Pulsatility Index Calculator

Pulsatility Index Formula:

\[ PI = \frac{(v_{systole} - v_{diastole})}{v_{avg}} \]

Pulsatility Index (PI):

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1. What is Pulsatility Index?

The Pulsatility Index (PI) (also known as the Gosling index) is a calculated flow parameter in ultrasound, derived from the maximum, minimum, and mean Doppler frequency shifts. It provides valuable information about vascular resistance and compliance.

2. How Does the Calculator Work?

The calculator uses the Pulsatility Index formula:

\[ PI = \frac{(v_{systole} - v_{diastole})}{v_{avg}} \]

Where:

\( v_{systole} \) — Peak Systolic Velocity (m/s)
\( v_{diastole} \) — Minimum Diastolic Velocity (m/s)
\( v_{avg} \) — Average Velocity in terms of Cardiac Cycle (m/s)

Explanation: The PI quantifies the pulsatility of blood flow by comparing the difference between peak systolic and minimum diastolic velocities to the average velocity throughout the cardiac cycle.

3. Importance of PI Calculation

Details: Pulsatility Index is crucial for assessing vascular resistance in various clinical applications, including cerebrovascular, peripheral vascular, and obstetric ultrasound examinations. Higher PI values typically indicate increased downstream resistance.

4. Using the Calculator

Tips: Enter all velocity values in meters per second (m/s). Ensure that Peak Systolic Velocity is greater than Minimum Diastolic Velocity, and Average Velocity is greater than zero for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal Pulsatility Index range?
A: Normal PI values vary by vascular bed. For middle cerebral artery, normal PI is typically 0.6-1.1. Always consult specific reference ranges for the vessel being examined.

Q2: What does a high PI indicate?
A: Elevated PI typically suggests increased downstream vascular resistance, which could indicate various pathological conditions depending on the vascular bed being examined.

Q3: What does a low PI indicate?
A: Reduced PI may indicate decreased vascular resistance or high-flow states, such as in arteriovenous malformations or hyperemic conditions.

Q4: How is PI different from Resistance Index (RI)?
A: While both measure vascular resistance, PI incorporates the mean velocity in its calculation, making it potentially more sensitive to changes in the entire waveform shape compared to RI.

Q5: What are the limitations of PI measurement?
A: PI can be affected by various factors including heart rate, blood pressure, vessel compliance, and the angle of ultrasound insonation. It should be interpreted in clinical context.