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 ]
Improvement of spectral density-based activation detection of event-related fMRI data. Ngan SC, Hu X, Tan LH, Khong PL
Related Articles
Improvement of spectral density-based activation detection of event-related fMRI data.
Magn Reson Imaging. 2009 Sep;27(7):879-94
Authors: Ngan SC, Hu X, Tan LH, Khong PL
For event-related data obtained from an experimental paradigm with a periodic design, spectral density at the fundamental frequency of the paradigm has been used as a template-free activation detection measure. In this article, we build and expand upon this detection measure to create an improved, integrated measure. Such an integrated measure linearly combines information contained in the spectral densities at the fundamental frequency as well as the harmonics of the paradigm and in a spatial correlation function characterizing the degree of co-activation among neighboring voxels. Several figures of merit are described and used to find appropriate values for the coefficients in the linear combination. Using receiver-operating characteristic analysis on simulated functional magnetic resonance imaging (fMRI) data sets, we quantify and validate the improved performance of the integrated measure over the spectral density measure based on the fundamental frequency as well as over some other popular template-free data analysis methods. We then demonstrate the application of the new method on an experimental fMRI data set. Finally, several extensions to this work are suggested.
PMID: 19535208 [PubMed - indexed for MEDLINE]
On MRI turbulence quantification. Dyverfeldt P, Gårdhagen R, Sigfridsson A, Karlsson M, Ebbers T
Related Articles
On MRI turbulence quantification.
Magn Reson Imaging. 2009 Sep;27(7):913-22
Authors: Dyverfeldt P, Gårdhagen R, Sigfridsson A, Karlsson M, Ebbers T
Turbulent flow, characterized by velocity fluctuations, accompanies many forms of cardiovascular disease and may contribute to their progression and hemodynamic consequences. Several studies have investigated the effects of turbulence on the magnetic resonance imaging (MRI) signal. Quantitative MRI turbulence measurements have recently been shown to have great potential for application both in human cardiovascular flow and in engineering flow. In this article, potential pitfalls and sources of error in MRI turbulence measurements are theoretically and numerically investigated. Data acquisition strategies suitable for turbulence quantification are outlined. The results show that the sensitivity of MRI turbulence measurements to intravoxel mean velocity variations is negligible, but that noise may degrade the estimates if the turbulence encoding parameter is set improperly. Different approaches for utilizing a given amount of scan time were shown to influence the dynamic range and the uncertainty in the turbulence estimates due to noise. The findings reported in this work may be valuable for both in vitro and in vivo studies employing MRI methods for turbulence quantification.
PMID: 19525079 [PubMed - indexed for MEDLINE]
Relaxo-volumetric multispectral quantitative magnetic resonance imaging of the brain over the human lifespan: global and regional aging patterns. Saito N, Sakai O, Ozonoff A, Jara H
Related Articles
Relaxo-volumetric multispectral quantitative magnetic resonance imaging of the brain over the human lifespan: global and regional aging patterns.
Magn Reson Imaging. 2009 Sep;27(7):895-906
Authors: Saito N, Sakai O, Ozonoff A, Jara H
The objective of this study was to determine the T1, T2 and secular-T2 relaxo-volumetric brain aging patterns using multispectral quantitative magnetic resonance imaging, both globally and regionally, and covering an age range approaching the full human lifespan. Fifty-one subjects (28 males, 23 females; age range: 0.5-87 years) were studied consisting of 18 healthy volunteers and 33 patients. Patients were selected after carefully reviewing their radiology reports to have either normal-by-MRI findings (25 patient subjects) or small focal pathology less than 6 mm in size (eight patient subjects). All subjects were MR imaged at 1.5 T with the mixed turbo spin echo pulse sequence. The soft tissues inside the cranial vault, termed intracranial matter (ICM), were segmented using a dual-clustering segmentation algorithm. ICM segments were further divided into six subsegments: bilateral anterior cerebral, posterior cerebral and cerebellar subsegments. T1, T2 and secular-T2 relaxation time histograms of all segments were generated and modeled with Gaussian functions. For each segment, the volumes of white matter, gray matter and cerebrospinal fluid were calculated from the T1 histograms. The age-related tendencies of three quantitative MRI parameters (T1, T2 and secular-T2) and the fractional tissue volumes showed four distinct periods of life, specifically a maturation period (0-2 years), a development period (2-20 years), an adulthood period (20-60 years) and a senescence period (60 years and older). For all ages, the anterior cerebral subsegment exhibited consistently longer gray matter T1s and shorter white matter T1s than the posterior cerebral and cerebellar subsegments. Volumetric age-related changes of the cerebellar subsegment were more gradual than in the cerebral subsegments. This study shows that relaxometric and volumetric age-related changes are synchronized and define the same four periods of brain evolution both globally and regionally.
