MRI Pulse Sequence for Bone and Soft Tissue Segmentation
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Solution Overview
Problem
Current MRI methods struggle to accurately image and segment bone and soft tissues without exposing patients to ionizing radiation or using radiotracers, and face challenges in registering bone and soft tissue images from different scans, leading to errors in PET attenuation correction and other applications.
Innovation Solution
A method using a pulse sequence that includes a non-selective RF pulse, ultra-short echo time radial k-space trajectory for bone imaging, and additional echoes with a FLASH-based Cartesian k-space sampling for soft tissue imaging, allowing for simultaneous acquisition and reconstruction of MR images that accurately depict both bone and soft tissue without increasing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate pulse sequences are used to image bone and soft tissue, then both tissues can be visualized, but image registration errors occur and scan time increases
Solution Approach 1:
The patent combines bone imaging and soft tissue imaging into a single pulse sequence by acquiring ultra-short echo time data and conventional echo time data in succession within one scan, eliminating the need for separate scans and improving registration accuracy
Solution Approach 2:
The patent acquires bone signal data at ultra-short echo times immediately after the RF excitation pulse, before the signal decays, preserving bone information that would otherwise be lost in conventional imaging sequences
2Measurement precision
If conventional MRI pulse sequences are used, then soft tissue imaging is accurate, but bone signal is insufficient for proper segmentation
Solution Approach 1:
The patent segments the imaging process into two distinct data acquisition phases within one pulse sequence: ultra-short echo time data acquisition for bone signal and conventional echo time data acquisition for soft tissue, allowing each to be optimized independently
Solution Approach 2:
The patent changes the echo time parameter to ultra-short durations immediately after RF excitation to capture bone signal, then transitions to conventional echo times for soft tissue imaging within the same pulse sequence
3Measurement precision
If CT imaging is used to obtain bone data for PET attenuation correction, then accurate attenuation maps are produced, but patients are exposed to ionizing radiation
Solution Approach 1:
The patent replaces the mechanical/physical CT imaging process with magnetic resonance imaging to acquire bone data, eliminating ionizing radiation while providing sufficient bone signal for PET attenuation correction through ultra-short echo time sequences
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate and automatic segmentation of bone and soft tissue in MRI images, improving registration accuracy and reducing errors in applications like PET attenuation correction, while avoiding radiation exposure and complex modeling schemes.
Implementation Method 1
When utilizing these 'MR' signals to produce images, magnetic field gradients (Gx, Gy and Gz) are employed
Implementation Method 2
the individual magnetic moments of the excited nuclei in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 3
A signal is emitted by the excited nuclei or 'spins', after the excitation signal B1 is terminated
Data Source
AI summary
A system and method for producing MR images in which bone and soft tissue are identified. The method includes applying a pulse sequence that includes a first stage configured to acquire a radially-encoded FID and radially-encoded echoes performed after a non-selective RF excitation pulse and before a second stage, which is configured to acquire additional echoes. The radially-encoded MR data acquired during the first stage is substantially representative of bone, while the MR data acquired during the second stage is substantially representative of soft tissues. MR images in which bone and soft tissue are identified are reconstructed from these MR data sets.