What is QSM in MRI?

QSM in MRI stands for Quantitative Susceptibility Mapping, a technique used to measure the magnetic properties of tissues.

Quantitative susceptibility mapping (QSM) is a recently developed magnetic resonance imaging (MRI) technique for quantifying the spatial distribution of magnetic susceptibility within biological tissues. This means it creates detailed maps showing how different parts of the body's tissues interact with a magnetic field.

How QSM Works (Based on Reference)

The core principle behind QSM involves using the magnetic field disturbances caused by tissues to create the susceptibility map. According to the provided reference:

1. Step 1: Map the Magnetic Field Profile: QSM first utilizes the frequency shift observed in the MRI signal. Tissues with different magnetic properties cause local changes in the magnetic field, which in turn alter the frequency of the MRI signal. By analyzing these frequency shifts throughout the tissue, QSM can map out the magnetic field variations.
2. Step 2: Quantify Susceptibility: From this magnetic field map, QSM then calculates the magnetic susceptibility value for each point (voxel) in the tissue. This provides a quantitative measure of how strongly that tissue is magnetized by the external MRI field.

Key Aspects of QSM

Based on the definition, here are the essential points about QSM:

• Purpose: To quantify the spatial distribution of magnetic susceptibility.
• Basis: Relies on measuring frequency shifts in the MRI signal.
• Output: Creates a map of magnetic susceptibility values within tissues.
• Technology: A relatively new MRI technique.

Summary Table

While the reference is concise, we can summarize the core process described:

By mapping magnetic susceptibility, QSM provides unique contrast compared to traditional MRI techniques, offering insights into tissue composition that are not always visible otherwise.