The Lake Louise criteria provides a diagnostic framework for evaluating myocarditis using MRI by considering three distinct imaging findings. Each identified finding is assessed with a binary response, either present (true) or absent (false), and is assigned a score.

The combined score, ranging from 0 to 3, provides a concise interpretation of potential myocardial inflammation or injury. The three MRI criteria evaluated are:

- **Regional or global myocardial signal intensity increase in T2-weighted images:** If present, this contributes 1 point to the total score.
- **Increased global myocardial early gadolinium enhancement ratio between myocardium and skeletal muscle in gadolinium-enhanced T1-weighted images:** This finding also adds 1 point if present.
- **At least one focal lesion with a non-ischemic regional distribution in inversion recovery-prepared gadolinium-enhanced T1-weighted images (late gadolinium enhancement):** Similarly, a true response here adds 1 point to the total.

These criteria aim to capture the complexity of myocarditis through reliable and measurable imaging changes. The summed score facilitates the interpretation as follows:

- **Score 0:** This suggests repeating the MRI in 1-2 weeks if initial results are negative yet there is a significant clinical suspicion of myocardial inflammation.
- **Score 1:** Indicates a need to consider a follow-up MRI within 1-2 weeks to confirm or exclude myocarditis.
- **Score 2:** Represents findings consistent with myocardial inflammation, implying the presence of an active inflammatory process affecting the myocardium.
- **Score 3:** Denotes MRI evidence of myocyte injury and/or scarring attributed to myocardial inflammation, indicating potential past or ongoing tissue damage.

Each step in this diagnostic process emphasizes using the MRI findings to drive clinical decision-making and adaptation of patient management strategies.

The Lake Louise Criteria for Magnetic Resonance Imaging Diagnosis of Myocarditis is a diagnostic tool used specifically in the field of cardiology. This calculator is applied to patients suspected of having myocarditis, an inflammation of the heart muscle. The Lake Louise Criteria utilizes cardiac magnetic resonance imaging (MRI) findings to aid in the diagnosis of myocarditis. 

The clinical utility of this calculator lies in its ability to provide a standardized approach to the interpretation of cardiac MRI findings in suspected myocarditis, thereby aiding in the accurate diagnosis and subsequent management of this condition. 

Exclusion criteria for the use of the Lake Louise Criteria include patients who are contraindicated for MRI such as those with certain types of implanted medical devices (e.g., certain pacemakers or neurostimulators), severe kidney disease, or claustrophobia. Additionally, it may not be applicable in cases where myocarditis is not the primary differential diagnosis.

Lake Louise criteria for magnetic resonance imaging diagnosis of myocarditis