Basic Processing in Cardiac MRI: Tips and Tricks

Cardiac MRI has gained immense popularity in the last few years as a comprehensive tool to examine patients with heart diseases. It is now routinely used to study myocardial structure, macrovascular blood flow, and cardiac functions.

However, the data generated by CMR is difficult to interpret for someone who is just entering into the cardiac MRI course.

So, the Society of Cardiovascular Magnetic Resonance (SCMR) has issued some guidelines to understand CMR imaging and processing.

This article lists the guidelines issued and explains how to interpret the images captured by Cardiovascular Magnetic Resonance Imaging.

The basic CMR processing includes the following measurements.

Basic CMR Processing: What Measurements Does It Provide?

1. Left Ventricular assessment

Left ventricular CMR measurements are obtained from a single short-axis cine state free precision (SSFP) images.

For the basic processing of the left ventricle:

• First, show the cine movie of the short axis images: It provides an overview of the wall motion and left ventricular function and shows visual measurements of the LV.
• Now scroll from basal slice to cardiac apex to include the data set of the whole ventricular and deleted the repeated slices that occur.
• Check the end-systolic and end-diastolic phases to calculate the ventricular volume.
• Determine the endocardial and epicardial borders, include or exclude papillary muscles as per the operator’s preference.
• Finally, evaluate the ventricular volume.

2. Right Ventricular function

Since the shape of the right ventricule is non-geometric, so it demands 3-D assessment for accurate measurements.

The same principles used for LV assessment is used for right ventricular assessments- playing cine movie, deleting repeated slice, selecting end-systolic and end-diastolic phases, and tracing endocardial and epicardial borders. Only the Right ventricular endocardial border is determined as the RV myocardium is very thin. RV can be calculated using short-axis image or transaxial images.

If short-axis images are used, then it saves time as they are the same axis used for LV assessment. But the disadvantage is that the selection of basal slice is very difficult on the short axis, so the pulmonary wall is not clearly visible.

If transaxial images are used, then pulmonary and tricuspid valves can be clearly seen, but for this, an extra data stack is required.

By both the means, the right ventricular assessment can be done.

3. Atrial size measurements

Atrial size measurements are done during ventricular systole. Usually, the atria measurements are done by measuring the diameter of the atrium. The normal size of the atrium is less than 4 cm by this measurement.

4. Flow analysis

This analysis plays a very important role in the assessment of patients with valvular heart diseases. So, it is very important to acquire these sequences accurately.  The images are required to be acquired perpendicular to the vessel in the question. Generally, this is calculated for aorta and pulmonary artery and used to calculate pulmonary to systemic flow ratio.

5. T2 analysis

T2 analysis is done to evaluate the amount of iron in the myocardium. The measurement is done in short axis orientation and gives a stack of images with different time-to-echo times for the same slice position.

Cardiovascular MRI is a rapidly growing field that has advanced the treatment of cardiac patients. So, it is crucial to maintain accuracy and precision to gain the clinical’s confidence in the use of MRI processing.