Principles of magnetic resonance imaging
- Daniel Chernoff, MD, PhD
Daniel Chernoff, MD, PhD
- Director of MRI
- Adirondack Radiology Associates
- Paul Stark, MD
Paul Stark, MD
- Professor of Radiology
- University of California San Diego
Magnetic resonance (MR) imaging is an important tool in the diagnosis and evaluation of diseases . In the early 1970s, Paul Lauterbur and Raymond Damadian applied nuclear magnetic resonance (NMR) technology to the imaging of living organisms, generating images referred to as zeugmatographs [2-5]. Subsequent refinements in image acquisition and processing, developed by Sir Peter Mansfield and others, allowed improved visualization of anatomic detail and broader clinical application of MR imaging [1,6-8]. Lauterbur and Mansfield were awarded the 2003 Nobel Prize in Medicine and Physiology for their contributions to medical imaging.
This topic will review the principles of magnetic resonance imaging. Clinical applications of MR are discussed in individual topic reviews.
Atoms are characterized by mass, electrical charge, and a magnetic property called spin. Atomic nuclei that contain an odd number of protons or neutrons possess a magnetic moment, which describes the strength and direction of a microscopic magnetic field surrounding the nucleus. In the presence of a strong, constant external magnetic field, such as that produced inside an imaging magnet, a small excess fraction of nuclei, on average, align themselves with the magnetic field, producing a macroscopic, measurable magnetic moment (figure 1) [9-11].
In addition, the interaction between the magnetic moment of the nucleus and the external field causes each spinning nucleus to precess (ie, change the orientation of the rotation axis of the spinning nucleus). Each nucleus precesses at a characteristic (resonant) frequency that is proportional to the strength of the external field. The resonant frequency can be calculated with the Larmor equation:
Resonant frequency F = B0 x Larmor constant
- Andrew ER. Nuclear magnetic resonance and the brain. Brain Topogr 1992; 5:129.
- Lauterbur PC. Progress in n.m.r. zeugmatography imaging. Philos Trans R Soc Lond B Biol Sci 1980; 289:483.
- Damadian R. Field focusing n.m.r. (FONAR) and the formation of chemical images in man. Philos Trans R Soc Lond B Biol Sci 1980; 289:489.
- Lai CM, Lauterbur PC. True three-dimensional image reconstruction by nuclear magnetic resonance zeugmatography. Phys Med Biol 1981; 26:851.
- Seynaeve PC, Broos JI. [The history of tomography]. J Belge Radiol 1995; 78:284.
- Andrew ER. The Wellcome Foundation lecture, 1981. Nuclear magnetic resonance imaging in medicine: physical principles. Proc R Soc Lond B Biol Sci 1985; 225:399.
- Garroway AN. Solid state NMR, MRI and Sir Peter Mansfield: (1) from broad lines to narrow and back again; and (2) a highly tenuous link to landmine detection. MAGMA 1999; 9:103.
- Mustarelli P, Rudnicki M, Savini A, et al. Synthesis of magnetic gradients for NMR tomography. Magn Reson Imaging 1990; 8:101.
- Morelli JN, Runge VM, Ai F, et al. An image-based approach to understanding the physics of MR artifacts. Radiographics 2011; 31:849.
- Pooley RA. AAPM/RSNA physics tutorial for residents: fundamental physics of MR imaging. Radiographics 2005; 25:1087.
- Elster AD: Questions and Answers in Magnetic Resonance Imaging www.mri-q.com (Accessed on July 15, 2015).
- Yanasak NE, Kelly MJ. MR imaging artifacts and parallel imaging techniques with calibration scanning: a new twist on old problems. Radiographics 2014; 34:532.
- Bitar R, Leung G, Perng R, et al. MR pulse sequences: what every radiologist wants to know but is afraid to ask. Radiographics 2006; 26:513.
- Vogt FM, Goyen M, Debatin JF. MR angiography of the chest. Radiol Clin North Am 2003; 41:29.
- Finn JP, Baskaran V, Carr JC, et al. Thorax: low-dose contrast-enhanced three-dimensional MR angiography with subsecond temporal resolution--initial results. Radiology 2002; 224:896.
- Riederer SJ, Bernstein MA, Breen JF, et al. Three-dimensional contrast-enhanced MR angiography with real-time fluoroscopic triggering: design specifications and technical reliability in 330 patient studies. Radiology 2000; 215:584.
- Holmqvist C, Ståhlberg F, Laurin S. Contrast-enhanced thoracic 3D-MR angiography in infants and children. Acta Radiol 2001; 42:50.
- Okuda S, Kikinis R, Geva T, et al. 3D-shaded surface rendering of gadolinium-enhanced MR angiography in congenital heart disease. Pediatr Radiol 2000; 30:540.
- White CS. MR imaging of thoracic veins. Magn Reson Imaging Clin N Am 2000; 8:17.
- Cohen MS, Weisskoff RM. Ultra-fast imaging. Magn Reson Imaging 1991; 9:1.
- Finn JP, Nael K, Deshpande V, et al. Cardiac MR imaging: state of the technology. Radiology 2006; 241:338.
- Kanal E, Borgstede JP, Barkovich AJ, et al. American College of Radiology White Paper on MR Safety: 2004 update and revisions. AJR Am J Roentgenol 2004; 182:1111.
- Marcu CB, Beek AM, van Rossum AC. Clinical applications of cardiovascular magnetic resonance imaging. CMAJ 2006; 175:911.
- American Society for Testing and Materials (ASTM) International. ASTM F2503-05: Standard Practice for Marking Medical Devices and Other Itmes for Safety in the Magnetic Resonance Environment. ASTM International ,West Conshohocken, PA. 2005. Available at: http://www.astm.org.