PMID: 19520539 [PubMed - indexed for MEDLINE]
Fast low-angle positive contrast steady-state free precession imaging of USPIO-labeled macrophages: theory and in vitro experiment. Mascheri N, Dharmakumar R, Zhang Z, Paunesku T, Woloschak G, Li D
Related Articles
Fast low-angle positive contrast steady-state free precession imaging of USPIO-labeled macrophages: theory and in vitro experiment.
Magn Reson Imaging. 2009 Sep;27(7):961-9
Authors: Mascheri N, Dharmakumar R, Zhang Z, Paunesku T, Woloschak G, Li D
The feasibility of imaging macrophages labeled with ultrasmall superparamagnetic iron-oxide nanoparticles (USPIO) with fast low-angle positive contrast steady-state free precession (FLAPS) was investigated through theory and in vitro experiment. Human macrophage cells were labeled with USPIO and imaged at 1.5 T. The metric "visibility," which combines magnitude and spatial extent of positive contrast, was used to evaluate the images. Negative contrast steady-state free precession (SSFP) and gradient-echo (GRE) imaging were also evaluated. Positive contrast was observed for relatively high concentrations of labeled cells for flip angles less than alpha=25 degrees . Theoretical and experimental results indicate that positive visibility (VIS(POS)) was maximized at alpha=10 degrees and 15 degrees. Low flip angle SSFP also provided negative contrast comparable to standard SSFP and GRE imaging. Results suggest that USPIO-labeled macrophages are capable of producing the conditions necessary for positive contrast with FLAPS at clinical field strength (1.5 T) and resolution (0.8x0.8x3 mm(3)).
PMID: 19520536 [PubMed - indexed for MEDLINE]
A fully automated algorithm under modified FCM framework for improved brain MR image segmentation. Sikka K, Sinha N, Singh PK, Mishra AK
Related Articles
A fully automated algorithm under modified FCM framework for improved brain MR image segmentation.
Magn Reson Imaging. 2009 Sep;27(7):994-1004
Authors: Sikka K, Sinha N, Singh PK, Mishra AK
Automated brain magnetic resonance image (MRI) segmentation is a complex problem especially if accompanied by quality depreciating factors such as intensity inhomogeneity and noise. This article presents a new algorithm for automated segmentation of both normal and diseased brain MRI. An entropy driven homomorphic filtering technique has been employed in this work to remove the bias field. The initial cluster centers are estimated using a proposed algorithm called histogram-based local peak merger using adaptive window. Subsequently, a modified fuzzy c-mean (MFCM) technique using the neighborhood pixel considerations is applied. Finally, a new technique called neighborhood-based membership ambiguity correction (NMAC) has been used for smoothing the boundaries between different tissue classes as well as to remove small pixel level noise, which appear as misclassified pixels even after the MFCM approach. NMAC leads to much sharper boundaries between tissues and, hence, has been found to be highly effective in prominently estimating the tissue and tumor areas in a brain MR scan. The algorithm has been validated against MFCM and FMRIB software library using MRI scans from BrainWeb. Superior results to those achieved with MFCM technique have been observed along with the collateral advantages of fully automatic segmentation, faster computation and faster convergence of the objective function.
PMID: 19395212 [PubMed - indexed for MEDLINE]
Image correction during large and rapid B(0) variations in an open MRI system with permanent magnets using navigator echoes and phase compensation. Li J, Wang Y, Jiang Y, Xie H, Li G
Related Articles
Image correction during large and rapid B(0) variations in an open MRI system with permanent magnets using navigator echoes and phase compensation.
Magn Reson Imaging. 2009 Sep;27(7):988-93
Authors: Li J, Wang Y, Jiang Y, Xie H, Li G
An open permanent magnet system with vertical B(0) field and without self-shielding can be quite susceptible to perturbations from external magnetic sources. B(0) variation in such a system located close to a subway station was measured to be greater than 0.7 microT by both MRI and a fluxgate magnetometer. This B(0) variation caused image artifacts. A navigator echo approach that monitored and compensated the view-to-view variation in magnetic resonance signal phase was developed to correct for image artifacts. Human brain imaging experiments using a multislice gradient-echo sequence demonstrated that the ghosting and blurring artifacts associated with B(0) variations were effectively removed using the navigator method.
PMID: 19369023 [PubMed - indexed for MEDLINE]
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
Brainscans.com - Scheduling service for obtaining an MRI brainscan.
Meta Description: [ Brainscans.com offers a scheduling service for obtaining an MRI brainscan for $169. It is available to anyone 21 years or older without existing medical or health conditions that would be adversely affected by an MRI. As a result, for the first time members of the general public will be able to o... ]
Cardiac MRI Anatomical Atlas - A unique cardiac MRI resource. Interesting cardiac anatomy section. Detailed information about the Society for Cardiovascular Magnetic Resonance (SCMR).
