Magnetic Resonance Imaging

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Contents 1 More Specific Terms 2 Introduction 3 Indications 4 Contraindications 5 Procedure 6 Notes 7 More General Terms 8 Additional Terms 9 References

More Specific Terms

• cardiac magnetic resonance imaging (CMR imaging)
• functional magnetic resonance imaging (fMRI)
• magnetic resonance angiography (MRA)
• magnetic resonance cholangiopancreatograph (MRCP)
• magnetic resonance neurography
• open MRI (includes standing MRI)

Introduction

• Also see principles of magnetic resonance imaging

Indications

• (clinical indications for MRI)
• structural diseases of the brain (MRI is the imaging modality of choice)

• primary brain tumor, metastatic brain tumor
• meningeal tumors
• acoustic neuromas
• pituitary tumors
• cerebral hemorrhage
• cerebral ischemia detected within a few hours of vascular occlusion
• multiple sclerosis
• radiation injury

• structural diseases of the spine & spinal cord

• spinal cord neoplasm, meningeal neoplasm
• syringomyelia
• osteomyelitis of the spine
• degenerative disc disease
• herniated nucleus pulposis
• nerve root compression with radiculopathy
• cervical spine pannus
• spinal cord compression

• suspected dissecting aortic aneurysm
• pelvic tumors

• endometrial carcinoma
• cervical carcinoma
• prostate cancer

• structural musculoskeletal disorders

• bone tumors
• joint disease, especially knee osteoarthritis
• avascular necrosis of bone
• rotator cuff tear/injury

• soft tissue masses
• pulmonary

• pulmonary neoplasm, lung cancer
• assessment of superior sulcus tumors
• small hilar tumors
• tumor invasion of the chest wall ( metastases)
• tumors that involve the aortopulmonary window
• mediastinal tumors

• mediastinal lymphadenopathy
  

• indications for contrast MRI imaging with gadolinium:*

• suspected process interrupting blood brain barrier

• infection
• inflammation
• neoplasm
• stroke
  

• * gadolinium is the enhancing agent commonly used for MRI superparamagnetic iron oxides is another enhancing agent [6]

Contraindications

• ( contraindications for MRI) [5]
• metal (any ferromagnetic material)

• aneurysm clips
• intraorbital of intraocular metallic fragments
• mechanical cardiac valves

• Star-Edwards valve (caged ball valve)

• dental alloys, wires, splints & prosthesis do not appear to pose risk to patient, but may result in artifactual changes
• skin contact with metal objects can result in cutaneous burns - neurosurgical halo pins, pulse oximetry probes, nicotine patch

• electronic or magnetic implanted devices [7]

• pacemaker, AICD
• may be safe with modified protcols [8,9]
• no cardiac device has been FDA-approved for MRI compatibility [7]

• unstable patient
• pregnancy, risk to fetus unknown (relative contraindication)
• claustaphobia, sedation may mitigate
• obesity, devise has size limitations
  

• Contrast MRI imaging with gadolinium:*

• risk for nephrogenic fibrosing dermopathy with glomerular filtration rates < 30 mL/min/1.73 m2
• use alternative forms of imaging in patients with low GFR if possible
• hemodialysis: perform dialysis promptly after gadolinium administration [11]

Procedure

• patient is advanced into bore of magnet in supine position on floating table
• ear-plugs or ear-music systems are commonly used because of high noise level
• entire exam takes 20-45 minutes

• multiple imaging sequences in multiple planes b)imaging sequences range from 1 second to 10 minutes

• patients asked to remove jewlery, metallic objects, including cutaneous metal devices ( nicotine patch)

Notes

• Advantages of MRI over CT

• high sensitivity
• sectional images in multiple planes

• transverse sections
• longitudinal sections: coronal & sagital

• can show fluids in motion
• no ionizing radiation
• imaging of structure surrounded by bone
• better for imaging of the spinal cord & posterior fossa ( cerebellum)
  

• Limitations of MRI

• small bore & long hollow tube of the magnet excludes:

• obese patients
• patients with claustrophobia
• critically ill patients on life-support equipment

• strong magnetic field excludes:

• patients with pacemakers
• patients with ferromagnetic appliances

• changes in calcified tissue are not revealed

• pathologic changes in cortical bone
• calcification of tissues: tumors, vasculature, etc.

