The Extracellular Volume (ECV) Calculator is used in cardiac imaging, especially in cardiovascular magnetic resonance (CMR), to quantify the fraction of myocardial tissue that is extracellular. This measurement is useful for assessing conditions like fibrosis, infiltrative cardiomyopathies, or edema. By analyzing the tissue response to contrast agents before and after injection, the ECV provides insights into the microscopic structure of the heart, even when traditional imaging looks normal.
This calculator plays an essential role in clinical decision-making, helping doctors determine disease severity and progression. It’s widely used in both research settings and modern cardiology practice to support diagnostic and treatment strategies based on tissue characteristics.
Formula of Extracellular Volume Calculator
Where:
- ECV is the extracellular volume fraction (unitless or in percentage form)
- Hematocrit is the decimal fraction of blood volume made up by red blood cells (e.g., 0.45)
- ΔR1_myocardium = (1 / T1_post_myocardium) − (1 / T1_pre_myocardium)
- ΔR1_blood = (1 / T1_post_blood) − (1 / T1_pre_blood)
- T1_pre and T1_post are the relaxation times before and after contrast injection, either in milliseconds or seconds
This formula assumes steady-state contrast equilibrium and is typically used in gadolinium-enhanced MRI scans to derive myocardial ECV values.
Common Reference Table
| Parameter | Typical Value | Unit |
|---|---|---|
| Hematocrit (average adult) | 0.40 – 0.50 | (unitless) |
| T1_pre_myocardium | 950 – 1200 | ms |
| T1_post_myocardium | 400 – 600 | ms |
| T1_pre_blood | 1400 – 1600 | ms |
| T1_post_blood | 300 – 500 | ms |
| Normal ECV Range (Healthy Heart) | 20% – 28% | % |
| ECV indicating Fibrosis | > 30% | % |
These values provide quick guidance for expected ranges and interpretation of results.
Example of Extracellular Volume Calculator
A patient undergoes a cardiac MRI scan with the following results:
- Hematocrit = 0.42
- T1_pre_myocardium = 1000 ms
- T1_post_myocardium = 500 ms
- T1_pre_blood = 1500 ms
- T1_post_blood = 400 ms
Step 1: Convert T1 values to R1 (1/T1)
ΔR1_myocardium = (1 / 0.5) − (1 / 1.0) = 2.0 − 1.0 = 1.0
ΔR1_blood = (1 / 0.4) − (1 / 1.5) = 2.5 − 0.6667 ≈ 1.8333
Step 2: Apply formula
ECV = (1 − 0.42) × (1.0 / 1.8333)
ECV ≈ 0.58 × 0.5455 ≈ 0.316 or 31.6%
This ECV result suggests elevated extracellular volume, which may indicate myocardial fibrosis or other abnormality.
Most Common FAQs
This calculator is part of the medical imaging and cardiovascular diagnostics category, especially used in radiology and cardiology.
It helps detect changes in myocardial tissue composition, such as fibrosis or infiltration, which are not always visible on standard imaging.
Yes, ECV varies based on age, disease status, and individual hematocrit levels. That’s why personalized inputs are important for accurate calculation.