Calculate Extracellular Volume Fraction from T1 Mapping
Enter as decimal (0.40) or percentage (40)
Milliseconds (ms)
Milliseconds (ms)
Milliseconds (ms)
Milliseconds (ms)
Please enter valid numeric values for all fields. T1 values cannot be zero.
Extracellular Volume Fraction (ECV)
—
Partition Coefficient (λ):—
function calculateECV() {
// 1. Get Elements
var hctInput = document.getElementById('ecv_hct');
var preMyoInput = document.getElementById('ecv_t1_myo_pre');
var preBloodInput = document.getElementById('ecv_t1_blood_pre');
var postMyoInput = document.getElementById('ecv_t1_myo_post');
var postBloodInput = document.getElementById('ecv_t1_blood_post');
var resultBox = document.getElementById('ecv_result');
var resultOutput = document.getElementById('ecv_output');
var lambdaOutput = document.getElementById('lambda_output');
var errorMsg = document.getElementById('ecv_error');
// 2. Parse Values
var hct = parseFloat(hctInput.value);
var t1MyoPre = parseFloat(preMyoInput.value);
var t1BloodPre = parseFloat(preBloodInput.value);
var t1MyoPost = parseFloat(postMyoInput.value);
var t1BloodPost = parseFloat(postBloodInput.value);
// 3. Validation
if (isNaN(hct) || isNaN(t1MyoPre) || isNaN(t1BloodPre) || isNaN(t1MyoPost) || isNaN(t1BloodPost)) {
errorMsg.style.display = 'block';
resultBox.style.display = 'none';
return;
}
if (t1MyoPre === 0 || t1BloodPre === 0 || t1MyoPost === 0 || t1BloodPost === 0) {
errorMsg.innerText = "T1 values cannot be zero.";
errorMsg.style.display = 'block';
resultBox.style.display = 'none';
return;
}
errorMsg.style.display = 'none';
// 4. Normalize Hematocrit
// If user enters integer like 40, treat as 40%. If 0.40, treat as 40%.
if (hct > 1) {
hct = hct / 100;
}
// 5. Calculation Logic
// R1 = 1 / T1
// ΔR1 = (1/T1_post) – (1/T1_pre)
// Since T1 is ms, 1/T1 is small, but the ratio cancels units out.
var r1MyoDiff = (1 / t1MyoPost) – (1 / t1MyoPre);
var r1BloodDiff = (1 / t1BloodPost) – (1 / t1BloodPre);
// Avoid division by zero in the ratio
if (r1BloodDiff === 0) {
errorMsg.innerText = "Invalid Blood T1 change (Delta R1 is zero). Check inputs.";
errorMsg.style.display = 'block';
resultBox.style.display = 'none';
return;
}
// Partition Coefficient (Lambda) = ΔR1_myo / ΔR1_blood
var lambda = r1MyoDiff / r1BloodDiff;
// ECV = (1 – Hct) * Lambda
var ecv = (1 – hct) * lambda;
// Convert to Percentage
var ecvPercentage = ecv * 100;
// 6. Display Results
resultOutput.innerText = ecvPercentage.toFixed(1) + "%";
lambdaOutput.innerText = lambda.toFixed(3);
resultBox.style.display = 'block';
}
Extracellular Volume (ECV) Calculator
The Extracellular Volume (ECV) Calculator is a specialized tool used in Cardiac Magnetic Resonance (CMR) imaging to quantify the fraction of myocardial tissue volume that is occupied by the extracellular space. This biomarker is crucial for assessing myocardial fibrosis and infiltrative diseases.
What is ECV in Cardiac MRI?
In healthy myocardium, the cardiac muscle cells (myocytes) occupy the vast majority of the tissue volume. The extracellular matrix—the space between cells—is relatively small. However, in pathological conditions such as diffuse myocardial fibrosis or cardiac amyloidosis, the extracellular space expands.
ECV provides a non-invasive histological assessment of the myocardium. By measuring the T1 relaxation times of both the blood pool and the myocardium before and after the administration of a gadolinium-based contrast agent, clinicians can calculate the partition coefficient and subsequently the ECV.
The ECV Formula
The calculation of ECV relies on T1 mapping. The fundamental premise is that gadolinium contrast agents are extracellular and equilibrate between the blood and the myocardial interstitium. The formula is derived as follows:
To ensure accurate calculation, precise inputs from your T1 mapping sequence are required:
Hematocrit (Hct): The volume percentage of red blood cells in the blood. This should be measured close to the time of the MRI scan. Standard range is often 0.35–0.50 (35–50%).
Pre-contrast T1: Native T1 values for the myocardium and blood pool before contrast injection. Native myocardial T1 at 1.5T is typically ~950-1050ms, and at 3T is ~1150-1250ms.
Post-contrast T1: T1 values measured typically 15-20 minutes after gadolinium bolus. T1 shortens significantly (e.g., to 400-600ms) due to contrast accumulation.
Clinical Significance and Normal Ranges
ECV is a robust marker because, unlike native T1 mapping alone, it is less dependent on magnetic field strength and sequence parameters.
Normal ECV: Typically ranges between 25% and 28% (0.25 – 0.28).
Elevated ECV: Values >30% often indicate diffuse myocardial fibrosis or scar tissue.
Significantly Elevated ECV: Values >40-50% are highly suggestive of cardiac amyloidosis.
Why Use an ECV Calculator?
Automated inline processing is becoming common on modern MRI scanners, but manual calculation is frequently necessary for research verification or when post-processing software is unavailable. This tool allows radiologists and cardiologists to quickly derive the ECV fraction from standard T1 mapping ROI (Region of Interest) measurements.