More General Terms

• radiography (diagnostic imaging, roentgenography)

Additional Terms

• gadolinium [Gd]
• magnetic resonance angiography (MRA)
• magnetic resonance neurography
• MRI cerebral white matter lesion (white matter hyperintensity)
• open MRI (includes standing MRI)
• principles of magnetic resonance imaging (MRI)

References

1. Introduction to Clinical Imaging, Radiology Syllabus, UCSF, 1993
2. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
3. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 2289
4. Veterans Affairs (VA) National Center for Patient Safety Magnetic Resonance Imaging (MR) Hazard Summary [1]
5. UpToDate 14.1 [2]
6. Aguirre DA, Behling CA, Alpert E, Hassanein TI, Sirlin CB. Liver fibrosis: noninvasive diagnosis with double contrast material-enhanced MR imaging. Radiology. 2006 May;239(2):425-37. PMID: [3]
7. Sommer T et al, Strategy for safe performance of extrathoracix magnetic resonance imaging at 1.5 tesla in the presence of cardiac pacemakers in non-pacemaker-dependent patients: A prospective study with 115 examinations. Circulation 2006, 114:1285 PMID: [4]
   - Nazarian S et al, Clinical utility and safety of a protocol for non-cardiac magnetic resonance imaging of patients with permanent pacemakers and implantable-cardioverter defibrillators at 1.5 tesla. Circulation 2006, 114:1277 PMID: [5]
8. Nazarian S et al A Prospective Evaluation of a Protocol for Magnetic Resonance Imaging of Patients With Implanted Cardiac Devices Annals of Internal Medicine October 4, 2011, 155(7):415-424 <PubMed> PMID: [6] <Internet> [7]
   - Reynolds MR Zimetbaum P Magnetic Resonance Imaging and Cardiac Devices: How Safe Is Safe Enough? Annals of Internal Medicine October 4, 2011, 155(7):470-472 <PubMed> PMID: [8] <Internet> [9]
9. Nazarian S et al. A prospective evaluation of a protocol for magnetic resonance imaging of patients with implanted cardiac devices. Ann Intern Med 2011 Oct 4; 155:415 PMID: [10]
   - Reynolds MR and Zimetbaum P. Magnetic resonance imaging and cardiac devices: How safe is safe enough? Ann Intern Med 2011 Oct 4; 155:470. PMID: [11]
10. National Guideline Clearinghouse
    - Practice advisory on anesthetic care for magnetic resonance imaging. A report by the American Society of Anesthesiologists Task Force on Anesthetic Care for Magnetic Resonance Imaging. American Society of Anesthesiologists ngc-guideline: [12]
    - ACR practice guideline for the performance of magnetic resonance imaging (MRI) of the abdomen (excluding the liver). American College of Radiology (ACR) ngc-guideline: [13]
    - ACR-SPR practice guideline for the safe and optimal performance of fetal magnetic resonance imaging (MRI). American College of Radiology (ACR) ngc-guideline: [14]
    - ACR-SSR practice guideline for the performance and interpretation of magnetic resonance imaging (MRI) of bone and soft tissue tumors. American College of Radiology (ACR) ngc-guideline: [15]
    - ACR-SSR practice guideline for the performance and interpretation of magnetic resonance imaging (MRI) of the knee. American College of Radiology (ACR) ngc-guideline: [16]
    - ACR-SSR practice guideline for the performance and interpretation of magnetic resonance imaging (MRI) of the shoulder. American College of Radiology (ACR) ngc-guideline: [17]
    - ACR practice guideline for the performance of magnetic resonance imaging (MRI) of the liver. American College of Radiology ngc-guideline: [18]
    - ACR practice guideline for the performance of magnetic resonance imaging (MRI) of the soft-tissue components of the pelvis. American College of Radiology ngc-guideline: [19]

magnetic resonance imaging (MRI)