Pulsatility Index (PI) Calculator
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Pulsatility Index (PI) Calculator
Pulsatility Index (PI) Result
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cm/s
Understanding the Pulsatility Index (PI)
The Pulsatility Index (PI) is a Doppler ultrasound measurement used to assess the resistance to blood flow in vessels. It quantizes the pulsatile nature of blood flow, which is typically high in arteries close to the heart and decreases as the vessels branch into smaller, more peripheral arteries. The PI is calculated by measuring the difference between the peak systolic velocity and the end-diastolic velocity, then dividing by the peak systolic velocity.
The Formula
The mathematical formula for the Pulsatility Index is:
PI = (Peak Systolic Velocity – End Diastolic Velocity) / Peak Systolic Velocity
Or, using abbreviations:
PI = (PSV – EDV) / PSV
How to Use This Calculator
This calculator simplifies the process of determining the Pulsatility Index:
- Peak Systolic Velocity (PSV): Enter the highest velocity of blood flow detected during the systolic phase (contraction of the heart). This is usually measured in centimeters per second (cm/s).
- End Diastolic Velocity (EDV): Enter the lowest velocity of blood flow detected during the diastolic phase (relaxation of the heart) just before the next systolic peak. This is also typically measured in cm/s.
After entering these two values, click the "Calculate Pulsatility Index" button. The calculator will display the computed PI value. Note that PI is a dimensionless ratio, though the units of velocity (e.g., cm/s) are often stated for context.
Clinical Significance and Applications
The Pulsatility Index is a valuable tool in various medical fields, particularly cardiology, radiology, and obstetrics:
- Assessing Vascular Resistance: A high PI indicates high resistance to flow, while a low PI suggests low resistance.
- Monitoring Conditions: It is used to monitor the progression or regression of conditions like peripheral artery disease, renal artery stenosis, and intrauterine growth restriction (IUGR) in pregnancy.
- Evaluating Transplanted Organs: PI can help assess the blood flow and health of transplanted organs, such as kidneys.
- Interpreting Doppler Signals: It helps clinicians interpret Doppler ultrasound findings in a standardized and quantifiable manner.
Normal PI values vary depending on the specific vessel being examined and the patient's condition. Deviations from expected ranges can prompt further investigation or adjustments in treatment plans.
function calculatePI() {
var psv = parseFloat(document.getElementById("peakSystolicVelocity").value);
var edv = parseFloat(document.getElementById("endDiastolicVelocity").value);
var resultValueElement = document.getElementById("result-value");
var resultUnitElement = document.getElementById("result-unit");
if (isNaN(psv) || isNaN(edv)) {
resultValueElement.innerText = "Invalid Input";
resultValueElement.style.color = "#dc3545";
resultUnitElement.innerText = "";
return;
}
if (psv === 0) {
resultValueElement.innerText = "Undefined";
resultValueElement.style.color = "#dc3545";
resultUnitElement.innerText = "";
return;
}
var pi = (psv – edv) / psv;
// Format the result to a reasonable number of decimal places, e.g., 2
var formattedPI = pi.toFixed(2);
resultValueElement.innerText = formattedPI;
resultValueElement.style.color = "#004a99"; // Reset to default color
resultUnitElement.innerText = ""; // PI is dimensionless
}