CARDIAC MAGNETIC RESONANCE IMAGING Flashcards
What is cardiac magnetic resonance (CMR)?
A non-invasive imaging technique that uses a strong magnet, radiofrequency pulses, and gradient magnetic fields to produce detailed images of the heart.
CMR is essential for evaluating various cardiac conditions without ionizing radiation.
What strength of magnet does CMR typically use?
1.5 to 3.0 Tesla
This is equivalent to 30,000–60,000 times the strength of the earth’s magnetic field.
What fundamental process allows CMR to produce images?
The alignment of positively charged protons in a magnetic field, followed by relaxation and signal emission.
This involves T1 and T2 relaxation components.
What is k-space in CMR?
A data space where collected signals are organized before creating an image.
It is essential for image reconstruction in CMR.
How does CMR differ from echocardiography?
CMR does not expose patients to ionizing radiation and has superior contrast-to-noise and signal-to-noise ratios.
This allows better delineation of tissue borders.
What are some limitations of CMR?
Availability, portability, contraindications, difficulty with irregular rhythms, and claustrophobia.
CMR requires specialized facilities and trained personnel.
What are common indications for CMR?
- Evaluation of chest pain syndrome
- Assessment of coronary anomalies
- Evaluation of LV function after myocardial infarction
- Assessment of myocardial viability
- Evaluation of myocarditis
- Evaluation of specific cardiomyopathies
- Characterization of cardiac valve dysfunction
- Evaluation of cardiac masses
- Assessment of congenital heart disease
- Evaluation for aortic dissection
These indications highlight CMR’s versatility in cardiac assessment.
What pulse sequences are commonly used in CMR?
- Bright blood gradient echo sequences
- Dark blood spin echo sequences
- Steady-state free precession sequences
- Inversion recovery sequences
These sequences help in visualizing different aspects of cardiac structures.
What is late gadolinium enhancement (LGE) imaging?
A CMR technique used to identify myocardial scar/fibrosis by administering gadolinium-based contrast agents.
LGE imaging helps in assessing areas of scar after myocardial infarction.
Can CMR be used for stress testing in patients with chest pain?
Yes, CMR stress testing can assess flow-limiting coronary stenosis in patients with intermediate pretest probability of CAD.
Methods include vasodilator perfusion CMR and dobutamine stress function CMR.
What is the role of CMR in evaluating ventricular function?
CMR is the reference standard for assessing ventricular volumes, ejection fraction, and ventricular mass.
It is particularly useful after myocardial infarction or in heart failure.
What specific cardiomyopathies can CMR assess?
- Infiltrative diseases (e.g., amyloid, sarcoid)
- Hypertrophic cardiomyopathy
- Arrhythmogenic right ventricular cardiomyopathy
CMR can reveal unique LGE patterns associated with various cardiomyopathies.
What is the importance of T1 and T2 mapping in CMR?
They provide direct quantification of myocardial tissue properties, aiding in the assessment of conditions like edema and fibrosis.
These mapping techniques are evolving for better accuracy in diagnoses.
How can CMR be used in the context of myocardial infarction?
CMR identifies myocardial necrosis, microvascular obstruction, and myocardial thrombus using LGE imaging.
It also assesses the likelihood of recovery of function with revascularization.
What role does CMR play in assessing valvular disease?
CMR assists in evaluating valve lesions when echocardiographic images are technically limited and provides quantitative assessments of stenosis and regurgitation.
Techniques such as phase-contrast imaging are utilized for flow measurements.
What technique is used to assess flow volumes of the great vessels?
Phase-contrast imaging
This technique is analogous to Doppler imaging in echocardiography.
What is a major advantage of four-dimensional flow techniques in cardiac imaging?
Provides flow data in all three dimensions of space over time
This helps assess regurgitant or stenotic lesions more comprehensively.
What is a limitation of four-dimensional flow techniques?
Length of acquisition and limited ability to postprocess data
Why is CMR often considered the best modality for assessing congenital heart disease?
Unique ability to assess heart and circulation in three-dimensional space and obtain hemodynamic data
What can CMR accurately measure in patients with congenital heart disease?
LV and RV volumes and function
What is a significant benefit of CMR for young patients requiring multiple imaging studies?
No ionizing radiation exposure
What is a major limitation of CMR in patients with congenital heart disease?
Susceptibility to artifacts from previous surgeries
What is CMR’s effectiveness in assessing cardiac masses?
Good modality for assessment and tissue characterization
What is a key limitation of CMR in characterizing tumor tissue?
Initial hopes for noninvasive biopsy have not been fully realized
What other clinical uses does CMR have?
Assessment of pericardial conditions and pulmonary vein anatomy
What does CMR assess in constrictive pericarditis?
Thickness of the pericardium and signs of inflammation
What are some common contraindications to CMR?
Ferromagnetic objects and certain metallic implants
Can CMR be performed in patients with implanted cardiovascular devices?
Yes, most devices are nonferromagnetic or weakly ferromagnetic
What is nephrogenic systemic fibrosis (NSF)?
A fibrosing condition affecting skin, joints, muscles, and internal organs
What are the main risk factors for developing NSF with GBCAs?
- Advanced renal disease
- Recent vascular surgical procedures
- Dialysis
- Acute renal failure
- Higher doses of contrast agent
What is the time interval between GBCA administration and the onset of NSF?
60 to 90 days
What concern has arisen regarding gadolinium-based contrast agents?
Brain deposition of gadolinium
Is there evidence of clinical consequences from gadolinium brain deposition?
No studies have demonstrated clinical, behavioral, or biological consequences
What is the significance of the Revo MRI SureScan system?
First MRI-safe pacemaker approved by the FDA
What is the Evera MRI ICD?
First ICD approved by the FDA as an MRI-conditional device
What should be done prior to GBCA administration in patients with advanced renal disease?
Carefully weigh risks and benefits, consider alternate imaging modalities