- MRI safety. Institute for Magnetic Resonance Safety, Education, and Research Web site. http://222.MRIsafety.com (Accessed on February 06, 2008).
- MR safety. 2006. http//www.acr.org/SecondaryMainMenuCategories/quality_safety/MRSafety.aspx (Accessed on February 06, 2008).
- Levine GN, Gomes AS, Arai AE, et al. Safety of magnetic resonance imaging in patients with cardiovascular devices: an American Heart Association scientific statement from the Committee on Diagnostic and Interventional Cardiac Catheterization, Council on Clinical Cardiology, and the Council on Cardiovascular Radiology and Intervention: endorsed by the American College of Cardiology Foundation, the North American Society for Cardiac Imaging, and the Society for Cardiovascular Magnetic Resonance. Circulation 2007; 116:2878.
- American College of Cardiology Foundation Task Force on Expert Consensus Documents, Hundley WG, Bluemke DA, et al. ACCF/ACR/AHA/NASCI/SCMR 2010 expert consensus document on cardiovascular magnetic resonance: a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents. J Am Coll Cardiol 2010; 55:2614.
- Zikria JF, Machnicki S, Rhim E, et al. MRI of patients with cardiac pacemakers: a review of the medical literature. AJR Am J Roentgenol 2011; 196:390.
- Roguin A, Schwitter J, Vahlhaus C, et al. Magnetic resonance imaging in individuals with cardiovascular implantable electronic devices. Europace 2008; 10:336.
- Sharan A, Rezai AR, Nyenhuis JA, et al. MR safety in patients with implanted deep brain stimulation systems (DBS). Acta Neurochir Suppl 2003; 87:141.
- Romner B, Olsson M, Ljunggren B, et al. Magnetic resonance imaging and aneurysm clips. Magnetic properties and image artifacts. J Neurosurg 1989; 70:426.
- Shellock FG. MR imaging of metallic implants and materials: a compilation of the literature. AJR Am J Roentgenol 1988; 151:811.
- Hubálková H, Hora K, Seidl Z, Krásenský J. Dental materials and magnetic resonance imaging. Eur J Prosthodont Restor Dent 2002; 10:125.
- Kim LJ, Sonntag VK, Hott JT, et al. Scalp burns from halo pins following magnetic resonance imaging. Case illustration. J Neurosurg 2003; 99:186.
- Karch AM. Don't get burnt by the MRI: transdermal patches can be a hazard to patients. Am J Nurs 2004; 104:31.
- Dempsey MF, Condon B. Thermal injuries associated with MRI. Clin Radiol 2001; 56:457.
- Dempsey MF, Condon B, Hadley DM. Investigation of the factors responsible for burns during MRI. J Magn Reson Imaging 2001; 13:627.
- Nakamura T, Fukuda K, Hayakawa K, et al. Mechanism of burn injury during magnetic resonance imaging (MRI)--simple loops can induce heat injury. Front Med Biol Eng 2001; 11:117.
- Severinghaus JW, Kelleher JF. Recent developments in pulse oximetry. Anesthesiology 1992; 76:1018.
- Guidelines for screening patients for MR procedures and individuals for the MR environment, institute for magnetic resonance safety, education, and research, 2009. http://www.imrser.org/PaperPDFRecord.asp?WebRecID=102&PgName=Guidelines&WebRecID=&sb_SummaryTitle=&).
- http://www.fda.gov/Drugs/DrugSafety/PublicHealthAdvisories/ucm111313.htm (Accessed on August 06, 2010).
- Shellock FG, Kanal E. Policies, guidelines, and recommendations for MR imaging safety and patient management. SMRI Safety Committee. J Magn Reson Imaging 1991; 1:97.
- Beckett KR, Moriarity AK, Langer JM. Safe Use of Contrast Media: What the Radiologist Needs to Know. Radiographics 2015; 35:1738.
- McDonald RJ, McDonald JS, Kallmes DF, et al. Intracranial Gadolinium Deposition after Contrast-enhanced MR Imaging. Radiology 2015; 275:772.
- Darrah TH, Prutsman-Pfeiffer JJ, Poreda RJ, et al. Incorporation of excess gadolinium into human bone from medical contrast agents. Metallomics 2009; 1:479.
- Kanal E, Tweedle MF. Residual or retained gadolinium: practical implications for radiologists and our patients. Radiology 2015; 275:630.
- MR PHYSICS
- MR IMAGING TECHNOLOGY AND PULSE SEQUENCES
- Magnet and coil design
- Pulse sequences
- - Spin echo
- - Gradient echo
- - Other sequences
- MAGNETIC RESONANCE CONTRAST AGENTS
- MOTION COMPENSATION TECHNIQUES
- Cardiac gating
- Respiratory compensation
- Flow compensation (gradient moment nulling)
- SPATIAL AND CHEMICAL PRESATURATION
- Suppression of signal from flowing blood
- Suppression of respiratory motion artifact
- Suppression of signal from fat
- PRACTICAL ASPECTS
- Cardiovascular devices
- - Timing of MR examination
- - Coronary artery and peripheral vascular stents
- - Aortic stent grafts
- - Mechanical cardiac valves
- - Cardiac closure and occluder devices
- - Inferior vena cava filters
- - Embolization coils
- - Loop recorder (Event monitor)
- - Hemodynamic monitoring and temporary pacing devices
- - Permanent pacemakers and implantable cardioverter-defibrillators
- - Retained transvenous pacemaker and defibrillator leads
- - Hemodynamic support devices
- Other implanted electronic devices
- Aneurysm clips
- Other foreign materials
- - Transdermal patches
- Unstable patient
- MR contrast agent
- - Kidney disease
- - Retained gadolinium