What is viability in Magnetic Resonance Imaging (MRI)?

From the Guidelines

Viability in MRI can be accurately assessed using a combination of MR diffusion-weighted imaging (DWI) and MR perfusion (MRP) to differentiate viable from probably nonviable hypoperfused tissue. This approach is supported by a study from the American Heart Association, which recommends the use of MRI for imaging of acute ischemic stroke 1. The study highlights the importance of imaging in evaluating tissue viability and perfusion, and notes that MR DWI is the most sensitive and specific technique available for demonstrating acute infarction.

Key points to consider when assessing viability in MRI include:

• The use of MR DWI to demonstrate acute infarction within minutes after its occurrence
• The combination of MR DWI with MR perfusion (MRP) to differentiate viable from probably nonviable hypoperfused tissue
• The use of MR angiography (MRA) to demonstrate vascular occlusion
• The use of gradient-recalled echo (GRE) sequence to exclude intracerebral hemorrhage (ICH)
• The use of fluid-attenuated inversion recovery (FLAIR) sequence to show abnormal accumulations of fluid

According to the study, a combination of these MR sequences can be performed in 10 minutes, providing essential information for patient triage and treatment decisions 1. The study also notes that imaging at a single point in time presents only a portion of the desired information, and that the evolution of tissue perfusion and viability is the ultimate goal. Therefore, the use of MRI, particularly MR DWI and MRP, is recommended for assessing viability in patients with acute ischemic stroke.

From the Research

Viability in MRI

• The assessment of myocardial viability using Magnetic Resonance Imaging (MRI) is a crucial aspect of diagnosing and treating heart failure 2.
• Cardiac MRI is a non-invasive, x-ray free technique that uses a powerful magnetic field, radio frequency pulses, and a computer to produce detailed images of the structure and function of the heart 2.
• The diagnostic accuracy of cardiac MRI in predicting functional recovery and its impact on prognosis (mortality and other patient outcomes) has been evaluated in various studies 2.

Comparison with Other Imaging Modalities

• A 2005 review determined that positron emission tomography (PET) was more sensitive than dobutamine echocardiography and single photon emission computed tomography (SPECT) 2.
• However, there was inadequate evidence to compare PET and cardiac MRI, highlighting the need for further research in this area 2.
• Other imaging modalities, such as stress echocardiography, SPECT, and PET, can also be used to assess myocardial viability, but each has its own strengths and limitations 2.

Clinical Applications

• The identification and quantification of myocardial viability are essential in determining the most appropriate treatment path for patients with heart failure 2.
• Cardiac MRI can help identify viable myocardium, which can benefit from revascularization, and distinguish it from scar tissue or non-viable myocardium 2.
• The use of cardiac MRI in clinical practice can improve patient outcomes by guiding treatment decisions and reducing the risk of unnecessary procedures 2.

Limitations and Future Directions

• While cardiac MRI has shown promise in assessing myocardial viability, further research is needed to fully understand its diagnostic accuracy and clinical applications 2.
• The comparison of cardiac MRI with other imaging modalities, such as PET, is an area of ongoing research, and more studies are needed to determine the optimal imaging strategy for assessing myocardial viability 2.