculated up to 3000Hz with various boundary conditions. Coupling modes were clearly revealed using the analysis procedures presented in this paper and were found to be in agreement with the ones identified from experimental measurements. Conclusion  These methods are effective for coupled and uncoupled modal analysis of MRI scanner systems and can be used for quiet MRI design or sound absorber design for existing MRI systems. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0185-zAuthors Gemin Li, Queen’s University Department of Mechanical Engineering McLaughlin Hall Kingston ON K7L 3N6 CanadaChris K. Mechefske, Queen’s University Department of Mechanical Engineering McLaughlin Hall Kingston ON K7L 3N6 Canada Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Number 6 / December, 2009
Quantitative metabolic profiles of 2nd and 3rd trimester human amniotic fluid using 1H HR-MAS spectroscopy
Thu, 24 Sep 2009 16:42:27 -0000
Abstract Object  To establish and compare normative metabolite concentrations in 2nd and 3rd trimester human amniotic fluid samples in an effort to reveal metabolic biomarkers of fetal health and development. Materials and methods  Twenty-one metabolite concentrations were compared between 2nd (15–27 weeks gestation, N = 23) and 3rd (29–39 weeks gestation, N = 27) trimester amniotic fluid samples using 1H high resolution magic angle spinning (HR-MAS) spectroscopy. Data were acquired using the electronic reference to access in vivo concentrations method and quantified using a modified semi-parametric quantum estimation algorithm modified for high-resolution ex vivo data. Results  Sixteen of 21 metabolite concentrations differed significantly between 2nd and 3rd trimester groups. Betaine (0.00846±0.00206 mmol/kg vs. 0.0133±0.0058 mmol/kg, P < 0.002) and creatinine (0.0124±0.0058 mmol/kg vs. 0.247±0.011 mmol/kg, P < 0.001) concentrations increased significantly, while glucose (5.96±1.66 mmol/kg vs. 2.41±1.69 mmol/kg, P < 0.001), citrate (0.740±0.217 mmol/kg vs. 0.399±0.137 mmol/kg, P < 0.001), pyruvate (0.0659±0.0103 mmol/kg vs. 0.0299±0.286 mmol/kg, P < 0.001), and numerous amino acid (e.g. alanine, glutamate, isoleucine, leucine, lysine, and valine) concentrations decreased significantly with advancing gestation. A stepwise multiple linear regression model applied to 50 samples showed that gestational age can be accurately predicted using combinations of alanine, glucose and creatinine concentrations. Conclusion  These results provide key normative data for 2nd and 3rd trimester amniotic fluid metabolite concentrations and provide the foundation for future development of magnetic resonance spectroscopy (MRS) biomarkers to evaluate fetal health and development. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0184-0Authors Brad R. Cohn, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USABonnie N. Joe, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USAShoujun Zhao, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USAJohn Kornak, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USAVickie Y. Zhang, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USARahwa Iman, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USAJohn Kurhanewicz, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USAKiarash Vahidi, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USAJingwei Yu, University of California Department of Laboratory Medicine San Francisco CA USAAaron B. Caughey, University of California Department of Obstetrics & Gynecology San Francisco CA USAMark G. Swanson, University of California Department of Radiology & Biomedical Imaging 1600 Divisadero Street, Room C-250 Box 1667 San Francisco CA 94115 USA Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Number 6 / December, 2009
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: Abstracts, Thursday
Thu, 24 Sep 2009 14:34:38 -0000
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: Abstracts, Thursday Content Type Journal ArticleDOI 10.1007/s10334-009-0175-1 Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Supplement 1 / October, 2009
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: Abstracts, Saturday
Thu, 24 Sep 2009 14:34:38 -0000
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: Abstracts, Saturday Content Type Journal ArticleDOI 10.1007/s10334-009-0177-z Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Supplement 1 / October, 2009

Subscribe to MRI RSS feed