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

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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

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
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
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
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: Abstracts, Friday
Thu, 24 Sep 2009 14:34:36 -0000
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: Abstracts, Friday Content Type Journal ArticleDOI 10.1007/s10334-009-0176-0 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: EPOStm Posters / Paper Posters / Info-RESO
Thu, 24 Sep 2009 14:34:35 -0000
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: EPOStm Posters / Paper Posters / Info-RESO Content Type Journal ArticleDOI 10.1007/s10334-009-0178-y 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: Author Index
Thu, 24 Sep 2009 14:34:34 -0000
ESMRMB 2009 Congress, Antalya, Turkey, 1–3 October: Author Index Content Type Journal ArticleDOI 10.1007/s10334-009-0179-x 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
A digital receiver with fast frequency- and gain-switching capabilities for MRI systems
Thu, 24 Sep 2009 14:31:48 -0000
Abstract Object  In this article, two issues pertaining to MRI digital receivers are addressed. One is the maintenance of phase coherence between the transmitter and the receiver—an effective solution is proposed, in which the receiver frequency is switched synchronously with the transmitter frequency. The other is the dynamic range of the receiver—gain-switching technique is utilized to improve the dynamic range. To meet the hardware requirements of these solutions, a digital receiver with fast frequency- and gain-switching capabilities was implemented. Materials and methods  The primary components of the proposed digital receiver are a variable gain amplifier, a high-speed analog-to-digital converter and a single-chip digital receiver core. The radio-frequency magnetic resonance signal is directly sampled by the analog-to-digital converter and processed in the digital receiver core. By pre-storing the receiver waveform in the on-board SDRAM, the frequency and gain of the receiver may be switched very quickly. Results  The performance of the proposed digital receiver is verified by embedding it in an imaging spectrometer. It is then demonstrated by conducting experiments on a home-built 0.3-T magnetic resonance imaging system. Conclusion  The results show that the phase coherence between the transmitter and the receiver and the dynamic range of the receiver are greatly improved. Consequently, the proposed digital receiver may be useful for obtaining multiple-slice two-dimensional magnetic resonance images with very high resolution. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0182-2Authors Ning Ruipeng, East China Normal University Shanghai Key Laboratory of Functional Magnetic Resonance Imaging, Department of Physics 3663 North Zhong-Shan Road 200062 Shanghai People’s Republic of ChinaDai Yidong, East China Normal University Shanghai Key Laboratory of Functional Magnetic Resonance Imaging, Department of Physics 3663 North Zhong-Shan Road 200062 Shanghai People’s Republic of ChinaYang Guang, East China Normal University Shanghai Key Laboratory of Functional Magnetic Resonance Imaging, Department of Physics 3663 North Zhong-Shan Road 200062 Shanghai People’s Republic of ChinaLi Gengying, East China Normal University Shanghai Key Laboratory of Functional Magnetic Resonance Imaging, Department of Physics 3663 North Zhong-Shan Road 200062 Shanghai People’s Republic of China Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243
Influence of cardiac motion on diffusion-weighted magnetic resonance imaging of the liver
Tue, 01 Sep 2009 16:47:55 -0000
Abstract Purpose  To assess cardiac motion-induced signal loss in diffusion-weighted magnetic resonance imaging (DWI) of the liver using dynamic DWI. Materials and methods  Three volunteers underwent dynamic coronal DWI of the liver under breathholding, in the diastolic (DWIdiast) or systolic (DWIsyst) cardiac phase, and with motion probing gradients (MPGs) in phase encoding (P, left–right), frequency encoding (M, superior–inferior), or slice select (S, anterior–posterior) direction. Liver-to-background contrasts (LBCs) of DWIsyst were compared to those of DWIdiast, for both the left and right liver lobes, using nonparametric tests. Signal decrease ratios (SDRs) were calculated as (1−(LBCDWIsyst/LBCDWIdiast)) × 100%. DWIsyst was further analyzed to determine which direction of MPGs was most affected by cardiac motion. Results  In the left liver lobe, LBCs of DWIsyst (median 3.35) were significantly lower (P < 0.0001) than those of DWIdiast (median 4.84). In the right liver lobe, LBCs of DWIsyst (median 4.17) were also significantly lower (P < 0.0001) than those of DWIdiast (median 5.35 ). SDRs of the left and right liver lobes were 25.5% and 17.3%, respectively. In DWIsyst, the significantly lowest (P < 0.05) LBCs were observed in the M direction (left liver lobe) and P direction (right liver lobe) of MPGs. Conclusion  Signal intensity of both liver lobes are affected by cardiac motion in DWI. In the left liver lobe, signal loss especially occurs in the superior–inferior direction of MPGs, whereas in the right lobe, signal loss especially occurs in the left-right direction of MPGs. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-009-0183-1Authors Thomas C. Kwee, University Medical Center Utrecht Department of Radiology Heidelberglaan 100 3584 CX Utrecht The NetherlandsTaro Takahara, University Medical Center Utrecht Department of Radiology Heidelberglaan 100 3584 CX Utrecht The NetherlandsTetsu Niwa, University Medical Center Utrecht Department of Radiology Heidelberglaan 100 3584 CX Utrecht The NetherlandsMarko K. Ivancevic, University of Michigan Medical Center Department of Radiology Ann Arbor MI USAGwenael Herigault, Philips Healthcare Best The NetherlandsMarc Van Cauteren, Philips Healthcare Asia Pacific Tokyo JapanPeter R. Luijten, University Medical Center Utrecht Department of Radiology Heidelberglaan 100 3584 CX Utrecht The Netherlands Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243 Journal Volume Volume 22 Journal Issue Volume 22, Number 5 / October, 2009

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