Meta Description: [ The Society of Cardiovascular Magnetic Resonance (SCMR) represents physicians, scientists, and technologists working in CMR. We are committed developing CMR through education, quality control, research, and training ]
Cognitive Engineering - Cognitive Engineering analyzes Functional MRI for forensic (truth deception interrogation and image recognition), pharmaceutical research and marketing studies
Meta Description: [ Cognitive Engineering analyzes Functional MRI for forensic (truth deception interrogation and image recognition), pharmaceutical research and marketing studies, cognition, memory, thought, security ]
functional MRI (fMRI) - fMRI related links and information, such as brain atlas, funding opportunities, jobs, conferences, journals, books, and message boards.
Meta Description: [ functional MRI ( fMRI ) links and information ]
Hamilton-Smith Consultants - Specializes in arranging MRI scans in southern Ontario, Canada.
Meta Description: [ MRI Services ]
How Stuff Works: Magnetic Resonance Imaging (MRI) - Informative illustrated explanation of Magnetic Resonance Imaging (MRI) written by a Registered Technologist in Radiography and Magnetic Resonance Imaging.
Meta Description: [ The biggest and most important component in an MRI system is the magnet; its so strong, it could suck a metal watch right off your wrist and into the machine. Find out about magnetic resonance imaging. ]
International Society for Magnetic Resonance in Medicine - A nonprofit professional association devoted to furthering the development and application of magnetic resonance techniques in medicine and biology.
Meta Description: [ The ISMRM is a nonprofit professional association devoted to furthering the development and application of magnetic resonance techniques in medicine and biology. ]
Laboratory of Diagnostic Radiology Research - Clinical research in the imaging sciences within the areas of Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Molecular Imaging, Image Processing as well as other areas of imaging sciences. (National Institute of Health)
Leeds Cardiac Magnetic Resonance, UK - Cardiac courses, research and contact information.
Meta Description: [ Info on Leeds Cardiac Magnetic Resonance and educational Cardiac Courses. ]
Magnetic Resonance Technology Information Portal - Information about Magnetic Resonance Imaging - MRI - acronyms, artifacts, basics, contrast agents, coils, examinations, devices, sequences, business directory, congresses, forum, links/resources, market, and news.
Meta Description: [ Magnetic Resonance - Technology Information Portal (www.mr-tip.com) is a free web portal for magnetic resonance imaging. Radiologists, technicians, technologists, administrators, and industry professionals can find information about magnetic resonance basics, technology, artifacts, contrast agent... ]
500Maryland Open MRI - Information about this MRI service provider. Includes a description of an MRI, and a patient checklist of how best to prepare for this diagnostic process.
Meta Description: [ Maryland Open MRI offices serving you ... ]
Max MR Imaging, Inc. - Provideing information about Max MR Imaging Inc., provider of shared diagnostic imaging, treatment and related management services through a combination of mobile and fixed-site MRI facilities.
MRI Net - This is a free listing service for any MRI facility in the US. Search by zip code, find any MRI facility.
Meta Description: [ Find a Nuclear Medicine, MRI(Magnetic Resonance Imaging ), PET, CATSCAN, or Ultrasound Facility in the United States. Search by zip code. FREE Listings, marketing, web hosting and web page design, PACS/RIS,
DICOM, Patient information ]
MRI Practice - This site links MRI physics with clinical conditions using case studies.
Meta Description: [ enter a description here ]
RadiologyInfo - Magnetic Resonance Imaging (MRI) - Easy to understand information for patients about MRI procedures. Learn what patients might experience, how to prepare for exams, and the benefits, risks, and limitations.
Meta Description: [ Links to current and accurate information for patients about Magnetic Resonance Imaging (MRI) procedures. ]
Spine-Health - Information on when an MRI scan is recommended for back pain diagnosis.
Meta Description: [ Do I need an MRI scan for my back pain or neck pain? By Spine-health ]
The Adelaide MR Website - A collection of links to web based resources on MRI and MR spectoscopy designed for MR users. This page is provided to collate web resources and disseminate information on issues of MRI Scanning.
Meta Description: [ A page of MRI resources and links maintained by a working MRI Radiographer ]
The Future of MRI and MRS - An abstract on the future trends of MRI and MRS authored by Andrew A. Maudsley Ph.D and Michael W. Weiner M.D.
The Hipax PC Archive System - Hipax PC-Archive, MRI-Storage for Archiving DICOM Images on Optical Media (e.g. MRI, CT images).
Meta Description: [ The Hipax Medical Imaging and Communication System/Hipax is DIOCOM 3 multi modality image processing tool/PC Win95,98,NT4.0 ]
Magnetic resonance imaging:
Referred to as magnetic resonance tomography (MRT) or, in chemistry nuclear magnetic resonance (NMR), is a non-invasive method used to render images of the inside of an object.
The scanners used in medicine cost approximately US$ 1 million per tesla (T) and have a typical field strength of 0.3 to 3 T, with several hundred thousand dollars paid per year just for maintenance.